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