1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_tcpdebug.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/domain.h> 43 #include <sys/hhook.h> 44 #include <sys/kernel.h> 45 #include <sys/lock.h> 46 #include <sys/mbuf.h> 47 #include <sys/mutex.h> 48 #include <sys/protosw.h> 49 #include <sys/sdt.h> 50 #include <sys/socket.h> 51 #include <sys/socketvar.h> 52 #include <sys/sysctl.h> 53 54 #include <net/if.h> 55 #include <net/route.h> 56 #include <net/vnet.h> 57 58 #include <netinet/in.h> 59 #include <netinet/in_kdtrace.h> 60 #include <netinet/in_systm.h> 61 #include <netinet/ip.h> 62 #include <netinet/in_pcb.h> 63 #include <netinet/ip_var.h> 64 #include <netinet/ip_options.h> 65 #ifdef INET6 66 #include <netinet6/in6_pcb.h> 67 #include <netinet/ip6.h> 68 #include <netinet6/ip6_var.h> 69 #endif 70 #ifdef TCP_RFC7413 71 #include <netinet/tcp_fastopen.h> 72 #endif 73 #include <netinet/tcp.h> 74 #define TCPOUTFLAGS 75 #include <netinet/tcp_fsm.h> 76 #include <netinet/tcp_seq.h> 77 #include <netinet/tcp_timer.h> 78 #include <netinet/tcp_var.h> 79 #include <netinet/tcpip.h> 80 #include <netinet/cc/cc.h> 81 #ifdef TCPPCAP 82 #include <netinet/tcp_pcap.h> 83 #endif 84 #ifdef TCPDEBUG 85 #include <netinet/tcp_debug.h> 86 #endif 87 #ifdef TCP_OFFLOAD 88 #include <netinet/tcp_offload.h> 89 #endif 90 91 #ifdef IPSEC 92 #include <netipsec/ipsec.h> 93 #endif /*IPSEC*/ 94 95 #include <machine/in_cksum.h> 96 97 #include <security/mac/mac_framework.h> 98 99 VNET_DEFINE(int, path_mtu_discovery) = 1; 100 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 101 &VNET_NAME(path_mtu_discovery), 1, 102 "Enable Path MTU Discovery"); 103 104 VNET_DEFINE(int, tcp_do_tso) = 1; 105 #define V_tcp_do_tso VNET(tcp_do_tso) 106 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 107 &VNET_NAME(tcp_do_tso), 0, 108 "Enable TCP Segmentation Offload"); 109 110 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 111 #define V_tcp_sendspace VNET(tcp_sendspace) 112 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 113 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 114 115 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 116 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf) 117 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 118 &VNET_NAME(tcp_do_autosndbuf), 0, 119 "Enable automatic send buffer sizing"); 120 121 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 122 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc) 123 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 124 &VNET_NAME(tcp_autosndbuf_inc), 0, 125 "Incrementor step size of automatic send buffer"); 126 127 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 128 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max) 129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 130 &VNET_NAME(tcp_autosndbuf_max), 0, 131 "Max size of automatic send buffer"); 132 133 /* 134 * Make sure that either retransmit or persist timer is set for SYN, FIN and 135 * non-ACK. 136 */ 137 #define TCP_XMIT_TIMER_ASSERT(tp, len, th_flags) \ 138 KASSERT(((len) == 0 && ((th_flags) & (TH_SYN | TH_FIN)) == 0) ||\ 139 tcp_timer_active((tp), TT_REXMT) || \ 140 tcp_timer_active((tp), TT_PERSIST), \ 141 ("neither rexmt nor persist timer is set")) 142 143 static void inline hhook_run_tcp_est_out(struct tcpcb *tp, 144 struct tcphdr *th, struct tcpopt *to, 145 uint32_t len, int tso); 146 static void inline cc_after_idle(struct tcpcb *tp); 147 148 /* 149 * Wrapper for the TCP established output helper hook. 150 */ 151 static void inline 152 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 153 struct tcpopt *to, uint32_t len, int tso) 154 { 155 struct tcp_hhook_data hhook_data; 156 157 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 158 hhook_data.tp = tp; 159 hhook_data.th = th; 160 hhook_data.to = to; 161 hhook_data.len = len; 162 hhook_data.tso = tso; 163 164 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 165 tp->osd); 166 } 167 } 168 169 /* 170 * CC wrapper hook functions 171 */ 172 static void inline 173 cc_after_idle(struct tcpcb *tp) 174 { 175 INP_WLOCK_ASSERT(tp->t_inpcb); 176 177 if (CC_ALGO(tp)->after_idle != NULL) 178 CC_ALGO(tp)->after_idle(tp->ccv); 179 } 180 181 /* 182 * Tcp output routine: figure out what should be sent and send it. 183 */ 184 int 185 tcp_output(struct tcpcb *tp) 186 { 187 struct socket *so = tp->t_inpcb->inp_socket; 188 int32_t len; 189 uint32_t recwin, sendwin; 190 int off, flags, error = 0; /* Keep compiler happy */ 191 struct mbuf *m; 192 struct ip *ip = NULL; 193 struct ipovly *ipov = NULL; 194 struct tcphdr *th; 195 u_char opt[TCP_MAXOLEN]; 196 unsigned ipoptlen, optlen, hdrlen; 197 #ifdef IPSEC 198 unsigned ipsec_optlen = 0; 199 #endif 200 int idle, sendalot; 201 int sack_rxmit, sack_bytes_rxmt; 202 struct sackhole *p; 203 int tso, mtu; 204 struct tcpopt to; 205 #if 0 206 int maxburst = TCP_MAXBURST; 207 #endif 208 #ifdef INET6 209 struct ip6_hdr *ip6 = NULL; 210 int isipv6; 211 212 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 213 #endif 214 215 INP_WLOCK_ASSERT(tp->t_inpcb); 216 217 #ifdef TCP_OFFLOAD 218 if (tp->t_flags & TF_TOE) 219 return (tcp_offload_output(tp)); 220 #endif 221 222 #ifdef TCP_RFC7413 223 /* 224 * For TFO connections in SYN_RECEIVED, only allow the initial 225 * SYN|ACK and those sent by the retransmit timer. 226 */ 227 if ((tp->t_flags & TF_FASTOPEN) && 228 (tp->t_state == TCPS_SYN_RECEIVED) && 229 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN|ACK sent */ 230 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 231 return (0); 232 #endif 233 /* 234 * Determine length of data that should be transmitted, 235 * and flags that will be used. 236 * If there is some data or critical controls (SYN, RST) 237 * to send, then transmit; otherwise, investigate further. 238 */ 239 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 240 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 241 cc_after_idle(tp); 242 tp->t_flags &= ~TF_LASTIDLE; 243 if (idle) { 244 if (tp->t_flags & TF_MORETOCOME) { 245 tp->t_flags |= TF_LASTIDLE; 246 idle = 0; 247 } 248 } 249 again: 250 /* 251 * If we've recently taken a timeout, snd_max will be greater than 252 * snd_nxt. There may be SACK information that allows us to avoid 253 * resending already delivered data. Adjust snd_nxt accordingly. 254 */ 255 if ((tp->t_flags & TF_SACK_PERMIT) && 256 SEQ_LT(tp->snd_nxt, tp->snd_max)) 257 tcp_sack_adjust(tp); 258 sendalot = 0; 259 tso = 0; 260 mtu = 0; 261 off = tp->snd_nxt - tp->snd_una; 262 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 263 264 flags = tcp_outflags[tp->t_state]; 265 /* 266 * Send any SACK-generated retransmissions. If we're explicitly trying 267 * to send out new data (when sendalot is 1), bypass this function. 268 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 269 * we're replacing a (future) new transmission with a retransmission 270 * now, and we previously incremented snd_cwnd in tcp_input(). 271 */ 272 /* 273 * Still in sack recovery , reset rxmit flag to zero. 274 */ 275 sack_rxmit = 0; 276 sack_bytes_rxmt = 0; 277 len = 0; 278 p = NULL; 279 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 280 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 281 uint32_t cwin; 282 283 cwin = 284 imax(min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt, 0); 285 /* Do not retransmit SACK segments beyond snd_recover */ 286 if (SEQ_GT(p->end, tp->snd_recover)) { 287 /* 288 * (At least) part of sack hole extends beyond 289 * snd_recover. Check to see if we can rexmit data 290 * for this hole. 291 */ 292 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 293 /* 294 * Can't rexmit any more data for this hole. 295 * That data will be rexmitted in the next 296 * sack recovery episode, when snd_recover 297 * moves past p->rxmit. 298 */ 299 p = NULL; 300 goto after_sack_rexmit; 301 } else 302 /* Can rexmit part of the current hole */ 303 len = ((int32_t)ulmin(cwin, 304 tp->snd_recover - p->rxmit)); 305 } else 306 len = ((int32_t)ulmin(cwin, p->end - p->rxmit)); 307 off = p->rxmit - tp->snd_una; 308 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 309 __func__, off)); 310 if (len > 0) { 311 sack_rxmit = 1; 312 sendalot = 1; 313 TCPSTAT_INC(tcps_sack_rexmits); 314 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 315 min(len, tp->t_maxseg)); 316 } 317 } 318 after_sack_rexmit: 319 /* 320 * Get standard flags, and add SYN or FIN if requested by 'hidden' 321 * state flags. 322 */ 323 if (tp->t_flags & TF_NEEDFIN) 324 flags |= TH_FIN; 325 if (tp->t_flags & TF_NEEDSYN) 326 flags |= TH_SYN; 327 328 SOCKBUF_LOCK(&so->so_snd); 329 /* 330 * If in persist timeout with window of 0, send 1 byte. 331 * Otherwise, if window is small but nonzero 332 * and timer expired, we will send what we can 333 * and go to transmit state. 334 */ 335 if (tp->t_flags & TF_FORCEDATA) { 336 if (sendwin == 0) { 337 /* 338 * If we still have some data to send, then 339 * clear the FIN bit. Usually this would 340 * happen below when it realizes that we 341 * aren't sending all the data. However, 342 * if we have exactly 1 byte of unsent data, 343 * then it won't clear the FIN bit below, 344 * and if we are in persist state, we wind 345 * up sending the packet without recording 346 * that we sent the FIN bit. 347 * 348 * We can't just blindly clear the FIN bit, 349 * because if we don't have any more data 350 * to send then the probe will be the FIN 351 * itself. 352 */ 353 if (off < sbused(&so->so_snd)) 354 flags &= ~TH_FIN; 355 sendwin = 1; 356 } else { 357 tcp_timer_activate(tp, TT_PERSIST, 0); 358 tp->t_rxtshift = 0; 359 } 360 } 361 362 /* 363 * If snd_nxt == snd_max and we have transmitted a FIN, the 364 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 365 * a negative length. This can also occur when TCP opens up 366 * its congestion window while receiving additional duplicate 367 * acks after fast-retransmit because TCP will reset snd_nxt 368 * to snd_max after the fast-retransmit. 369 * 370 * In the normal retransmit-FIN-only case, however, snd_nxt will 371 * be set to snd_una, the offset will be 0, and the length may 372 * wind up 0. 373 * 374 * If sack_rxmit is true we are retransmitting from the scoreboard 375 * in which case len is already set. 376 */ 377 if (sack_rxmit == 0) { 378 if (sack_bytes_rxmt == 0) 379 len = ((int32_t)ulmin(sbavail(&so->so_snd), sendwin) - 380 off); 381 else { 382 int32_t cwin; 383 384 /* 385 * We are inside of a SACK recovery episode and are 386 * sending new data, having retransmitted all the 387 * data possible in the scoreboard. 388 */ 389 len = ((int32_t)min(sbavail(&so->so_snd), tp->snd_wnd) - 390 off); 391 /* 392 * Don't remove this (len > 0) check ! 393 * We explicitly check for len > 0 here (although it 394 * isn't really necessary), to work around a gcc 395 * optimization issue - to force gcc to compute 396 * len above. Without this check, the computation 397 * of len is bungled by the optimizer. 398 */ 399 if (len > 0) { 400 cwin = tp->snd_cwnd - 401 (tp->snd_nxt - tp->sack_newdata) - 402 sack_bytes_rxmt; 403 if (cwin < 0) 404 cwin = 0; 405 len = imin(len, cwin); 406 } 407 } 408 } 409 410 /* 411 * Lop off SYN bit if it has already been sent. However, if this 412 * is SYN-SENT state and if segment contains data and if we don't 413 * know that foreign host supports TAO, suppress sending segment. 414 */ 415 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 416 if (tp->t_state != TCPS_SYN_RECEIVED) 417 flags &= ~TH_SYN; 418 #ifdef TCP_RFC7413 419 /* 420 * When sending additional segments following a TFO SYN|ACK, 421 * do not include the SYN bit. 422 */ 423 if ((tp->t_flags & TF_FASTOPEN) && 424 (tp->t_state == TCPS_SYN_RECEIVED)) 425 flags &= ~TH_SYN; 426 #endif 427 off--, len++; 428 } 429 430 /* 431 * Be careful not to send data and/or FIN on SYN segments. 432 * This measure is needed to prevent interoperability problems 433 * with not fully conformant TCP implementations. 434 */ 435 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 436 len = 0; 437 flags &= ~TH_FIN; 438 } 439 440 #ifdef TCP_RFC7413 441 /* 442 * When retransmitting SYN|ACK on a passively-created TFO socket, 443 * don't include data, as the presence of data may have caused the 444 * original SYN|ACK to have been dropped by a middlebox. 445 */ 446 if ((tp->t_flags & TF_FASTOPEN) && 447 (((tp->t_state == TCPS_SYN_RECEIVED) && (tp->t_rxtshift > 0)) || 448 (flags & TH_RST))) 449 len = 0; 450 #endif 451 if (len <= 0) { 452 /* 453 * If FIN has been sent but not acked, 454 * but we haven't been called to retransmit, 455 * len will be < 0. Otherwise, window shrank 456 * after we sent into it. If window shrank to 0, 457 * cancel pending retransmit, pull snd_nxt back 458 * to (closed) window, and set the persist timer 459 * if it isn't already going. If the window didn't 460 * close completely, just wait for an ACK. 461 * 462 * We also do a general check here to ensure that 463 * we will set the persist timer when we have data 464 * to send, but a 0-byte window. This makes sure 465 * the persist timer is set even if the packet 466 * hits one of the "goto send" lines below. 467 */ 468 len = 0; 469 if ((sendwin == 0) && (TCPS_HAVEESTABLISHED(tp->t_state)) && 470 (off < (int) sbavail(&so->so_snd))) { 471 tcp_timer_activate(tp, TT_REXMT, 0); 472 tp->t_rxtshift = 0; 473 tp->snd_nxt = tp->snd_una; 474 if (!tcp_timer_active(tp, TT_PERSIST)) 475 tcp_setpersist(tp); 476 } 477 } 478 479 /* len will be >= 0 after this point. */ 480 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 481 482 /* 483 * Automatic sizing of send socket buffer. Often the send buffer 484 * size is not optimally adjusted to the actual network conditions 485 * at hand (delay bandwidth product). Setting the buffer size too 486 * small limits throughput on links with high bandwidth and high 487 * delay (eg. trans-continental/oceanic links). Setting the 488 * buffer size too big consumes too much real kernel memory, 489 * especially with many connections on busy servers. 490 * 491 * The criteria to step up the send buffer one notch are: 492 * 1. receive window of remote host is larger than send buffer 493 * (with a fudge factor of 5/4th); 494 * 2. send buffer is filled to 7/8th with data (so we actually 495 * have data to make use of it); 496 * 3. send buffer fill has not hit maximal automatic size; 497 * 4. our send window (slow start and cogestion controlled) is 498 * larger than sent but unacknowledged data in send buffer. 499 * 500 * The remote host receive window scaling factor may limit the 501 * growing of the send buffer before it reaches its allowed 502 * maximum. 503 * 504 * It scales directly with slow start or congestion window 505 * and does at most one step per received ACK. This fast 506 * scaling has the drawback of growing the send buffer beyond 507 * what is strictly necessary to make full use of a given 508 * delay*bandwidth product. However testing has shown this not 509 * to be much of an problem. At worst we are trading wasting 510 * of available bandwidth (the non-use of it) for wasting some 511 * socket buffer memory. 512 * 513 * TODO: Shrink send buffer during idle periods together 514 * with congestion window. Requires another timer. Has to 515 * wait for upcoming tcp timer rewrite. 516 * 517 * XXXGL: should there be used sbused() or sbavail()? 518 */ 519 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 520 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 521 sbused(&so->so_snd) >= (so->so_snd.sb_hiwat / 8 * 7) && 522 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 523 sendwin >= (sbused(&so->so_snd) - 524 (tp->snd_nxt - tp->snd_una))) { 525 if (!sbreserve_locked(&so->so_snd, 526 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 527 V_tcp_autosndbuf_max), so, curthread)) 528 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 529 } 530 } 531 532 /* 533 * Decide if we can use TCP Segmentation Offloading (if supported by 534 * hardware). 535 * 536 * TSO may only be used if we are in a pure bulk sending state. The 537 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 538 * IP options prevent using TSO. With TSO the TCP header is the same 539 * (except for the sequence number) for all generated packets. This 540 * makes it impossible to transmit any options which vary per generated 541 * segment or packet. 542 */ 543 #ifdef IPSEC 544 /* 545 * Pre-calculate here as we save another lookup into the darknesses 546 * of IPsec that way and can actually decide if TSO is ok. 547 */ 548 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 549 #endif 550 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 551 ((tp->t_flags & TF_SIGNATURE) == 0) && 552 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 553 #ifdef IPSEC 554 ipsec_optlen == 0 && 555 #endif 556 tp->t_inpcb->inp_options == NULL && 557 tp->t_inpcb->in6p_options == NULL) 558 tso = 1; 559 560 if (sack_rxmit) { 561 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 562 flags &= ~TH_FIN; 563 } else { 564 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 565 sbused(&so->so_snd))) 566 flags &= ~TH_FIN; 567 } 568 569 recwin = lmin(lmax(sbspace(&so->so_rcv), 0), 570 (long)TCP_MAXWIN << tp->rcv_scale); 571 572 /* 573 * Sender silly window avoidance. We transmit under the following 574 * conditions when len is non-zero: 575 * 576 * - We have a full segment (or more with TSO) 577 * - This is the last buffer in a write()/send() and we are 578 * either idle or running NODELAY 579 * - we've timed out (e.g. persist timer) 580 * - we have more then 1/2 the maximum send window's worth of 581 * data (receiver may be limited the window size) 582 * - we need to retransmit 583 */ 584 if (len) { 585 if (len >= tp->t_maxseg) 586 goto send; 587 /* 588 * NOTE! on localhost connections an 'ack' from the remote 589 * end may occur synchronously with the output and cause 590 * us to flush a buffer queued with moretocome. XXX 591 * 592 * note: the len + off check is almost certainly unnecessary. 593 */ 594 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 595 (idle || (tp->t_flags & TF_NODELAY)) && 596 (uint32_t)len + (uint32_t)off >= sbavail(&so->so_snd) && 597 (tp->t_flags & TF_NOPUSH) == 0) { 598 goto send; 599 } 600 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 601 goto send; 602 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 603 goto send; 604 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 605 goto send; 606 if (sack_rxmit) 607 goto send; 608 } 609 610 /* 611 * Sending of standalone window updates. 612 * 613 * Window updates are important when we close our window due to a 614 * full socket buffer and are opening it again after the application 615 * reads data from it. Once the window has opened again and the 616 * remote end starts to send again the ACK clock takes over and 617 * provides the most current window information. 618 * 619 * We must avoid the silly window syndrome whereas every read 620 * from the receive buffer, no matter how small, causes a window 621 * update to be sent. We also should avoid sending a flurry of 622 * window updates when the socket buffer had queued a lot of data 623 * and the application is doing small reads. 624 * 625 * Prevent a flurry of pointless window updates by only sending 626 * an update when we can increase the advertized window by more 627 * than 1/4th of the socket buffer capacity. When the buffer is 628 * getting full or is very small be more aggressive and send an 629 * update whenever we can increase by two mss sized segments. 630 * In all other situations the ACK's to new incoming data will 631 * carry further window increases. 632 * 633 * Don't send an independent window update if a delayed 634 * ACK is pending (it will get piggy-backed on it) or the 635 * remote side already has done a half-close and won't send 636 * more data. Skip this if the connection is in T/TCP 637 * half-open state. 638 */ 639 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 640 !(tp->t_flags & TF_DELACK) && 641 !TCPS_HAVERCVDFIN(tp->t_state)) { 642 /* 643 * "adv" is the amount we could increase the window, 644 * taking into account that we are limited by 645 * TCP_MAXWIN << tp->rcv_scale. 646 */ 647 int32_t adv; 648 int oldwin; 649 650 adv = recwin; 651 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 652 oldwin = (tp->rcv_adv - tp->rcv_nxt); 653 adv -= oldwin; 654 } else 655 oldwin = 0; 656 657 /* 658 * If the new window size ends up being the same as or less 659 * than the old size when it is scaled, then don't force 660 * a window update. 661 */ 662 if (oldwin >> tp->rcv_scale >= (adv + oldwin) >> tp->rcv_scale) 663 goto dontupdate; 664 665 if (adv >= (int32_t)(2 * tp->t_maxseg) && 666 (adv >= (int32_t)(so->so_rcv.sb_hiwat / 4) || 667 recwin <= (so->so_rcv.sb_hiwat / 8) || 668 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 669 goto send; 670 } 671 dontupdate: 672 673 /* 674 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 675 * is also a catch-all for the retransmit timer timeout case. 676 */ 677 if (tp->t_flags & TF_ACKNOW) 678 goto send; 679 if ((flags & TH_RST) || 680 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 681 goto send; 682 if (SEQ_GT(tp->snd_up, tp->snd_una)) 683 goto send; 684 /* 685 * If our state indicates that FIN should be sent 686 * and we have not yet done so, then we need to send. 687 */ 688 if (flags & TH_FIN && 689 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 690 goto send; 691 /* 692 * In SACK, it is possible for tcp_output to fail to send a segment 693 * after the retransmission timer has been turned off. Make sure 694 * that the retransmission timer is set. 695 */ 696 if ((tp->t_flags & TF_SACK_PERMIT) && 697 SEQ_GT(tp->snd_max, tp->snd_una) && 698 !tcp_timer_active(tp, TT_REXMT) && 699 !tcp_timer_active(tp, TT_PERSIST)) { 700 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 701 goto just_return; 702 } 703 /* 704 * TCP window updates are not reliable, rather a polling protocol 705 * using ``persist'' packets is used to insure receipt of window 706 * updates. The three ``states'' for the output side are: 707 * idle not doing retransmits or persists 708 * persisting to move a small or zero window 709 * (re)transmitting and thereby not persisting 710 * 711 * tcp_timer_active(tp, TT_PERSIST) 712 * is true when we are in persist state. 713 * (tp->t_flags & TF_FORCEDATA) 714 * is set when we are called to send a persist packet. 715 * tcp_timer_active(tp, TT_REXMT) 716 * is set when we are retransmitting 717 * The output side is idle when both timers are zero. 718 * 719 * If send window is too small, there is data to transmit, and no 720 * retransmit or persist is pending, then go to persist state. 721 * If nothing happens soon, send when timer expires: 722 * if window is nonzero, transmit what we can, 723 * otherwise force out a byte. 724 */ 725 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 726 !tcp_timer_active(tp, TT_PERSIST)) { 727 tp->t_rxtshift = 0; 728 tcp_setpersist(tp); 729 } 730 731 /* 732 * No reason to send a segment, just return. 733 */ 734 just_return: 735 SOCKBUF_UNLOCK(&so->so_snd); 736 return (0); 737 738 send: 739 SOCKBUF_LOCK_ASSERT(&so->so_snd); 740 if (len > 0) { 741 if (len >= tp->t_maxseg) 742 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 743 else 744 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 745 } 746 /* 747 * Before ESTABLISHED, force sending of initial options 748 * unless TCP set not to do any options. 749 * NOTE: we assume that the IP/TCP header plus TCP options 750 * always fit in a single mbuf, leaving room for a maximum 751 * link header, i.e. 752 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 753 */ 754 optlen = 0; 755 #ifdef INET6 756 if (isipv6) 757 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 758 else 759 #endif 760 hdrlen = sizeof (struct tcpiphdr); 761 762 /* 763 * Compute options for segment. 764 * We only have to care about SYN and established connection 765 * segments. Options for SYN-ACK segments are handled in TCP 766 * syncache. 767 */ 768 to.to_flags = 0; 769 if ((tp->t_flags & TF_NOOPT) == 0) { 770 /* Maximum segment size. */ 771 if (flags & TH_SYN) { 772 tp->snd_nxt = tp->iss; 773 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 774 to.to_flags |= TOF_MSS; 775 #ifdef TCP_RFC7413 776 /* 777 * Only include the TFO option on the first 778 * transmission of the SYN|ACK on a 779 * passively-created TFO socket, as the presence of 780 * the TFO option may have caused the original 781 * SYN|ACK to have been dropped by a middlebox. 782 */ 783 if ((tp->t_flags & TF_FASTOPEN) && 784 (tp->t_state == TCPS_SYN_RECEIVED) && 785 (tp->t_rxtshift == 0)) { 786 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 787 to.to_tfo_cookie = (u_char *)&tp->t_tfo_cookie; 788 to.to_flags |= TOF_FASTOPEN; 789 } 790 #endif 791 } 792 /* Window scaling. */ 793 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 794 to.to_wscale = tp->request_r_scale; 795 to.to_flags |= TOF_SCALE; 796 } 797 /* Timestamps. */ 798 if ((tp->t_flags & TF_RCVD_TSTMP) || 799 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 800 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 801 to.to_tsecr = tp->ts_recent; 802 to.to_flags |= TOF_TS; 803 /* Set receive buffer autosizing timestamp. */ 804 if (tp->rfbuf_ts == 0 && 805 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 806 tp->rfbuf_ts = tcp_ts_getticks(); 807 } 808 /* Selective ACK's. */ 809 if (tp->t_flags & TF_SACK_PERMIT) { 810 if (flags & TH_SYN) 811 to.to_flags |= TOF_SACKPERM; 812 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 813 (tp->t_flags & TF_SACK_PERMIT) && 814 tp->rcv_numsacks > 0) { 815 to.to_flags |= TOF_SACK; 816 to.to_nsacks = tp->rcv_numsacks; 817 to.to_sacks = (u_char *)tp->sackblks; 818 } 819 } 820 #ifdef TCP_SIGNATURE 821 /* TCP-MD5 (RFC2385). */ 822 if (tp->t_flags & TF_SIGNATURE) 823 to.to_flags |= TOF_SIGNATURE; 824 #endif /* TCP_SIGNATURE */ 825 826 /* Processing the options. */ 827 hdrlen += optlen = tcp_addoptions(&to, opt); 828 } 829 830 #ifdef INET6 831 if (isipv6) 832 ipoptlen = ip6_optlen(tp->t_inpcb); 833 else 834 #endif 835 if (tp->t_inpcb->inp_options) 836 ipoptlen = tp->t_inpcb->inp_options->m_len - 837 offsetof(struct ipoption, ipopt_list); 838 else 839 ipoptlen = 0; 840 #ifdef IPSEC 841 ipoptlen += ipsec_optlen; 842 #endif 843 844 /* 845 * Adjust data length if insertion of options will 846 * bump the packet length beyond the t_maxseg length. 847 * Clear the FIN bit because we cut off the tail of 848 * the segment. 849 */ 850 if (len + optlen + ipoptlen > tp->t_maxseg) { 851 flags &= ~TH_FIN; 852 853 if (tso) { 854 u_int if_hw_tsomax; 855 u_int if_hw_tsomaxsegcount; 856 u_int if_hw_tsomaxsegsize; 857 struct mbuf *mb; 858 u_int moff; 859 int max_len; 860 861 /* extract TSO information */ 862 if_hw_tsomax = tp->t_tsomax; 863 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 864 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 865 866 /* 867 * Limit a TSO burst to prevent it from 868 * overflowing or exceeding the maximum length 869 * allowed by the network interface: 870 */ 871 KASSERT(ipoptlen == 0, 872 ("%s: TSO can't do IP options", __func__)); 873 874 /* 875 * Check if we should limit by maximum payload 876 * length: 877 */ 878 if (if_hw_tsomax != 0) { 879 /* compute maximum TSO length */ 880 max_len = (if_hw_tsomax - hdrlen - 881 max_linkhdr); 882 if (max_len <= 0) { 883 len = 0; 884 } else if (len > max_len) { 885 sendalot = 1; 886 len = max_len; 887 } 888 } 889 890 /* 891 * Check if we should limit by maximum segment 892 * size and count: 893 */ 894 if (if_hw_tsomaxsegcount != 0 && 895 if_hw_tsomaxsegsize != 0) { 896 /* 897 * Subtract one segment for the LINK 898 * and TCP/IP headers mbuf that will 899 * be prepended to this mbuf chain 900 * after the code in this section 901 * limits the number of mbufs in the 902 * chain to if_hw_tsomaxsegcount. 903 */ 904 if_hw_tsomaxsegcount -= 1; 905 max_len = 0; 906 mb = sbsndmbuf(&so->so_snd, off, &moff); 907 908 while (mb != NULL && max_len < len) { 909 u_int mlen; 910 u_int frags; 911 912 /* 913 * Get length of mbuf fragment 914 * and how many hardware frags, 915 * rounded up, it would use: 916 */ 917 mlen = (mb->m_len - moff); 918 frags = howmany(mlen, 919 if_hw_tsomaxsegsize); 920 921 /* Handle special case: Zero Length Mbuf */ 922 if (frags == 0) 923 frags = 1; 924 925 /* 926 * Check if the fragment limit 927 * will be reached or exceeded: 928 */ 929 if (frags >= if_hw_tsomaxsegcount) { 930 max_len += min(mlen, 931 if_hw_tsomaxsegcount * 932 if_hw_tsomaxsegsize); 933 break; 934 } 935 max_len += mlen; 936 if_hw_tsomaxsegcount -= frags; 937 moff = 0; 938 mb = mb->m_next; 939 } 940 if (max_len <= 0) { 941 len = 0; 942 } else if (len > max_len) { 943 sendalot = 1; 944 len = max_len; 945 } 946 } 947 948 /* 949 * Prevent the last segment from being 950 * fractional unless the send sockbuf can be 951 * emptied: 952 */ 953 max_len = (tp->t_maxseg - optlen); 954 if (((uint32_t)off + (uint32_t)len) < 955 sbavail(&so->so_snd)) { 956 moff = len % max_len; 957 if (moff != 0) { 958 len -= moff; 959 sendalot = 1; 960 } 961 } 962 963 /* 964 * In case there are too many small fragments 965 * don't use TSO: 966 */ 967 if (len <= max_len) { 968 len = max_len; 969 sendalot = 1; 970 tso = 0; 971 } 972 973 /* 974 * Send the FIN in a separate segment 975 * after the bulk sending is done. 976 * We don't trust the TSO implementations 977 * to clear the FIN flag on all but the 978 * last segment. 979 */ 980 if (tp->t_flags & TF_NEEDFIN) 981 sendalot = 1; 982 983 } else { 984 len = tp->t_maxseg - optlen - ipoptlen; 985 sendalot = 1; 986 } 987 } else 988 tso = 0; 989 990 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 991 ("%s: len > IP_MAXPACKET", __func__)); 992 993 /*#ifdef DIAGNOSTIC*/ 994 #ifdef INET6 995 if (max_linkhdr + hdrlen > MCLBYTES) 996 #else 997 if (max_linkhdr + hdrlen > MHLEN) 998 #endif 999 panic("tcphdr too big"); 1000 /*#endif*/ 1001 1002 /* 1003 * This KASSERT is here to catch edge cases at a well defined place. 1004 * Before, those had triggered (random) panic conditions further down. 1005 */ 1006 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1007 1008 /* 1009 * Grab a header mbuf, attaching a copy of data to 1010 * be transmitted, and initialize the header from 1011 * the template for sends on this connection. 1012 */ 1013 if (len) { 1014 struct mbuf *mb; 1015 u_int moff; 1016 1017 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 1018 TCPSTAT_INC(tcps_sndprobe); 1019 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1020 tp->t_sndrexmitpack++; 1021 TCPSTAT_INC(tcps_sndrexmitpack); 1022 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1023 } else { 1024 TCPSTAT_INC(tcps_sndpack); 1025 TCPSTAT_ADD(tcps_sndbyte, len); 1026 } 1027 #ifdef INET6 1028 if (MHLEN < hdrlen + max_linkhdr) 1029 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1030 else 1031 #endif 1032 m = m_gethdr(M_NOWAIT, MT_DATA); 1033 1034 if (m == NULL) { 1035 SOCKBUF_UNLOCK(&so->so_snd); 1036 error = ENOBUFS; 1037 sack_rxmit = 0; 1038 goto out; 1039 } 1040 1041 m->m_data += max_linkhdr; 1042 m->m_len = hdrlen; 1043 1044 /* 1045 * Start the m_copy functions from the closest mbuf 1046 * to the offset in the socket buffer chain. 1047 */ 1048 mb = sbsndptr(&so->so_snd, off, len, &moff); 1049 1050 if (len <= MHLEN - hdrlen - max_linkhdr) { 1051 m_copydata(mb, moff, len, 1052 mtod(m, caddr_t) + hdrlen); 1053 m->m_len += len; 1054 } else { 1055 m->m_next = m_copym(mb, moff, len, M_NOWAIT); 1056 if (m->m_next == NULL) { 1057 SOCKBUF_UNLOCK(&so->so_snd); 1058 (void) m_free(m); 1059 error = ENOBUFS; 1060 sack_rxmit = 0; 1061 goto out; 1062 } 1063 } 1064 1065 /* 1066 * If we're sending everything we've got, set PUSH. 1067 * (This will keep happy those implementations which only 1068 * give data to the user when a buffer fills or 1069 * a PUSH comes in.) 1070 */ 1071 if (((uint32_t)off + (uint32_t)len == sbused(&so->so_snd)) && 1072 !(flags & TH_SYN)) 1073 flags |= TH_PUSH; 1074 SOCKBUF_UNLOCK(&so->so_snd); 1075 } else { 1076 SOCKBUF_UNLOCK(&so->so_snd); 1077 if (tp->t_flags & TF_ACKNOW) 1078 TCPSTAT_INC(tcps_sndacks); 1079 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1080 TCPSTAT_INC(tcps_sndctrl); 1081 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1082 TCPSTAT_INC(tcps_sndurg); 1083 else 1084 TCPSTAT_INC(tcps_sndwinup); 1085 1086 m = m_gethdr(M_NOWAIT, MT_DATA); 1087 if (m == NULL) { 1088 error = ENOBUFS; 1089 sack_rxmit = 0; 1090 goto out; 1091 } 1092 #ifdef INET6 1093 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1094 MHLEN >= hdrlen) { 1095 M_ALIGN(m, hdrlen); 1096 } else 1097 #endif 1098 m->m_data += max_linkhdr; 1099 m->m_len = hdrlen; 1100 } 1101 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1102 m->m_pkthdr.rcvif = (struct ifnet *)0; 1103 #ifdef MAC 1104 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1105 #endif 1106 #ifdef INET6 1107 if (isipv6) { 1108 ip6 = mtod(m, struct ip6_hdr *); 1109 th = (struct tcphdr *)(ip6 + 1); 1110 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1111 } else 1112 #endif /* INET6 */ 1113 { 1114 ip = mtod(m, struct ip *); 1115 ipov = (struct ipovly *)ip; 1116 th = (struct tcphdr *)(ip + 1); 1117 tcpip_fillheaders(tp->t_inpcb, ip, th); 1118 } 1119 1120 /* 1121 * Fill in fields, remembering maximum advertised 1122 * window for use in delaying messages about window sizes. 1123 * If resending a FIN, be sure not to use a new sequence number. 1124 */ 1125 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1126 tp->snd_nxt == tp->snd_max) 1127 tp->snd_nxt--; 1128 /* 1129 * If we are starting a connection, send ECN setup 1130 * SYN packet. If we are on a retransmit, we may 1131 * resend those bits a number of times as per 1132 * RFC 3168. 1133 */ 1134 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1135 if (tp->t_rxtshift >= 1) { 1136 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1137 flags |= TH_ECE|TH_CWR; 1138 } else 1139 flags |= TH_ECE|TH_CWR; 1140 } 1141 1142 if (tp->t_state == TCPS_ESTABLISHED && 1143 (tp->t_flags & TF_ECN_PERMIT)) { 1144 /* 1145 * If the peer has ECN, mark data packets with 1146 * ECN capable transmission (ECT). 1147 * Ignore pure ack packets, retransmissions and window probes. 1148 */ 1149 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1150 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1151 #ifdef INET6 1152 if (isipv6) 1153 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1154 else 1155 #endif 1156 ip->ip_tos |= IPTOS_ECN_ECT0; 1157 TCPSTAT_INC(tcps_ecn_ect0); 1158 } 1159 1160 /* 1161 * Reply with proper ECN notifications. 1162 */ 1163 if (tp->t_flags & TF_ECN_SND_CWR) { 1164 flags |= TH_CWR; 1165 tp->t_flags &= ~TF_ECN_SND_CWR; 1166 } 1167 if (tp->t_flags & TF_ECN_SND_ECE) 1168 flags |= TH_ECE; 1169 } 1170 1171 /* 1172 * If we are doing retransmissions, then snd_nxt will 1173 * not reflect the first unsent octet. For ACK only 1174 * packets, we do not want the sequence number of the 1175 * retransmitted packet, we want the sequence number 1176 * of the next unsent octet. So, if there is no data 1177 * (and no SYN or FIN), use snd_max instead of snd_nxt 1178 * when filling in ti_seq. But if we are in persist 1179 * state, snd_max might reflect one byte beyond the 1180 * right edge of the window, so use snd_nxt in that 1181 * case, since we know we aren't doing a retransmission. 1182 * (retransmit and persist are mutually exclusive...) 1183 */ 1184 if (sack_rxmit == 0) { 1185 if (len || (flags & (TH_SYN|TH_FIN)) || 1186 tcp_timer_active(tp, TT_PERSIST)) 1187 th->th_seq = htonl(tp->snd_nxt); 1188 else 1189 th->th_seq = htonl(tp->snd_max); 1190 } else { 1191 th->th_seq = htonl(p->rxmit); 1192 p->rxmit += len; 1193 tp->sackhint.sack_bytes_rexmit += len; 1194 } 1195 th->th_ack = htonl(tp->rcv_nxt); 1196 if (optlen) { 1197 bcopy(opt, th + 1, optlen); 1198 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1199 } 1200 th->th_flags = flags; 1201 /* 1202 * Calculate receive window. Don't shrink window, 1203 * but avoid silly window syndrome. 1204 */ 1205 if (recwin < (so->so_rcv.sb_hiwat / 4) && 1206 recwin < tp->t_maxseg) 1207 recwin = 0; 1208 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1209 recwin < (tp->rcv_adv - tp->rcv_nxt)) 1210 recwin = (tp->rcv_adv - tp->rcv_nxt); 1211 1212 /* 1213 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1214 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1215 * case is handled in syncache. 1216 */ 1217 if (flags & TH_SYN) 1218 th->th_win = htons((u_short) 1219 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1220 else 1221 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1222 1223 /* 1224 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1225 * a 0 window. This may cause the remote transmitter to stall. This 1226 * flag tells soreceive() to disable delayed acknowledgements when 1227 * draining the buffer. This can occur if the receiver is attempting 1228 * to read more data than can be buffered prior to transmitting on 1229 * the connection. 1230 */ 1231 if (th->th_win == 0) { 1232 tp->t_sndzerowin++; 1233 tp->t_flags |= TF_RXWIN0SENT; 1234 } else 1235 tp->t_flags &= ~TF_RXWIN0SENT; 1236 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1237 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1238 th->th_flags |= TH_URG; 1239 } else 1240 /* 1241 * If no urgent pointer to send, then we pull 1242 * the urgent pointer to the left edge of the send window 1243 * so that it doesn't drift into the send window on sequence 1244 * number wraparound. 1245 */ 1246 tp->snd_up = tp->snd_una; /* drag it along */ 1247 1248 #ifdef TCP_SIGNATURE 1249 if (to.to_flags & TOF_SIGNATURE) { 1250 int sigoff = to.to_signature - opt; 1251 tcp_signature_compute(m, 0, len, optlen, 1252 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1253 } 1254 #endif 1255 1256 /* 1257 * Put TCP length in extended header, and then 1258 * checksum extended header and data. 1259 */ 1260 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1261 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1262 #ifdef INET6 1263 if (isipv6) { 1264 /* 1265 * ip6_plen is not need to be filled now, and will be filled 1266 * in ip6_output. 1267 */ 1268 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1269 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1270 optlen + len, IPPROTO_TCP, 0); 1271 } 1272 #endif 1273 #if defined(INET6) && defined(INET) 1274 else 1275 #endif 1276 #ifdef INET 1277 { 1278 m->m_pkthdr.csum_flags = CSUM_TCP; 1279 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1280 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1281 1282 /* IP version must be set here for ipv4/ipv6 checking later */ 1283 KASSERT(ip->ip_v == IPVERSION, 1284 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1285 } 1286 #endif 1287 1288 /* 1289 * Enable TSO and specify the size of the segments. 1290 * The TCP pseudo header checksum is always provided. 1291 */ 1292 if (tso) { 1293 KASSERT(len > tp->t_maxseg - optlen, 1294 ("%s: len <= tso_segsz", __func__)); 1295 m->m_pkthdr.csum_flags |= CSUM_TSO; 1296 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1297 } 1298 1299 #ifdef IPSEC 1300 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1301 ("%s: mbuf chain shorter than expected: %d + %u + %u - %u != %u", 1302 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1303 #else 1304 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1305 ("%s: mbuf chain shorter than expected: %d + %u + %u != %u", 1306 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1307 #endif 1308 1309 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1310 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1311 1312 #ifdef TCPDEBUG 1313 /* 1314 * Trace. 1315 */ 1316 if (so->so_options & SO_DEBUG) { 1317 u_short save = 0; 1318 #ifdef INET6 1319 if (!isipv6) 1320 #endif 1321 { 1322 save = ipov->ih_len; 1323 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1324 } 1325 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1326 #ifdef INET6 1327 if (!isipv6) 1328 #endif 1329 ipov->ih_len = save; 1330 } 1331 #endif /* TCPDEBUG */ 1332 TCP_PROBE3(debug__output, tp, th, mtod(m, const char *)); 1333 1334 /* 1335 * Fill in IP length and desired time to live and 1336 * send to IP level. There should be a better way 1337 * to handle ttl and tos; we could keep them in 1338 * the template, but need a way to checksum without them. 1339 */ 1340 /* 1341 * m->m_pkthdr.len should have been set before checksum calculation, 1342 * because in6_cksum() need it. 1343 */ 1344 #ifdef INET6 1345 if (isipv6) { 1346 struct route_in6 ro; 1347 1348 bzero(&ro, sizeof(ro)); 1349 /* 1350 * we separately set hoplimit for every segment, since the 1351 * user might want to change the value via setsockopt. 1352 * Also, desired default hop limit might be changed via 1353 * Neighbor Discovery. 1354 */ 1355 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1356 1357 /* 1358 * Set the packet size here for the benefit of DTrace probes. 1359 * ip6_output() will set it properly; it's supposed to include 1360 * the option header lengths as well. 1361 */ 1362 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1363 1364 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1365 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1366 else 1367 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1368 1369 if (tp->t_state == TCPS_SYN_SENT) 1370 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1371 1372 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1373 1374 #ifdef TCPPCAP 1375 /* Save packet, if requested. */ 1376 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1377 #endif 1378 1379 /* TODO: IPv6 IP6TOS_ECT bit on */ 1380 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro, 1381 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1382 NULL, NULL, tp->t_inpcb); 1383 1384 if (error == EMSGSIZE && ro.ro_rt != NULL) 1385 mtu = ro.ro_rt->rt_mtu; 1386 RO_RTFREE(&ro); 1387 } 1388 #endif /* INET6 */ 1389 #if defined(INET) && defined(INET6) 1390 else 1391 #endif 1392 #ifdef INET 1393 { 1394 ip->ip_len = htons(m->m_pkthdr.len); 1395 #ifdef INET6 1396 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1397 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1398 #endif /* INET6 */ 1399 /* 1400 * If we do path MTU discovery, then we set DF on every packet. 1401 * This might not be the best thing to do according to RFC3390 1402 * Section 2. However the tcp hostcache migitates the problem 1403 * so it affects only the first tcp connection with a host. 1404 * 1405 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1406 */ 1407 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1408 ip->ip_off |= htons(IP_DF); 1409 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1410 } else { 1411 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1412 } 1413 1414 if (tp->t_state == TCPS_SYN_SENT) 1415 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1416 1417 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1418 1419 #ifdef TCPPCAP 1420 /* Save packet, if requested. */ 1421 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1422 #endif 1423 1424 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1425 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1426 tp->t_inpcb); 1427 1428 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_rt != NULL) 1429 mtu = tp->t_inpcb->inp_route.ro_rt->rt_mtu; 1430 } 1431 #endif /* INET */ 1432 1433 out: 1434 /* 1435 * In transmit state, time the transmission and arrange for 1436 * the retransmit. In persist state, just set snd_max. 1437 */ 1438 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1439 !tcp_timer_active(tp, TT_PERSIST)) { 1440 tcp_seq startseq = tp->snd_nxt; 1441 1442 /* 1443 * Advance snd_nxt over sequence space of this segment. 1444 */ 1445 if (flags & (TH_SYN|TH_FIN)) { 1446 if (flags & TH_SYN) 1447 tp->snd_nxt++; 1448 if (flags & TH_FIN) { 1449 tp->snd_nxt++; 1450 tp->t_flags |= TF_SENTFIN; 1451 } 1452 } 1453 if (sack_rxmit) 1454 goto timer; 1455 tp->snd_nxt += len; 1456 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1457 tp->snd_max = tp->snd_nxt; 1458 /* 1459 * Time this transmission if not a retransmission and 1460 * not currently timing anything. 1461 */ 1462 if (tp->t_rtttime == 0) { 1463 tp->t_rtttime = ticks; 1464 tp->t_rtseq = startseq; 1465 TCPSTAT_INC(tcps_segstimed); 1466 } 1467 } 1468 1469 /* 1470 * Set retransmit timer if not currently set, 1471 * and not doing a pure ack or a keep-alive probe. 1472 * Initial value for retransmit timer is smoothed 1473 * round-trip time + 2 * round-trip time variance. 1474 * Initialize shift counter which is used for backoff 1475 * of retransmit time. 1476 */ 1477 timer: 1478 if (!tcp_timer_active(tp, TT_REXMT) && 1479 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1480 (tp->snd_nxt != tp->snd_una))) { 1481 if (tcp_timer_active(tp, TT_PERSIST)) { 1482 tcp_timer_activate(tp, TT_PERSIST, 0); 1483 tp->t_rxtshift = 0; 1484 } 1485 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1486 } else if (len == 0 && sbavail(&so->so_snd) && 1487 !tcp_timer_active(tp, TT_REXMT) && 1488 !tcp_timer_active(tp, TT_PERSIST)) { 1489 /* 1490 * Avoid a situation where we do not set persist timer 1491 * after a zero window condition. For example: 1492 * 1) A -> B: packet with enough data to fill the window 1493 * 2) B -> A: ACK for #1 + new data (0 window 1494 * advertisement) 1495 * 3) A -> B: ACK for #2, 0 len packet 1496 * 1497 * In this case, A will not activate the persist timer, 1498 * because it chose to send a packet. Unless tcp_output 1499 * is called for some other reason (delayed ack timer, 1500 * another input packet from B, socket syscall), A will 1501 * not send zero window probes. 1502 * 1503 * So, if you send a 0-length packet, but there is data 1504 * in the socket buffer, and neither the rexmt or 1505 * persist timer is already set, then activate the 1506 * persist timer. 1507 */ 1508 tp->t_rxtshift = 0; 1509 tcp_setpersist(tp); 1510 } 1511 } else { 1512 /* 1513 * Persist case, update snd_max but since we are in 1514 * persist mode (no window) we do not update snd_nxt. 1515 */ 1516 int xlen = len; 1517 if (flags & TH_SYN) 1518 ++xlen; 1519 if (flags & TH_FIN) { 1520 ++xlen; 1521 tp->t_flags |= TF_SENTFIN; 1522 } 1523 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1524 tp->snd_max = tp->snd_nxt + xlen; 1525 } 1526 1527 if (error) { 1528 1529 /* 1530 * We know that the packet was lost, so back out the 1531 * sequence number advance, if any. 1532 * 1533 * If the error is EPERM the packet got blocked by the 1534 * local firewall. Normally we should terminate the 1535 * connection but the blocking may have been spurious 1536 * due to a firewall reconfiguration cycle. So we treat 1537 * it like a packet loss and let the retransmit timer and 1538 * timeouts do their work over time. 1539 * XXX: It is a POLA question whether calling tcp_drop right 1540 * away would be the really correct behavior instead. 1541 */ 1542 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1543 !tcp_timer_active(tp, TT_PERSIST)) && 1544 ((flags & TH_SYN) == 0) && 1545 (error != EPERM)) { 1546 if (sack_rxmit) { 1547 p->rxmit -= len; 1548 tp->sackhint.sack_bytes_rexmit -= len; 1549 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1550 ("sackhint bytes rtx >= 0")); 1551 } else 1552 tp->snd_nxt -= len; 1553 } 1554 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1555 switch (error) { 1556 case EPERM: 1557 tp->t_softerror = error; 1558 return (error); 1559 case ENOBUFS: 1560 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1561 tp->snd_cwnd = tp->t_maxseg; 1562 return (0); 1563 case EMSGSIZE: 1564 /* 1565 * For some reason the interface we used initially 1566 * to send segments changed to another or lowered 1567 * its MTU. 1568 * If TSO was active we either got an interface 1569 * without TSO capabilits or TSO was turned off. 1570 * If we obtained mtu from ip_output() then update 1571 * it and try again. 1572 */ 1573 if (tso) 1574 tp->t_flags &= ~TF_TSO; 1575 if (mtu != 0) { 1576 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1577 goto again; 1578 } 1579 return (error); 1580 case EHOSTDOWN: 1581 case EHOSTUNREACH: 1582 case ENETDOWN: 1583 case ENETUNREACH: 1584 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1585 tp->t_softerror = error; 1586 return (0); 1587 } 1588 /* FALLTHROUGH */ 1589 default: 1590 return (error); 1591 } 1592 } 1593 TCPSTAT_INC(tcps_sndtotal); 1594 1595 /* 1596 * Data sent (as far as we can tell). 1597 * If this advertises a larger window than any other segment, 1598 * then remember the size of the advertised window. 1599 * Any pending ACK has now been sent. 1600 */ 1601 if (SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1602 tp->rcv_adv = tp->rcv_nxt + recwin; 1603 tp->last_ack_sent = tp->rcv_nxt; 1604 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1605 if (tcp_timer_active(tp, TT_DELACK)) 1606 tcp_timer_activate(tp, TT_DELACK, 0); 1607 #if 0 1608 /* 1609 * This completely breaks TCP if newreno is turned on. What happens 1610 * is that if delayed-acks are turned on on the receiver, this code 1611 * on the transmitter effectively destroys the TCP window, forcing 1612 * it to four packets (1.5Kx4 = 6K window). 1613 */ 1614 if (sendalot && --maxburst) 1615 goto again; 1616 #endif 1617 if (sendalot) 1618 goto again; 1619 return (0); 1620 } 1621 1622 void 1623 tcp_setpersist(struct tcpcb *tp) 1624 { 1625 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1626 int tt; 1627 1628 tp->t_flags &= ~TF_PREVVALID; 1629 if (tcp_timer_active(tp, TT_REXMT)) 1630 panic("tcp_setpersist: retransmit pending"); 1631 /* 1632 * Start/restart persistence timer. 1633 */ 1634 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1635 tcp_persmin, tcp_persmax); 1636 tcp_timer_activate(tp, TT_PERSIST, tt); 1637 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1638 tp->t_rxtshift++; 1639 } 1640 1641 /* 1642 * Insert TCP options according to the supplied parameters to the place 1643 * optp in a consistent way. Can handle unaligned destinations. 1644 * 1645 * The order of the option processing is crucial for optimal packing and 1646 * alignment for the scarce option space. 1647 * 1648 * The optimal order for a SYN/SYN-ACK segment is: 1649 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1650 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1651 * 1652 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1653 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1654 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1655 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1656 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1657 */ 1658 int 1659 tcp_addoptions(struct tcpopt *to, u_char *optp) 1660 { 1661 u_int32_t mask, optlen = 0; 1662 1663 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1664 if ((to->to_flags & mask) != mask) 1665 continue; 1666 if (optlen == TCP_MAXOLEN) 1667 break; 1668 switch (to->to_flags & mask) { 1669 case TOF_MSS: 1670 while (optlen % 4) { 1671 optlen += TCPOLEN_NOP; 1672 *optp++ = TCPOPT_NOP; 1673 } 1674 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1675 continue; 1676 optlen += TCPOLEN_MAXSEG; 1677 *optp++ = TCPOPT_MAXSEG; 1678 *optp++ = TCPOLEN_MAXSEG; 1679 to->to_mss = htons(to->to_mss); 1680 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1681 optp += sizeof(to->to_mss); 1682 break; 1683 case TOF_SCALE: 1684 while (!optlen || optlen % 2 != 1) { 1685 optlen += TCPOLEN_NOP; 1686 *optp++ = TCPOPT_NOP; 1687 } 1688 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1689 continue; 1690 optlen += TCPOLEN_WINDOW; 1691 *optp++ = TCPOPT_WINDOW; 1692 *optp++ = TCPOLEN_WINDOW; 1693 *optp++ = to->to_wscale; 1694 break; 1695 case TOF_SACKPERM: 1696 while (optlen % 2) { 1697 optlen += TCPOLEN_NOP; 1698 *optp++ = TCPOPT_NOP; 1699 } 1700 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1701 continue; 1702 optlen += TCPOLEN_SACK_PERMITTED; 1703 *optp++ = TCPOPT_SACK_PERMITTED; 1704 *optp++ = TCPOLEN_SACK_PERMITTED; 1705 break; 1706 case TOF_TS: 1707 while (!optlen || optlen % 4 != 2) { 1708 optlen += TCPOLEN_NOP; 1709 *optp++ = TCPOPT_NOP; 1710 } 1711 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1712 continue; 1713 optlen += TCPOLEN_TIMESTAMP; 1714 *optp++ = TCPOPT_TIMESTAMP; 1715 *optp++ = TCPOLEN_TIMESTAMP; 1716 to->to_tsval = htonl(to->to_tsval); 1717 to->to_tsecr = htonl(to->to_tsecr); 1718 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1719 optp += sizeof(to->to_tsval); 1720 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1721 optp += sizeof(to->to_tsecr); 1722 break; 1723 #ifdef TCP_SIGNATURE 1724 case TOF_SIGNATURE: 1725 { 1726 int siglen = TCPOLEN_SIGNATURE - 2; 1727 1728 while (!optlen || optlen % 4 != 2) { 1729 optlen += TCPOLEN_NOP; 1730 *optp++ = TCPOPT_NOP; 1731 } 1732 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1733 continue; 1734 optlen += TCPOLEN_SIGNATURE; 1735 *optp++ = TCPOPT_SIGNATURE; 1736 *optp++ = TCPOLEN_SIGNATURE; 1737 to->to_signature = optp; 1738 while (siglen--) 1739 *optp++ = 0; 1740 break; 1741 } 1742 #endif 1743 case TOF_SACK: 1744 { 1745 int sackblks = 0; 1746 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1747 tcp_seq sack_seq; 1748 1749 while (!optlen || optlen % 4 != 2) { 1750 optlen += TCPOLEN_NOP; 1751 *optp++ = TCPOPT_NOP; 1752 } 1753 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1754 continue; 1755 optlen += TCPOLEN_SACKHDR; 1756 *optp++ = TCPOPT_SACK; 1757 sackblks = min(to->to_nsacks, 1758 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1759 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1760 while (sackblks--) { 1761 sack_seq = htonl(sack->start); 1762 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1763 optp += sizeof(sack_seq); 1764 sack_seq = htonl(sack->end); 1765 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1766 optp += sizeof(sack_seq); 1767 optlen += TCPOLEN_SACK; 1768 sack++; 1769 } 1770 TCPSTAT_INC(tcps_sack_send_blocks); 1771 break; 1772 } 1773 #ifdef TCP_RFC7413 1774 case TOF_FASTOPEN: 1775 { 1776 int total_len; 1777 1778 /* XXX is there any point to aligning this option? */ 1779 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1780 if (TCP_MAXOLEN - optlen < total_len) 1781 continue; 1782 *optp++ = TCPOPT_FAST_OPEN; 1783 *optp++ = total_len; 1784 if (to->to_tfo_len > 0) { 1785 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1786 optp += to->to_tfo_len; 1787 } 1788 optlen += total_len; 1789 break; 1790 } 1791 #endif 1792 default: 1793 panic("%s: unknown TCP option type", __func__); 1794 break; 1795 } 1796 } 1797 1798 /* Terminate and pad TCP options to a 4 byte boundary. */ 1799 if (optlen % 4) { 1800 optlen += TCPOLEN_EOL; 1801 *optp++ = TCPOPT_EOL; 1802 } 1803 /* 1804 * According to RFC 793 (STD0007): 1805 * "The content of the header beyond the End-of-Option option 1806 * must be header padding (i.e., zero)." 1807 * and later: "The padding is composed of zeros." 1808 */ 1809 while (optlen % 4) { 1810 optlen += TCPOLEN_PAD; 1811 *optp++ = TCPOPT_PAD; 1812 } 1813 1814 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1815 return (optlen); 1816 } 1817