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 long 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, long 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 long len, recwin, sendwin; 189 int off, flags, error = 0; /* Keep compiler happy */ 190 struct mbuf *m; 191 struct ip *ip = NULL; 192 struct ipovly *ipov = NULL; 193 struct tcphdr *th; 194 u_char opt[TCP_MAXOLEN]; 195 unsigned ipoptlen, optlen, hdrlen; 196 #ifdef IPSEC 197 unsigned ipsec_optlen = 0; 198 #endif 199 int idle, sendalot; 200 int sack_rxmit, sack_bytes_rxmt; 201 struct sackhole *p; 202 int tso, mtu; 203 struct tcpopt to; 204 #if 0 205 int maxburst = TCP_MAXBURST; 206 #endif 207 #ifdef INET6 208 struct ip6_hdr *ip6 = NULL; 209 int isipv6; 210 211 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 212 #endif 213 214 INP_WLOCK_ASSERT(tp->t_inpcb); 215 216 #ifdef TCP_OFFLOAD 217 if (tp->t_flags & TF_TOE) 218 return (tcp_offload_output(tp)); 219 #endif 220 221 #ifdef TCP_RFC7413 222 /* 223 * For TFO connections in SYN_RECEIVED, only allow the initial 224 * SYN|ACK and those sent by the retransmit timer. 225 */ 226 if ((tp->t_flags & TF_FASTOPEN) && 227 (tp->t_state == TCPS_SYN_RECEIVED) && 228 SEQ_GT(tp->snd_max, tp->snd_una) && /* initial SYN|ACK sent */ 229 (tp->snd_nxt != tp->snd_una)) /* not a retransmit */ 230 return (0); 231 #endif 232 /* 233 * Determine length of data that should be transmitted, 234 * and flags that will be used. 235 * If there is some data or critical controls (SYN, RST) 236 * to send, then transmit; otherwise, investigate further. 237 */ 238 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 239 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 240 cc_after_idle(tp); 241 tp->t_flags &= ~TF_LASTIDLE; 242 if (idle) { 243 if (tp->t_flags & TF_MORETOCOME) { 244 tp->t_flags |= TF_LASTIDLE; 245 idle = 0; 246 } 247 } 248 again: 249 /* 250 * If we've recently taken a timeout, snd_max will be greater than 251 * snd_nxt. There may be SACK information that allows us to avoid 252 * resending already delivered data. Adjust snd_nxt accordingly. 253 */ 254 if ((tp->t_flags & TF_SACK_PERMIT) && 255 SEQ_LT(tp->snd_nxt, tp->snd_max)) 256 tcp_sack_adjust(tp); 257 sendalot = 0; 258 tso = 0; 259 mtu = 0; 260 off = tp->snd_nxt - tp->snd_una; 261 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 262 263 flags = tcp_outflags[tp->t_state]; 264 /* 265 * Send any SACK-generated retransmissions. If we're explicitly trying 266 * to send out new data (when sendalot is 1), bypass this function. 267 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 268 * we're replacing a (future) new transmission with a retransmission 269 * now, and we previously incremented snd_cwnd in tcp_input(). 270 */ 271 /* 272 * Still in sack recovery , reset rxmit flag to zero. 273 */ 274 sack_rxmit = 0; 275 sack_bytes_rxmt = 0; 276 len = 0; 277 p = NULL; 278 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 279 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 280 long cwin; 281 282 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 283 if (cwin < 0) 284 cwin = 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 = ((long)ulmin(cwin, 304 tp->snd_recover - p->rxmit)); 305 } else 306 len = ((long)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 = ((long)ulmin(sbavail(&so->so_snd), sendwin) - 380 off); 381 else { 382 long 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 = ((long)ulmin(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 = lmin(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 = sbspace(&so->so_rcv); 570 571 /* 572 * Sender silly window avoidance. We transmit under the following 573 * conditions when len is non-zero: 574 * 575 * - We have a full segment (or more with TSO) 576 * - This is the last buffer in a write()/send() and we are 577 * either idle or running NODELAY 578 * - we've timed out (e.g. persist timer) 579 * - we have more then 1/2 the maximum send window's worth of 580 * data (receiver may be limited the window size) 581 * - we need to retransmit 582 */ 583 if (len) { 584 if (len >= tp->t_maxseg) 585 goto send; 586 /* 587 * NOTE! on localhost connections an 'ack' from the remote 588 * end may occur synchronously with the output and cause 589 * us to flush a buffer queued with moretocome. XXX 590 * 591 * note: the len + off check is almost certainly unnecessary. 592 */ 593 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 594 (idle || (tp->t_flags & TF_NODELAY)) && 595 len + off >= sbavail(&so->so_snd) && 596 (tp->t_flags & TF_NOPUSH) == 0) { 597 goto send; 598 } 599 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 600 goto send; 601 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 602 goto send; 603 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 604 goto send; 605 if (sack_rxmit) 606 goto send; 607 } 608 609 /* 610 * Sending of standalone window updates. 611 * 612 * Window updates are important when we close our window due to a 613 * full socket buffer and are opening it again after the application 614 * reads data from it. Once the window has opened again and the 615 * remote end starts to send again the ACK clock takes over and 616 * provides the most current window information. 617 * 618 * We must avoid the silly window syndrome whereas every read 619 * from the receive buffer, no matter how small, causes a window 620 * update to be sent. We also should avoid sending a flurry of 621 * window updates when the socket buffer had queued a lot of data 622 * and the application is doing small reads. 623 * 624 * Prevent a flurry of pointless window updates by only sending 625 * an update when we can increase the advertized window by more 626 * than 1/4th of the socket buffer capacity. When the buffer is 627 * getting full or is very small be more aggressive and send an 628 * update whenever we can increase by two mss sized segments. 629 * In all other situations the ACK's to new incoming data will 630 * carry further window increases. 631 * 632 * Don't send an independent window update if a delayed 633 * ACK is pending (it will get piggy-backed on it) or the 634 * remote side already has done a half-close and won't send 635 * more data. Skip this if the connection is in T/TCP 636 * half-open state. 637 */ 638 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 639 !(tp->t_flags & TF_DELACK) && 640 !TCPS_HAVERCVDFIN(tp->t_state)) { 641 /* 642 * "adv" is the amount we could increase the window, 643 * taking into account that we are limited by 644 * TCP_MAXWIN << tp->rcv_scale. 645 */ 646 long adv; 647 int oldwin; 648 649 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale); 650 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 651 oldwin = (tp->rcv_adv - tp->rcv_nxt); 652 adv -= oldwin; 653 } else 654 oldwin = 0; 655 656 /* 657 * If the new window size ends up being the same as the old 658 * size when it is scaled, then don't force a window update. 659 */ 660 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale) 661 goto dontupdate; 662 663 if (adv >= (long)(2 * tp->t_maxseg) && 664 (adv >= (long)(so->so_rcv.sb_hiwat / 4) || 665 recwin <= (long)(so->so_rcv.sb_hiwat / 8) || 666 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 667 goto send; 668 } 669 dontupdate: 670 671 /* 672 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 673 * is also a catch-all for the retransmit timer timeout case. 674 */ 675 if (tp->t_flags & TF_ACKNOW) 676 goto send; 677 if ((flags & TH_RST) || 678 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 679 goto send; 680 if (SEQ_GT(tp->snd_up, tp->snd_una)) 681 goto send; 682 /* 683 * If our state indicates that FIN should be sent 684 * and we have not yet done so, then we need to send. 685 */ 686 if (flags & TH_FIN && 687 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 688 goto send; 689 /* 690 * In SACK, it is possible for tcp_output to fail to send a segment 691 * after the retransmission timer has been turned off. Make sure 692 * that the retransmission timer is set. 693 */ 694 if ((tp->t_flags & TF_SACK_PERMIT) && 695 SEQ_GT(tp->snd_max, tp->snd_una) && 696 !tcp_timer_active(tp, TT_REXMT) && 697 !tcp_timer_active(tp, TT_PERSIST)) { 698 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 699 goto just_return; 700 } 701 /* 702 * TCP window updates are not reliable, rather a polling protocol 703 * using ``persist'' packets is used to insure receipt of window 704 * updates. The three ``states'' for the output side are: 705 * idle not doing retransmits or persists 706 * persisting to move a small or zero window 707 * (re)transmitting and thereby not persisting 708 * 709 * tcp_timer_active(tp, TT_PERSIST) 710 * is true when we are in persist state. 711 * (tp->t_flags & TF_FORCEDATA) 712 * is set when we are called to send a persist packet. 713 * tcp_timer_active(tp, TT_REXMT) 714 * is set when we are retransmitting 715 * The output side is idle when both timers are zero. 716 * 717 * If send window is too small, there is data to transmit, and no 718 * retransmit or persist is pending, then go to persist state. 719 * If nothing happens soon, send when timer expires: 720 * if window is nonzero, transmit what we can, 721 * otherwise force out a byte. 722 */ 723 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 724 !tcp_timer_active(tp, TT_PERSIST)) { 725 tp->t_rxtshift = 0; 726 tcp_setpersist(tp); 727 } 728 729 /* 730 * No reason to send a segment, just return. 731 */ 732 just_return: 733 SOCKBUF_UNLOCK(&so->so_snd); 734 return (0); 735 736 send: 737 SOCKBUF_LOCK_ASSERT(&so->so_snd); 738 if (len > 0) { 739 if (len >= tp->t_maxseg) 740 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 741 else 742 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 743 } 744 /* 745 * Before ESTABLISHED, force sending of initial options 746 * unless TCP set not to do any options. 747 * NOTE: we assume that the IP/TCP header plus TCP options 748 * always fit in a single mbuf, leaving room for a maximum 749 * link header, i.e. 750 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 751 */ 752 optlen = 0; 753 #ifdef INET6 754 if (isipv6) 755 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 756 else 757 #endif 758 hdrlen = sizeof (struct tcpiphdr); 759 760 /* 761 * Compute options for segment. 762 * We only have to care about SYN and established connection 763 * segments. Options for SYN-ACK segments are handled in TCP 764 * syncache. 765 */ 766 to.to_flags = 0; 767 if ((tp->t_flags & TF_NOOPT) == 0) { 768 /* Maximum segment size. */ 769 if (flags & TH_SYN) { 770 tp->snd_nxt = tp->iss; 771 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 772 to.to_flags |= TOF_MSS; 773 #ifdef TCP_RFC7413 774 /* 775 * Only include the TFO option on the first 776 * transmission of the SYN|ACK on a 777 * passively-created TFO socket, as the presence of 778 * the TFO option may have caused the original 779 * SYN|ACK to have been dropped by a middlebox. 780 */ 781 if ((tp->t_flags & TF_FASTOPEN) && 782 (tp->t_state == TCPS_SYN_RECEIVED) && 783 (tp->t_rxtshift == 0)) { 784 to.to_tfo_len = TCP_FASTOPEN_COOKIE_LEN; 785 to.to_tfo_cookie = (u_char *)&tp->t_tfo_cookie; 786 to.to_flags |= TOF_FASTOPEN; 787 } 788 #endif 789 } 790 /* Window scaling. */ 791 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 792 to.to_wscale = tp->request_r_scale; 793 to.to_flags |= TOF_SCALE; 794 } 795 /* Timestamps. */ 796 if ((tp->t_flags & TF_RCVD_TSTMP) || 797 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 798 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 799 to.to_tsecr = tp->ts_recent; 800 to.to_flags |= TOF_TS; 801 /* Set receive buffer autosizing timestamp. */ 802 if (tp->rfbuf_ts == 0 && 803 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 804 tp->rfbuf_ts = tcp_ts_getticks(); 805 } 806 /* Selective ACK's. */ 807 if (tp->t_flags & TF_SACK_PERMIT) { 808 if (flags & TH_SYN) 809 to.to_flags |= TOF_SACKPERM; 810 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 811 (tp->t_flags & TF_SACK_PERMIT) && 812 tp->rcv_numsacks > 0) { 813 to.to_flags |= TOF_SACK; 814 to.to_nsacks = tp->rcv_numsacks; 815 to.to_sacks = (u_char *)tp->sackblks; 816 } 817 } 818 #ifdef TCP_SIGNATURE 819 /* TCP-MD5 (RFC2385). */ 820 if (tp->t_flags & TF_SIGNATURE) 821 to.to_flags |= TOF_SIGNATURE; 822 #endif /* TCP_SIGNATURE */ 823 824 /* Processing the options. */ 825 hdrlen += optlen = tcp_addoptions(&to, opt); 826 } 827 828 #ifdef INET6 829 if (isipv6) 830 ipoptlen = ip6_optlen(tp->t_inpcb); 831 else 832 #endif 833 if (tp->t_inpcb->inp_options) 834 ipoptlen = tp->t_inpcb->inp_options->m_len - 835 offsetof(struct ipoption, ipopt_list); 836 else 837 ipoptlen = 0; 838 #ifdef IPSEC 839 ipoptlen += ipsec_optlen; 840 #endif 841 842 /* 843 * Adjust data length if insertion of options will 844 * bump the packet length beyond the t_maxseg length. 845 * Clear the FIN bit because we cut off the tail of 846 * the segment. 847 */ 848 if (len + optlen + ipoptlen > tp->t_maxseg) { 849 flags &= ~TH_FIN; 850 851 if (tso) { 852 u_int if_hw_tsomax; 853 u_int if_hw_tsomaxsegcount; 854 u_int if_hw_tsomaxsegsize; 855 struct mbuf *mb; 856 u_int moff; 857 int max_len; 858 859 /* extract TSO information */ 860 if_hw_tsomax = tp->t_tsomax; 861 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 862 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 863 864 /* 865 * Limit a TSO burst to prevent it from 866 * overflowing or exceeding the maximum length 867 * allowed by the network interface: 868 */ 869 KASSERT(ipoptlen == 0, 870 ("%s: TSO can't do IP options", __func__)); 871 872 /* 873 * Check if we should limit by maximum payload 874 * length: 875 */ 876 if (if_hw_tsomax != 0) { 877 /* compute maximum TSO length */ 878 max_len = (if_hw_tsomax - hdrlen - 879 max_linkhdr); 880 if (max_len <= 0) { 881 len = 0; 882 } else if (len > max_len) { 883 sendalot = 1; 884 len = max_len; 885 } 886 } 887 888 /* 889 * Check if we should limit by maximum segment 890 * size and count: 891 */ 892 if (if_hw_tsomaxsegcount != 0 && 893 if_hw_tsomaxsegsize != 0) { 894 /* 895 * Subtract one segment for the LINK 896 * and TCP/IP headers mbuf that will 897 * be prepended to this mbuf chain 898 * after the code in this section 899 * limits the number of mbufs in the 900 * chain to if_hw_tsomaxsegcount. 901 */ 902 if_hw_tsomaxsegcount -= 1; 903 max_len = 0; 904 mb = sbsndmbuf(&so->so_snd, off, &moff); 905 906 while (mb != NULL && max_len < len) { 907 u_int mlen; 908 u_int frags; 909 910 /* 911 * Get length of mbuf fragment 912 * and how many hardware frags, 913 * rounded up, it would use: 914 */ 915 mlen = (mb->m_len - moff); 916 frags = howmany(mlen, 917 if_hw_tsomaxsegsize); 918 919 /* Handle special case: Zero Length Mbuf */ 920 if (frags == 0) 921 frags = 1; 922 923 /* 924 * Check if the fragment limit 925 * will be reached or exceeded: 926 */ 927 if (frags >= if_hw_tsomaxsegcount) { 928 max_len += min(mlen, 929 if_hw_tsomaxsegcount * 930 if_hw_tsomaxsegsize); 931 break; 932 } 933 max_len += mlen; 934 if_hw_tsomaxsegcount -= frags; 935 moff = 0; 936 mb = mb->m_next; 937 } 938 if (max_len <= 0) { 939 len = 0; 940 } else if (len > max_len) { 941 sendalot = 1; 942 len = max_len; 943 } 944 } 945 946 /* 947 * Prevent the last segment from being 948 * fractional unless the send sockbuf can be 949 * emptied: 950 */ 951 max_len = (tp->t_maxseg - optlen); 952 if ((off + len) < sbavail(&so->so_snd)) { 953 moff = len % max_len; 954 if (moff != 0) { 955 len -= moff; 956 sendalot = 1; 957 } 958 } 959 960 /* 961 * In case there are too many small fragments 962 * don't use TSO: 963 */ 964 if (len <= max_len) { 965 len = max_len; 966 sendalot = 1; 967 tso = 0; 968 } 969 970 /* 971 * Send the FIN in a separate segment 972 * after the bulk sending is done. 973 * We don't trust the TSO implementations 974 * to clear the FIN flag on all but the 975 * last segment. 976 */ 977 if (tp->t_flags & TF_NEEDFIN) 978 sendalot = 1; 979 980 } else { 981 len = tp->t_maxseg - optlen - ipoptlen; 982 sendalot = 1; 983 } 984 } else 985 tso = 0; 986 987 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 988 ("%s: len > IP_MAXPACKET", __func__)); 989 990 /*#ifdef DIAGNOSTIC*/ 991 #ifdef INET6 992 if (max_linkhdr + hdrlen > MCLBYTES) 993 #else 994 if (max_linkhdr + hdrlen > MHLEN) 995 #endif 996 panic("tcphdr too big"); 997 /*#endif*/ 998 999 /* 1000 * This KASSERT is here to catch edge cases at a well defined place. 1001 * Before, those had triggered (random) panic conditions further down. 1002 */ 1003 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 1004 1005 /* 1006 * Grab a header mbuf, attaching a copy of data to 1007 * be transmitted, and initialize the header from 1008 * the template for sends on this connection. 1009 */ 1010 if (len) { 1011 struct mbuf *mb; 1012 u_int moff; 1013 1014 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 1015 TCPSTAT_INC(tcps_sndprobe); 1016 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 1017 tp->t_sndrexmitpack++; 1018 TCPSTAT_INC(tcps_sndrexmitpack); 1019 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 1020 } else { 1021 TCPSTAT_INC(tcps_sndpack); 1022 TCPSTAT_ADD(tcps_sndbyte, len); 1023 } 1024 #ifdef INET6 1025 if (MHLEN < hdrlen + max_linkhdr) 1026 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 1027 else 1028 #endif 1029 m = m_gethdr(M_NOWAIT, MT_DATA); 1030 1031 if (m == NULL) { 1032 SOCKBUF_UNLOCK(&so->so_snd); 1033 error = ENOBUFS; 1034 sack_rxmit = 0; 1035 goto out; 1036 } 1037 1038 m->m_data += max_linkhdr; 1039 m->m_len = hdrlen; 1040 1041 /* 1042 * Start the m_copy functions from the closest mbuf 1043 * to the offset in the socket buffer chain. 1044 */ 1045 mb = sbsndptr(&so->so_snd, off, len, &moff); 1046 1047 if (len <= MHLEN - hdrlen - max_linkhdr) { 1048 m_copydata(mb, moff, (int)len, 1049 mtod(m, caddr_t) + hdrlen); 1050 m->m_len += len; 1051 } else { 1052 m->m_next = m_copym(mb, moff, len, M_NOWAIT); 1053 if (m->m_next == NULL) { 1054 SOCKBUF_UNLOCK(&so->so_snd); 1055 (void) m_free(m); 1056 error = ENOBUFS; 1057 sack_rxmit = 0; 1058 goto out; 1059 } 1060 } 1061 1062 /* 1063 * If we're sending everything we've got, set PUSH. 1064 * (This will keep happy those implementations which only 1065 * give data to the user when a buffer fills or 1066 * a PUSH comes in.) 1067 */ 1068 if ((off + len == sbused(&so->so_snd)) && !(flags & TH_SYN)) 1069 flags |= TH_PUSH; 1070 SOCKBUF_UNLOCK(&so->so_snd); 1071 } else { 1072 SOCKBUF_UNLOCK(&so->so_snd); 1073 if (tp->t_flags & TF_ACKNOW) 1074 TCPSTAT_INC(tcps_sndacks); 1075 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 1076 TCPSTAT_INC(tcps_sndctrl); 1077 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 1078 TCPSTAT_INC(tcps_sndurg); 1079 else 1080 TCPSTAT_INC(tcps_sndwinup); 1081 1082 m = m_gethdr(M_NOWAIT, MT_DATA); 1083 if (m == NULL) { 1084 error = ENOBUFS; 1085 sack_rxmit = 0; 1086 goto out; 1087 } 1088 #ifdef INET6 1089 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1090 MHLEN >= hdrlen) { 1091 M_ALIGN(m, hdrlen); 1092 } else 1093 #endif 1094 m->m_data += max_linkhdr; 1095 m->m_len = hdrlen; 1096 } 1097 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1098 m->m_pkthdr.rcvif = (struct ifnet *)0; 1099 #ifdef MAC 1100 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1101 #endif 1102 #ifdef INET6 1103 if (isipv6) { 1104 ip6 = mtod(m, struct ip6_hdr *); 1105 th = (struct tcphdr *)(ip6 + 1); 1106 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1107 } else 1108 #endif /* INET6 */ 1109 { 1110 ip = mtod(m, struct ip *); 1111 ipov = (struct ipovly *)ip; 1112 th = (struct tcphdr *)(ip + 1); 1113 tcpip_fillheaders(tp->t_inpcb, ip, th); 1114 } 1115 1116 /* 1117 * Fill in fields, remembering maximum advertised 1118 * window for use in delaying messages about window sizes. 1119 * If resending a FIN, be sure not to use a new sequence number. 1120 */ 1121 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1122 tp->snd_nxt == tp->snd_max) 1123 tp->snd_nxt--; 1124 /* 1125 * If we are starting a connection, send ECN setup 1126 * SYN packet. If we are on a retransmit, we may 1127 * resend those bits a number of times as per 1128 * RFC 3168. 1129 */ 1130 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn == 1) { 1131 if (tp->t_rxtshift >= 1) { 1132 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1133 flags |= TH_ECE|TH_CWR; 1134 } else 1135 flags |= TH_ECE|TH_CWR; 1136 } 1137 1138 if (tp->t_state == TCPS_ESTABLISHED && 1139 (tp->t_flags & TF_ECN_PERMIT)) { 1140 /* 1141 * If the peer has ECN, mark data packets with 1142 * ECN capable transmission (ECT). 1143 * Ignore pure ack packets, retransmissions and window probes. 1144 */ 1145 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1146 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1147 #ifdef INET6 1148 if (isipv6) 1149 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1150 else 1151 #endif 1152 ip->ip_tos |= IPTOS_ECN_ECT0; 1153 TCPSTAT_INC(tcps_ecn_ect0); 1154 } 1155 1156 /* 1157 * Reply with proper ECN notifications. 1158 */ 1159 if (tp->t_flags & TF_ECN_SND_CWR) { 1160 flags |= TH_CWR; 1161 tp->t_flags &= ~TF_ECN_SND_CWR; 1162 } 1163 if (tp->t_flags & TF_ECN_SND_ECE) 1164 flags |= TH_ECE; 1165 } 1166 1167 /* 1168 * If we are doing retransmissions, then snd_nxt will 1169 * not reflect the first unsent octet. For ACK only 1170 * packets, we do not want the sequence number of the 1171 * retransmitted packet, we want the sequence number 1172 * of the next unsent octet. So, if there is no data 1173 * (and no SYN or FIN), use snd_max instead of snd_nxt 1174 * when filling in ti_seq. But if we are in persist 1175 * state, snd_max might reflect one byte beyond the 1176 * right edge of the window, so use snd_nxt in that 1177 * case, since we know we aren't doing a retransmission. 1178 * (retransmit and persist are mutually exclusive...) 1179 */ 1180 if (sack_rxmit == 0) { 1181 if (len || (flags & (TH_SYN|TH_FIN)) || 1182 tcp_timer_active(tp, TT_PERSIST)) 1183 th->th_seq = htonl(tp->snd_nxt); 1184 else 1185 th->th_seq = htonl(tp->snd_max); 1186 } else { 1187 th->th_seq = htonl(p->rxmit); 1188 p->rxmit += len; 1189 tp->sackhint.sack_bytes_rexmit += len; 1190 } 1191 th->th_ack = htonl(tp->rcv_nxt); 1192 if (optlen) { 1193 bcopy(opt, th + 1, optlen); 1194 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1195 } 1196 th->th_flags = flags; 1197 /* 1198 * Calculate receive window. Don't shrink window, 1199 * but avoid silly window syndrome. 1200 */ 1201 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 1202 recwin < (long)tp->t_maxseg) 1203 recwin = 0; 1204 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1205 recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 1206 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 1207 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 1208 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 1209 1210 /* 1211 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1212 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1213 * case is handled in syncache. 1214 */ 1215 if (flags & TH_SYN) 1216 th->th_win = htons((u_short) 1217 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1218 else 1219 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1220 1221 /* 1222 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1223 * a 0 window. This may cause the remote transmitter to stall. This 1224 * flag tells soreceive() to disable delayed acknowledgements when 1225 * draining the buffer. This can occur if the receiver is attempting 1226 * to read more data than can be buffered prior to transmitting on 1227 * the connection. 1228 */ 1229 if (th->th_win == 0) { 1230 tp->t_sndzerowin++; 1231 tp->t_flags |= TF_RXWIN0SENT; 1232 } else 1233 tp->t_flags &= ~TF_RXWIN0SENT; 1234 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1235 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1236 th->th_flags |= TH_URG; 1237 } else 1238 /* 1239 * If no urgent pointer to send, then we pull 1240 * the urgent pointer to the left edge of the send window 1241 * so that it doesn't drift into the send window on sequence 1242 * number wraparound. 1243 */ 1244 tp->snd_up = tp->snd_una; /* drag it along */ 1245 1246 #ifdef TCP_SIGNATURE 1247 if (to.to_flags & TOF_SIGNATURE) { 1248 int sigoff = to.to_signature - opt; 1249 tcp_signature_compute(m, 0, len, optlen, 1250 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1251 } 1252 #endif 1253 1254 /* 1255 * Put TCP length in extended header, and then 1256 * checksum extended header and data. 1257 */ 1258 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1259 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1260 #ifdef INET6 1261 if (isipv6) { 1262 /* 1263 * ip6_plen is not need to be filled now, and will be filled 1264 * in ip6_output. 1265 */ 1266 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1267 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1268 optlen + len, IPPROTO_TCP, 0); 1269 } 1270 #endif 1271 #if defined(INET6) && defined(INET) 1272 else 1273 #endif 1274 #ifdef INET 1275 { 1276 m->m_pkthdr.csum_flags = CSUM_TCP; 1277 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1278 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1279 1280 /* IP version must be set here for ipv4/ipv6 checking later */ 1281 KASSERT(ip->ip_v == IPVERSION, 1282 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1283 } 1284 #endif 1285 1286 /* 1287 * Enable TSO and specify the size of the segments. 1288 * The TCP pseudo header checksum is always provided. 1289 */ 1290 if (tso) { 1291 KASSERT(len > tp->t_maxseg - optlen, 1292 ("%s: len <= tso_segsz", __func__)); 1293 m->m_pkthdr.csum_flags |= CSUM_TSO; 1294 m->m_pkthdr.tso_segsz = tp->t_maxseg - optlen; 1295 } 1296 1297 #ifdef IPSEC 1298 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1299 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u", 1300 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1301 #else 1302 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1303 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u", 1304 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1305 #endif 1306 1307 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1308 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1309 1310 #ifdef TCPDEBUG 1311 /* 1312 * Trace. 1313 */ 1314 if (so->so_options & SO_DEBUG) { 1315 u_short save = 0; 1316 #ifdef INET6 1317 if (!isipv6) 1318 #endif 1319 { 1320 save = ipov->ih_len; 1321 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1322 } 1323 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1324 #ifdef INET6 1325 if (!isipv6) 1326 #endif 1327 ipov->ih_len = save; 1328 } 1329 #endif /* TCPDEBUG */ 1330 TCP_PROBE3(debug__output, tp, th, mtod(m, const char *)); 1331 1332 /* 1333 * Fill in IP length and desired time to live and 1334 * send to IP level. There should be a better way 1335 * to handle ttl and tos; we could keep them in 1336 * the template, but need a way to checksum without them. 1337 */ 1338 /* 1339 * m->m_pkthdr.len should have been set before checksum calculation, 1340 * because in6_cksum() need it. 1341 */ 1342 #ifdef INET6 1343 if (isipv6) { 1344 struct route_in6 ro; 1345 1346 bzero(&ro, sizeof(ro)); 1347 /* 1348 * we separately set hoplimit for every segment, since the 1349 * user might want to change the value via setsockopt. 1350 * Also, desired default hop limit might be changed via 1351 * Neighbor Discovery. 1352 */ 1353 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1354 1355 /* 1356 * Set the packet size here for the benefit of DTrace probes. 1357 * ip6_output() will set it properly; it's supposed to include 1358 * the option header lengths as well. 1359 */ 1360 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1361 1362 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) 1363 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1364 else 1365 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1366 1367 if (tp->t_state == TCPS_SYN_SENT) 1368 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1369 1370 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1371 1372 #ifdef TCPPCAP 1373 /* Save packet, if requested. */ 1374 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1375 #endif 1376 1377 /* TODO: IPv6 IP6TOS_ECT bit on */ 1378 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro, 1379 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1380 NULL, NULL, tp->t_inpcb); 1381 1382 if (error == EMSGSIZE && ro.ro_rt != NULL) 1383 mtu = ro.ro_rt->rt_mtu; 1384 RO_RTFREE(&ro); 1385 } 1386 #endif /* INET6 */ 1387 #if defined(INET) && defined(INET6) 1388 else 1389 #endif 1390 #ifdef INET 1391 { 1392 ip->ip_len = htons(m->m_pkthdr.len); 1393 #ifdef INET6 1394 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1395 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1396 #endif /* INET6 */ 1397 /* 1398 * If we do path MTU discovery, then we set DF on every packet. 1399 * This might not be the best thing to do according to RFC3390 1400 * Section 2. However the tcp hostcache migitates the problem 1401 * so it affects only the first tcp connection with a host. 1402 * 1403 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1404 */ 1405 if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) { 1406 ip->ip_off |= htons(IP_DF); 1407 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1408 } else { 1409 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1410 } 1411 1412 if (tp->t_state == TCPS_SYN_SENT) 1413 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1414 1415 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1416 1417 #ifdef TCPPCAP 1418 /* Save packet, if requested. */ 1419 tcp_pcap_add(th, m, &(tp->t_outpkts)); 1420 #endif 1421 1422 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 1423 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1424 tp->t_inpcb); 1425 1426 if (error == EMSGSIZE && tp->t_inpcb->inp_route.ro_rt != NULL) 1427 mtu = tp->t_inpcb->inp_route.ro_rt->rt_mtu; 1428 } 1429 #endif /* INET */ 1430 1431 out: 1432 /* 1433 * In transmit state, time the transmission and arrange for 1434 * the retransmit. In persist state, just set snd_max. 1435 */ 1436 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1437 !tcp_timer_active(tp, TT_PERSIST)) { 1438 tcp_seq startseq = tp->snd_nxt; 1439 1440 /* 1441 * Advance snd_nxt over sequence space of this segment. 1442 */ 1443 if (flags & (TH_SYN|TH_FIN)) { 1444 if (flags & TH_SYN) 1445 tp->snd_nxt++; 1446 if (flags & TH_FIN) { 1447 tp->snd_nxt++; 1448 tp->t_flags |= TF_SENTFIN; 1449 } 1450 } 1451 if (sack_rxmit) 1452 goto timer; 1453 tp->snd_nxt += len; 1454 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1455 tp->snd_max = tp->snd_nxt; 1456 /* 1457 * Time this transmission if not a retransmission and 1458 * not currently timing anything. 1459 */ 1460 if (tp->t_rtttime == 0) { 1461 tp->t_rtttime = ticks; 1462 tp->t_rtseq = startseq; 1463 TCPSTAT_INC(tcps_segstimed); 1464 } 1465 } 1466 1467 /* 1468 * Set retransmit timer if not currently set, 1469 * and not doing a pure ack or a keep-alive probe. 1470 * Initial value for retransmit timer is smoothed 1471 * round-trip time + 2 * round-trip time variance. 1472 * Initialize shift counter which is used for backoff 1473 * of retransmit time. 1474 */ 1475 timer: 1476 if (!tcp_timer_active(tp, TT_REXMT) && 1477 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1478 (tp->snd_nxt != tp->snd_una))) { 1479 if (tcp_timer_active(tp, TT_PERSIST)) { 1480 tcp_timer_activate(tp, TT_PERSIST, 0); 1481 tp->t_rxtshift = 0; 1482 } 1483 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1484 } else if (len == 0 && sbavail(&so->so_snd) && 1485 !tcp_timer_active(tp, TT_REXMT) && 1486 !tcp_timer_active(tp, TT_PERSIST)) { 1487 /* 1488 * Avoid a situation where we do not set persist timer 1489 * after a zero window condition. For example: 1490 * 1) A -> B: packet with enough data to fill the window 1491 * 2) B -> A: ACK for #1 + new data (0 window 1492 * advertisement) 1493 * 3) A -> B: ACK for #2, 0 len packet 1494 * 1495 * In this case, A will not activate the persist timer, 1496 * because it chose to send a packet. Unless tcp_output 1497 * is called for some other reason (delayed ack timer, 1498 * another input packet from B, socket syscall), A will 1499 * not send zero window probes. 1500 * 1501 * So, if you send a 0-length packet, but there is data 1502 * in the socket buffer, and neither the rexmt or 1503 * persist timer is already set, then activate the 1504 * persist timer. 1505 */ 1506 tp->t_rxtshift = 0; 1507 tcp_setpersist(tp); 1508 } 1509 } else { 1510 /* 1511 * Persist case, update snd_max but since we are in 1512 * persist mode (no window) we do not update snd_nxt. 1513 */ 1514 int xlen = len; 1515 if (flags & TH_SYN) 1516 ++xlen; 1517 if (flags & TH_FIN) { 1518 ++xlen; 1519 tp->t_flags |= TF_SENTFIN; 1520 } 1521 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1522 tp->snd_max = tp->snd_nxt + len; 1523 } 1524 1525 if (error) { 1526 1527 /* 1528 * We know that the packet was lost, so back out the 1529 * sequence number advance, if any. 1530 * 1531 * If the error is EPERM the packet got blocked by the 1532 * local firewall. Normally we should terminate the 1533 * connection but the blocking may have been spurious 1534 * due to a firewall reconfiguration cycle. So we treat 1535 * it like a packet loss and let the retransmit timer and 1536 * timeouts do their work over time. 1537 * XXX: It is a POLA question whether calling tcp_drop right 1538 * away would be the really correct behavior instead. 1539 */ 1540 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1541 !tcp_timer_active(tp, TT_PERSIST)) && 1542 ((flags & TH_SYN) == 0) && 1543 (error != EPERM)) { 1544 if (sack_rxmit) { 1545 p->rxmit -= len; 1546 tp->sackhint.sack_bytes_rexmit -= len; 1547 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1548 ("sackhint bytes rtx >= 0")); 1549 } else 1550 tp->snd_nxt -= len; 1551 } 1552 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1553 switch (error) { 1554 case EPERM: 1555 tp->t_softerror = error; 1556 return (error); 1557 case ENOBUFS: 1558 TCP_XMIT_TIMER_ASSERT(tp, len, flags); 1559 tp->snd_cwnd = tp->t_maxseg; 1560 return (0); 1561 case EMSGSIZE: 1562 /* 1563 * For some reason the interface we used initially 1564 * to send segments changed to another or lowered 1565 * its MTU. 1566 * If TSO was active we either got an interface 1567 * without TSO capabilits or TSO was turned off. 1568 * If we obtained mtu from ip_output() then update 1569 * it and try again. 1570 */ 1571 if (tso) 1572 tp->t_flags &= ~TF_TSO; 1573 if (mtu != 0) { 1574 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1575 goto again; 1576 } 1577 return (error); 1578 case EHOSTDOWN: 1579 case EHOSTUNREACH: 1580 case ENETDOWN: 1581 case ENETUNREACH: 1582 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1583 tp->t_softerror = error; 1584 return (0); 1585 } 1586 /* FALLTHROUGH */ 1587 default: 1588 return (error); 1589 } 1590 } 1591 TCPSTAT_INC(tcps_sndtotal); 1592 1593 /* 1594 * Data sent (as far as we can tell). 1595 * If this advertises a larger window than any other segment, 1596 * then remember the size of the advertised window. 1597 * Any pending ACK has now been sent. 1598 */ 1599 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1600 tp->rcv_adv = tp->rcv_nxt + recwin; 1601 tp->last_ack_sent = tp->rcv_nxt; 1602 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1603 if (tcp_timer_active(tp, TT_DELACK)) 1604 tcp_timer_activate(tp, TT_DELACK, 0); 1605 #if 0 1606 /* 1607 * This completely breaks TCP if newreno is turned on. What happens 1608 * is that if delayed-acks are turned on on the receiver, this code 1609 * on the transmitter effectively destroys the TCP window, forcing 1610 * it to four packets (1.5Kx4 = 6K window). 1611 */ 1612 if (sendalot && --maxburst) 1613 goto again; 1614 #endif 1615 if (sendalot) 1616 goto again; 1617 return (0); 1618 } 1619 1620 void 1621 tcp_setpersist(struct tcpcb *tp) 1622 { 1623 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1624 int tt; 1625 1626 tp->t_flags &= ~TF_PREVVALID; 1627 if (tcp_timer_active(tp, TT_REXMT)) 1628 panic("tcp_setpersist: retransmit pending"); 1629 /* 1630 * Start/restart persistence timer. 1631 */ 1632 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1633 tcp_persmin, tcp_persmax); 1634 tcp_timer_activate(tp, TT_PERSIST, tt); 1635 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1636 tp->t_rxtshift++; 1637 } 1638 1639 /* 1640 * Insert TCP options according to the supplied parameters to the place 1641 * optp in a consistent way. Can handle unaligned destinations. 1642 * 1643 * The order of the option processing is crucial for optimal packing and 1644 * alignment for the scarce option space. 1645 * 1646 * The optimal order for a SYN/SYN-ACK segment is: 1647 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1648 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1649 * 1650 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1651 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1652 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1653 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1654 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1655 */ 1656 int 1657 tcp_addoptions(struct tcpopt *to, u_char *optp) 1658 { 1659 u_int32_t mask, optlen = 0; 1660 1661 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1662 if ((to->to_flags & mask) != mask) 1663 continue; 1664 if (optlen == TCP_MAXOLEN) 1665 break; 1666 switch (to->to_flags & mask) { 1667 case TOF_MSS: 1668 while (optlen % 4) { 1669 optlen += TCPOLEN_NOP; 1670 *optp++ = TCPOPT_NOP; 1671 } 1672 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1673 continue; 1674 optlen += TCPOLEN_MAXSEG; 1675 *optp++ = TCPOPT_MAXSEG; 1676 *optp++ = TCPOLEN_MAXSEG; 1677 to->to_mss = htons(to->to_mss); 1678 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1679 optp += sizeof(to->to_mss); 1680 break; 1681 case TOF_SCALE: 1682 while (!optlen || optlen % 2 != 1) { 1683 optlen += TCPOLEN_NOP; 1684 *optp++ = TCPOPT_NOP; 1685 } 1686 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1687 continue; 1688 optlen += TCPOLEN_WINDOW; 1689 *optp++ = TCPOPT_WINDOW; 1690 *optp++ = TCPOLEN_WINDOW; 1691 *optp++ = to->to_wscale; 1692 break; 1693 case TOF_SACKPERM: 1694 while (optlen % 2) { 1695 optlen += TCPOLEN_NOP; 1696 *optp++ = TCPOPT_NOP; 1697 } 1698 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1699 continue; 1700 optlen += TCPOLEN_SACK_PERMITTED; 1701 *optp++ = TCPOPT_SACK_PERMITTED; 1702 *optp++ = TCPOLEN_SACK_PERMITTED; 1703 break; 1704 case TOF_TS: 1705 while (!optlen || optlen % 4 != 2) { 1706 optlen += TCPOLEN_NOP; 1707 *optp++ = TCPOPT_NOP; 1708 } 1709 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1710 continue; 1711 optlen += TCPOLEN_TIMESTAMP; 1712 *optp++ = TCPOPT_TIMESTAMP; 1713 *optp++ = TCPOLEN_TIMESTAMP; 1714 to->to_tsval = htonl(to->to_tsval); 1715 to->to_tsecr = htonl(to->to_tsecr); 1716 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1717 optp += sizeof(to->to_tsval); 1718 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1719 optp += sizeof(to->to_tsecr); 1720 break; 1721 #ifdef TCP_SIGNATURE 1722 case TOF_SIGNATURE: 1723 { 1724 int siglen = TCPOLEN_SIGNATURE - 2; 1725 1726 while (!optlen || optlen % 4 != 2) { 1727 optlen += TCPOLEN_NOP; 1728 *optp++ = TCPOPT_NOP; 1729 } 1730 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1731 continue; 1732 optlen += TCPOLEN_SIGNATURE; 1733 *optp++ = TCPOPT_SIGNATURE; 1734 *optp++ = TCPOLEN_SIGNATURE; 1735 to->to_signature = optp; 1736 while (siglen--) 1737 *optp++ = 0; 1738 break; 1739 } 1740 #endif 1741 case TOF_SACK: 1742 { 1743 int sackblks = 0; 1744 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1745 tcp_seq sack_seq; 1746 1747 while (!optlen || optlen % 4 != 2) { 1748 optlen += TCPOLEN_NOP; 1749 *optp++ = TCPOPT_NOP; 1750 } 1751 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1752 continue; 1753 optlen += TCPOLEN_SACKHDR; 1754 *optp++ = TCPOPT_SACK; 1755 sackblks = min(to->to_nsacks, 1756 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1757 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1758 while (sackblks--) { 1759 sack_seq = htonl(sack->start); 1760 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1761 optp += sizeof(sack_seq); 1762 sack_seq = htonl(sack->end); 1763 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1764 optp += sizeof(sack_seq); 1765 optlen += TCPOLEN_SACK; 1766 sack++; 1767 } 1768 TCPSTAT_INC(tcps_sack_send_blocks); 1769 break; 1770 } 1771 #ifdef TCP_RFC7413 1772 case TOF_FASTOPEN: 1773 { 1774 int total_len; 1775 1776 /* XXX is there any point to aligning this option? */ 1777 total_len = TCPOLEN_FAST_OPEN_EMPTY + to->to_tfo_len; 1778 if (TCP_MAXOLEN - optlen < total_len) 1779 continue; 1780 *optp++ = TCPOPT_FAST_OPEN; 1781 *optp++ = total_len; 1782 if (to->to_tfo_len > 0) { 1783 bcopy(to->to_tfo_cookie, optp, to->to_tfo_len); 1784 optp += to->to_tfo_len; 1785 } 1786 optlen += total_len; 1787 break; 1788 } 1789 #endif 1790 default: 1791 panic("%s: unknown TCP option type", __func__); 1792 break; 1793 } 1794 } 1795 1796 /* Terminate and pad TCP options to a 4 byte boundary. */ 1797 if (optlen % 4) { 1798 optlen += TCPOLEN_EOL; 1799 *optp++ = TCPOPT_EOL; 1800 } 1801 /* 1802 * According to RFC 793 (STD0007): 1803 * "The content of the header beyond the End-of-Option option 1804 * must be header padding (i.e., zero)." 1805 * and later: "The padding is composed of zeros." 1806 */ 1807 while (optlen % 4) { 1808 optlen += TCPOLEN_PAD; 1809 *optp++ = TCPOPT_PAD; 1810 } 1811 1812 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1813 return (optlen); 1814 } 1815