1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 5 * The Regents of the University of California. All rights reserved. 6 * Copyright (c) 2007-2008,2010 7 * Swinburne University of Technology, Melbourne, Australia. 8 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org> 9 * Copyright (c) 2010 The FreeBSD Foundation 10 * Copyright (c) 2010-2011 Juniper Networks, Inc. 11 * All rights reserved. 12 * 13 * Portions of this software were developed at the Centre for Advanced Internet 14 * Architectures, Swinburne University of Technology, by Lawrence Stewart, 15 * James Healy and David Hayes, made possible in part by a grant from the Cisco 16 * University Research Program Fund at Community Foundation Silicon Valley. 17 * 18 * Portions of this software were developed at the Centre for Advanced 19 * Internet Architectures, Swinburne University of Technology, Melbourne, 20 * Australia by David Hayes under sponsorship from the FreeBSD Foundation. 21 * 22 * Portions of this software were developed by Robert N. M. Watson under 23 * contract to Juniper Networks, Inc. 24 * 25 * Redistribution and use in source and binary forms, with or without 26 * modification, are permitted provided that the following conditions 27 * are met: 28 * 1. Redistributions of source code must retain the above copyright 29 * notice, this list of conditions and the following disclaimer. 30 * 2. Redistributions in binary form must reproduce the above copyright 31 * notice, this list of conditions and the following disclaimer in the 32 * documentation and/or other materials provided with the distribution. 33 * 3. Neither the name of the University nor the names of its contributors 34 * may be used to endorse or promote products derived from this software 35 * without specific prior written permission. 36 * 37 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 38 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 39 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 40 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 41 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 42 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 43 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 45 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 46 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 47 * SUCH DAMAGE. 48 * 49 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 50 */ 51 52 #include <sys/cdefs.h> 53 __FBSDID("$FreeBSD$"); 54 55 #include "opt_inet.h" 56 #include "opt_inet6.h" 57 #include "opt_ipsec.h" 58 #include "opt_tcpdebug.h" 59 60 #include <sys/param.h> 61 #include <sys/arb.h> 62 #include <sys/kernel.h> 63 #ifdef TCP_HHOOK 64 #include <sys/hhook.h> 65 #endif 66 #include <sys/malloc.h> 67 #include <sys/mbuf.h> 68 #include <sys/proc.h> /* for proc0 declaration */ 69 #include <sys/protosw.h> 70 #include <sys/qmath.h> 71 #include <sys/sdt.h> 72 #include <sys/signalvar.h> 73 #include <sys/socket.h> 74 #include <sys/socketvar.h> 75 #include <sys/sysctl.h> 76 #include <sys/syslog.h> 77 #include <sys/systm.h> 78 #include <sys/stats.h> 79 80 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 81 82 #include <vm/uma.h> 83 84 #include <net/if.h> 85 #include <net/if_var.h> 86 #include <net/route.h> 87 #include <net/vnet.h> 88 89 #define TCPSTATES /* for logging */ 90 91 #include <netinet/in.h> 92 #include <netinet/in_kdtrace.h> 93 #include <netinet/in_pcb.h> 94 #include <netinet/in_systm.h> 95 #include <netinet/ip.h> 96 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 97 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 98 #include <netinet/ip_var.h> 99 #include <netinet/ip_options.h> 100 #include <netinet/ip6.h> 101 #include <netinet/icmp6.h> 102 #include <netinet6/in6_pcb.h> 103 #include <netinet6/in6_var.h> 104 #include <netinet6/ip6_var.h> 105 #include <netinet6/nd6.h> 106 #include <netinet/tcp.h> 107 #include <netinet/tcp_fsm.h> 108 #include <netinet/tcp_log_buf.h> 109 #include <netinet/tcp_seq.h> 110 #include <netinet/tcp_timer.h> 111 #include <netinet/tcp_var.h> 112 #include <netinet6/tcp6_var.h> 113 #include <netinet/tcpip.h> 114 #include <netinet/cc/cc.h> 115 #include <netinet/tcp_fastopen.h> 116 #ifdef TCPPCAP 117 #include <netinet/tcp_pcap.h> 118 #endif 119 #include <netinet/tcp_syncache.h> 120 #ifdef TCPDEBUG 121 #include <netinet/tcp_debug.h> 122 #endif /* TCPDEBUG */ 123 #ifdef TCP_OFFLOAD 124 #include <netinet/tcp_offload.h> 125 #endif 126 #include <netinet/tcp_ecn.h> 127 #include <netinet/udp.h> 128 129 #include <netipsec/ipsec_support.h> 130 131 #include <machine/in_cksum.h> 132 133 #include <security/mac/mac_framework.h> 134 135 const int tcprexmtthresh = 3; 136 137 VNET_DEFINE(int, tcp_log_in_vain) = 0; 138 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_VNET | CTLFLAG_RW, 139 &VNET_NAME(tcp_log_in_vain), 0, 140 "Log all incoming TCP segments to closed ports"); 141 142 VNET_DEFINE(int, blackhole) = 0; 143 #define V_blackhole VNET(blackhole) 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW, 145 &VNET_NAME(blackhole), 0, 146 "Do not send RST on segments to closed ports"); 147 148 VNET_DEFINE(bool, blackhole_local) = false; 149 #define V_blackhole_local VNET(blackhole_local) 150 SYSCTL_BOOL(_net_inet_tcp, OID_AUTO, blackhole_local, CTLFLAG_VNET | 151 CTLFLAG_RW, &VNET_NAME(blackhole_local), false, 152 "Enforce net.inet.tcp.blackhole for locally originated packets"); 153 154 VNET_DEFINE(int, tcp_delack_enabled) = 1; 155 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW, 156 &VNET_NAME(tcp_delack_enabled), 0, 157 "Delay ACK to try and piggyback it onto a data packet"); 158 159 VNET_DEFINE(int, drop_synfin) = 0; 160 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW, 161 &VNET_NAME(drop_synfin), 0, 162 "Drop TCP packets with SYN+FIN set"); 163 164 VNET_DEFINE(int, tcp_do_prr_conservative) = 0; 165 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_prr_conservative, CTLFLAG_VNET | CTLFLAG_RW, 166 &VNET_NAME(tcp_do_prr_conservative), 0, 167 "Do conservative Proportional Rate Reduction"); 168 169 VNET_DEFINE(int, tcp_do_prr) = 1; 170 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_prr, CTLFLAG_VNET | CTLFLAG_RW, 171 &VNET_NAME(tcp_do_prr), 1, 172 "Enable Proportional Rate Reduction per RFC 6937"); 173 174 VNET_DEFINE(int, tcp_do_lrd) = 0; 175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_lrd, CTLFLAG_VNET | CTLFLAG_RW, 176 &VNET_NAME(tcp_do_lrd), 1, 177 "Perform Lost Retransmission Detection"); 178 179 VNET_DEFINE(int, tcp_do_newcwv) = 0; 180 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newcwv, CTLFLAG_VNET | CTLFLAG_RW, 181 &VNET_NAME(tcp_do_newcwv), 0, 182 "Enable New Congestion Window Validation per RFC7661"); 183 184 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 185 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW, 186 &VNET_NAME(tcp_do_rfc3042), 0, 187 "Enable RFC 3042 (Limited Transmit)"); 188 189 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 190 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW, 191 &VNET_NAME(tcp_do_rfc3390), 0, 192 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 193 194 VNET_DEFINE(int, tcp_initcwnd_segments) = 10; 195 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments, 196 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0, 197 "Slow-start flight size (initial congestion window) in number of segments"); 198 199 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 200 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW, 201 &VNET_NAME(tcp_do_rfc3465), 0, 202 "Enable RFC 3465 (Appropriate Byte Counting)"); 203 204 VNET_DEFINE(int, tcp_abc_l_var) = 2; 205 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW, 206 &VNET_NAME(tcp_abc_l_var), 2, 207 "Cap the max cwnd increment during slow-start to this number of segments"); 208 209 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, 210 CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 211 "TCP ECN"); 212 213 VNET_DEFINE(int, tcp_do_ecn) = 2; 214 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 215 &VNET_NAME(tcp_do_ecn), 0, 216 "TCP ECN support"); 217 218 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 219 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW, 220 &VNET_NAME(tcp_ecn_maxretries), 0, 221 "Max retries before giving up on ECN"); 222 223 VNET_DEFINE(int, tcp_insecure_syn) = 0; 224 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW, 225 &VNET_NAME(tcp_insecure_syn), 0, 226 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets"); 227 228 VNET_DEFINE(int, tcp_insecure_rst) = 0; 229 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW, 230 &VNET_NAME(tcp_insecure_rst), 0, 231 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets"); 232 233 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 234 #define V_tcp_recvspace VNET(tcp_recvspace) 235 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW, 236 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 237 238 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 239 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 240 &VNET_NAME(tcp_do_autorcvbuf), 0, 241 "Enable automatic receive buffer sizing"); 242 243 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 244 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 245 &VNET_NAME(tcp_autorcvbuf_max), 0, 246 "Max size of automatic receive buffer"); 247 248 VNET_DEFINE(struct inpcbinfo, tcbinfo); 249 250 /* 251 * TCP statistics are stored in an array of counter(9)s, which size matches 252 * size of struct tcpstat. TCP running connection count is a regular array. 253 */ 254 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 255 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 256 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 257 VNET_DEFINE(counter_u64_t, tcps_states[TCP_NSTATES]); 258 SYSCTL_COUNTER_U64_ARRAY(_net_inet_tcp, TCPCTL_STATES, states, CTLFLAG_RD | 259 CTLFLAG_VNET, &VNET_NAME(tcps_states)[0], TCP_NSTATES, 260 "TCP connection counts by TCP state"); 261 262 /* 263 * Kernel module interface for updating tcpstat. The first argument is an index 264 * into tcpstat treated as an array. 265 */ 266 void 267 kmod_tcpstat_add(int statnum, int val) 268 { 269 270 counter_u64_add(VNET(tcpstat)[statnum], val); 271 } 272 273 #ifdef TCP_HHOOK 274 /* 275 * Wrapper for the TCP established input helper hook. 276 */ 277 void 278 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 279 { 280 struct tcp_hhook_data hhook_data; 281 282 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 283 hhook_data.tp = tp; 284 hhook_data.th = th; 285 hhook_data.to = to; 286 287 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 288 tp->osd); 289 } 290 } 291 #endif 292 293 /* 294 * CC wrapper hook functions 295 */ 296 void 297 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t nsegs, 298 uint16_t type) 299 { 300 #ifdef STATS 301 int32_t gput; 302 #endif 303 304 INP_WLOCK_ASSERT(tp->t_inpcb); 305 306 tp->ccv->nsegs = nsegs; 307 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); 308 if ((!V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd)) || 309 (V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd) && 310 (tp->snd_cwnd < (tcp_compute_pipe(tp) * 2)))) 311 tp->ccv->flags |= CCF_CWND_LIMITED; 312 else 313 tp->ccv->flags &= ~CCF_CWND_LIMITED; 314 315 if (type == CC_ACK) { 316 #ifdef STATS 317 stats_voi_update_abs_s32(tp->t_stats, VOI_TCP_CALCFRWINDIFF, 318 ((int32_t)tp->snd_cwnd) - tp->snd_wnd); 319 if (!IN_RECOVERY(tp->t_flags)) 320 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_ACKLEN, 321 tp->ccv->bytes_this_ack / (tcp_maxseg(tp) * nsegs)); 322 if ((tp->t_flags & TF_GPUTINPROG) && 323 SEQ_GEQ(th->th_ack, tp->gput_ack)) { 324 /* 325 * Compute goodput in bits per millisecond. 326 */ 327 gput = (((int64_t)(th->th_ack - tp->gput_seq)) << 3) / 328 max(1, tcp_ts_getticks() - tp->gput_ts); 329 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_GPUT, 330 gput); 331 /* 332 * XXXLAS: This is a temporary hack, and should be 333 * chained off VOI_TCP_GPUT when stats(9) grows an API 334 * to deal with chained VOIs. 335 */ 336 if (tp->t_stats_gput_prev > 0) 337 stats_voi_update_abs_s32(tp->t_stats, 338 VOI_TCP_GPUT_ND, 339 ((gput - tp->t_stats_gput_prev) * 100) / 340 tp->t_stats_gput_prev); 341 tp->t_flags &= ~TF_GPUTINPROG; 342 tp->t_stats_gput_prev = gput; 343 } 344 #endif /* STATS */ 345 if (tp->snd_cwnd > tp->snd_ssthresh) { 346 tp->t_bytes_acked += tp->ccv->bytes_this_ack; 347 if (tp->t_bytes_acked >= tp->snd_cwnd) { 348 tp->t_bytes_acked -= tp->snd_cwnd; 349 tp->ccv->flags |= CCF_ABC_SENTAWND; 350 } 351 } else { 352 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 353 tp->t_bytes_acked = 0; 354 } 355 } 356 357 if (CC_ALGO(tp)->ack_received != NULL) { 358 /* XXXLAS: Find a way to live without this */ 359 tp->ccv->curack = th->th_ack; 360 CC_ALGO(tp)->ack_received(tp->ccv, type); 361 } 362 #ifdef STATS 363 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_LCWIN, tp->snd_cwnd); 364 #endif 365 } 366 367 void 368 cc_conn_init(struct tcpcb *tp) 369 { 370 struct hc_metrics_lite metrics; 371 struct inpcb *inp = tp->t_inpcb; 372 u_int maxseg; 373 int rtt; 374 375 INP_WLOCK_ASSERT(tp->t_inpcb); 376 377 tcp_hc_get(&inp->inp_inc, &metrics); 378 maxseg = tcp_maxseg(tp); 379 380 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 381 tp->t_srtt = rtt; 382 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 383 TCPSTAT_INC(tcps_usedrtt); 384 if (metrics.rmx_rttvar) { 385 tp->t_rttvar = metrics.rmx_rttvar; 386 TCPSTAT_INC(tcps_usedrttvar); 387 } else { 388 /* default variation is +- 1 rtt */ 389 tp->t_rttvar = 390 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 391 } 392 TCPT_RANGESET(tp->t_rxtcur, 393 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 394 tp->t_rttmin, TCPTV_REXMTMAX); 395 } 396 if (metrics.rmx_ssthresh) { 397 /* 398 * There's some sort of gateway or interface 399 * buffer limit on the path. Use this to set 400 * the slow start threshold, but set the 401 * threshold to no less than 2*mss. 402 */ 403 tp->snd_ssthresh = max(2 * maxseg, metrics.rmx_ssthresh); 404 TCPSTAT_INC(tcps_usedssthresh); 405 } 406 407 /* 408 * Set the initial slow-start flight size. 409 * 410 * If a SYN or SYN/ACK was lost and retransmitted, we have to 411 * reduce the initial CWND to one segment as congestion is likely 412 * requiring us to be cautious. 413 */ 414 if (tp->snd_cwnd == 1) 415 tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */ 416 else 417 tp->snd_cwnd = tcp_compute_initwnd(maxseg); 418 419 if (CC_ALGO(tp)->conn_init != NULL) 420 CC_ALGO(tp)->conn_init(tp->ccv); 421 } 422 423 void inline 424 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) 425 { 426 INP_WLOCK_ASSERT(tp->t_inpcb); 427 428 #ifdef STATS 429 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_CSIG, type); 430 #endif 431 432 switch(type) { 433 case CC_NDUPACK: 434 if (!IN_FASTRECOVERY(tp->t_flags)) { 435 tp->snd_recover = tp->snd_max; 436 if (tp->t_flags2 & TF2_ECN_PERMIT) 437 tp->t_flags2 |= TF2_ECN_SND_CWR; 438 } 439 break; 440 case CC_ECN: 441 if (!IN_CONGRECOVERY(tp->t_flags) || 442 /* 443 * Allow ECN reaction on ACK to CWR, if 444 * that data segment was also CE marked. 445 */ 446 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 447 EXIT_CONGRECOVERY(tp->t_flags); 448 TCPSTAT_INC(tcps_ecn_rcwnd); 449 tp->snd_recover = tp->snd_max + 1; 450 if (tp->t_flags2 & TF2_ECN_PERMIT) 451 tp->t_flags2 |= TF2_ECN_SND_CWR; 452 } 453 break; 454 case CC_RTO: 455 tp->t_dupacks = 0; 456 tp->t_bytes_acked = 0; 457 EXIT_RECOVERY(tp->t_flags); 458 if (tp->t_flags2 & TF2_ECN_PERMIT) 459 tp->t_flags2 |= TF2_ECN_SND_CWR; 460 break; 461 case CC_RTO_ERR: 462 TCPSTAT_INC(tcps_sndrexmitbad); 463 /* RTO was unnecessary, so reset everything. */ 464 tp->snd_cwnd = tp->snd_cwnd_prev; 465 tp->snd_ssthresh = tp->snd_ssthresh_prev; 466 tp->snd_recover = tp->snd_recover_prev; 467 if (tp->t_flags & TF_WASFRECOVERY) 468 ENTER_FASTRECOVERY(tp->t_flags); 469 if (tp->t_flags & TF_WASCRECOVERY) 470 ENTER_CONGRECOVERY(tp->t_flags); 471 tp->snd_nxt = tp->snd_max; 472 tp->t_flags &= ~TF_PREVVALID; 473 tp->t_badrxtwin = 0; 474 break; 475 } 476 477 if (CC_ALGO(tp)->cong_signal != NULL) { 478 if (th != NULL) 479 tp->ccv->curack = th->th_ack; 480 CC_ALGO(tp)->cong_signal(tp->ccv, type); 481 } 482 } 483 484 void inline 485 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 486 { 487 INP_WLOCK_ASSERT(tp->t_inpcb); 488 489 /* XXXLAS: KASSERT that we're in recovery? */ 490 491 if (CC_ALGO(tp)->post_recovery != NULL) { 492 tp->ccv->curack = th->th_ack; 493 CC_ALGO(tp)->post_recovery(tp->ccv); 494 } 495 /* XXXLAS: EXIT_RECOVERY ? */ 496 tp->t_bytes_acked = 0; 497 tp->sackhint.delivered_data = 0; 498 tp->sackhint.prr_out = 0; 499 } 500 501 /* 502 * Indicate whether this ack should be delayed. We can delay the ack if 503 * following conditions are met: 504 * - There is no delayed ack timer in progress. 505 * - Our last ack wasn't a 0-sized window. We never want to delay 506 * the ack that opens up a 0-sized window. 507 * - LRO wasn't used for this segment. We make sure by checking that the 508 * segment size is not larger than the MSS. 509 */ 510 #define DELAY_ACK(tp, tlen) \ 511 ((!tcp_timer_active(tp, TT_DELACK) && \ 512 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 513 (tlen <= tp->t_maxseg) && \ 514 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 515 516 void inline 517 cc_ecnpkt_handler_flags(struct tcpcb *tp, uint16_t flags, uint8_t iptos) 518 { 519 INP_WLOCK_ASSERT(tp->t_inpcb); 520 521 if (CC_ALGO(tp)->ecnpkt_handler != NULL) { 522 switch (iptos & IPTOS_ECN_MASK) { 523 case IPTOS_ECN_CE: 524 tp->ccv->flags |= CCF_IPHDR_CE; 525 break; 526 case IPTOS_ECN_ECT0: 527 /* FALLTHROUGH */ 528 case IPTOS_ECN_ECT1: 529 /* FALLTHROUGH */ 530 case IPTOS_ECN_NOTECT: 531 tp->ccv->flags &= ~CCF_IPHDR_CE; 532 break; 533 } 534 535 if (flags & TH_CWR) 536 tp->ccv->flags |= CCF_TCPHDR_CWR; 537 else 538 tp->ccv->flags &= ~CCF_TCPHDR_CWR; 539 540 CC_ALGO(tp)->ecnpkt_handler(tp->ccv); 541 542 if (tp->ccv->flags & CCF_ACKNOW) { 543 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 544 tp->t_flags |= TF_ACKNOW; 545 } 546 } 547 } 548 549 void inline 550 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos) 551 { 552 cc_ecnpkt_handler_flags(tp, tcp_get_flags(th), iptos); 553 } 554 555 /* 556 * TCP input handling is split into multiple parts: 557 * tcp6_input is a thin wrapper around tcp_input for the extended 558 * ip6_protox[] call format in ip6_input 559 * tcp_input handles primary segment validation, inpcb lookup and 560 * SYN processing on listen sockets 561 * tcp_do_segment processes the ACK and text of the segment for 562 * establishing, established and closing connections 563 */ 564 #ifdef INET6 565 int 566 tcp6_input_with_port(struct mbuf **mp, int *offp, int proto, uint16_t port) 567 { 568 struct mbuf *m; 569 struct in6_ifaddr *ia6; 570 struct ip6_hdr *ip6; 571 572 m = *mp; 573 if (m->m_len < *offp + sizeof(struct tcphdr)) { 574 m = m_pullup(m, *offp + sizeof(struct tcphdr)); 575 if (m == NULL) { 576 *mp = m; 577 TCPSTAT_INC(tcps_rcvshort); 578 return (IPPROTO_DONE); 579 } 580 } 581 582 /* 583 * draft-itojun-ipv6-tcp-to-anycast 584 * better place to put this in? 585 */ 586 ip6 = mtod(m, struct ip6_hdr *); 587 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */, false); 588 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 589 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 590 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 591 *mp = NULL; 592 return (IPPROTO_DONE); 593 } 594 595 *mp = m; 596 return (tcp_input_with_port(mp, offp, proto, port)); 597 } 598 599 int 600 tcp6_input(struct mbuf **mp, int *offp, int proto) 601 { 602 603 return(tcp6_input_with_port(mp, offp, proto, 0)); 604 } 605 #endif /* INET6 */ 606 607 int 608 tcp_input_with_port(struct mbuf **mp, int *offp, int proto, uint16_t port) 609 { 610 struct mbuf *m = *mp; 611 struct tcphdr *th = NULL; 612 struct ip *ip = NULL; 613 struct inpcb *inp = NULL; 614 struct tcpcb *tp = NULL; 615 struct socket *so = NULL; 616 u_char *optp = NULL; 617 int off0; 618 int optlen = 0; 619 #ifdef INET 620 int len; 621 uint8_t ipttl; 622 #endif 623 int tlen = 0, off; 624 int drop_hdrlen; 625 int thflags; 626 int rstreason = 0; /* For badport_bandlim accounting purposes */ 627 int lookupflag; 628 uint8_t iptos; 629 struct m_tag *fwd_tag = NULL; 630 #ifdef INET6 631 struct ip6_hdr *ip6 = NULL; 632 int isipv6; 633 #else 634 const void *ip6 = NULL; 635 #endif /* INET6 */ 636 struct tcpopt to; /* options in this segment */ 637 char *s = NULL; /* address and port logging */ 638 #ifdef TCPDEBUG 639 /* 640 * The size of tcp_saveipgen must be the size of the max ip header, 641 * now IPv6. 642 */ 643 u_char tcp_saveipgen[IP6_HDR_LEN]; 644 struct tcphdr tcp_savetcp; 645 short ostate = 0; 646 #endif 647 648 NET_EPOCH_ASSERT(); 649 650 #ifdef INET6 651 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 652 #endif 653 654 off0 = *offp; 655 m = *mp; 656 *mp = NULL; 657 to.to_flags = 0; 658 TCPSTAT_INC(tcps_rcvtotal); 659 660 #ifdef INET6 661 if (isipv6) { 662 ip6 = mtod(m, struct ip6_hdr *); 663 th = (struct tcphdr *)((caddr_t)ip6 + off0); 664 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 665 if (port) 666 goto skip6_csum; 667 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 668 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 669 th->th_sum = m->m_pkthdr.csum_data; 670 else 671 th->th_sum = in6_cksum_pseudo(ip6, tlen, 672 IPPROTO_TCP, m->m_pkthdr.csum_data); 673 th->th_sum ^= 0xffff; 674 } else 675 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 676 if (th->th_sum) { 677 TCPSTAT_INC(tcps_rcvbadsum); 678 goto drop; 679 } 680 skip6_csum: 681 /* 682 * Be proactive about unspecified IPv6 address in source. 683 * As we use all-zero to indicate unbounded/unconnected pcb, 684 * unspecified IPv6 address can be used to confuse us. 685 * 686 * Note that packets with unspecified IPv6 destination is 687 * already dropped in ip6_input. 688 */ 689 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 690 /* XXX stat */ 691 goto drop; 692 } 693 iptos = IPV6_TRAFFIC_CLASS(ip6); 694 } 695 #endif 696 #if defined(INET) && defined(INET6) 697 else 698 #endif 699 #ifdef INET 700 { 701 /* 702 * Get IP and TCP header together in first mbuf. 703 * Note: IP leaves IP header in first mbuf. 704 */ 705 if (off0 > sizeof (struct ip)) { 706 ip_stripoptions(m); 707 off0 = sizeof(struct ip); 708 } 709 if (m->m_len < sizeof (struct tcpiphdr)) { 710 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 711 == NULL) { 712 TCPSTAT_INC(tcps_rcvshort); 713 return (IPPROTO_DONE); 714 } 715 } 716 ip = mtod(m, struct ip *); 717 th = (struct tcphdr *)((caddr_t)ip + off0); 718 tlen = ntohs(ip->ip_len) - off0; 719 720 iptos = ip->ip_tos; 721 if (port) 722 goto skip_csum; 723 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 724 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 725 th->th_sum = m->m_pkthdr.csum_data; 726 else 727 th->th_sum = in_pseudo(ip->ip_src.s_addr, 728 ip->ip_dst.s_addr, 729 htonl(m->m_pkthdr.csum_data + tlen + 730 IPPROTO_TCP)); 731 th->th_sum ^= 0xffff; 732 } else { 733 struct ipovly *ipov = (struct ipovly *)ip; 734 735 /* 736 * Checksum extended TCP header and data. 737 */ 738 len = off0 + tlen; 739 ipttl = ip->ip_ttl; 740 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 741 ipov->ih_len = htons(tlen); 742 th->th_sum = in_cksum(m, len); 743 /* Reset length for SDT probes. */ 744 ip->ip_len = htons(len); 745 /* Reset TOS bits */ 746 ip->ip_tos = iptos; 747 /* Re-initialization for later version check */ 748 ip->ip_ttl = ipttl; 749 ip->ip_v = IPVERSION; 750 ip->ip_hl = off0 >> 2; 751 } 752 skip_csum: 753 if (th->th_sum && (port == 0)) { 754 TCPSTAT_INC(tcps_rcvbadsum); 755 goto drop; 756 } 757 } 758 #endif /* INET */ 759 760 /* 761 * Check that TCP offset makes sense, 762 * pull out TCP options and adjust length. XXX 763 */ 764 off = th->th_off << 2; 765 if (off < sizeof (struct tcphdr) || off > tlen) { 766 TCPSTAT_INC(tcps_rcvbadoff); 767 goto drop; 768 } 769 tlen -= off; /* tlen is used instead of ti->ti_len */ 770 if (off > sizeof (struct tcphdr)) { 771 #ifdef INET6 772 if (isipv6) { 773 if (m->m_len < off0 + off) { 774 m = m_pullup(m, off0 + off); 775 if (m == NULL) { 776 TCPSTAT_INC(tcps_rcvshort); 777 return (IPPROTO_DONE); 778 } 779 } 780 ip6 = mtod(m, struct ip6_hdr *); 781 th = (struct tcphdr *)((caddr_t)ip6 + off0); 782 } 783 #endif 784 #if defined(INET) && defined(INET6) 785 else 786 #endif 787 #ifdef INET 788 { 789 if (m->m_len < sizeof(struct ip) + off) { 790 if ((m = m_pullup(m, sizeof (struct ip) + off)) 791 == NULL) { 792 TCPSTAT_INC(tcps_rcvshort); 793 return (IPPROTO_DONE); 794 } 795 ip = mtod(m, struct ip *); 796 th = (struct tcphdr *)((caddr_t)ip + off0); 797 } 798 } 799 #endif 800 optlen = off - sizeof (struct tcphdr); 801 optp = (u_char *)(th + 1); 802 } 803 thflags = tcp_get_flags(th); 804 805 /* 806 * Convert TCP protocol specific fields to host format. 807 */ 808 tcp_fields_to_host(th); 809 810 /* 811 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 812 */ 813 drop_hdrlen = off0 + off; 814 815 /* 816 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 817 */ 818 if ( 819 #ifdef INET6 820 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 821 #ifdef INET 822 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 823 #endif 824 #endif 825 #if defined(INET) && !defined(INET6) 826 (m->m_flags & M_IP_NEXTHOP) 827 #endif 828 ) 829 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 830 831 /* 832 * For initial SYN packets we don't need write lock on matching 833 * PCB, be it a listening one or a synchronized one. The packet 834 * shall not modify its state. 835 */ 836 lookupflag = (thflags & (TH_ACK|TH_SYN)) == TH_SYN ? 837 INPLOOKUP_RLOCKPCB : INPLOOKUP_WLOCKPCB; 838 findpcb: 839 #ifdef INET6 840 if (isipv6 && fwd_tag != NULL) { 841 struct sockaddr_in6 *next_hop6; 842 843 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 844 /* 845 * Transparently forwarded. Pretend to be the destination. 846 * Already got one like this? 847 */ 848 inp = in6_pcblookup_mbuf(&V_tcbinfo, 849 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 850 lookupflag, m->m_pkthdr.rcvif, m); 851 if (!inp) { 852 /* 853 * It's new. Try to find the ambushing socket. 854 * Because we've rewritten the destination address, 855 * any hardware-generated hash is ignored. 856 */ 857 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 858 th->th_sport, &next_hop6->sin6_addr, 859 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 860 th->th_dport, INPLOOKUP_WILDCARD | lookupflag, 861 m->m_pkthdr.rcvif); 862 } 863 } else if (isipv6) { 864 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 865 th->th_sport, &ip6->ip6_dst, th->th_dport, 866 INPLOOKUP_WILDCARD | lookupflag, m->m_pkthdr.rcvif, m); 867 } 868 #endif /* INET6 */ 869 #if defined(INET6) && defined(INET) 870 else 871 #endif 872 #ifdef INET 873 if (fwd_tag != NULL) { 874 struct sockaddr_in *next_hop; 875 876 next_hop = (struct sockaddr_in *)(fwd_tag+1); 877 /* 878 * Transparently forwarded. Pretend to be the destination. 879 * already got one like this? 880 */ 881 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 882 ip->ip_dst, th->th_dport, lookupflag, m->m_pkthdr.rcvif, m); 883 if (!inp) { 884 /* 885 * It's new. Try to find the ambushing socket. 886 * Because we've rewritten the destination address, 887 * any hardware-generated hash is ignored. 888 */ 889 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 890 th->th_sport, next_hop->sin_addr, 891 next_hop->sin_port ? ntohs(next_hop->sin_port) : 892 th->th_dport, INPLOOKUP_WILDCARD | lookupflag, 893 m->m_pkthdr.rcvif); 894 } 895 } else 896 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 897 th->th_sport, ip->ip_dst, th->th_dport, 898 INPLOOKUP_WILDCARD | lookupflag, m->m_pkthdr.rcvif, m); 899 #endif /* INET */ 900 901 /* 902 * If the INPCB does not exist then all data in the incoming 903 * segment is discarded and an appropriate RST is sent back. 904 * XXX MRT Send RST using which routing table? 905 */ 906 if (inp == NULL) { 907 /* 908 * Log communication attempts to ports that are not 909 * in use. 910 */ 911 if ((V_tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 912 V_tcp_log_in_vain == 2) { 913 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 914 log(LOG_INFO, "%s; %s: Connection attempt " 915 "to closed port\n", s, __func__); 916 } 917 /* 918 * When blackholing do not respond with a RST but 919 * completely ignore the segment and drop it. 920 */ 921 if (((V_blackhole == 1 && (thflags & TH_SYN)) || 922 V_blackhole == 2) && (V_blackhole_local || 923 #ifdef INET6 924 isipv6 ? !in6_localaddr(&ip6->ip6_src) : 925 #endif 926 #ifdef INET 927 !in_localip(ip->ip_src) 928 #else 929 true 930 #endif 931 )) 932 goto dropunlock; 933 934 rstreason = BANDLIM_RST_CLOSEDPORT; 935 goto dropwithreset; 936 } 937 INP_LOCK_ASSERT(inp); 938 /* 939 * While waiting for inp lock during the lookup, another thread 940 * can have dropped the inpcb, in which case we need to loop back 941 * and try to find a new inpcb to deliver to. 942 */ 943 if (inp->inp_flags & INP_DROPPED) { 944 INP_UNLOCK(inp); 945 inp = NULL; 946 goto findpcb; 947 } 948 if ((inp->inp_flowtype == M_HASHTYPE_NONE) && 949 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) && 950 ((inp->inp_socket == NULL) || !SOLISTENING(inp->inp_socket))) { 951 inp->inp_flowid = m->m_pkthdr.flowid; 952 inp->inp_flowtype = M_HASHTYPE_GET(m); 953 } 954 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 955 #ifdef INET6 956 if (isipv6 && IPSEC_ENABLED(ipv6) && 957 IPSEC_CHECK_POLICY(ipv6, m, inp) != 0) { 958 goto dropunlock; 959 } 960 #ifdef INET 961 else 962 #endif 963 #endif /* INET6 */ 964 #ifdef INET 965 if (IPSEC_ENABLED(ipv4) && 966 IPSEC_CHECK_POLICY(ipv4, m, inp) != 0) { 967 goto dropunlock; 968 } 969 #endif /* INET */ 970 #endif /* IPSEC */ 971 972 /* 973 * Check the minimum TTL for socket. 974 */ 975 if (inp->inp_ip_minttl != 0) { 976 #ifdef INET6 977 if (isipv6) { 978 if (inp->inp_ip_minttl > ip6->ip6_hlim) 979 goto dropunlock; 980 } else 981 #endif 982 if (inp->inp_ip_minttl > ip->ip_ttl) 983 goto dropunlock; 984 } 985 986 /* 987 * A previous connection in TIMEWAIT state is supposed to catch stray 988 * or duplicate segments arriving late. If this segment was a 989 * legitimate new connection attempt, the old INPCB gets removed and 990 * we can try again to find a listening socket. 991 */ 992 if (inp->inp_flags & INP_TIMEWAIT) { 993 tcp_dooptions(&to, optp, optlen, 994 (thflags & TH_SYN) ? TO_SYN : 0); 995 /* 996 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 997 */ 998 if (tcp_twcheck(inp, &to, th, m, tlen)) 999 goto findpcb; 1000 return (IPPROTO_DONE); 1001 } 1002 /* 1003 * The TCPCB may no longer exist if the connection is winding 1004 * down or it is in the CLOSED state. Either way we drop the 1005 * segment and send an appropriate response. 1006 */ 1007 tp = intotcpcb(inp); 1008 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 1009 rstreason = BANDLIM_RST_CLOSEDPORT; 1010 goto dropwithreset; 1011 } 1012 1013 if ((tp->t_port != port) && (tp->t_state > TCPS_LISTEN)) { 1014 rstreason = BANDLIM_RST_CLOSEDPORT; 1015 goto dropwithreset; 1016 } 1017 1018 #ifdef TCP_OFFLOAD 1019 if (tp->t_flags & TF_TOE) { 1020 tcp_offload_input(tp, m); 1021 m = NULL; /* consumed by the TOE driver */ 1022 goto dropunlock; 1023 } 1024 #endif 1025 1026 #ifdef MAC 1027 if (mac_inpcb_check_deliver(inp, m)) 1028 goto dropunlock; 1029 #endif 1030 so = inp->inp_socket; 1031 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1032 #ifdef TCPDEBUG 1033 if (so->so_options & SO_DEBUG) { 1034 ostate = tp->t_state; 1035 #ifdef INET6 1036 if (isipv6) { 1037 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1038 } else 1039 #endif 1040 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1041 tcp_savetcp = *th; 1042 } 1043 #endif /* TCPDEBUG */ 1044 /* 1045 * When the socket is accepting connections (the INPCB is in LISTEN 1046 * state) we look into the SYN cache if this is a new connection 1047 * attempt or the completion of a previous one. 1048 */ 1049 KASSERT(tp->t_state == TCPS_LISTEN || !SOLISTENING(so), 1050 ("%s: so accepting but tp %p not listening", __func__, tp)); 1051 if (tp->t_state == TCPS_LISTEN && SOLISTENING(so)) { 1052 struct in_conninfo inc; 1053 1054 bzero(&inc, sizeof(inc)); 1055 #ifdef INET6 1056 if (isipv6) { 1057 inc.inc_flags |= INC_ISIPV6; 1058 if (inp->inp_inc.inc_flags & INC_IPV6MINMTU) 1059 inc.inc_flags |= INC_IPV6MINMTU; 1060 inc.inc6_faddr = ip6->ip6_src; 1061 inc.inc6_laddr = ip6->ip6_dst; 1062 } else 1063 #endif 1064 { 1065 inc.inc_faddr = ip->ip_src; 1066 inc.inc_laddr = ip->ip_dst; 1067 } 1068 inc.inc_fport = th->th_sport; 1069 inc.inc_lport = th->th_dport; 1070 inc.inc_fibnum = so->so_fibnum; 1071 1072 /* 1073 * Check for an existing connection attempt in syncache if 1074 * the flag is only ACK. A successful lookup creates a new 1075 * socket appended to the listen queue in SYN_RECEIVED state. 1076 */ 1077 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1078 /* 1079 * Parse the TCP options here because 1080 * syncookies need access to the reflected 1081 * timestamp. 1082 */ 1083 tcp_dooptions(&to, optp, optlen, 0); 1084 /* 1085 * NB: syncache_expand() doesn't unlock 1086 * inp and tcpinfo locks. 1087 */ 1088 rstreason = syncache_expand(&inc, &to, th, &so, m, port); 1089 if (rstreason < 0) { 1090 /* 1091 * A failing TCP MD5 signature comparison 1092 * must result in the segment being dropped 1093 * and must not produce any response back 1094 * to the sender. 1095 */ 1096 goto dropunlock; 1097 } else if (rstreason == 0) { 1098 /* 1099 * No syncache entry or ACK was not 1100 * for our SYN/ACK. Send a RST. 1101 * NB: syncache did its own logging 1102 * of the failure cause. 1103 */ 1104 rstreason = BANDLIM_RST_OPENPORT; 1105 goto dropwithreset; 1106 } 1107 tfo_socket_result: 1108 if (so == NULL) { 1109 /* 1110 * We completed the 3-way handshake 1111 * but could not allocate a socket 1112 * either due to memory shortage, 1113 * listen queue length limits or 1114 * global socket limits. Send RST 1115 * or wait and have the remote end 1116 * retransmit the ACK for another 1117 * try. 1118 */ 1119 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1120 log(LOG_DEBUG, "%s; %s: Listen socket: " 1121 "Socket allocation failed due to " 1122 "limits or memory shortage, %s\n", 1123 s, __func__, 1124 V_tcp_sc_rst_sock_fail ? 1125 "sending RST" : "try again"); 1126 if (V_tcp_sc_rst_sock_fail) { 1127 rstreason = BANDLIM_UNLIMITED; 1128 goto dropwithreset; 1129 } else 1130 goto dropunlock; 1131 } 1132 /* 1133 * Socket is created in state SYN_RECEIVED. 1134 * Unlock the listen socket, lock the newly 1135 * created socket and update the tp variable. 1136 * If we came here via jump to tfo_socket_result, 1137 * then listening socket is read-locked. 1138 */ 1139 INP_UNLOCK(inp); /* listen socket */ 1140 inp = sotoinpcb(so); 1141 /* 1142 * New connection inpcb is already locked by 1143 * syncache_expand(). 1144 */ 1145 INP_WLOCK_ASSERT(inp); 1146 tp = intotcpcb(inp); 1147 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1148 ("%s: ", __func__)); 1149 /* 1150 * Process the segment and the data it 1151 * contains. tcp_do_segment() consumes 1152 * the mbuf chain and unlocks the inpcb. 1153 */ 1154 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1155 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1156 iptos); 1157 return (IPPROTO_DONE); 1158 } 1159 /* 1160 * Segment flag validation for new connection attempts: 1161 * 1162 * Our (SYN|ACK) response was rejected. 1163 * Check with syncache and remove entry to prevent 1164 * retransmits. 1165 * 1166 * NB: syncache_chkrst does its own logging of failure 1167 * causes. 1168 */ 1169 if (thflags & TH_RST) { 1170 syncache_chkrst(&inc, th, m, port); 1171 goto dropunlock; 1172 } 1173 /* 1174 * We can't do anything without SYN. 1175 */ 1176 if ((thflags & TH_SYN) == 0) { 1177 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1178 log(LOG_DEBUG, "%s; %s: Listen socket: " 1179 "SYN is missing, segment ignored\n", 1180 s, __func__); 1181 TCPSTAT_INC(tcps_badsyn); 1182 goto dropunlock; 1183 } 1184 /* 1185 * (SYN|ACK) is bogus on a listen socket. 1186 */ 1187 if (thflags & TH_ACK) { 1188 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1189 log(LOG_DEBUG, "%s; %s: Listen socket: " 1190 "SYN|ACK invalid, segment rejected\n", 1191 s, __func__); 1192 syncache_badack(&inc, port); /* XXX: Not needed! */ 1193 TCPSTAT_INC(tcps_badsyn); 1194 rstreason = BANDLIM_RST_OPENPORT; 1195 goto dropwithreset; 1196 } 1197 /* 1198 * If the drop_synfin option is enabled, drop all 1199 * segments with both the SYN and FIN bits set. 1200 * This prevents e.g. nmap from identifying the 1201 * TCP/IP stack. 1202 * XXX: Poor reasoning. nmap has other methods 1203 * and is constantly refining its stack detection 1204 * strategies. 1205 * XXX: This is a violation of the TCP specification 1206 * and was used by RFC1644. 1207 */ 1208 if ((thflags & TH_FIN) && V_drop_synfin) { 1209 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1210 log(LOG_DEBUG, "%s; %s: Listen socket: " 1211 "SYN|FIN segment ignored (based on " 1212 "sysctl setting)\n", s, __func__); 1213 TCPSTAT_INC(tcps_badsyn); 1214 goto dropunlock; 1215 } 1216 /* 1217 * Segment's flags are (SYN) or (SYN|FIN). 1218 * 1219 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1220 * as they do not affect the state of the TCP FSM. 1221 * The data pointed to by TH_URG and th_urp is ignored. 1222 */ 1223 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1224 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1225 KASSERT(thflags & (TH_SYN), 1226 ("%s: Listen socket: TH_SYN not set", __func__)); 1227 INP_RLOCK_ASSERT(inp); 1228 #ifdef INET6 1229 /* 1230 * If deprecated address is forbidden, 1231 * we do not accept SYN to deprecated interface 1232 * address to prevent any new inbound connection from 1233 * getting established. 1234 * When we do not accept SYN, we send a TCP RST, 1235 * with deprecated source address (instead of dropping 1236 * it). We compromise it as it is much better for peer 1237 * to send a RST, and RST will be the final packet 1238 * for the exchange. 1239 * 1240 * If we do not forbid deprecated addresses, we accept 1241 * the SYN packet. RFC2462 does not suggest dropping 1242 * SYN in this case. 1243 * If we decipher RFC2462 5.5.4, it says like this: 1244 * 1. use of deprecated addr with existing 1245 * communication is okay - "SHOULD continue to be 1246 * used" 1247 * 2. use of it with new communication: 1248 * (2a) "SHOULD NOT be used if alternate address 1249 * with sufficient scope is available" 1250 * (2b) nothing mentioned otherwise. 1251 * Here we fall into (2b) case as we have no choice in 1252 * our source address selection - we must obey the peer. 1253 * 1254 * The wording in RFC2462 is confusing, and there are 1255 * multiple description text for deprecated address 1256 * handling - worse, they are not exactly the same. 1257 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1258 */ 1259 if (isipv6 && !V_ip6_use_deprecated) { 1260 struct in6_ifaddr *ia6; 1261 1262 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */, false); 1263 if (ia6 != NULL && 1264 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1265 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1266 log(LOG_DEBUG, "%s; %s: Listen socket: " 1267 "Connection attempt to deprecated " 1268 "IPv6 address rejected\n", 1269 s, __func__); 1270 rstreason = BANDLIM_RST_OPENPORT; 1271 goto dropwithreset; 1272 } 1273 } 1274 #endif /* INET6 */ 1275 /* 1276 * Basic sanity checks on incoming SYN requests: 1277 * Don't respond if the destination is a link layer 1278 * broadcast according to RFC1122 4.2.3.10, p. 104. 1279 * If it is from this socket it must be forged. 1280 * Don't respond if the source or destination is a 1281 * global or subnet broad- or multicast address. 1282 * Note that it is quite possible to receive unicast 1283 * link-layer packets with a broadcast IP address. Use 1284 * in_broadcast() to find them. 1285 */ 1286 if (m->m_flags & (M_BCAST|M_MCAST)) { 1287 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1288 log(LOG_DEBUG, "%s; %s: Listen socket: " 1289 "Connection attempt from broad- or multicast " 1290 "link layer address ignored\n", s, __func__); 1291 goto dropunlock; 1292 } 1293 #ifdef INET6 1294 if (isipv6) { 1295 if (th->th_dport == th->th_sport && 1296 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1297 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1298 log(LOG_DEBUG, "%s; %s: Listen socket: " 1299 "Connection attempt to/from self " 1300 "ignored\n", s, __func__); 1301 goto dropunlock; 1302 } 1303 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1304 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1305 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1306 log(LOG_DEBUG, "%s; %s: Listen socket: " 1307 "Connection attempt from/to multicast " 1308 "address ignored\n", s, __func__); 1309 goto dropunlock; 1310 } 1311 } 1312 #endif 1313 #if defined(INET) && defined(INET6) 1314 else 1315 #endif 1316 #ifdef INET 1317 { 1318 if (th->th_dport == th->th_sport && 1319 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1320 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1321 log(LOG_DEBUG, "%s; %s: Listen socket: " 1322 "Connection attempt from/to self " 1323 "ignored\n", s, __func__); 1324 goto dropunlock; 1325 } 1326 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1327 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1328 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1329 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1330 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1331 log(LOG_DEBUG, "%s; %s: Listen socket: " 1332 "Connection attempt from/to broad- " 1333 "or multicast address ignored\n", 1334 s, __func__); 1335 goto dropunlock; 1336 } 1337 } 1338 #endif 1339 /* 1340 * SYN appears to be valid. Create compressed TCP state 1341 * for syncache. 1342 */ 1343 #ifdef TCPDEBUG 1344 if (so->so_options & SO_DEBUG) 1345 tcp_trace(TA_INPUT, ostate, tp, 1346 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1347 #endif 1348 TCP_PROBE3(debug__input, tp, th, m); 1349 tcp_dooptions(&to, optp, optlen, TO_SYN); 1350 if ((so = syncache_add(&inc, &to, th, inp, so, m, NULL, NULL, 1351 iptos, port)) != NULL) 1352 goto tfo_socket_result; 1353 1354 /* 1355 * Entry added to syncache and mbuf consumed. 1356 * Only the listen socket is unlocked by syncache_add(). 1357 */ 1358 return (IPPROTO_DONE); 1359 } else if (tp->t_state == TCPS_LISTEN) { 1360 /* 1361 * When a listen socket is torn down the SO_ACCEPTCONN 1362 * flag is removed first while connections are drained 1363 * from the accept queue in a unlock/lock cycle of the 1364 * ACCEPT_LOCK, opening a race condition allowing a SYN 1365 * attempt go through unhandled. 1366 */ 1367 goto dropunlock; 1368 } 1369 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1370 if (tp->t_flags & TF_SIGNATURE) { 1371 tcp_dooptions(&to, optp, optlen, thflags); 1372 if ((to.to_flags & TOF_SIGNATURE) == 0) { 1373 TCPSTAT_INC(tcps_sig_err_nosigopt); 1374 goto dropunlock; 1375 } 1376 if (!TCPMD5_ENABLED() || 1377 TCPMD5_INPUT(m, th, to.to_signature) != 0) 1378 goto dropunlock; 1379 } 1380 #endif 1381 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1382 1383 /* 1384 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1385 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1386 * the inpcb, and unlocks pcbinfo. 1387 * 1388 * XXXGL: in case of a pure SYN arriving on existing connection 1389 * TCP stacks won't need to modify the PCB, they would either drop 1390 * the segment silently, or send a challenge ACK. However, we try 1391 * to upgrade the lock, because calling convention for stacks is 1392 * write-lock on PCB. If upgrade fails, drop the SYN. 1393 */ 1394 if (lookupflag == INPLOOKUP_RLOCKPCB && INP_TRY_UPGRADE(inp) == 0) 1395 goto dropunlock; 1396 1397 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos); 1398 return (IPPROTO_DONE); 1399 1400 dropwithreset: 1401 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1402 1403 if (inp != NULL) { 1404 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1405 INP_UNLOCK(inp); 1406 } else 1407 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1408 m = NULL; /* mbuf chain got consumed. */ 1409 goto drop; 1410 1411 dropunlock: 1412 if (m != NULL) 1413 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1414 1415 if (inp != NULL) 1416 INP_UNLOCK(inp); 1417 1418 drop: 1419 if (s != NULL) 1420 free(s, M_TCPLOG); 1421 if (m != NULL) 1422 m_freem(m); 1423 return (IPPROTO_DONE); 1424 } 1425 1426 /* 1427 * Automatic sizing of receive socket buffer. Often the send 1428 * buffer size is not optimally adjusted to the actual network 1429 * conditions at hand (delay bandwidth product). Setting the 1430 * buffer size too small limits throughput on links with high 1431 * bandwidth and high delay (eg. trans-continental/oceanic links). 1432 * 1433 * On the receive side the socket buffer memory is only rarely 1434 * used to any significant extent. This allows us to be much 1435 * more aggressive in scaling the receive socket buffer. For 1436 * the case that the buffer space is actually used to a large 1437 * extent and we run out of kernel memory we can simply drop 1438 * the new segments; TCP on the sender will just retransmit it 1439 * later. Setting the buffer size too big may only consume too 1440 * much kernel memory if the application doesn't read() from 1441 * the socket or packet loss or reordering makes use of the 1442 * reassembly queue. 1443 * 1444 * The criteria to step up the receive buffer one notch are: 1445 * 1. Application has not set receive buffer size with 1446 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. 1447 * 2. the number of bytes received during 1/2 of an sRTT 1448 * is at least 3/8 of the current socket buffer size. 1449 * 3. receive buffer size has not hit maximal automatic size; 1450 * 1451 * If all of the criteria are met we increaset the socket buffer 1452 * by a 1/2 (bounded by the max). This allows us to keep ahead 1453 * of slow-start but also makes it so our peer never gets limited 1454 * by our rwnd which we then open up causing a burst. 1455 * 1456 * This algorithm does two steps per RTT at most and only if 1457 * we receive a bulk stream w/o packet losses or reorderings. 1458 * Shrinking the buffer during idle times is not necessary as 1459 * it doesn't consume any memory when idle. 1460 * 1461 * TODO: Only step up if the application is actually serving 1462 * the buffer to better manage the socket buffer resources. 1463 */ 1464 int 1465 tcp_autorcvbuf(struct mbuf *m, struct tcphdr *th, struct socket *so, 1466 struct tcpcb *tp, int tlen) 1467 { 1468 int newsize = 0; 1469 1470 if (V_tcp_do_autorcvbuf && (so->so_rcv.sb_flags & SB_AUTOSIZE) && 1471 tp->t_srtt != 0 && tp->rfbuf_ts != 0 && 1472 TCP_TS_TO_TICKS(tcp_ts_getticks() - tp->rfbuf_ts) > 1473 ((tp->t_srtt >> TCP_RTT_SHIFT)/2)) { 1474 if (tp->rfbuf_cnt > ((so->so_rcv.sb_hiwat / 2)/ 4 * 3) && 1475 so->so_rcv.sb_hiwat < V_tcp_autorcvbuf_max) { 1476 newsize = min((so->so_rcv.sb_hiwat + (so->so_rcv.sb_hiwat/2)), V_tcp_autorcvbuf_max); 1477 } 1478 TCP_PROBE6(receive__autoresize, NULL, tp, m, tp, th, newsize); 1479 1480 /* Start over with next RTT. */ 1481 tp->rfbuf_ts = 0; 1482 tp->rfbuf_cnt = 0; 1483 } else { 1484 tp->rfbuf_cnt += tlen; /* add up */ 1485 } 1486 return (newsize); 1487 } 1488 1489 int 1490 tcp_input(struct mbuf **mp, int *offp, int proto) 1491 { 1492 return(tcp_input_with_port(mp, offp, proto, 0)); 1493 } 1494 1495 void 1496 tcp_handle_wakeup(struct tcpcb *tp, struct socket *so) 1497 { 1498 /* 1499 * Since tp might be gone if the session entered 1500 * the TIME_WAIT state before coming here, we need 1501 * to check if the socket is still connected. 1502 */ 1503 if (tp == NULL) { 1504 return; 1505 } 1506 if (so == NULL) { 1507 return; 1508 } 1509 INP_LOCK_ASSERT(tp->t_inpcb); 1510 if (tp->t_flags & TF_WAKESOR) { 1511 tp->t_flags &= ~TF_WAKESOR; 1512 SOCKBUF_LOCK_ASSERT(&so->so_rcv); 1513 sorwakeup_locked(so); 1514 } 1515 } 1516 1517 void 1518 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1519 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos) 1520 { 1521 uint16_t thflags; 1522 int acked, ourfinisacked, needoutput = 0, sack_changed; 1523 int rstreason, todrop, win, incforsyn = 0; 1524 uint32_t tiwin; 1525 uint16_t nsegs; 1526 char *s; 1527 struct in_conninfo *inc; 1528 struct mbuf *mfree; 1529 struct tcpopt to; 1530 int tfo_syn; 1531 u_int maxseg; 1532 1533 #ifdef TCPDEBUG 1534 /* 1535 * The size of tcp_saveipgen must be the size of the max ip header, 1536 * now IPv6. 1537 */ 1538 u_char tcp_saveipgen[IP6_HDR_LEN]; 1539 struct tcphdr tcp_savetcp; 1540 short ostate = 0; 1541 #endif 1542 thflags = tcp_get_flags(th); 1543 inc = &tp->t_inpcb->inp_inc; 1544 tp->sackhint.last_sack_ack = 0; 1545 sack_changed = 0; 1546 nsegs = max(1, m->m_pkthdr.lro_nsegs); 1547 1548 NET_EPOCH_ASSERT(); 1549 INP_WLOCK_ASSERT(tp->t_inpcb); 1550 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1551 __func__)); 1552 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1553 __func__)); 1554 1555 #ifdef TCPPCAP 1556 /* Save segment, if requested. */ 1557 tcp_pcap_add(th, m, &(tp->t_inpkts)); 1558 #endif 1559 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_IN, 0, 1560 tlen, NULL, true); 1561 1562 if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) { 1563 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1564 log(LOG_DEBUG, "%s; %s: " 1565 "SYN|FIN segment ignored (based on " 1566 "sysctl setting)\n", s, __func__); 1567 free(s, M_TCPLOG); 1568 } 1569 goto drop; 1570 } 1571 1572 /* 1573 * If a segment with the ACK-bit set arrives in the SYN-SENT state 1574 * check SEQ.ACK first. 1575 */ 1576 if ((tp->t_state == TCPS_SYN_SENT) && (thflags & TH_ACK) && 1577 (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) { 1578 rstreason = BANDLIM_UNLIMITED; 1579 goto dropwithreset; 1580 } 1581 1582 /* 1583 * Segment received on connection. 1584 * Reset idle time and keep-alive timer. 1585 * XXX: This should be done after segment 1586 * validation to ignore broken/spoofed segs. 1587 */ 1588 tp->t_rcvtime = ticks; 1589 1590 /* 1591 * Scale up the window into a 32-bit value. 1592 * For the SYN_SENT state the scale is zero. 1593 */ 1594 tiwin = th->th_win << tp->snd_scale; 1595 #ifdef STATS 1596 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_FRWIN, tiwin); 1597 #endif 1598 1599 /* 1600 * TCP ECN processing. 1601 */ 1602 if (tcp_ecn_input_segment(tp, thflags, iptos)) 1603 cc_cong_signal(tp, th, CC_ECN); 1604 1605 /* 1606 * Parse options on any incoming segment. 1607 */ 1608 tcp_dooptions(&to, (u_char *)(th + 1), 1609 (th->th_off << 2) - sizeof(struct tcphdr), 1610 (thflags & TH_SYN) ? TO_SYN : 0); 1611 1612 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1613 if ((tp->t_flags & TF_SIGNATURE) != 0 && 1614 (to.to_flags & TOF_SIGNATURE) == 0) { 1615 TCPSTAT_INC(tcps_sig_err_sigopt); 1616 /* XXX: should drop? */ 1617 } 1618 #endif 1619 /* 1620 * If echoed timestamp is later than the current time, 1621 * fall back to non RFC1323 RTT calculation. Normalize 1622 * timestamp if syncookies were used when this connection 1623 * was established. 1624 */ 1625 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1626 to.to_tsecr -= tp->ts_offset; 1627 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1628 to.to_tsecr = 0; 1629 else if (tp->t_rxtshift == 1 && 1630 tp->t_flags & TF_PREVVALID && 1631 tp->t_badrxtwin != 0 && 1632 TSTMP_LT(to.to_tsecr, tp->t_badrxtwin)) 1633 cc_cong_signal(tp, th, CC_RTO_ERR); 1634 } 1635 /* 1636 * Process options only when we get SYN/ACK back. The SYN case 1637 * for incoming connections is handled in tcp_syncache. 1638 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1639 * or <SYN,ACK>) segment itself is never scaled. 1640 * XXX this is traditional behavior, may need to be cleaned up. 1641 */ 1642 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1643 /* Handle parallel SYN for ECN */ 1644 tcp_ecn_input_parallel_syn(tp, thflags, iptos); 1645 if ((to.to_flags & TOF_SCALE) && 1646 (tp->t_flags & TF_REQ_SCALE) && 1647 !(tp->t_flags & TF_NOOPT)) { 1648 tp->t_flags |= TF_RCVD_SCALE; 1649 tp->snd_scale = to.to_wscale; 1650 } else 1651 tp->t_flags &= ~TF_REQ_SCALE; 1652 /* 1653 * Initial send window. It will be updated with 1654 * the next incoming segment to the scaled value. 1655 */ 1656 tp->snd_wnd = th->th_win; 1657 if ((to.to_flags & TOF_TS) && 1658 (tp->t_flags & TF_REQ_TSTMP) && 1659 !(tp->t_flags & TF_NOOPT)) { 1660 tp->t_flags |= TF_RCVD_TSTMP; 1661 tp->ts_recent = to.to_tsval; 1662 tp->ts_recent_age = tcp_ts_getticks(); 1663 } else 1664 tp->t_flags &= ~TF_REQ_TSTMP; 1665 if (to.to_flags & TOF_MSS) 1666 tcp_mss(tp, to.to_mss); 1667 if ((tp->t_flags & TF_SACK_PERMIT) && 1668 (!(to.to_flags & TOF_SACKPERM) || 1669 (tp->t_flags & TF_NOOPT))) 1670 tp->t_flags &= ~TF_SACK_PERMIT; 1671 if (IS_FASTOPEN(tp->t_flags)) { 1672 if ((to.to_flags & TOF_FASTOPEN) && 1673 !(tp->t_flags & TF_NOOPT)) { 1674 uint16_t mss; 1675 1676 if (to.to_flags & TOF_MSS) 1677 mss = to.to_mss; 1678 else 1679 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 1680 mss = TCP6_MSS; 1681 else 1682 mss = TCP_MSS; 1683 tcp_fastopen_update_cache(tp, mss, 1684 to.to_tfo_len, to.to_tfo_cookie); 1685 } else 1686 tcp_fastopen_disable_path(tp); 1687 } 1688 } 1689 1690 /* 1691 * If timestamps were negotiated during SYN/ACK and a 1692 * segment without a timestamp is received, silently drop 1693 * the segment, unless it is a RST segment or missing timestamps are 1694 * tolerated. 1695 * See section 3.2 of RFC 7323. 1696 */ 1697 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1698 if (((thflags & TH_RST) != 0) || V_tcp_tolerate_missing_ts) { 1699 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1700 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1701 "segment processed normally\n", 1702 s, __func__); 1703 free(s, M_TCPLOG); 1704 } 1705 } else { 1706 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1707 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1708 "segment silently dropped\n", s, __func__); 1709 free(s, M_TCPLOG); 1710 } 1711 goto drop; 1712 } 1713 } 1714 /* 1715 * If timestamps were not negotiated during SYN/ACK and a 1716 * segment with a timestamp is received, ignore the 1717 * timestamp and process the packet normally. 1718 * See section 3.2 of RFC 7323. 1719 */ 1720 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1721 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1722 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1723 "segment processed normally\n", s, __func__); 1724 free(s, M_TCPLOG); 1725 } 1726 } 1727 1728 /* 1729 * Header prediction: check for the two common cases 1730 * of a uni-directional data xfer. If the packet has 1731 * no control flags, is in-sequence, the window didn't 1732 * change and we're not retransmitting, it's a 1733 * candidate. If the length is zero and the ack moved 1734 * forward, we're the sender side of the xfer. Just 1735 * free the data acked & wake any higher level process 1736 * that was blocked waiting for space. If the length 1737 * is non-zero and the ack didn't move, we're the 1738 * receiver side. If we're getting packets in-order 1739 * (the reassembly queue is empty), add the data to 1740 * the socket buffer and note that we need a delayed ack. 1741 * Make sure that the hidden state-flags are also off. 1742 * Since we check for TCPS_ESTABLISHED first, it can only 1743 * be TH_NEEDSYN. 1744 */ 1745 if (tp->t_state == TCPS_ESTABLISHED && 1746 th->th_seq == tp->rcv_nxt && 1747 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1748 tp->snd_nxt == tp->snd_max && 1749 tiwin && tiwin == tp->snd_wnd && 1750 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1751 SEGQ_EMPTY(tp) && 1752 ((to.to_flags & TOF_TS) == 0 || 1753 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1754 /* 1755 * If last ACK falls within this segment's sequence numbers, 1756 * record the timestamp. 1757 * NOTE that the test is modified according to the latest 1758 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1759 */ 1760 if ((to.to_flags & TOF_TS) != 0 && 1761 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1762 tp->ts_recent_age = tcp_ts_getticks(); 1763 tp->ts_recent = to.to_tsval; 1764 } 1765 1766 if (tlen == 0) { 1767 if (SEQ_GT(th->th_ack, tp->snd_una) && 1768 SEQ_LEQ(th->th_ack, tp->snd_max) && 1769 !IN_RECOVERY(tp->t_flags) && 1770 (to.to_flags & TOF_SACK) == 0 && 1771 TAILQ_EMPTY(&tp->snd_holes)) { 1772 /* 1773 * This is a pure ack for outstanding data. 1774 */ 1775 TCPSTAT_INC(tcps_predack); 1776 1777 /* 1778 * "bad retransmit" recovery without timestamps. 1779 */ 1780 if ((to.to_flags & TOF_TS) == 0 && 1781 tp->t_rxtshift == 1 && 1782 tp->t_flags & TF_PREVVALID && 1783 tp->t_badrxtwin != 0 && 1784 TSTMP_LT(ticks, tp->t_badrxtwin)) { 1785 cc_cong_signal(tp, th, CC_RTO_ERR); 1786 } 1787 1788 /* 1789 * Recalculate the transmit timer / rtt. 1790 * 1791 * Some boxes send broken timestamp replies 1792 * during the SYN+ACK phase, ignore 1793 * timestamps of 0 or we could calculate a 1794 * huge RTT and blow up the retransmit timer. 1795 */ 1796 if ((to.to_flags & TOF_TS) != 0 && 1797 to.to_tsecr) { 1798 uint32_t t; 1799 1800 t = tcp_ts_getticks() - to.to_tsecr; 1801 if (!tp->t_rttlow || tp->t_rttlow > t) 1802 tp->t_rttlow = t; 1803 tcp_xmit_timer(tp, 1804 TCP_TS_TO_TICKS(t) + 1); 1805 } else if (tp->t_rtttime && 1806 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1807 if (!tp->t_rttlow || 1808 tp->t_rttlow > ticks - tp->t_rtttime) 1809 tp->t_rttlow = ticks - tp->t_rtttime; 1810 tcp_xmit_timer(tp, 1811 ticks - tp->t_rtttime); 1812 } 1813 acked = BYTES_THIS_ACK(tp, th); 1814 1815 #ifdef TCP_HHOOK 1816 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1817 hhook_run_tcp_est_in(tp, th, &to); 1818 #endif 1819 1820 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 1821 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1822 sbdrop(&so->so_snd, acked); 1823 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1824 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1825 tp->snd_recover = th->th_ack - 1; 1826 1827 /* 1828 * Let the congestion control algorithm update 1829 * congestion control related information. This 1830 * typically means increasing the congestion 1831 * window. 1832 */ 1833 cc_ack_received(tp, th, nsegs, CC_ACK); 1834 1835 tp->snd_una = th->th_ack; 1836 /* 1837 * Pull snd_wl2 up to prevent seq wrap relative 1838 * to th_ack. 1839 */ 1840 tp->snd_wl2 = th->th_ack; 1841 tp->t_dupacks = 0; 1842 m_freem(m); 1843 1844 /* 1845 * If all outstanding data are acked, stop 1846 * retransmit timer, otherwise restart timer 1847 * using current (possibly backed-off) value. 1848 * If process is waiting for space, 1849 * wakeup/selwakeup/signal. If data 1850 * are ready to send, let tcp_output 1851 * decide between more output or persist. 1852 */ 1853 #ifdef TCPDEBUG 1854 if (so->so_options & SO_DEBUG) 1855 tcp_trace(TA_INPUT, ostate, tp, 1856 (void *)tcp_saveipgen, 1857 &tcp_savetcp, 0); 1858 #endif 1859 TCP_PROBE3(debug__input, tp, th, m); 1860 if (tp->snd_una == tp->snd_max) 1861 tcp_timer_activate(tp, TT_REXMT, 0); 1862 else if (!tcp_timer_active(tp, TT_PERSIST)) 1863 tcp_timer_activate(tp, TT_REXMT, 1864 tp->t_rxtcur); 1865 sowwakeup(so); 1866 if (sbavail(&so->so_snd)) 1867 (void) tcp_output(tp); 1868 goto check_delack; 1869 } 1870 } else if (th->th_ack == tp->snd_una && 1871 tlen <= sbspace(&so->so_rcv)) { 1872 int newsize = 0; /* automatic sockbuf scaling */ 1873 1874 /* 1875 * This is a pure, in-sequence data packet with 1876 * nothing on the reassembly queue and we have enough 1877 * buffer space to take it. 1878 */ 1879 /* Clean receiver SACK report if present */ 1880 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1881 tcp_clean_sackreport(tp); 1882 TCPSTAT_INC(tcps_preddat); 1883 tp->rcv_nxt += tlen; 1884 if (tlen && 1885 ((tp->t_flags2 & TF2_FBYTES_COMPLETE) == 0) && 1886 (tp->t_fbyte_in == 0)) { 1887 tp->t_fbyte_in = ticks; 1888 if (tp->t_fbyte_in == 0) 1889 tp->t_fbyte_in = 1; 1890 if (tp->t_fbyte_out && tp->t_fbyte_in) 1891 tp->t_flags2 |= TF2_FBYTES_COMPLETE; 1892 } 1893 /* 1894 * Pull snd_wl1 up to prevent seq wrap relative to 1895 * th_seq. 1896 */ 1897 tp->snd_wl1 = th->th_seq; 1898 /* 1899 * Pull rcv_up up to prevent seq wrap relative to 1900 * rcv_nxt. 1901 */ 1902 tp->rcv_up = tp->rcv_nxt; 1903 TCPSTAT_ADD(tcps_rcvpack, nsegs); 1904 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1905 #ifdef TCPDEBUG 1906 if (so->so_options & SO_DEBUG) 1907 tcp_trace(TA_INPUT, ostate, tp, 1908 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1909 #endif 1910 TCP_PROBE3(debug__input, tp, th, m); 1911 1912 newsize = tcp_autorcvbuf(m, th, so, tp, tlen); 1913 1914 /* Add data to socket buffer. */ 1915 SOCKBUF_LOCK(&so->so_rcv); 1916 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1917 m_freem(m); 1918 } else { 1919 /* 1920 * Set new socket buffer size. 1921 * Give up when limit is reached. 1922 */ 1923 if (newsize) 1924 if (!sbreserve_locked(&so->so_rcv, 1925 newsize, so, NULL)) 1926 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1927 m_adj(m, drop_hdrlen); /* delayed header drop */ 1928 sbappendstream_locked(&so->so_rcv, m, 0); 1929 } 1930 /* NB: sorwakeup_locked() does an implicit unlock. */ 1931 sorwakeup_locked(so); 1932 if (DELAY_ACK(tp, tlen)) { 1933 tp->t_flags |= TF_DELACK; 1934 } else { 1935 tp->t_flags |= TF_ACKNOW; 1936 tcp_output(tp); 1937 } 1938 goto check_delack; 1939 } 1940 } 1941 1942 /* 1943 * Calculate amount of space in receive window, 1944 * and then do TCP input processing. 1945 * Receive window is amount of space in rcv queue, 1946 * but not less than advertised window. 1947 */ 1948 win = sbspace(&so->so_rcv); 1949 if (win < 0) 1950 win = 0; 1951 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1952 1953 switch (tp->t_state) { 1954 /* 1955 * If the state is SYN_RECEIVED: 1956 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1957 */ 1958 case TCPS_SYN_RECEIVED: 1959 if ((thflags & TH_ACK) && 1960 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1961 SEQ_GT(th->th_ack, tp->snd_max))) { 1962 rstreason = BANDLIM_RST_OPENPORT; 1963 goto dropwithreset; 1964 } 1965 if (IS_FASTOPEN(tp->t_flags)) { 1966 /* 1967 * When a TFO connection is in SYN_RECEIVED, the 1968 * only valid packets are the initial SYN, a 1969 * retransmit/copy of the initial SYN (possibly with 1970 * a subset of the original data), a valid ACK, a 1971 * FIN, or a RST. 1972 */ 1973 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) { 1974 rstreason = BANDLIM_RST_OPENPORT; 1975 goto dropwithreset; 1976 } else if (thflags & TH_SYN) { 1977 /* non-initial SYN is ignored */ 1978 if ((tcp_timer_active(tp, TT_DELACK) || 1979 tcp_timer_active(tp, TT_REXMT))) 1980 goto drop; 1981 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) { 1982 goto drop; 1983 } 1984 } 1985 break; 1986 1987 /* 1988 * If the state is SYN_SENT: 1989 * if seg contains a RST with valid ACK (SEQ.ACK has already 1990 * been verified), then drop the connection. 1991 * if seg contains a RST without an ACK, drop the seg. 1992 * if seg does not contain SYN, then drop the seg. 1993 * Otherwise this is an acceptable SYN segment 1994 * initialize tp->rcv_nxt and tp->irs 1995 * if seg contains ack then advance tp->snd_una 1996 * if seg contains an ECE and ECN support is enabled, the stream 1997 * is ECN capable. 1998 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1999 * arrange for segment to be acked (eventually) 2000 * continue processing rest of data/controls, beginning with URG 2001 */ 2002 case TCPS_SYN_SENT: 2003 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 2004 TCP_PROBE5(connect__refused, NULL, tp, 2005 m, tp, th); 2006 tp = tcp_drop(tp, ECONNREFUSED); 2007 } 2008 if (thflags & TH_RST) 2009 goto drop; 2010 if (!(thflags & TH_SYN)) 2011 goto drop; 2012 2013 tp->irs = th->th_seq; 2014 tcp_rcvseqinit(tp); 2015 if (thflags & TH_ACK) { 2016 int tfo_partial_ack = 0; 2017 2018 TCPSTAT_INC(tcps_connects); 2019 soisconnected(so); 2020 #ifdef MAC 2021 mac_socketpeer_set_from_mbuf(m, so); 2022 #endif 2023 /* Do window scaling on this connection? */ 2024 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2025 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2026 tp->rcv_scale = tp->request_r_scale; 2027 } 2028 tp->rcv_adv += min(tp->rcv_wnd, 2029 TCP_MAXWIN << tp->rcv_scale); 2030 tp->snd_una++; /* SYN is acked */ 2031 /* 2032 * If not all the data that was sent in the TFO SYN 2033 * has been acked, resend the remainder right away. 2034 */ 2035 if (IS_FASTOPEN(tp->t_flags) && 2036 (tp->snd_una != tp->snd_max)) { 2037 tp->snd_nxt = th->th_ack; 2038 tfo_partial_ack = 1; 2039 } 2040 /* 2041 * If there's data, delay ACK; if there's also a FIN 2042 * ACKNOW will be turned on later. 2043 */ 2044 if (DELAY_ACK(tp, tlen) && tlen != 0 && !tfo_partial_ack) 2045 tcp_timer_activate(tp, TT_DELACK, 2046 tcp_delacktime); 2047 else 2048 tp->t_flags |= TF_ACKNOW; 2049 2050 tcp_ecn_input_syn_sent(tp, thflags, iptos); 2051 2052 /* 2053 * Received <SYN,ACK> in SYN_SENT[*] state. 2054 * Transitions: 2055 * SYN_SENT --> ESTABLISHED 2056 * SYN_SENT* --> FIN_WAIT_1 2057 */ 2058 tp->t_starttime = ticks; 2059 if (tp->t_flags & TF_NEEDFIN) { 2060 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2061 tp->t_flags &= ~TF_NEEDFIN; 2062 thflags &= ~TH_SYN; 2063 } else { 2064 tcp_state_change(tp, TCPS_ESTABLISHED); 2065 TCP_PROBE5(connect__established, NULL, tp, 2066 m, tp, th); 2067 cc_conn_init(tp); 2068 tcp_timer_activate(tp, TT_KEEP, 2069 TP_KEEPIDLE(tp)); 2070 } 2071 } else { 2072 /* 2073 * Received initial SYN in SYN-SENT[*] state => 2074 * simultaneous open. 2075 * If it succeeds, connection is * half-synchronized. 2076 * Otherwise, do 3-way handshake: 2077 * SYN-SENT -> SYN-RECEIVED 2078 * SYN-SENT* -> SYN-RECEIVED* 2079 */ 2080 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 2081 tcp_timer_activate(tp, TT_REXMT, 0); 2082 tcp_state_change(tp, TCPS_SYN_RECEIVED); 2083 } 2084 2085 INP_WLOCK_ASSERT(tp->t_inpcb); 2086 2087 /* 2088 * Advance th->th_seq to correspond to first data byte. 2089 * If data, trim to stay within window, 2090 * dropping FIN if necessary. 2091 */ 2092 th->th_seq++; 2093 if (tlen > tp->rcv_wnd) { 2094 todrop = tlen - tp->rcv_wnd; 2095 m_adj(m, -todrop); 2096 tlen = tp->rcv_wnd; 2097 thflags &= ~TH_FIN; 2098 TCPSTAT_INC(tcps_rcvpackafterwin); 2099 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2100 } 2101 tp->snd_wl1 = th->th_seq - 1; 2102 tp->rcv_up = th->th_seq; 2103 /* 2104 * Client side of transaction: already sent SYN and data. 2105 * If the remote host used T/TCP to validate the SYN, 2106 * our data will be ACK'd; if so, enter normal data segment 2107 * processing in the middle of step 5, ack processing. 2108 * Otherwise, goto step 6. 2109 */ 2110 if (thflags & TH_ACK) 2111 goto process_ACK; 2112 2113 goto step6; 2114 2115 /* 2116 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2117 * do normal processing. 2118 * 2119 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2120 */ 2121 case TCPS_LAST_ACK: 2122 case TCPS_CLOSING: 2123 break; /* continue normal processing */ 2124 } 2125 2126 /* 2127 * States other than LISTEN or SYN_SENT. 2128 * First check the RST flag and sequence number since reset segments 2129 * are exempt from the timestamp and connection count tests. This 2130 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2131 * below which allowed reset segments in half the sequence space 2132 * to fall though and be processed (which gives forged reset 2133 * segments with a random sequence number a 50 percent chance of 2134 * killing a connection). 2135 * Then check timestamp, if present. 2136 * Then check the connection count, if present. 2137 * Then check that at least some bytes of segment are within 2138 * receive window. If segment begins before rcv_nxt, 2139 * drop leading data (and SYN); if nothing left, just ack. 2140 */ 2141 if (thflags & TH_RST) { 2142 /* 2143 * RFC5961 Section 3.2 2144 * 2145 * - RST drops connection only if SEG.SEQ == RCV.NXT. 2146 * - If RST is in window, we send challenge ACK. 2147 * 2148 * Note: to take into account delayed ACKs, we should 2149 * test against last_ack_sent instead of rcv_nxt. 2150 * Note 2: we handle special case of closed window, not 2151 * covered by the RFC. 2152 */ 2153 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2154 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 2155 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 2156 KASSERT(tp->t_state != TCPS_SYN_SENT, 2157 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p", 2158 __func__, th, tp)); 2159 2160 if (V_tcp_insecure_rst || 2161 tp->last_ack_sent == th->th_seq) { 2162 TCPSTAT_INC(tcps_drops); 2163 /* Drop the connection. */ 2164 switch (tp->t_state) { 2165 case TCPS_SYN_RECEIVED: 2166 so->so_error = ECONNREFUSED; 2167 goto close; 2168 case TCPS_ESTABLISHED: 2169 case TCPS_FIN_WAIT_1: 2170 case TCPS_FIN_WAIT_2: 2171 case TCPS_CLOSE_WAIT: 2172 case TCPS_CLOSING: 2173 case TCPS_LAST_ACK: 2174 so->so_error = ECONNRESET; 2175 close: 2176 /* FALLTHROUGH */ 2177 default: 2178 tp = tcp_close(tp); 2179 } 2180 } else { 2181 TCPSTAT_INC(tcps_badrst); 2182 /* Send challenge ACK. */ 2183 tcp_respond(tp, mtod(m, void *), th, m, 2184 tp->rcv_nxt, tp->snd_nxt, TH_ACK); 2185 tp->last_ack_sent = tp->rcv_nxt; 2186 m = NULL; 2187 } 2188 } 2189 goto drop; 2190 } 2191 2192 /* 2193 * RFC5961 Section 4.2 2194 * Send challenge ACK for any SYN in synchronized state. 2195 */ 2196 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT && 2197 tp->t_state != TCPS_SYN_RECEIVED) { 2198 TCPSTAT_INC(tcps_badsyn); 2199 if (V_tcp_insecure_syn && 2200 SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2201 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2202 tp = tcp_drop(tp, ECONNRESET); 2203 rstreason = BANDLIM_UNLIMITED; 2204 } else { 2205 /* Send challenge ACK. */ 2206 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 2207 tp->snd_nxt, TH_ACK); 2208 tp->last_ack_sent = tp->rcv_nxt; 2209 m = NULL; 2210 } 2211 goto drop; 2212 } 2213 2214 /* 2215 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2216 * and it's less than ts_recent, drop it. 2217 */ 2218 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2219 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2220 /* Check to see if ts_recent is over 24 days old. */ 2221 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2222 /* 2223 * Invalidate ts_recent. If this segment updates 2224 * ts_recent, the age will be reset later and ts_recent 2225 * will get a valid value. If it does not, setting 2226 * ts_recent to zero will at least satisfy the 2227 * requirement that zero be placed in the timestamp 2228 * echo reply when ts_recent isn't valid. The 2229 * age isn't reset until we get a valid ts_recent 2230 * because we don't want out-of-order segments to be 2231 * dropped when ts_recent is old. 2232 */ 2233 tp->ts_recent = 0; 2234 } else { 2235 TCPSTAT_INC(tcps_rcvduppack); 2236 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2237 TCPSTAT_INC(tcps_pawsdrop); 2238 if (tlen) 2239 goto dropafterack; 2240 goto drop; 2241 } 2242 } 2243 2244 /* 2245 * In the SYN-RECEIVED state, validate that the packet belongs to 2246 * this connection before trimming the data to fit the receive 2247 * window. Check the sequence number versus IRS since we know 2248 * the sequence numbers haven't wrapped. This is a partial fix 2249 * for the "LAND" DoS attack. 2250 */ 2251 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2252 rstreason = BANDLIM_RST_OPENPORT; 2253 goto dropwithreset; 2254 } 2255 2256 todrop = tp->rcv_nxt - th->th_seq; 2257 if (todrop > 0) { 2258 if (thflags & TH_SYN) { 2259 thflags &= ~TH_SYN; 2260 th->th_seq++; 2261 if (th->th_urp > 1) 2262 th->th_urp--; 2263 else 2264 thflags &= ~TH_URG; 2265 todrop--; 2266 } 2267 /* 2268 * Following if statement from Stevens, vol. 2, p. 960. 2269 */ 2270 if (todrop > tlen 2271 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2272 /* 2273 * Any valid FIN must be to the left of the window. 2274 * At this point the FIN must be a duplicate or out 2275 * of sequence; drop it. 2276 */ 2277 thflags &= ~TH_FIN; 2278 2279 /* 2280 * Send an ACK to resynchronize and drop any data. 2281 * But keep on processing for RST or ACK. 2282 */ 2283 tp->t_flags |= TF_ACKNOW; 2284 todrop = tlen; 2285 TCPSTAT_INC(tcps_rcvduppack); 2286 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2287 } else { 2288 TCPSTAT_INC(tcps_rcvpartduppack); 2289 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2290 } 2291 /* 2292 * DSACK - add SACK block for dropped range 2293 */ 2294 if ((todrop > 0) && (tp->t_flags & TF_SACK_PERMIT)) { 2295 tcp_update_sack_list(tp, th->th_seq, 2296 th->th_seq + todrop); 2297 /* 2298 * ACK now, as the next in-sequence segment 2299 * will clear the DSACK block again 2300 */ 2301 tp->t_flags |= TF_ACKNOW; 2302 } 2303 drop_hdrlen += todrop; /* drop from the top afterwards */ 2304 th->th_seq += todrop; 2305 tlen -= todrop; 2306 if (th->th_urp > todrop) 2307 th->th_urp -= todrop; 2308 else { 2309 thflags &= ~TH_URG; 2310 th->th_urp = 0; 2311 } 2312 } 2313 2314 /* 2315 * If new data are received on a connection after the 2316 * user processes are gone, then RST the other end. 2317 */ 2318 if ((so->so_state & SS_NOFDREF) && 2319 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2320 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2321 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2322 "after socket was closed, " 2323 "sending RST and removing tcpcb\n", 2324 s, __func__, tcpstates[tp->t_state], tlen); 2325 free(s, M_TCPLOG); 2326 } 2327 tp = tcp_close(tp); 2328 TCPSTAT_INC(tcps_rcvafterclose); 2329 rstreason = BANDLIM_UNLIMITED; 2330 goto dropwithreset; 2331 } 2332 2333 /* 2334 * If segment ends after window, drop trailing data 2335 * (and PUSH and FIN); if nothing left, just ACK. 2336 */ 2337 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2338 if (todrop > 0) { 2339 TCPSTAT_INC(tcps_rcvpackafterwin); 2340 if (todrop >= tlen) { 2341 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2342 /* 2343 * If window is closed can only take segments at 2344 * window edge, and have to drop data and PUSH from 2345 * incoming segments. Continue processing, but 2346 * remember to ack. Otherwise, drop segment 2347 * and ack. 2348 */ 2349 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2350 tp->t_flags |= TF_ACKNOW; 2351 TCPSTAT_INC(tcps_rcvwinprobe); 2352 } else 2353 goto dropafterack; 2354 } else 2355 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2356 m_adj(m, -todrop); 2357 tlen -= todrop; 2358 thflags &= ~(TH_PUSH|TH_FIN); 2359 } 2360 2361 /* 2362 * If last ACK falls within this segment's sequence numbers, 2363 * record its timestamp. 2364 * NOTE: 2365 * 1) That the test incorporates suggestions from the latest 2366 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2367 * 2) That updating only on newer timestamps interferes with 2368 * our earlier PAWS tests, so this check should be solely 2369 * predicated on the sequence space of this segment. 2370 * 3) That we modify the segment boundary check to be 2371 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2372 * instead of RFC1323's 2373 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2374 * This modified check allows us to overcome RFC1323's 2375 * limitations as described in Stevens TCP/IP Illustrated 2376 * Vol. 2 p.869. In such cases, we can still calculate the 2377 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2378 */ 2379 if ((to.to_flags & TOF_TS) != 0 && 2380 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2381 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2382 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2383 tp->ts_recent_age = tcp_ts_getticks(); 2384 tp->ts_recent = to.to_tsval; 2385 } 2386 2387 /* 2388 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2389 * flag is on (half-synchronized state), then queue data for 2390 * later processing; else drop segment and return. 2391 */ 2392 if ((thflags & TH_ACK) == 0) { 2393 if (tp->t_state == TCPS_SYN_RECEIVED || 2394 (tp->t_flags & TF_NEEDSYN)) { 2395 if (tp->t_state == TCPS_SYN_RECEIVED && 2396 IS_FASTOPEN(tp->t_flags)) { 2397 tp->snd_wnd = tiwin; 2398 cc_conn_init(tp); 2399 } 2400 goto step6; 2401 } else if (tp->t_flags & TF_ACKNOW) 2402 goto dropafterack; 2403 else 2404 goto drop; 2405 } 2406 2407 /* 2408 * Ack processing. 2409 */ 2410 switch (tp->t_state) { 2411 /* 2412 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2413 * ESTABLISHED state and continue processing. 2414 * The ACK was checked above. 2415 */ 2416 case TCPS_SYN_RECEIVED: 2417 2418 TCPSTAT_INC(tcps_connects); 2419 soisconnected(so); 2420 /* Do window scaling? */ 2421 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2422 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2423 tp->rcv_scale = tp->request_r_scale; 2424 } 2425 tp->snd_wnd = tiwin; 2426 /* 2427 * Make transitions: 2428 * SYN-RECEIVED -> ESTABLISHED 2429 * SYN-RECEIVED* -> FIN-WAIT-1 2430 */ 2431 tp->t_starttime = ticks; 2432 if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) { 2433 tcp_fastopen_decrement_counter(tp->t_tfo_pending); 2434 tp->t_tfo_pending = NULL; 2435 } 2436 if (tp->t_flags & TF_NEEDFIN) { 2437 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2438 tp->t_flags &= ~TF_NEEDFIN; 2439 } else { 2440 tcp_state_change(tp, TCPS_ESTABLISHED); 2441 TCP_PROBE5(accept__established, NULL, tp, 2442 m, tp, th); 2443 /* 2444 * TFO connections call cc_conn_init() during SYN 2445 * processing. Calling it again here for such 2446 * connections is not harmless as it would undo the 2447 * snd_cwnd reduction that occurs when a TFO SYN|ACK 2448 * is retransmitted. 2449 */ 2450 if (!IS_FASTOPEN(tp->t_flags)) 2451 cc_conn_init(tp); 2452 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2453 } 2454 /* 2455 * Account for the ACK of our SYN prior to 2456 * regular ACK processing below, except for 2457 * simultaneous SYN, which is handled later. 2458 */ 2459 if (SEQ_GT(th->th_ack, tp->snd_una) && !(tp->t_flags & TF_NEEDSYN)) 2460 incforsyn = 1; 2461 /* 2462 * If segment contains data or ACK, will call tcp_reass() 2463 * later; if not, do so now to pass queued data to user. 2464 */ 2465 if (tlen == 0 && (thflags & TH_FIN) == 0) { 2466 (void) tcp_reass(tp, (struct tcphdr *)0, NULL, 0, 2467 (struct mbuf *)0); 2468 tcp_handle_wakeup(tp, so); 2469 } 2470 tp->snd_wl1 = th->th_seq - 1; 2471 /* FALLTHROUGH */ 2472 2473 /* 2474 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2475 * ACKs. If the ack is in the range 2476 * tp->snd_una < th->th_ack <= tp->snd_max 2477 * then advance tp->snd_una to th->th_ack and drop 2478 * data from the retransmission queue. If this ACK reflects 2479 * more up to date window information we update our window information. 2480 */ 2481 case TCPS_ESTABLISHED: 2482 case TCPS_FIN_WAIT_1: 2483 case TCPS_FIN_WAIT_2: 2484 case TCPS_CLOSE_WAIT: 2485 case TCPS_CLOSING: 2486 case TCPS_LAST_ACK: 2487 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2488 TCPSTAT_INC(tcps_rcvacktoomuch); 2489 goto dropafterack; 2490 } 2491 if ((tp->t_flags & TF_SACK_PERMIT) && 2492 ((to.to_flags & TOF_SACK) || 2493 !TAILQ_EMPTY(&tp->snd_holes))) { 2494 if (((sack_changed = tcp_sack_doack(tp, &to, th->th_ack)) != 0) && 2495 (tp->t_flags & TF_LRD)) { 2496 tcp_sack_lost_retransmission(tp, th); 2497 } 2498 } else 2499 /* 2500 * Reset the value so that previous (valid) value 2501 * from the last ack with SACK doesn't get used. 2502 */ 2503 tp->sackhint.sacked_bytes = 0; 2504 2505 #ifdef TCP_HHOOK 2506 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2507 hhook_run_tcp_est_in(tp, th, &to); 2508 #endif 2509 2510 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2511 maxseg = tcp_maxseg(tp); 2512 if (tlen == 0 && 2513 (tiwin == tp->snd_wnd || 2514 (tp->t_flags & TF_SACK_PERMIT))) { 2515 /* 2516 * If this is the first time we've seen a 2517 * FIN from the remote, this is not a 2518 * duplicate and it needs to be processed 2519 * normally. This happens during a 2520 * simultaneous close. 2521 */ 2522 if ((thflags & TH_FIN) && 2523 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2524 tp->t_dupacks = 0; 2525 break; 2526 } 2527 TCPSTAT_INC(tcps_rcvdupack); 2528 /* 2529 * If we have outstanding data (other than 2530 * a window probe), this is a completely 2531 * duplicate ack (ie, window info didn't 2532 * change and FIN isn't set), 2533 * the ack is the biggest we've 2534 * seen and we've seen exactly our rexmt 2535 * threshold of them, assume a packet 2536 * has been dropped and retransmit it. 2537 * Kludge snd_nxt & the congestion 2538 * window so we send only this one 2539 * packet. 2540 * 2541 * We know we're losing at the current 2542 * window size so do congestion avoidance 2543 * (set ssthresh to half the current window 2544 * and pull our congestion window back to 2545 * the new ssthresh). 2546 * 2547 * Dup acks mean that packets have left the 2548 * network (they're now cached at the receiver) 2549 * so bump cwnd by the amount in the receiver 2550 * to keep a constant cwnd packets in the 2551 * network. 2552 * 2553 * When using TCP ECN, notify the peer that 2554 * we reduced the cwnd. 2555 */ 2556 /* 2557 * Following 2 kinds of acks should not affect 2558 * dupack counting: 2559 * 1) Old acks 2560 * 2) Acks with SACK but without any new SACK 2561 * information in them. These could result from 2562 * any anomaly in the network like a switch 2563 * duplicating packets or a possible DoS attack. 2564 */ 2565 if (th->th_ack != tp->snd_una || 2566 ((tp->t_flags & TF_SACK_PERMIT) && 2567 (to.to_flags & TOF_SACK) && 2568 !sack_changed)) 2569 break; 2570 else if (!tcp_timer_active(tp, TT_REXMT)) 2571 tp->t_dupacks = 0; 2572 else if (++tp->t_dupacks > tcprexmtthresh || 2573 IN_FASTRECOVERY(tp->t_flags)) { 2574 cc_ack_received(tp, th, nsegs, 2575 CC_DUPACK); 2576 if (V_tcp_do_prr && 2577 IN_FASTRECOVERY(tp->t_flags)) { 2578 tcp_do_prr_ack(tp, th, &to); 2579 } else if ((tp->t_flags & TF_SACK_PERMIT) && 2580 (to.to_flags & TOF_SACK) && 2581 IN_FASTRECOVERY(tp->t_flags)) { 2582 int awnd; 2583 2584 /* 2585 * Compute the amount of data in flight first. 2586 * We can inject new data into the pipe iff 2587 * we have less than 1/2 the original window's 2588 * worth of data in flight. 2589 */ 2590 if (V_tcp_do_newsack) 2591 awnd = tcp_compute_pipe(tp); 2592 else 2593 awnd = (tp->snd_nxt - tp->snd_fack) + 2594 tp->sackhint.sack_bytes_rexmit; 2595 2596 if (awnd < tp->snd_ssthresh) { 2597 tp->snd_cwnd += maxseg; 2598 if (tp->snd_cwnd > tp->snd_ssthresh) 2599 tp->snd_cwnd = tp->snd_ssthresh; 2600 } 2601 } else 2602 tp->snd_cwnd += maxseg; 2603 (void) tcp_output(tp); 2604 goto drop; 2605 } else if (tp->t_dupacks == tcprexmtthresh || 2606 (tp->t_flags & TF_SACK_PERMIT && 2607 V_tcp_do_newsack && 2608 tp->sackhint.sacked_bytes > 2609 (tcprexmtthresh - 1) * maxseg)) { 2610 enter_recovery: 2611 /* 2612 * Above is the RFC6675 trigger condition of 2613 * more than (dupthresh-1)*maxseg sacked data. 2614 * If the count of holes in the 2615 * scoreboard is >= dupthresh, we could 2616 * also enter loss recovery, but don't 2617 * have that value readily available. 2618 */ 2619 tp->t_dupacks = tcprexmtthresh; 2620 tcp_seq onxt = tp->snd_nxt; 2621 2622 /* 2623 * If we're doing sack, or prr, check 2624 * to see if we're already in sack 2625 * recovery. If we're not doing sack, 2626 * check to see if we're in newreno 2627 * recovery. 2628 */ 2629 if (V_tcp_do_prr || 2630 (tp->t_flags & TF_SACK_PERMIT)) { 2631 if (IN_FASTRECOVERY(tp->t_flags)) { 2632 tp->t_dupacks = 0; 2633 break; 2634 } 2635 } else { 2636 if (SEQ_LEQ(th->th_ack, 2637 tp->snd_recover)) { 2638 tp->t_dupacks = 0; 2639 break; 2640 } 2641 } 2642 /* Congestion signal before ack. */ 2643 cc_cong_signal(tp, th, CC_NDUPACK); 2644 cc_ack_received(tp, th, nsegs, 2645 CC_DUPACK); 2646 tcp_timer_activate(tp, TT_REXMT, 0); 2647 tp->t_rtttime = 0; 2648 if (V_tcp_do_prr) { 2649 /* 2650 * snd_ssthresh is already updated by 2651 * cc_cong_signal. 2652 */ 2653 if ((tp->t_flags & TF_SACK_PERMIT) && 2654 (to.to_flags & TOF_SACK)) { 2655 tp->sackhint.prr_delivered = 2656 tp->sackhint.sacked_bytes; 2657 } else { 2658 tp->sackhint.prr_delivered = 2659 imin(tp->snd_max - tp->snd_una, 2660 imin(INT_MAX / 65536, 2661 tp->t_dupacks) * maxseg); 2662 } 2663 tp->sackhint.recover_fs = max(1, 2664 tp->snd_nxt - tp->snd_una); 2665 } 2666 if ((tp->t_flags & TF_SACK_PERMIT) && 2667 (to.to_flags & TOF_SACK)) { 2668 TCPSTAT_INC( 2669 tcps_sack_recovery_episode); 2670 tp->snd_recover = tp->snd_nxt; 2671 tp->snd_cwnd = maxseg; 2672 (void) tcp_output(tp); 2673 if (SEQ_GT(th->th_ack, tp->snd_una)) 2674 goto resume_partialack; 2675 goto drop; 2676 } 2677 tp->snd_nxt = th->th_ack; 2678 tp->snd_cwnd = maxseg; 2679 (void) tcp_output(tp); 2680 KASSERT(tp->snd_limited <= 2, 2681 ("%s: tp->snd_limited too big", 2682 __func__)); 2683 tp->snd_cwnd = tp->snd_ssthresh + 2684 maxseg * 2685 (tp->t_dupacks - tp->snd_limited); 2686 if (SEQ_GT(onxt, tp->snd_nxt)) 2687 tp->snd_nxt = onxt; 2688 goto drop; 2689 } else if (V_tcp_do_rfc3042) { 2690 /* 2691 * Process first and second duplicate 2692 * ACKs. Each indicates a segment 2693 * leaving the network, creating room 2694 * for more. Make sure we can send a 2695 * packet on reception of each duplicate 2696 * ACK by increasing snd_cwnd by one 2697 * segment. Restore the original 2698 * snd_cwnd after packet transmission. 2699 */ 2700 cc_ack_received(tp, th, nsegs, 2701 CC_DUPACK); 2702 uint32_t oldcwnd = tp->snd_cwnd; 2703 tcp_seq oldsndmax = tp->snd_max; 2704 u_int sent; 2705 int avail; 2706 2707 KASSERT(tp->t_dupacks == 1 || 2708 tp->t_dupacks == 2, 2709 ("%s: dupacks not 1 or 2", 2710 __func__)); 2711 if (tp->t_dupacks == 1) 2712 tp->snd_limited = 0; 2713 tp->snd_cwnd = 2714 (tp->snd_nxt - tp->snd_una) + 2715 (tp->t_dupacks - tp->snd_limited) * 2716 maxseg; 2717 /* 2718 * Only call tcp_output when there 2719 * is new data available to be sent. 2720 * Otherwise we would send pure ACKs. 2721 */ 2722 SOCKBUF_LOCK(&so->so_snd); 2723 avail = sbavail(&so->so_snd) - 2724 (tp->snd_nxt - tp->snd_una); 2725 SOCKBUF_UNLOCK(&so->so_snd); 2726 if (avail > 0) 2727 (void) tcp_output(tp); 2728 sent = tp->snd_max - oldsndmax; 2729 if (sent > maxseg) { 2730 KASSERT((tp->t_dupacks == 2 && 2731 tp->snd_limited == 0) || 2732 (sent == maxseg + 1 && 2733 tp->t_flags & TF_SENTFIN), 2734 ("%s: sent too much", 2735 __func__)); 2736 tp->snd_limited = 2; 2737 } else if (sent > 0) 2738 ++tp->snd_limited; 2739 tp->snd_cwnd = oldcwnd; 2740 goto drop; 2741 } 2742 } 2743 break; 2744 } else { 2745 /* 2746 * This ack is advancing the left edge, reset the 2747 * counter. 2748 */ 2749 tp->t_dupacks = 0; 2750 /* 2751 * If this ack also has new SACK info, increment the 2752 * counter as per rfc6675. The variable 2753 * sack_changed tracks all changes to the SACK 2754 * scoreboard, including when partial ACKs without 2755 * SACK options are received, and clear the scoreboard 2756 * from the left side. Such partial ACKs should not be 2757 * counted as dupacks here. 2758 */ 2759 if ((tp->t_flags & TF_SACK_PERMIT) && 2760 (to.to_flags & TOF_SACK) && 2761 sack_changed) { 2762 tp->t_dupacks++; 2763 /* limit overhead by setting maxseg last */ 2764 if (!IN_FASTRECOVERY(tp->t_flags) && 2765 (tp->sackhint.sacked_bytes > 2766 ((tcprexmtthresh - 1) * 2767 (maxseg = tcp_maxseg(tp))))) { 2768 goto enter_recovery; 2769 } 2770 } 2771 } 2772 2773 resume_partialack: 2774 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2775 ("%s: th_ack <= snd_una", __func__)); 2776 2777 /* 2778 * If the congestion window was inflated to account 2779 * for the other side's cached packets, retract it. 2780 */ 2781 if (IN_FASTRECOVERY(tp->t_flags)) { 2782 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2783 if (tp->t_flags & TF_SACK_PERMIT) 2784 if (V_tcp_do_prr && to.to_flags & TOF_SACK) { 2785 tcp_timer_activate(tp, TT_REXMT, 0); 2786 tp->t_rtttime = 0; 2787 tcp_do_prr_ack(tp, th, &to); 2788 tp->t_flags |= TF_ACKNOW; 2789 (void) tcp_output(tp); 2790 } else 2791 tcp_sack_partialack(tp, th); 2792 else 2793 tcp_newreno_partial_ack(tp, th); 2794 } else 2795 cc_post_recovery(tp, th); 2796 } else if (IN_CONGRECOVERY(tp->t_flags)) { 2797 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2798 if (V_tcp_do_prr) { 2799 tp->sackhint.delivered_data = BYTES_THIS_ACK(tp, th); 2800 tp->snd_fack = th->th_ack; 2801 tcp_do_prr_ack(tp, th, &to); 2802 (void) tcp_output(tp); 2803 } 2804 } else 2805 cc_post_recovery(tp, th); 2806 } 2807 /* 2808 * If we reach this point, ACK is not a duplicate, 2809 * i.e., it ACKs something we sent. 2810 */ 2811 if (tp->t_flags & TF_NEEDSYN) { 2812 /* 2813 * T/TCP: Connection was half-synchronized, and our 2814 * SYN has been ACK'd (so connection is now fully 2815 * synchronized). Go to non-starred state, 2816 * increment snd_una for ACK of SYN, and check if 2817 * we can do window scaling. 2818 */ 2819 tp->t_flags &= ~TF_NEEDSYN; 2820 tp->snd_una++; 2821 /* Do window scaling? */ 2822 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2823 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2824 tp->rcv_scale = tp->request_r_scale; 2825 /* Send window already scaled. */ 2826 } 2827 } 2828 2829 process_ACK: 2830 INP_WLOCK_ASSERT(tp->t_inpcb); 2831 2832 /* 2833 * Adjust for the SYN bit in sequence space, 2834 * but don't account for it in cwnd calculations. 2835 * This is for the SYN_RECEIVED, non-simultaneous 2836 * SYN case. SYN_SENT and simultaneous SYN are 2837 * treated elsewhere. 2838 */ 2839 if (incforsyn) 2840 tp->snd_una++; 2841 acked = BYTES_THIS_ACK(tp, th); 2842 KASSERT(acked >= 0, ("%s: acked unexepectedly negative " 2843 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__, 2844 tp->snd_una, th->th_ack, tp, m)); 2845 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 2846 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2847 2848 /* 2849 * If we just performed our first retransmit, and the ACK 2850 * arrives within our recovery window, then it was a mistake 2851 * to do the retransmit in the first place. Recover our 2852 * original cwnd and ssthresh, and proceed to transmit where 2853 * we left off. 2854 */ 2855 if (tp->t_rxtshift == 1 && 2856 tp->t_flags & TF_PREVVALID && 2857 tp->t_badrxtwin != 0 && 2858 to.to_flags & TOF_TS && 2859 to.to_tsecr != 0 && 2860 TSTMP_LT(to.to_tsecr, tp->t_badrxtwin)) 2861 cc_cong_signal(tp, th, CC_RTO_ERR); 2862 2863 /* 2864 * If we have a timestamp reply, update smoothed 2865 * round trip time. If no timestamp is present but 2866 * transmit timer is running and timed sequence 2867 * number was acked, update smoothed round trip time. 2868 * Since we now have an rtt measurement, cancel the 2869 * timer backoff (cf., Phil Karn's retransmit alg.). 2870 * Recompute the initial retransmit timer. 2871 * 2872 * Some boxes send broken timestamp replies 2873 * during the SYN+ACK phase, ignore 2874 * timestamps of 0 or we could calculate a 2875 * huge RTT and blow up the retransmit timer. 2876 */ 2877 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2878 uint32_t t; 2879 2880 t = tcp_ts_getticks() - to.to_tsecr; 2881 if (!tp->t_rttlow || tp->t_rttlow > t) 2882 tp->t_rttlow = t; 2883 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2884 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2885 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2886 tp->t_rttlow = ticks - tp->t_rtttime; 2887 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2888 } 2889 2890 /* 2891 * If all outstanding data is acked, stop retransmit 2892 * timer and remember to restart (more output or persist). 2893 * If there is more data to be acked, restart retransmit 2894 * timer, using current (possibly backed-off) value. 2895 */ 2896 if (th->th_ack == tp->snd_max) { 2897 tcp_timer_activate(tp, TT_REXMT, 0); 2898 needoutput = 1; 2899 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2900 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2901 2902 /* 2903 * If no data (only SYN) was ACK'd, 2904 * skip rest of ACK processing. 2905 */ 2906 if (acked == 0) 2907 goto step6; 2908 2909 /* 2910 * Let the congestion control algorithm update congestion 2911 * control related information. This typically means increasing 2912 * the congestion window. 2913 */ 2914 cc_ack_received(tp, th, nsegs, CC_ACK); 2915 2916 SOCKBUF_LOCK(&so->so_snd); 2917 if (acked > sbavail(&so->so_snd)) { 2918 if (tp->snd_wnd >= sbavail(&so->so_snd)) 2919 tp->snd_wnd -= sbavail(&so->so_snd); 2920 else 2921 tp->snd_wnd = 0; 2922 mfree = sbcut_locked(&so->so_snd, 2923 (int)sbavail(&so->so_snd)); 2924 ourfinisacked = 1; 2925 } else { 2926 mfree = sbcut_locked(&so->so_snd, acked); 2927 if (tp->snd_wnd >= (uint32_t) acked) 2928 tp->snd_wnd -= acked; 2929 else 2930 tp->snd_wnd = 0; 2931 ourfinisacked = 0; 2932 } 2933 /* NB: sowwakeup_locked() does an implicit unlock. */ 2934 sowwakeup_locked(so); 2935 m_freem(mfree); 2936 /* Detect una wraparound. */ 2937 if (!IN_RECOVERY(tp->t_flags) && 2938 SEQ_GT(tp->snd_una, tp->snd_recover) && 2939 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2940 tp->snd_recover = th->th_ack - 1; 2941 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2942 if (IN_RECOVERY(tp->t_flags) && 2943 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2944 EXIT_RECOVERY(tp->t_flags); 2945 } 2946 tp->snd_una = th->th_ack; 2947 if (tp->t_flags & TF_SACK_PERMIT) { 2948 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2949 tp->snd_recover = tp->snd_una; 2950 } 2951 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2952 tp->snd_nxt = tp->snd_una; 2953 2954 switch (tp->t_state) { 2955 /* 2956 * In FIN_WAIT_1 STATE in addition to the processing 2957 * for the ESTABLISHED state if our FIN is now acknowledged 2958 * then enter FIN_WAIT_2. 2959 */ 2960 case TCPS_FIN_WAIT_1: 2961 if (ourfinisacked) { 2962 /* 2963 * If we can't receive any more 2964 * data, then closing user can proceed. 2965 * Starting the timer is contrary to the 2966 * specification, but if we don't get a FIN 2967 * we'll hang forever. 2968 * 2969 * XXXjl: 2970 * we should release the tp also, and use a 2971 * compressed state. 2972 */ 2973 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2974 soisdisconnected(so); 2975 tcp_timer_activate(tp, TT_2MSL, 2976 (tcp_fast_finwait2_recycle ? 2977 tcp_finwait2_timeout : 2978 TP_MAXIDLE(tp))); 2979 } 2980 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2981 } 2982 break; 2983 2984 /* 2985 * In CLOSING STATE in addition to the processing for 2986 * the ESTABLISHED state if the ACK acknowledges our FIN 2987 * then enter the TIME-WAIT state, otherwise ignore 2988 * the segment. 2989 */ 2990 case TCPS_CLOSING: 2991 if (ourfinisacked) { 2992 tcp_twstart(tp); 2993 m_freem(m); 2994 return; 2995 } 2996 break; 2997 2998 /* 2999 * In LAST_ACK, we may still be waiting for data to drain 3000 * and/or to be acked, as well as for the ack of our FIN. 3001 * If our FIN is now acknowledged, delete the TCB, 3002 * enter the closed state and return. 3003 */ 3004 case TCPS_LAST_ACK: 3005 if (ourfinisacked) { 3006 tp = tcp_close(tp); 3007 goto drop; 3008 } 3009 break; 3010 } 3011 } 3012 3013 step6: 3014 INP_WLOCK_ASSERT(tp->t_inpcb); 3015 3016 /* 3017 * Update window information. 3018 * Don't look at window if no ACK: TAC's send garbage on first SYN. 3019 */ 3020 if ((thflags & TH_ACK) && 3021 (SEQ_LT(tp->snd_wl1, th->th_seq) || 3022 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 3023 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 3024 /* keep track of pure window updates */ 3025 if (tlen == 0 && 3026 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 3027 TCPSTAT_INC(tcps_rcvwinupd); 3028 tp->snd_wnd = tiwin; 3029 tp->snd_wl1 = th->th_seq; 3030 tp->snd_wl2 = th->th_ack; 3031 if (tp->snd_wnd > tp->max_sndwnd) 3032 tp->max_sndwnd = tp->snd_wnd; 3033 needoutput = 1; 3034 } 3035 3036 /* 3037 * Process segments with URG. 3038 */ 3039 if ((thflags & TH_URG) && th->th_urp && 3040 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3041 /* 3042 * This is a kludge, but if we receive and accept 3043 * random urgent pointers, we'll crash in 3044 * soreceive. It's hard to imagine someone 3045 * actually wanting to send this much urgent data. 3046 */ 3047 SOCKBUF_LOCK(&so->so_rcv); 3048 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) { 3049 th->th_urp = 0; /* XXX */ 3050 thflags &= ~TH_URG; /* XXX */ 3051 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 3052 goto dodata; /* XXX */ 3053 } 3054 /* 3055 * If this segment advances the known urgent pointer, 3056 * then mark the data stream. This should not happen 3057 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 3058 * a FIN has been received from the remote side. 3059 * In these states we ignore the URG. 3060 * 3061 * According to RFC961 (Assigned Protocols), 3062 * the urgent pointer points to the last octet 3063 * of urgent data. We continue, however, 3064 * to consider it to indicate the first octet 3065 * of data past the urgent section as the original 3066 * spec states (in one of two places). 3067 */ 3068 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 3069 tp->rcv_up = th->th_seq + th->th_urp; 3070 so->so_oobmark = sbavail(&so->so_rcv) + 3071 (tp->rcv_up - tp->rcv_nxt) - 1; 3072 if (so->so_oobmark == 0) 3073 so->so_rcv.sb_state |= SBS_RCVATMARK; 3074 sohasoutofband(so); 3075 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 3076 } 3077 SOCKBUF_UNLOCK(&so->so_rcv); 3078 /* 3079 * Remove out of band data so doesn't get presented to user. 3080 * This can happen independent of advancing the URG pointer, 3081 * but if two URG's are pending at once, some out-of-band 3082 * data may creep in... ick. 3083 */ 3084 if (th->th_urp <= (uint32_t)tlen && 3085 !(so->so_options & SO_OOBINLINE)) { 3086 /* hdr drop is delayed */ 3087 tcp_pulloutofband(so, th, m, drop_hdrlen); 3088 } 3089 } else { 3090 /* 3091 * If no out of band data is expected, 3092 * pull receive urgent pointer along 3093 * with the receive window. 3094 */ 3095 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 3096 tp->rcv_up = tp->rcv_nxt; 3097 } 3098 dodata: /* XXX */ 3099 INP_WLOCK_ASSERT(tp->t_inpcb); 3100 3101 /* 3102 * Process the segment text, merging it into the TCP sequencing queue, 3103 * and arranging for acknowledgment of receipt if necessary. 3104 * This process logically involves adjusting tp->rcv_wnd as data 3105 * is presented to the user (this happens in tcp_usrreq.c, 3106 * case PRU_RCVD). If a FIN has already been received on this 3107 * connection then we just ignore the text. 3108 */ 3109 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) && 3110 IS_FASTOPEN(tp->t_flags)); 3111 if ((tlen || (thflags & TH_FIN) || (tfo_syn && tlen > 0)) && 3112 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3113 tcp_seq save_start = th->th_seq; 3114 tcp_seq save_rnxt = tp->rcv_nxt; 3115 int save_tlen = tlen; 3116 m_adj(m, drop_hdrlen); /* delayed header drop */ 3117 /* 3118 * Insert segment which includes th into TCP reassembly queue 3119 * with control block tp. Set thflags to whether reassembly now 3120 * includes a segment with FIN. This handles the common case 3121 * inline (segment is the next to be received on an established 3122 * connection, and the queue is empty), avoiding linkage into 3123 * and removal from the queue and repetition of various 3124 * conversions. 3125 * Set DELACK for segments received in order, but ack 3126 * immediately when segments are out of order (so 3127 * fast retransmit can work). 3128 */ 3129 if (th->th_seq == tp->rcv_nxt && 3130 SEGQ_EMPTY(tp) && 3131 (TCPS_HAVEESTABLISHED(tp->t_state) || 3132 tfo_syn)) { 3133 if (DELAY_ACK(tp, tlen) || tfo_syn) 3134 tp->t_flags |= TF_DELACK; 3135 else 3136 tp->t_flags |= TF_ACKNOW; 3137 tp->rcv_nxt += tlen; 3138 if (tlen && 3139 ((tp->t_flags2 & TF2_FBYTES_COMPLETE) == 0) && 3140 (tp->t_fbyte_in == 0)) { 3141 tp->t_fbyte_in = ticks; 3142 if (tp->t_fbyte_in == 0) 3143 tp->t_fbyte_in = 1; 3144 if (tp->t_fbyte_out && tp->t_fbyte_in) 3145 tp->t_flags2 |= TF2_FBYTES_COMPLETE; 3146 } 3147 thflags = tcp_get_flags(th) & TH_FIN; 3148 TCPSTAT_INC(tcps_rcvpack); 3149 TCPSTAT_ADD(tcps_rcvbyte, tlen); 3150 SOCKBUF_LOCK(&so->so_rcv); 3151 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 3152 m_freem(m); 3153 else 3154 sbappendstream_locked(&so->so_rcv, m, 0); 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 3165 thflags = tcp_reass(tp, th, &temp, &tlen, m); 3166 tp->t_flags |= TF_ACKNOW; 3167 } 3168 if ((tp->t_flags & TF_SACK_PERMIT) && 3169 (save_tlen > 0) && 3170 TCPS_HAVEESTABLISHED(tp->t_state)) { 3171 if ((tlen == 0) && (SEQ_LT(save_start, save_rnxt))) { 3172 /* 3173 * DSACK actually handled in the fastpath 3174 * above. 3175 */ 3176 tcp_update_sack_list(tp, save_start, 3177 save_start + save_tlen); 3178 } else if ((tlen > 0) && SEQ_GT(tp->rcv_nxt, save_rnxt)) { 3179 if ((tp->rcv_numsacks >= 1) && 3180 (tp->sackblks[0].end == save_start)) { 3181 /* 3182 * Partial overlap, recorded at todrop 3183 * above. 3184 */ 3185 tcp_update_sack_list(tp, 3186 tp->sackblks[0].start, 3187 tp->sackblks[0].end); 3188 } else { 3189 tcp_update_dsack_list(tp, save_start, 3190 save_start + save_tlen); 3191 } 3192 } else if (tlen >= save_tlen) { 3193 /* Update of sackblks. */ 3194 tcp_update_dsack_list(tp, save_start, 3195 save_start + save_tlen); 3196 } else if (tlen > 0) { 3197 tcp_update_dsack_list(tp, save_start, 3198 save_start + tlen); 3199 } 3200 } 3201 tcp_handle_wakeup(tp, so); 3202 #if 0 3203 /* 3204 * Note the amount of data that peer has sent into 3205 * our window, in order to estimate the sender's 3206 * buffer size. 3207 * XXX: Unused. 3208 */ 3209 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 3210 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 3211 else 3212 len = so->so_rcv.sb_hiwat; 3213 #endif 3214 } else { 3215 m_freem(m); 3216 thflags &= ~TH_FIN; 3217 } 3218 3219 /* 3220 * If FIN is received ACK the FIN and let the user know 3221 * that the connection is closing. 3222 */ 3223 if (thflags & TH_FIN) { 3224 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3225 /* The socket upcall is handled by socantrcvmore. */ 3226 socantrcvmore(so); 3227 /* 3228 * If connection is half-synchronized 3229 * (ie NEEDSYN flag on) then delay ACK, 3230 * so it may be piggybacked when SYN is sent. 3231 * Otherwise, since we received a FIN then no 3232 * more input can be expected, send ACK now. 3233 */ 3234 if (tp->t_flags & TF_NEEDSYN) 3235 tp->t_flags |= TF_DELACK; 3236 else 3237 tp->t_flags |= TF_ACKNOW; 3238 tp->rcv_nxt++; 3239 } 3240 switch (tp->t_state) { 3241 /* 3242 * In SYN_RECEIVED and ESTABLISHED STATES 3243 * enter the CLOSE_WAIT state. 3244 */ 3245 case TCPS_SYN_RECEIVED: 3246 tp->t_starttime = ticks; 3247 /* FALLTHROUGH */ 3248 case TCPS_ESTABLISHED: 3249 tcp_state_change(tp, TCPS_CLOSE_WAIT); 3250 break; 3251 3252 /* 3253 * If still in FIN_WAIT_1 STATE FIN has not been acked so 3254 * enter the CLOSING state. 3255 */ 3256 case TCPS_FIN_WAIT_1: 3257 tcp_state_change(tp, TCPS_CLOSING); 3258 break; 3259 3260 /* 3261 * In FIN_WAIT_2 state enter the TIME_WAIT state, 3262 * starting the time-wait timer, turning off the other 3263 * standard timers. 3264 */ 3265 case TCPS_FIN_WAIT_2: 3266 tcp_twstart(tp); 3267 return; 3268 } 3269 } 3270 #ifdef TCPDEBUG 3271 if (so->so_options & SO_DEBUG) 3272 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3273 &tcp_savetcp, 0); 3274 #endif 3275 TCP_PROBE3(debug__input, tp, th, m); 3276 3277 /* 3278 * Return any desired output. 3279 */ 3280 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3281 (void) tcp_output(tp); 3282 3283 check_delack: 3284 INP_WLOCK_ASSERT(tp->t_inpcb); 3285 3286 if (tp->t_flags & TF_DELACK) { 3287 tp->t_flags &= ~TF_DELACK; 3288 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3289 } 3290 INP_WUNLOCK(tp->t_inpcb); 3291 return; 3292 3293 dropafterack: 3294 /* 3295 * Generate an ACK dropping incoming segment if it occupies 3296 * sequence space, where the ACK reflects our state. 3297 * 3298 * We can now skip the test for the RST flag since all 3299 * paths to this code happen after packets containing 3300 * RST have been dropped. 3301 * 3302 * In the SYN-RECEIVED state, don't send an ACK unless the 3303 * segment we received passes the SYN-RECEIVED ACK test. 3304 * If it fails send a RST. This breaks the loop in the 3305 * "LAND" DoS attack, and also prevents an ACK storm 3306 * between two listening ports that have been sent forged 3307 * SYN segments, each with the source address of the other. 3308 */ 3309 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3310 (SEQ_GT(tp->snd_una, th->th_ack) || 3311 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3312 rstreason = BANDLIM_RST_OPENPORT; 3313 goto dropwithreset; 3314 } 3315 #ifdef TCPDEBUG 3316 if (so->so_options & SO_DEBUG) 3317 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3318 &tcp_savetcp, 0); 3319 #endif 3320 TCP_PROBE3(debug__input, tp, th, m); 3321 tp->t_flags |= TF_ACKNOW; 3322 (void) tcp_output(tp); 3323 INP_WUNLOCK(tp->t_inpcb); 3324 m_freem(m); 3325 return; 3326 3327 dropwithreset: 3328 if (tp != NULL) { 3329 tcp_dropwithreset(m, th, tp, tlen, rstreason); 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 INP_WUNLOCK(tp->t_inpcb); 3347 } 3348 m_freem(m); 3349 } 3350 3351 /* 3352 * Issue RST and make ACK acceptable to originator of segment. 3353 * The mbuf must still include the original packet header. 3354 * tp may be NULL. 3355 */ 3356 void 3357 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3358 int tlen, int rstreason) 3359 { 3360 #ifdef INET 3361 struct ip *ip; 3362 #endif 3363 #ifdef INET6 3364 struct ip6_hdr *ip6; 3365 #endif 3366 3367 if (tp != NULL) { 3368 INP_LOCK_ASSERT(tp->t_inpcb); 3369 } 3370 3371 /* Don't bother if destination was broadcast/multicast. */ 3372 if ((tcp_get_flags(th) & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3373 goto drop; 3374 #ifdef INET6 3375 if (mtod(m, struct ip *)->ip_v == 6) { 3376 ip6 = mtod(m, struct ip6_hdr *); 3377 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3378 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3379 goto drop; 3380 /* IPv6 anycast check is done at tcp6_input() */ 3381 } 3382 #endif 3383 #if defined(INET) && defined(INET6) 3384 else 3385 #endif 3386 #ifdef INET 3387 { 3388 ip = mtod(m, struct ip *); 3389 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3390 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3391 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3392 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3393 goto drop; 3394 } 3395 #endif 3396 3397 /* Perform bandwidth limiting. */ 3398 if (badport_bandlim(rstreason) < 0) 3399 goto drop; 3400 3401 /* tcp_respond consumes the mbuf chain. */ 3402 if (tcp_get_flags(th) & TH_ACK) { 3403 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3404 th->th_ack, TH_RST); 3405 } else { 3406 if (tcp_get_flags(th) & TH_SYN) 3407 tlen++; 3408 if (tcp_get_flags(th) & TH_FIN) 3409 tlen++; 3410 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3411 (tcp_seq)0, TH_RST|TH_ACK); 3412 } 3413 return; 3414 drop: 3415 m_freem(m); 3416 } 3417 3418 /* 3419 * Parse TCP options and place in tcpopt. 3420 */ 3421 void 3422 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3423 { 3424 int opt, optlen; 3425 3426 to->to_flags = 0; 3427 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3428 opt = cp[0]; 3429 if (opt == TCPOPT_EOL) 3430 break; 3431 if (opt == TCPOPT_NOP) 3432 optlen = 1; 3433 else { 3434 if (cnt < 2) 3435 break; 3436 optlen = cp[1]; 3437 if (optlen < 2 || optlen > cnt) 3438 break; 3439 } 3440 switch (opt) { 3441 case TCPOPT_MAXSEG: 3442 if (optlen != TCPOLEN_MAXSEG) 3443 continue; 3444 if (!(flags & TO_SYN)) 3445 continue; 3446 to->to_flags |= TOF_MSS; 3447 bcopy((char *)cp + 2, 3448 (char *)&to->to_mss, sizeof(to->to_mss)); 3449 to->to_mss = ntohs(to->to_mss); 3450 break; 3451 case TCPOPT_WINDOW: 3452 if (optlen != TCPOLEN_WINDOW) 3453 continue; 3454 if (!(flags & TO_SYN)) 3455 continue; 3456 to->to_flags |= TOF_SCALE; 3457 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3458 break; 3459 case TCPOPT_TIMESTAMP: 3460 if (optlen != TCPOLEN_TIMESTAMP) 3461 continue; 3462 to->to_flags |= TOF_TS; 3463 bcopy((char *)cp + 2, 3464 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3465 to->to_tsval = ntohl(to->to_tsval); 3466 bcopy((char *)cp + 6, 3467 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3468 to->to_tsecr = ntohl(to->to_tsecr); 3469 break; 3470 case TCPOPT_SIGNATURE: 3471 /* 3472 * In order to reply to a host which has set the 3473 * TCP_SIGNATURE option in its initial SYN, we have 3474 * to record the fact that the option was observed 3475 * here for the syncache code to perform the correct 3476 * response. 3477 */ 3478 if (optlen != TCPOLEN_SIGNATURE) 3479 continue; 3480 to->to_flags |= TOF_SIGNATURE; 3481 to->to_signature = cp + 2; 3482 break; 3483 case TCPOPT_SACK_PERMITTED: 3484 if (optlen != TCPOLEN_SACK_PERMITTED) 3485 continue; 3486 if (!(flags & TO_SYN)) 3487 continue; 3488 if (!V_tcp_do_sack) 3489 continue; 3490 to->to_flags |= TOF_SACKPERM; 3491 break; 3492 case TCPOPT_SACK: 3493 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3494 continue; 3495 if (flags & TO_SYN) 3496 continue; 3497 to->to_flags |= TOF_SACK; 3498 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3499 to->to_sacks = cp + 2; 3500 TCPSTAT_INC(tcps_sack_rcv_blocks); 3501 break; 3502 case TCPOPT_FAST_OPEN: 3503 /* 3504 * Cookie length validation is performed by the 3505 * server side cookie checking code or the client 3506 * side cookie cache update code. 3507 */ 3508 if (!(flags & TO_SYN)) 3509 continue; 3510 if (!V_tcp_fastopen_client_enable && 3511 !V_tcp_fastopen_server_enable) 3512 continue; 3513 to->to_flags |= TOF_FASTOPEN; 3514 to->to_tfo_len = optlen - 2; 3515 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL; 3516 break; 3517 default: 3518 continue; 3519 } 3520 } 3521 } 3522 3523 /* 3524 * Pull out of band byte out of a segment so 3525 * it doesn't appear in the user's data queue. 3526 * It is still reflected in the segment length for 3527 * sequencing purposes. 3528 */ 3529 void 3530 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3531 int off) 3532 { 3533 int cnt = off + th->th_urp - 1; 3534 3535 while (cnt >= 0) { 3536 if (m->m_len > cnt) { 3537 char *cp = mtod(m, caddr_t) + cnt; 3538 struct tcpcb *tp = sototcpcb(so); 3539 3540 INP_WLOCK_ASSERT(tp->t_inpcb); 3541 3542 tp->t_iobc = *cp; 3543 tp->t_oobflags |= TCPOOB_HAVEDATA; 3544 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3545 m->m_len--; 3546 if (m->m_flags & M_PKTHDR) 3547 m->m_pkthdr.len--; 3548 return; 3549 } 3550 cnt -= m->m_len; 3551 m = m->m_next; 3552 if (m == NULL) 3553 break; 3554 } 3555 panic("tcp_pulloutofband"); 3556 } 3557 3558 /* 3559 * Collect new round-trip time estimate 3560 * and update averages and current timeout. 3561 */ 3562 void 3563 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3564 { 3565 int delta; 3566 3567 INP_WLOCK_ASSERT(tp->t_inpcb); 3568 3569 TCPSTAT_INC(tcps_rttupdated); 3570 tp->t_rttupdated++; 3571 #ifdef STATS 3572 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RTT, 3573 imax(0, rtt * 1000 / hz)); 3574 #endif 3575 if ((tp->t_srtt != 0) && (tp->t_rxtshift <= TCP_RTT_INVALIDATE)) { 3576 /* 3577 * srtt is stored as fixed point with 5 bits after the 3578 * binary point (i.e., scaled by 8). The following magic 3579 * is equivalent to the smoothing algorithm in rfc793 with 3580 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3581 * point). Adjust rtt to origin 0. 3582 */ 3583 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3584 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3585 3586 if ((tp->t_srtt += delta) <= 0) 3587 tp->t_srtt = 1; 3588 3589 /* 3590 * We accumulate a smoothed rtt variance (actually, a 3591 * smoothed mean difference), then set the retransmit 3592 * timer to smoothed rtt + 4 times the smoothed variance. 3593 * rttvar is stored as fixed point with 4 bits after the 3594 * binary point (scaled by 16). The following is 3595 * equivalent to rfc793 smoothing with an alpha of .75 3596 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3597 * rfc793's wired-in beta. 3598 */ 3599 if (delta < 0) 3600 delta = -delta; 3601 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3602 if ((tp->t_rttvar += delta) <= 0) 3603 tp->t_rttvar = 1; 3604 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3605 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3606 } else { 3607 /* 3608 * No rtt measurement yet - use the unsmoothed rtt. 3609 * Set the variance to half the rtt (so our first 3610 * retransmit happens at 3*rtt). 3611 */ 3612 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3613 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3614 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3615 } 3616 tp->t_rtttime = 0; 3617 tp->t_rxtshift = 0; 3618 3619 /* 3620 * the retransmit should happen at rtt + 4 * rttvar. 3621 * Because of the way we do the smoothing, srtt and rttvar 3622 * will each average +1/2 tick of bias. When we compute 3623 * the retransmit timer, we want 1/2 tick of rounding and 3624 * 1 extra tick because of +-1/2 tick uncertainty in the 3625 * firing of the timer. The bias will give us exactly the 3626 * 1.5 tick we need. But, because the bias is 3627 * statistical, we have to test that we don't drop below 3628 * the minimum feasible timer (which is 2 ticks). 3629 */ 3630 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3631 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3632 3633 /* 3634 * We received an ack for a packet that wasn't retransmitted; 3635 * it is probably safe to discard any error indications we've 3636 * received recently. This isn't quite right, but close enough 3637 * for now (a route might have failed after we sent a segment, 3638 * and the return path might not be symmetrical). 3639 */ 3640 tp->t_softerror = 0; 3641 } 3642 3643 /* 3644 * Determine a reasonable value for maxseg size. 3645 * If the route is known, check route for mtu. 3646 * If none, use an mss that can be handled on the outgoing interface 3647 * without forcing IP to fragment. If no route is found, route has no mtu, 3648 * or the destination isn't local, use a default, hopefully conservative 3649 * size (usually 512 or the default IP max size, but no more than the mtu 3650 * of the interface), as we can't discover anything about intervening 3651 * gateways or networks. We also initialize the congestion/slow start 3652 * window to be a single segment if the destination isn't local. 3653 * While looking at the routing entry, we also initialize other path-dependent 3654 * parameters from pre-set or cached values in the routing entry. 3655 * 3656 * NOTE that resulting t_maxseg doesn't include space for TCP options or 3657 * IP options, e.g. IPSEC data, since length of this data may vary, and 3658 * thus it is calculated for every segment separately in tcp_output(). 3659 * 3660 * NOTE that this routine is only called when we process an incoming 3661 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3662 * settings are handled in tcp_mssopt(). 3663 */ 3664 void 3665 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3666 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3667 { 3668 int mss = 0; 3669 uint32_t maxmtu = 0; 3670 struct inpcb *inp = tp->t_inpcb; 3671 struct hc_metrics_lite metrics; 3672 #ifdef INET6 3673 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3674 size_t min_protoh = isipv6 ? 3675 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3676 sizeof (struct tcpiphdr); 3677 #else 3678 size_t min_protoh = sizeof(struct tcpiphdr); 3679 #endif 3680 3681 INP_WLOCK_ASSERT(tp->t_inpcb); 3682 3683 if (tp->t_port) 3684 min_protoh += V_tcp_udp_tunneling_overhead; 3685 if (mtuoffer != -1) { 3686 KASSERT(offer == -1, ("%s: conflict", __func__)); 3687 offer = mtuoffer - min_protoh; 3688 } 3689 3690 /* Initialize. */ 3691 #ifdef INET6 3692 if (isipv6) { 3693 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3694 tp->t_maxseg = V_tcp_v6mssdflt; 3695 } 3696 #endif 3697 #if defined(INET) && defined(INET6) 3698 else 3699 #endif 3700 #ifdef INET 3701 { 3702 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3703 tp->t_maxseg = V_tcp_mssdflt; 3704 } 3705 #endif 3706 3707 /* 3708 * No route to sender, stay with default mss and return. 3709 */ 3710 if (maxmtu == 0) { 3711 /* 3712 * In case we return early we need to initialize metrics 3713 * to a defined state as tcp_hc_get() would do for us 3714 * if there was no cache hit. 3715 */ 3716 if (metricptr != NULL) 3717 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3718 return; 3719 } 3720 3721 /* What have we got? */ 3722 switch (offer) { 3723 case 0: 3724 /* 3725 * Offer == 0 means that there was no MSS on the SYN 3726 * segment, in this case we use tcp_mssdflt as 3727 * already assigned to t_maxseg above. 3728 */ 3729 offer = tp->t_maxseg; 3730 break; 3731 3732 case -1: 3733 /* 3734 * Offer == -1 means that we didn't receive SYN yet. 3735 */ 3736 /* FALLTHROUGH */ 3737 3738 default: 3739 /* 3740 * Prevent DoS attack with too small MSS. Round up 3741 * to at least minmss. 3742 */ 3743 offer = max(offer, V_tcp_minmss); 3744 } 3745 3746 /* 3747 * rmx information is now retrieved from tcp_hostcache. 3748 */ 3749 tcp_hc_get(&inp->inp_inc, &metrics); 3750 if (metricptr != NULL) 3751 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3752 3753 /* 3754 * If there's a discovered mtu in tcp hostcache, use it. 3755 * Else, use the link mtu. 3756 */ 3757 if (metrics.rmx_mtu) 3758 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3759 else { 3760 #ifdef INET6 3761 if (isipv6) { 3762 mss = maxmtu - min_protoh; 3763 if (!V_path_mtu_discovery && 3764 !in6_localaddr(&inp->in6p_faddr)) 3765 mss = min(mss, V_tcp_v6mssdflt); 3766 } 3767 #endif 3768 #if defined(INET) && defined(INET6) 3769 else 3770 #endif 3771 #ifdef INET 3772 { 3773 mss = maxmtu - min_protoh; 3774 if (!V_path_mtu_discovery && 3775 !in_localaddr(inp->inp_faddr)) 3776 mss = min(mss, V_tcp_mssdflt); 3777 } 3778 #endif 3779 /* 3780 * XXX - The above conditional (mss = maxmtu - min_protoh) 3781 * probably violates the TCP spec. 3782 * The problem is that, since we don't know the 3783 * other end's MSS, we are supposed to use a conservative 3784 * default. But, if we do that, then MTU discovery will 3785 * never actually take place, because the conservative 3786 * default is much less than the MTUs typically seen 3787 * on the Internet today. For the moment, we'll sweep 3788 * this under the carpet. 3789 * 3790 * The conservative default might not actually be a problem 3791 * if the only case this occurs is when sending an initial 3792 * SYN with options and data to a host we've never talked 3793 * to before. Then, they will reply with an MSS value which 3794 * will get recorded and the new parameters should get 3795 * recomputed. For Further Study. 3796 */ 3797 } 3798 mss = min(mss, offer); 3799 3800 /* 3801 * Sanity check: make sure that maxseg will be large 3802 * enough to allow some data on segments even if the 3803 * all the option space is used (40bytes). Otherwise 3804 * funny things may happen in tcp_output. 3805 * 3806 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3807 */ 3808 mss = max(mss, 64); 3809 3810 tp->t_maxseg = mss; 3811 } 3812 3813 void 3814 tcp_mss(struct tcpcb *tp, int offer) 3815 { 3816 int mss; 3817 uint32_t bufsize; 3818 struct inpcb *inp; 3819 struct socket *so; 3820 struct hc_metrics_lite metrics; 3821 struct tcp_ifcap cap; 3822 3823 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3824 3825 bzero(&cap, sizeof(cap)); 3826 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3827 3828 mss = tp->t_maxseg; 3829 inp = tp->t_inpcb; 3830 3831 /* 3832 * If there's a pipesize, change the socket buffer to that size, 3833 * don't change if sb_hiwat is different than default (then it 3834 * has been changed on purpose with setsockopt). 3835 * Make the socket buffers an integral number of mss units; 3836 * if the mss is larger than the socket buffer, decrease the mss. 3837 */ 3838 so = inp->inp_socket; 3839 SOCKBUF_LOCK(&so->so_snd); 3840 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3841 bufsize = metrics.rmx_sendpipe; 3842 else 3843 bufsize = so->so_snd.sb_hiwat; 3844 if (bufsize < mss) 3845 mss = bufsize; 3846 else { 3847 bufsize = roundup(bufsize, mss); 3848 if (bufsize > sb_max) 3849 bufsize = sb_max; 3850 if (bufsize > so->so_snd.sb_hiwat) 3851 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3852 } 3853 SOCKBUF_UNLOCK(&so->so_snd); 3854 /* 3855 * Sanity check: make sure that maxseg will be large 3856 * enough to allow some data on segments even if the 3857 * all the option space is used (40bytes). Otherwise 3858 * funny things may happen in tcp_output. 3859 * 3860 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3861 */ 3862 tp->t_maxseg = max(mss, 64); 3863 3864 SOCKBUF_LOCK(&so->so_rcv); 3865 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3866 bufsize = metrics.rmx_recvpipe; 3867 else 3868 bufsize = so->so_rcv.sb_hiwat; 3869 if (bufsize > mss) { 3870 bufsize = roundup(bufsize, mss); 3871 if (bufsize > sb_max) 3872 bufsize = sb_max; 3873 if (bufsize > so->so_rcv.sb_hiwat) 3874 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3875 } 3876 SOCKBUF_UNLOCK(&so->so_rcv); 3877 3878 /* Check the interface for TSO capabilities. */ 3879 if (cap.ifcap & CSUM_TSO) { 3880 tp->t_flags |= TF_TSO; 3881 tp->t_tsomax = cap.tsomax; 3882 tp->t_tsomaxsegcount = cap.tsomaxsegcount; 3883 tp->t_tsomaxsegsize = cap.tsomaxsegsize; 3884 } 3885 } 3886 3887 /* 3888 * Determine the MSS option to send on an outgoing SYN. 3889 */ 3890 int 3891 tcp_mssopt(struct in_conninfo *inc) 3892 { 3893 int mss = 0; 3894 uint32_t thcmtu = 0; 3895 uint32_t maxmtu = 0; 3896 size_t min_protoh; 3897 3898 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3899 3900 #ifdef INET6 3901 if (inc->inc_flags & INC_ISIPV6) { 3902 mss = V_tcp_v6mssdflt; 3903 maxmtu = tcp_maxmtu6(inc, NULL); 3904 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3905 } 3906 #endif 3907 #if defined(INET) && defined(INET6) 3908 else 3909 #endif 3910 #ifdef INET 3911 { 3912 mss = V_tcp_mssdflt; 3913 maxmtu = tcp_maxmtu(inc, NULL); 3914 min_protoh = sizeof(struct tcpiphdr); 3915 } 3916 #endif 3917 #if defined(INET6) || defined(INET) 3918 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3919 #endif 3920 3921 if (maxmtu && thcmtu) 3922 mss = min(maxmtu, thcmtu) - min_protoh; 3923 else if (maxmtu || thcmtu) 3924 mss = max(maxmtu, thcmtu) - min_protoh; 3925 3926 return (mss); 3927 } 3928 3929 void 3930 tcp_do_prr_ack(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 3931 { 3932 int snd_cnt = 0, limit = 0, del_data = 0, pipe = 0; 3933 int maxseg = tcp_maxseg(tp); 3934 3935 INP_WLOCK_ASSERT(tp->t_inpcb); 3936 3937 /* 3938 * Compute the amount of data that this ACK is indicating 3939 * (del_data) and an estimate of how many bytes are in the 3940 * network. 3941 */ 3942 if (((tp->t_flags & TF_SACK_PERMIT) && 3943 (to->to_flags & TOF_SACK)) || 3944 (IN_CONGRECOVERY(tp->t_flags) && 3945 !IN_FASTRECOVERY(tp->t_flags))) { 3946 del_data = tp->sackhint.delivered_data; 3947 if (V_tcp_do_newsack) 3948 pipe = tcp_compute_pipe(tp); 3949 else 3950 pipe = (tp->snd_nxt - tp->snd_fack) + 3951 tp->sackhint.sack_bytes_rexmit; 3952 } else { 3953 if (tp->sackhint.prr_delivered < (tcprexmtthresh * maxseg + 3954 tp->snd_recover - tp->snd_una)) 3955 del_data = maxseg; 3956 pipe = imax(0, tp->snd_max - tp->snd_una - 3957 imin(INT_MAX / 65536, tp->t_dupacks) * maxseg); 3958 } 3959 tp->sackhint.prr_delivered += del_data; 3960 /* 3961 * Proportional Rate Reduction 3962 */ 3963 if (pipe >= tp->snd_ssthresh) { 3964 if (tp->sackhint.recover_fs == 0) 3965 tp->sackhint.recover_fs = 3966 imax(1, tp->snd_nxt - tp->snd_una); 3967 snd_cnt = howmany((long)tp->sackhint.prr_delivered * 3968 tp->snd_ssthresh, tp->sackhint.recover_fs) - 3969 tp->sackhint.prr_out; 3970 } else { 3971 if (V_tcp_do_prr_conservative || (del_data == 0)) 3972 limit = tp->sackhint.prr_delivered - 3973 tp->sackhint.prr_out; 3974 else 3975 limit = imax(tp->sackhint.prr_delivered - 3976 tp->sackhint.prr_out, del_data) + 3977 maxseg; 3978 snd_cnt = imin((tp->snd_ssthresh - pipe), limit); 3979 } 3980 snd_cnt = imax(snd_cnt, 0) / maxseg; 3981 /* 3982 * Send snd_cnt new data into the network in response to this ack. 3983 * If there is going to be a SACK retransmission, adjust snd_cwnd 3984 * accordingly. 3985 */ 3986 if (IN_FASTRECOVERY(tp->t_flags)) { 3987 if ((tp->t_flags & TF_SACK_PERMIT) && 3988 (to->to_flags & TOF_SACK)) { 3989 tp->snd_cwnd = tp->snd_nxt - tp->snd_recover + 3990 tp->sackhint.sack_bytes_rexmit + 3991 (snd_cnt * maxseg); 3992 } else { 3993 tp->snd_cwnd = (tp->snd_max - tp->snd_una) + 3994 (snd_cnt * maxseg); 3995 } 3996 } else if (IN_CONGRECOVERY(tp->t_flags)) 3997 tp->snd_cwnd = pipe - del_data + (snd_cnt * maxseg); 3998 tp->snd_cwnd = imax(maxseg, tp->snd_cwnd); 3999 } 4000 4001 /* 4002 * On a partial ack arrives, force the retransmission of the 4003 * next unacknowledged segment. Do not clear tp->t_dupacks. 4004 * By setting snd_nxt to ti_ack, this forces retransmission timer to 4005 * be started again. 4006 */ 4007 void 4008 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 4009 { 4010 tcp_seq onxt = tp->snd_nxt; 4011 uint32_t ocwnd = tp->snd_cwnd; 4012 u_int maxseg = tcp_maxseg(tp); 4013 4014 INP_WLOCK_ASSERT(tp->t_inpcb); 4015 4016 tcp_timer_activate(tp, TT_REXMT, 0); 4017 tp->t_rtttime = 0; 4018 tp->snd_nxt = th->th_ack; 4019 /* 4020 * Set snd_cwnd to one segment beyond acknowledged offset. 4021 * (tp->snd_una has not yet been updated when this function is called.) 4022 */ 4023 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th); 4024 tp->t_flags |= TF_ACKNOW; 4025 (void) tcp_output(tp); 4026 tp->snd_cwnd = ocwnd; 4027 if (SEQ_GT(onxt, tp->snd_nxt)) 4028 tp->snd_nxt = onxt; 4029 /* 4030 * Partial window deflation. Relies on fact that tp->snd_una 4031 * not updated yet. 4032 */ 4033 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 4034 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 4035 else 4036 tp->snd_cwnd = 0; 4037 tp->snd_cwnd += maxseg; 4038 } 4039 4040 int 4041 tcp_compute_pipe(struct tcpcb *tp) 4042 { 4043 return (tp->snd_max - tp->snd_una + 4044 tp->sackhint.sack_bytes_rexmit - 4045 tp->sackhint.sacked_bytes); 4046 } 4047 4048 uint32_t 4049 tcp_compute_initwnd(uint32_t maxseg) 4050 { 4051 /* 4052 * Calculate the Initial Window, also used as Restart Window 4053 * 4054 * RFC5681 Section 3.1 specifies the default conservative values. 4055 * RFC3390 specifies slightly more aggressive values. 4056 * RFC6928 increases it to ten segments. 4057 * Support for user specified value for initial flight size. 4058 */ 4059 if (V_tcp_initcwnd_segments) 4060 return min(V_tcp_initcwnd_segments * maxseg, 4061 max(2 * maxseg, V_tcp_initcwnd_segments * 1460)); 4062 else if (V_tcp_do_rfc3390) 4063 return min(4 * maxseg, max(2 * maxseg, 4380)); 4064 else { 4065 /* Per RFC5681 Section 3.1 */ 4066 if (maxseg > 2190) 4067 return (2 * maxseg); 4068 else if (maxseg > 1095) 4069 return (3 * maxseg); 4070 else 4071 return (4 * maxseg); 4072 } 4073 } 4074