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, tcp_do_tso) = 1; 93 #define V_tcp_do_tso VNET(tcp_do_tso) 94 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 95 &VNET_NAME(tcp_do_tso), 0, 96 "Enable TCP Segmentation Offload"); 97 98 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 99 #define V_tcp_sendspace VNET(tcp_sendspace) 100 SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_RW, 101 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 102 103 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 104 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf) 105 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 106 &VNET_NAME(tcp_do_autosndbuf), 0, 107 "Enable automatic send buffer sizing"); 108 109 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 110 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc) 111 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 112 &VNET_NAME(tcp_autosndbuf_inc), 0, 113 "Incrementor step size of automatic send buffer"); 114 115 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 116 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max) 117 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 118 &VNET_NAME(tcp_autosndbuf_max), 0, 119 "Max size of automatic send buffer"); 120 121 static void inline hhook_run_tcp_est_out(struct tcpcb *tp, 122 struct tcphdr *th, struct tcpopt *to, 123 long len, int tso); 124 static void inline cc_after_idle(struct tcpcb *tp); 125 126 /* 127 * Wrapper for the TCP established ouput helper hook. 128 */ 129 static void inline 130 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 131 struct tcpopt *to, long len, int tso) 132 { 133 struct tcp_hhook_data hhook_data; 134 135 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 136 hhook_data.tp = tp; 137 hhook_data.th = th; 138 hhook_data.to = to; 139 hhook_data.len = len; 140 hhook_data.tso = tso; 141 142 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 143 tp->osd); 144 } 145 } 146 147 /* 148 * CC wrapper hook functions 149 */ 150 static void inline 151 cc_after_idle(struct tcpcb *tp) 152 { 153 INP_WLOCK_ASSERT(tp->t_inpcb); 154 155 if (CC_ALGO(tp)->after_idle != NULL) 156 CC_ALGO(tp)->after_idle(tp->ccv); 157 } 158 159 /* 160 * Tcp output routine: figure out what should be sent and send it. 161 */ 162 int 163 tcp_output(struct tcpcb *tp) 164 { 165 struct socket *so = tp->t_inpcb->inp_socket; 166 long len, recwin, sendwin; 167 int off, flags, error = 0; /* Keep compiler happy */ 168 struct mbuf *m; 169 struct ip *ip = NULL; 170 struct ipovly *ipov = NULL; 171 struct tcphdr *th; 172 u_char opt[TCP_MAXOLEN]; 173 unsigned ipoptlen, optlen, hdrlen; 174 #ifdef IPSEC 175 unsigned ipsec_optlen = 0; 176 #endif 177 int idle, sendalot; 178 int sack_rxmit, sack_bytes_rxmt; 179 struct sackhole *p; 180 int tso; 181 struct tcpopt to; 182 #if 0 183 int maxburst = TCP_MAXBURST; 184 #endif 185 #ifdef INET6 186 struct ip6_hdr *ip6 = NULL; 187 int isipv6; 188 189 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 190 #endif 191 192 INP_WLOCK_ASSERT(tp->t_inpcb); 193 194 /* 195 * Determine length of data that should be transmitted, 196 * and flags that will be used. 197 * If there is some data or critical controls (SYN, RST) 198 * to send, then transmit; otherwise, investigate further. 199 */ 200 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 201 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 202 cc_after_idle(tp); 203 tp->t_flags &= ~TF_LASTIDLE; 204 if (idle) { 205 if (tp->t_flags & TF_MORETOCOME) { 206 tp->t_flags |= TF_LASTIDLE; 207 idle = 0; 208 } 209 } 210 again: 211 /* 212 * If we've recently taken a timeout, snd_max will be greater than 213 * snd_nxt. There may be SACK information that allows us to avoid 214 * resending already delivered data. Adjust snd_nxt accordingly. 215 */ 216 if ((tp->t_flags & TF_SACK_PERMIT) && 217 SEQ_LT(tp->snd_nxt, tp->snd_max)) 218 tcp_sack_adjust(tp); 219 sendalot = 0; 220 tso = 0; 221 off = tp->snd_nxt - tp->snd_una; 222 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 223 224 flags = tcp_outflags[tp->t_state]; 225 /* 226 * Send any SACK-generated retransmissions. If we're explicitly trying 227 * to send out new data (when sendalot is 1), bypass this function. 228 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 229 * we're replacing a (future) new transmission with a retransmission 230 * now, and we previously incremented snd_cwnd in tcp_input(). 231 */ 232 /* 233 * Still in sack recovery , reset rxmit flag to zero. 234 */ 235 sack_rxmit = 0; 236 sack_bytes_rxmt = 0; 237 len = 0; 238 p = NULL; 239 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 240 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 241 long cwin; 242 243 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 244 if (cwin < 0) 245 cwin = 0; 246 /* Do not retransmit SACK segments beyond snd_recover */ 247 if (SEQ_GT(p->end, tp->snd_recover)) { 248 /* 249 * (At least) part of sack hole extends beyond 250 * snd_recover. Check to see if we can rexmit data 251 * for this hole. 252 */ 253 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 254 /* 255 * Can't rexmit any more data for this hole. 256 * That data will be rexmitted in the next 257 * sack recovery episode, when snd_recover 258 * moves past p->rxmit. 259 */ 260 p = NULL; 261 goto after_sack_rexmit; 262 } else 263 /* Can rexmit part of the current hole */ 264 len = ((long)ulmin(cwin, 265 tp->snd_recover - p->rxmit)); 266 } else 267 len = ((long)ulmin(cwin, p->end - p->rxmit)); 268 off = p->rxmit - tp->snd_una; 269 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 270 __func__, off)); 271 if (len > 0) { 272 sack_rxmit = 1; 273 sendalot = 1; 274 TCPSTAT_INC(tcps_sack_rexmits); 275 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 276 min(len, tp->t_maxseg)); 277 } 278 } 279 after_sack_rexmit: 280 /* 281 * Get standard flags, and add SYN or FIN if requested by 'hidden' 282 * state flags. 283 */ 284 if (tp->t_flags & TF_NEEDFIN) 285 flags |= TH_FIN; 286 if (tp->t_flags & TF_NEEDSYN) 287 flags |= TH_SYN; 288 289 SOCKBUF_LOCK(&so->so_snd); 290 /* 291 * If in persist timeout with window of 0, send 1 byte. 292 * Otherwise, if window is small but nonzero 293 * and timer expired, we will send what we can 294 * and go to transmit state. 295 */ 296 if (tp->t_flags & TF_FORCEDATA) { 297 if (sendwin == 0) { 298 /* 299 * If we still have some data to send, then 300 * clear the FIN bit. Usually this would 301 * happen below when it realizes that we 302 * aren't sending all the data. However, 303 * if we have exactly 1 byte of unsent data, 304 * then it won't clear the FIN bit below, 305 * and if we are in persist state, we wind 306 * up sending the packet without recording 307 * that we sent the FIN bit. 308 * 309 * We can't just blindly clear the FIN bit, 310 * because if we don't have any more data 311 * to send then the probe will be the FIN 312 * itself. 313 */ 314 if (off < so->so_snd.sb_cc) 315 flags &= ~TH_FIN; 316 sendwin = 1; 317 } else { 318 tcp_timer_activate(tp, TT_PERSIST, 0); 319 tp->t_rxtshift = 0; 320 } 321 } 322 323 /* 324 * If snd_nxt == snd_max and we have transmitted a FIN, the 325 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 326 * a negative length. This can also occur when TCP opens up 327 * its congestion window while receiving additional duplicate 328 * acks after fast-retransmit because TCP will reset snd_nxt 329 * to snd_max after the fast-retransmit. 330 * 331 * In the normal retransmit-FIN-only case, however, snd_nxt will 332 * be set to snd_una, the offset will be 0, and the length may 333 * wind up 0. 334 * 335 * If sack_rxmit is true we are retransmitting from the scoreboard 336 * in which case len is already set. 337 */ 338 if (sack_rxmit == 0) { 339 if (sack_bytes_rxmt == 0) 340 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 341 else { 342 long cwin; 343 344 /* 345 * We are inside of a SACK recovery episode and are 346 * sending new data, having retransmitted all the 347 * data possible in the scoreboard. 348 */ 349 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 350 - off); 351 /* 352 * Don't remove this (len > 0) check ! 353 * We explicitly check for len > 0 here (although it 354 * isn't really necessary), to work around a gcc 355 * optimization issue - to force gcc to compute 356 * len above. Without this check, the computation 357 * of len is bungled by the optimizer. 358 */ 359 if (len > 0) { 360 cwin = tp->snd_cwnd - 361 (tp->snd_nxt - tp->sack_newdata) - 362 sack_bytes_rxmt; 363 if (cwin < 0) 364 cwin = 0; 365 len = lmin(len, cwin); 366 } 367 } 368 } 369 370 /* 371 * Lop off SYN bit if it has already been sent. However, if this 372 * is SYN-SENT state and if segment contains data and if we don't 373 * know that foreign host supports TAO, suppress sending segment. 374 */ 375 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 376 if (tp->t_state != TCPS_SYN_RECEIVED) 377 flags &= ~TH_SYN; 378 off--, len++; 379 } 380 381 /* 382 * Be careful not to send data and/or FIN on SYN segments. 383 * This measure is needed to prevent interoperability problems 384 * with not fully conformant TCP implementations. 385 */ 386 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 387 len = 0; 388 flags &= ~TH_FIN; 389 } 390 391 if (len < 0) { 392 /* 393 * If FIN has been sent but not acked, 394 * but we haven't been called to retransmit, 395 * len will be < 0. Otherwise, window shrank 396 * after we sent into it. If window shrank to 0, 397 * cancel pending retransmit, pull snd_nxt back 398 * to (closed) window, and set the persist timer 399 * if it isn't already going. If the window didn't 400 * close completely, just wait for an ACK. 401 */ 402 len = 0; 403 if (sendwin == 0) { 404 tcp_timer_activate(tp, TT_REXMT, 0); 405 tp->t_rxtshift = 0; 406 tp->snd_nxt = tp->snd_una; 407 if (!tcp_timer_active(tp, TT_PERSIST)) 408 tcp_setpersist(tp); 409 } 410 } 411 412 /* len will be >= 0 after this point. */ 413 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 414 415 /* 416 * Automatic sizing of send socket buffer. Often the send buffer 417 * size is not optimally adjusted to the actual network conditions 418 * at hand (delay bandwidth product). Setting the buffer size too 419 * small limits throughput on links with high bandwidth and high 420 * delay (eg. trans-continental/oceanic links). Setting the 421 * buffer size too big consumes too much real kernel memory, 422 * especially with many connections on busy servers. 423 * 424 * The criteria to step up the send buffer one notch are: 425 * 1. receive window of remote host is larger than send buffer 426 * (with a fudge factor of 5/4th); 427 * 2. send buffer is filled to 7/8th with data (so we actually 428 * have data to make use of it); 429 * 3. send buffer fill has not hit maximal automatic size; 430 * 4. our send window (slow start and cogestion controlled) is 431 * larger than sent but unacknowledged data in send buffer. 432 * 433 * The remote host receive window scaling factor may limit the 434 * growing of the send buffer before it reaches its allowed 435 * maximum. 436 * 437 * It scales directly with slow start or congestion window 438 * and does at most one step per received ACK. This fast 439 * scaling has the drawback of growing the send buffer beyond 440 * what is strictly necessary to make full use of a given 441 * delay*bandwith product. However testing has shown this not 442 * to be much of an problem. At worst we are trading wasting 443 * of available bandwith (the non-use of it) for wasting some 444 * socket buffer memory. 445 * 446 * TODO: Shrink send buffer during idle periods together 447 * with congestion window. Requires another timer. Has to 448 * wait for upcoming tcp timer rewrite. 449 */ 450 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 451 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 452 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 453 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 454 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 455 if (!sbreserve_locked(&so->so_snd, 456 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 457 V_tcp_autosndbuf_max), so, curthread)) 458 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 459 } 460 } 461 462 /* 463 * Decide if we can use TCP Segmentation Offloading (if supported by 464 * hardware). 465 * 466 * TSO may only be used if we are in a pure bulk sending state. The 467 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 468 * IP options prevent using TSO. With TSO the TCP header is the same 469 * (except for the sequence number) for all generated packets. This 470 * makes it impossible to transmit any options which vary per generated 471 * segment or packet. 472 */ 473 #ifdef IPSEC 474 /* 475 * Pre-calculate here as we save another lookup into the darknesses 476 * of IPsec that way and can actually decide if TSO is ok. 477 */ 478 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 479 #endif 480 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 481 ((tp->t_flags & TF_SIGNATURE) == 0) && 482 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 483 #ifdef IPSEC 484 ipsec_optlen == 0 && 485 #endif 486 tp->t_inpcb->inp_options == NULL && 487 tp->t_inpcb->in6p_options == NULL) 488 tso = 1; 489 490 if (sack_rxmit) { 491 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 492 flags &= ~TH_FIN; 493 } else { 494 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 495 flags &= ~TH_FIN; 496 } 497 498 recwin = sbspace(&so->so_rcv); 499 500 /* 501 * Sender silly window avoidance. We transmit under the following 502 * conditions when len is non-zero: 503 * 504 * - We have a full segment (or more with TSO) 505 * - This is the last buffer in a write()/send() and we are 506 * either idle or running NODELAY 507 * - we've timed out (e.g. persist timer) 508 * - we have more then 1/2 the maximum send window's worth of 509 * data (receiver may be limited the window size) 510 * - we need to retransmit 511 */ 512 if (len) { 513 if (len >= tp->t_maxseg) 514 goto send; 515 /* 516 * NOTE! on localhost connections an 'ack' from the remote 517 * end may occur synchronously with the output and cause 518 * us to flush a buffer queued with moretocome. XXX 519 * 520 * note: the len + off check is almost certainly unnecessary. 521 */ 522 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 523 (idle || (tp->t_flags & TF_NODELAY)) && 524 len + off >= so->so_snd.sb_cc && 525 (tp->t_flags & TF_NOPUSH) == 0) { 526 goto send; 527 } 528 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 529 goto send; 530 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 531 goto send; 532 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 533 goto send; 534 if (sack_rxmit) 535 goto send; 536 } 537 538 /* 539 * Compare available window to amount of window 540 * known to peer (as advertised window less 541 * next expected input). If the difference is at least two 542 * max size segments, or at least 50% of the maximum possible 543 * window, then want to send a window update to peer. 544 * Skip this if the connection is in T/TCP half-open state. 545 * Don't send pure window updates when the peer has closed 546 * the connection and won't ever send more data. 547 */ 548 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 549 !TCPS_HAVERCVDFIN(tp->t_state)) { 550 /* 551 * "adv" is the amount we can increase the window, 552 * taking into account that we are limited by 553 * TCP_MAXWIN << tp->rcv_scale. 554 */ 555 long adv; 556 int oldwin; 557 558 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale); 559 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 560 oldwin = (tp->rcv_adv - tp->rcv_nxt); 561 adv -= oldwin; 562 } else 563 oldwin = 0; 564 565 /* 566 * If the new window size ends up being the same as the old 567 * size when it is scaled, then don't force a window update. 568 */ 569 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale) 570 goto dontupdate; 571 if (adv >= (long) (2 * tp->t_maxseg)) 572 goto send; 573 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 574 goto send; 575 } 576 dontupdate: 577 578 /* 579 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 580 * is also a catch-all for the retransmit timer timeout case. 581 */ 582 if (tp->t_flags & TF_ACKNOW) 583 goto send; 584 if ((flags & TH_RST) || 585 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 586 goto send; 587 if (SEQ_GT(tp->snd_up, tp->snd_una)) 588 goto send; 589 /* 590 * If our state indicates that FIN should be sent 591 * and we have not yet done so, then we need to send. 592 */ 593 if (flags & TH_FIN && 594 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 595 goto send; 596 /* 597 * In SACK, it is possible for tcp_output to fail to send a segment 598 * after the retransmission timer has been turned off. Make sure 599 * that the retransmission timer is set. 600 */ 601 if ((tp->t_flags & TF_SACK_PERMIT) && 602 SEQ_GT(tp->snd_max, tp->snd_una) && 603 !tcp_timer_active(tp, TT_REXMT) && 604 !tcp_timer_active(tp, TT_PERSIST)) { 605 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 606 goto just_return; 607 } 608 /* 609 * TCP window updates are not reliable, rather a polling protocol 610 * using ``persist'' packets is used to insure receipt of window 611 * updates. The three ``states'' for the output side are: 612 * idle not doing retransmits or persists 613 * persisting to move a small or zero window 614 * (re)transmitting and thereby not persisting 615 * 616 * tcp_timer_active(tp, TT_PERSIST) 617 * is true when we are in persist state. 618 * (tp->t_flags & TF_FORCEDATA) 619 * is set when we are called to send a persist packet. 620 * tcp_timer_active(tp, TT_REXMT) 621 * is set when we are retransmitting 622 * The output side is idle when both timers are zero. 623 * 624 * If send window is too small, there is data to transmit, and no 625 * retransmit or persist is pending, then go to persist state. 626 * If nothing happens soon, send when timer expires: 627 * if window is nonzero, transmit what we can, 628 * otherwise force out a byte. 629 */ 630 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 631 !tcp_timer_active(tp, TT_PERSIST)) { 632 tp->t_rxtshift = 0; 633 tcp_setpersist(tp); 634 } 635 636 /* 637 * No reason to send a segment, just return. 638 */ 639 just_return: 640 SOCKBUF_UNLOCK(&so->so_snd); 641 return (0); 642 643 send: 644 SOCKBUF_LOCK_ASSERT(&so->so_snd); 645 /* 646 * Before ESTABLISHED, force sending of initial options 647 * unless TCP set not to do any options. 648 * NOTE: we assume that the IP/TCP header plus TCP options 649 * always fit in a single mbuf, leaving room for a maximum 650 * link header, i.e. 651 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 652 */ 653 optlen = 0; 654 #ifdef INET6 655 if (isipv6) 656 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 657 else 658 #endif 659 hdrlen = sizeof (struct tcpiphdr); 660 661 /* 662 * Compute options for segment. 663 * We only have to care about SYN and established connection 664 * segments. Options for SYN-ACK segments are handled in TCP 665 * syncache. 666 */ 667 if ((tp->t_flags & TF_NOOPT) == 0) { 668 to.to_flags = 0; 669 /* Maximum segment size. */ 670 if (flags & TH_SYN) { 671 tp->snd_nxt = tp->iss; 672 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 673 to.to_flags |= TOF_MSS; 674 } 675 /* Window scaling. */ 676 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 677 to.to_wscale = tp->request_r_scale; 678 to.to_flags |= TOF_SCALE; 679 } 680 /* Timestamps. */ 681 if ((tp->t_flags & TF_RCVD_TSTMP) || 682 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 683 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 684 to.to_tsecr = tp->ts_recent; 685 to.to_flags |= TOF_TS; 686 /* Set receive buffer autosizing timestamp. */ 687 if (tp->rfbuf_ts == 0 && 688 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 689 tp->rfbuf_ts = tcp_ts_getticks(); 690 } 691 /* Selective ACK's. */ 692 if (tp->t_flags & TF_SACK_PERMIT) { 693 if (flags & TH_SYN) 694 to.to_flags |= TOF_SACKPERM; 695 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 696 (tp->t_flags & TF_SACK_PERMIT) && 697 tp->rcv_numsacks > 0) { 698 to.to_flags |= TOF_SACK; 699 to.to_nsacks = tp->rcv_numsacks; 700 to.to_sacks = (u_char *)tp->sackblks; 701 } 702 } 703 #ifdef TCP_SIGNATURE 704 /* TCP-MD5 (RFC2385). */ 705 if (tp->t_flags & TF_SIGNATURE) 706 to.to_flags |= TOF_SIGNATURE; 707 #endif /* TCP_SIGNATURE */ 708 709 /* Processing the options. */ 710 hdrlen += optlen = tcp_addoptions(&to, opt); 711 } 712 713 #ifdef INET6 714 if (isipv6) 715 ipoptlen = ip6_optlen(tp->t_inpcb); 716 else 717 #endif 718 if (tp->t_inpcb->inp_options) 719 ipoptlen = tp->t_inpcb->inp_options->m_len - 720 offsetof(struct ipoption, ipopt_list); 721 else 722 ipoptlen = 0; 723 #ifdef IPSEC 724 ipoptlen += ipsec_optlen; 725 #endif 726 727 /* 728 * Adjust data length if insertion of options will 729 * bump the packet length beyond the t_maxopd length. 730 * Clear the FIN bit because we cut off the tail of 731 * the segment. 732 */ 733 if (len + optlen + ipoptlen > tp->t_maxopd) { 734 flags &= ~TH_FIN; 735 736 if (tso) { 737 KASSERT(ipoptlen == 0, 738 ("%s: TSO can't do IP options", __func__)); 739 740 /* 741 * Limit a burst to IP_MAXPACKET minus IP, 742 * TCP and options length to keep ip->ip_len 743 * from overflowing. 744 */ 745 if (len > IP_MAXPACKET - hdrlen) { 746 len = IP_MAXPACKET - hdrlen; 747 sendalot = 1; 748 } 749 750 /* 751 * Prevent the last segment from being 752 * fractional unless the send sockbuf can 753 * be emptied. 754 */ 755 if (sendalot && off + len < so->so_snd.sb_cc) { 756 len -= len % (tp->t_maxopd - optlen); 757 sendalot = 1; 758 } 759 760 /* 761 * Send the FIN in a separate segment 762 * after the bulk sending is done. 763 * We don't trust the TSO implementations 764 * to clear the FIN flag on all but the 765 * last segment. 766 */ 767 if (tp->t_flags & TF_NEEDFIN) 768 sendalot = 1; 769 770 } else { 771 len = tp->t_maxopd - optlen - ipoptlen; 772 sendalot = 1; 773 } 774 } else 775 tso = 0; 776 777 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 778 ("%s: len > IP_MAXPACKET", __func__)); 779 780 /*#ifdef DIAGNOSTIC*/ 781 #ifdef INET6 782 if (max_linkhdr + hdrlen > MCLBYTES) 783 #else 784 if (max_linkhdr + hdrlen > MHLEN) 785 #endif 786 panic("tcphdr too big"); 787 /*#endif*/ 788 789 /* 790 * This KASSERT is here to catch edge cases at a well defined place. 791 * Before, those had triggered (random) panic conditions further down. 792 */ 793 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 794 795 /* 796 * Grab a header mbuf, attaching a copy of data to 797 * be transmitted, and initialize the header from 798 * the template for sends on this connection. 799 */ 800 if (len) { 801 struct mbuf *mb; 802 u_int moff; 803 804 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 805 TCPSTAT_INC(tcps_sndprobe); 806 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 807 tp->t_sndrexmitpack++; 808 TCPSTAT_INC(tcps_sndrexmitpack); 809 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 810 } else { 811 TCPSTAT_INC(tcps_sndpack); 812 TCPSTAT_ADD(tcps_sndbyte, len); 813 } 814 MGETHDR(m, M_DONTWAIT, MT_DATA); 815 if (m == NULL) { 816 SOCKBUF_UNLOCK(&so->so_snd); 817 error = ENOBUFS; 818 goto out; 819 } 820 #ifdef INET6 821 if (MHLEN < hdrlen + max_linkhdr) { 822 MCLGET(m, M_DONTWAIT); 823 if ((m->m_flags & M_EXT) == 0) { 824 SOCKBUF_UNLOCK(&so->so_snd); 825 m_freem(m); 826 error = ENOBUFS; 827 goto out; 828 } 829 } 830 #endif 831 m->m_data += max_linkhdr; 832 m->m_len = hdrlen; 833 834 /* 835 * Start the m_copy functions from the closest mbuf 836 * to the offset in the socket buffer chain. 837 */ 838 mb = sbsndptr(&so->so_snd, off, len, &moff); 839 840 if (len <= MHLEN - hdrlen - max_linkhdr) { 841 m_copydata(mb, moff, (int)len, 842 mtod(m, caddr_t) + hdrlen); 843 m->m_len += len; 844 } else { 845 m->m_next = m_copy(mb, moff, (int)len); 846 if (m->m_next == NULL) { 847 SOCKBUF_UNLOCK(&so->so_snd); 848 (void) m_free(m); 849 error = ENOBUFS; 850 goto out; 851 } 852 } 853 854 /* 855 * If we're sending everything we've got, set PUSH. 856 * (This will keep happy those implementations which only 857 * give data to the user when a buffer fills or 858 * a PUSH comes in.) 859 */ 860 if (off + len == so->so_snd.sb_cc) 861 flags |= TH_PUSH; 862 SOCKBUF_UNLOCK(&so->so_snd); 863 } else { 864 SOCKBUF_UNLOCK(&so->so_snd); 865 if (tp->t_flags & TF_ACKNOW) 866 TCPSTAT_INC(tcps_sndacks); 867 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 868 TCPSTAT_INC(tcps_sndctrl); 869 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 870 TCPSTAT_INC(tcps_sndurg); 871 else 872 TCPSTAT_INC(tcps_sndwinup); 873 874 MGETHDR(m, M_DONTWAIT, MT_DATA); 875 if (m == NULL) { 876 error = ENOBUFS; 877 goto out; 878 } 879 #ifdef INET6 880 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 881 MHLEN >= hdrlen) { 882 MH_ALIGN(m, hdrlen); 883 } else 884 #endif 885 m->m_data += max_linkhdr; 886 m->m_len = hdrlen; 887 } 888 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 889 m->m_pkthdr.rcvif = (struct ifnet *)0; 890 #ifdef MAC 891 mac_inpcb_create_mbuf(tp->t_inpcb, m); 892 #endif 893 #ifdef INET6 894 if (isipv6) { 895 ip6 = mtod(m, struct ip6_hdr *); 896 th = (struct tcphdr *)(ip6 + 1); 897 tcpip_fillheaders(tp->t_inpcb, ip6, th); 898 } else 899 #endif /* INET6 */ 900 { 901 ip = mtod(m, struct ip *); 902 ipov = (struct ipovly *)ip; 903 th = (struct tcphdr *)(ip + 1); 904 tcpip_fillheaders(tp->t_inpcb, ip, th); 905 } 906 907 /* 908 * Fill in fields, remembering maximum advertised 909 * window for use in delaying messages about window sizes. 910 * If resending a FIN, be sure not to use a new sequence number. 911 */ 912 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 913 tp->snd_nxt == tp->snd_max) 914 tp->snd_nxt--; 915 /* 916 * If we are starting a connection, send ECN setup 917 * SYN packet. If we are on a retransmit, we may 918 * resend those bits a number of times as per 919 * RFC 3168. 920 */ 921 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 922 if (tp->t_rxtshift >= 1) { 923 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 924 flags |= TH_ECE|TH_CWR; 925 } else 926 flags |= TH_ECE|TH_CWR; 927 } 928 929 if (tp->t_state == TCPS_ESTABLISHED && 930 (tp->t_flags & TF_ECN_PERMIT)) { 931 /* 932 * If the peer has ECN, mark data packets with 933 * ECN capable transmission (ECT). 934 * Ignore pure ack packets, retransmissions and window probes. 935 */ 936 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 937 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 938 #ifdef INET6 939 if (isipv6) 940 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 941 else 942 #endif 943 ip->ip_tos |= IPTOS_ECN_ECT0; 944 TCPSTAT_INC(tcps_ecn_ect0); 945 } 946 947 /* 948 * Reply with proper ECN notifications. 949 */ 950 if (tp->t_flags & TF_ECN_SND_CWR) { 951 flags |= TH_CWR; 952 tp->t_flags &= ~TF_ECN_SND_CWR; 953 } 954 if (tp->t_flags & TF_ECN_SND_ECE) 955 flags |= TH_ECE; 956 } 957 958 /* 959 * If we are doing retransmissions, then snd_nxt will 960 * not reflect the first unsent octet. For ACK only 961 * packets, we do not want the sequence number of the 962 * retransmitted packet, we want the sequence number 963 * of the next unsent octet. So, if there is no data 964 * (and no SYN or FIN), use snd_max instead of snd_nxt 965 * when filling in ti_seq. But if we are in persist 966 * state, snd_max might reflect one byte beyond the 967 * right edge of the window, so use snd_nxt in that 968 * case, since we know we aren't doing a retransmission. 969 * (retransmit and persist are mutually exclusive...) 970 */ 971 if (sack_rxmit == 0) { 972 if (len || (flags & (TH_SYN|TH_FIN)) || 973 tcp_timer_active(tp, TT_PERSIST)) 974 th->th_seq = htonl(tp->snd_nxt); 975 else 976 th->th_seq = htonl(tp->snd_max); 977 } else { 978 th->th_seq = htonl(p->rxmit); 979 p->rxmit += len; 980 tp->sackhint.sack_bytes_rexmit += len; 981 } 982 th->th_ack = htonl(tp->rcv_nxt); 983 if (optlen) { 984 bcopy(opt, th + 1, optlen); 985 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 986 } 987 th->th_flags = flags; 988 /* 989 * Calculate receive window. Don't shrink window, 990 * but avoid silly window syndrome. 991 */ 992 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 993 recwin < (long)tp->t_maxseg) 994 recwin = 0; 995 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 996 recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 997 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 998 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 999 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 1000 1001 /* 1002 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1003 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1004 * case is handled in syncache. 1005 */ 1006 if (flags & TH_SYN) 1007 th->th_win = htons((u_short) 1008 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1009 else 1010 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1011 1012 /* 1013 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1014 * a 0 window. This may cause the remote transmitter to stall. This 1015 * flag tells soreceive() to disable delayed acknowledgements when 1016 * draining the buffer. This can occur if the receiver is attempting 1017 * to read more data than can be buffered prior to transmitting on 1018 * the connection. 1019 */ 1020 if (th->th_win == 0) { 1021 tp->t_sndzerowin++; 1022 tp->t_flags |= TF_RXWIN0SENT; 1023 } else 1024 tp->t_flags &= ~TF_RXWIN0SENT; 1025 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1026 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1027 th->th_flags |= TH_URG; 1028 } else 1029 /* 1030 * If no urgent pointer to send, then we pull 1031 * the urgent pointer to the left edge of the send window 1032 * so that it doesn't drift into the send window on sequence 1033 * number wraparound. 1034 */ 1035 tp->snd_up = tp->snd_una; /* drag it along */ 1036 1037 #ifdef TCP_SIGNATURE 1038 if (tp->t_flags & TF_SIGNATURE) { 1039 int sigoff = to.to_signature - opt; 1040 tcp_signature_compute(m, 0, len, optlen, 1041 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1042 } 1043 #endif 1044 1045 /* 1046 * Put TCP length in extended header, and then 1047 * checksum extended header and data. 1048 */ 1049 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1050 #ifdef INET6 1051 if (isipv6) 1052 /* 1053 * ip6_plen is not need to be filled now, and will be filled 1054 * in ip6_output. 1055 */ 1056 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 1057 sizeof(struct tcphdr) + optlen + len); 1058 else 1059 #endif /* INET6 */ 1060 { 1061 m->m_pkthdr.csum_flags = CSUM_TCP; 1062 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1063 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1064 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1065 1066 /* IP version must be set here for ipv4/ipv6 checking later */ 1067 KASSERT(ip->ip_v == IPVERSION, 1068 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1069 } 1070 1071 /* 1072 * Enable TSO and specify the size of the segments. 1073 * The TCP pseudo header checksum is always provided. 1074 * XXX: Fixme: This is currently not the case for IPv6. 1075 */ 1076 if (tso) { 1077 KASSERT(len > tp->t_maxopd - optlen, 1078 ("%s: len <= tso_segsz", __func__)); 1079 m->m_pkthdr.csum_flags |= CSUM_TSO; 1080 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1081 } 1082 1083 #ifdef IPSEC 1084 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1085 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u", 1086 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1087 #else 1088 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1089 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u", 1090 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1091 #endif 1092 1093 /* 1094 * In transmit state, time the transmission and arrange for 1095 * the retransmit. In persist state, just set snd_max. 1096 */ 1097 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1098 !tcp_timer_active(tp, TT_PERSIST)) { 1099 tcp_seq startseq = tp->snd_nxt; 1100 1101 /* 1102 * Advance snd_nxt over sequence space of this segment. 1103 */ 1104 if (flags & (TH_SYN|TH_FIN)) { 1105 if (flags & TH_SYN) 1106 tp->snd_nxt++; 1107 if (flags & TH_FIN) { 1108 tp->snd_nxt++; 1109 tp->t_flags |= TF_SENTFIN; 1110 } 1111 } 1112 if (sack_rxmit) 1113 goto timer; 1114 tp->snd_nxt += len; 1115 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1116 tp->snd_max = tp->snd_nxt; 1117 /* 1118 * Time this transmission if not a retransmission and 1119 * not currently timing anything. 1120 */ 1121 if (tp->t_rtttime == 0) { 1122 tp->t_rtttime = ticks; 1123 tp->t_rtseq = startseq; 1124 TCPSTAT_INC(tcps_segstimed); 1125 } 1126 } 1127 1128 /* 1129 * Set retransmit timer if not currently set, 1130 * and not doing a pure ack or a keep-alive probe. 1131 * Initial value for retransmit timer is smoothed 1132 * round-trip time + 2 * round-trip time variance. 1133 * Initialize shift counter which is used for backoff 1134 * of retransmit time. 1135 */ 1136 timer: 1137 if (!tcp_timer_active(tp, TT_REXMT) && 1138 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1139 (tp->snd_nxt != tp->snd_una))) { 1140 if (tcp_timer_active(tp, TT_PERSIST)) { 1141 tcp_timer_activate(tp, TT_PERSIST, 0); 1142 tp->t_rxtshift = 0; 1143 } 1144 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1145 } 1146 } else { 1147 /* 1148 * Persist case, update snd_max but since we are in 1149 * persist mode (no window) we do not update snd_nxt. 1150 */ 1151 int xlen = len; 1152 if (flags & TH_SYN) 1153 ++xlen; 1154 if (flags & TH_FIN) { 1155 ++xlen; 1156 tp->t_flags |= TF_SENTFIN; 1157 } 1158 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1159 tp->snd_max = tp->snd_nxt + len; 1160 } 1161 1162 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1163 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1164 1165 #ifdef TCPDEBUG 1166 /* 1167 * Trace. 1168 */ 1169 if (so->so_options & SO_DEBUG) { 1170 u_short save = 0; 1171 #ifdef INET6 1172 if (!isipv6) 1173 #endif 1174 { 1175 save = ipov->ih_len; 1176 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1177 } 1178 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1179 #ifdef INET6 1180 if (!isipv6) 1181 #endif 1182 ipov->ih_len = save; 1183 } 1184 #endif /* TCPDEBUG */ 1185 1186 /* 1187 * Fill in IP length and desired time to live and 1188 * send to IP level. There should be a better way 1189 * to handle ttl and tos; we could keep them in 1190 * the template, but need a way to checksum without them. 1191 */ 1192 /* 1193 * m->m_pkthdr.len should have been set before cksum calcuration, 1194 * because in6_cksum() need it. 1195 */ 1196 #ifdef INET6 1197 if (isipv6) { 1198 /* 1199 * we separately set hoplimit for every segment, since the 1200 * user might want to change the value via setsockopt. 1201 * Also, desired default hop limit might be changed via 1202 * Neighbor Discovery. 1203 */ 1204 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1205 1206 /* TODO: IPv6 IP6TOS_ECT bit on */ 1207 error = ip6_output(m, 1208 tp->t_inpcb->in6p_outputopts, NULL, 1209 ((so->so_options & SO_DONTROUTE) ? 1210 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1211 } 1212 #endif /* INET6 */ 1213 #if defined(INET) && defined(INET6) 1214 else 1215 #endif 1216 #ifdef INET 1217 { 1218 ip->ip_len = m->m_pkthdr.len; 1219 #ifdef INET6 1220 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1221 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1222 #endif /* INET6 */ 1223 /* 1224 * If we do path MTU discovery, then we set DF on every packet. 1225 * This might not be the best thing to do according to RFC3390 1226 * Section 2. However the tcp hostcache migitates the problem 1227 * so it affects only the first tcp connection with a host. 1228 * 1229 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1230 */ 1231 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) 1232 ip->ip_off |= IP_DF; 1233 1234 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1235 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1236 tp->t_inpcb); 1237 } 1238 #endif /* INET */ 1239 if (error) { 1240 1241 /* 1242 * We know that the packet was lost, so back out the 1243 * sequence number advance, if any. 1244 * 1245 * If the error is EPERM the packet got blocked by the 1246 * local firewall. Normally we should terminate the 1247 * connection but the blocking may have been spurious 1248 * due to a firewall reconfiguration cycle. So we treat 1249 * it like a packet loss and let the retransmit timer and 1250 * timeouts do their work over time. 1251 * XXX: It is a POLA question whether calling tcp_drop right 1252 * away would be the really correct behavior instead. 1253 */ 1254 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1255 !tcp_timer_active(tp, TT_PERSIST)) && 1256 ((flags & TH_SYN) == 0) && 1257 (error != EPERM)) { 1258 if (sack_rxmit) { 1259 p->rxmit -= len; 1260 tp->sackhint.sack_bytes_rexmit -= len; 1261 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1262 ("sackhint bytes rtx >= 0")); 1263 } else 1264 tp->snd_nxt -= len; 1265 } 1266 out: 1267 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1268 switch (error) { 1269 case EPERM: 1270 tp->t_softerror = error; 1271 return (error); 1272 case ENOBUFS: 1273 if (!tcp_timer_active(tp, TT_REXMT) && 1274 !tcp_timer_active(tp, TT_PERSIST)) 1275 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1276 tp->snd_cwnd = tp->t_maxseg; 1277 return (0); 1278 case EMSGSIZE: 1279 /* 1280 * For some reason the interface we used initially 1281 * to send segments changed to another or lowered 1282 * its MTU. 1283 * 1284 * tcp_mtudisc() will find out the new MTU and as 1285 * its last action, initiate retransmission, so it 1286 * is important to not do so here. 1287 * 1288 * If TSO was active we either got an interface 1289 * without TSO capabilits or TSO was turned off. 1290 * Disable it for this connection as too and 1291 * immediatly retry with MSS sized segments generated 1292 * by this function. 1293 */ 1294 if (tso) 1295 tp->t_flags &= ~TF_TSO; 1296 tcp_mtudisc(tp->t_inpcb, 0); 1297 return (0); 1298 case EHOSTDOWN: 1299 case EHOSTUNREACH: 1300 case ENETDOWN: 1301 case ENETUNREACH: 1302 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1303 tp->t_softerror = error; 1304 return (0); 1305 } 1306 /* FALLTHROUGH */ 1307 default: 1308 return (error); 1309 } 1310 } 1311 TCPSTAT_INC(tcps_sndtotal); 1312 1313 /* 1314 * Data sent (as far as we can tell). 1315 * If this advertises a larger window than any other segment, 1316 * then remember the size of the advertised window. 1317 * Any pending ACK has now been sent. 1318 */ 1319 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1320 tp->rcv_adv = tp->rcv_nxt + recwin; 1321 tp->last_ack_sent = tp->rcv_nxt; 1322 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1323 if (tcp_timer_active(tp, TT_DELACK)) 1324 tcp_timer_activate(tp, TT_DELACK, 0); 1325 #if 0 1326 /* 1327 * This completely breaks TCP if newreno is turned on. What happens 1328 * is that if delayed-acks are turned on on the receiver, this code 1329 * on the transmitter effectively destroys the TCP window, forcing 1330 * it to four packets (1.5Kx4 = 6K window). 1331 */ 1332 if (sendalot && --maxburst) 1333 goto again; 1334 #endif 1335 if (sendalot) 1336 goto again; 1337 return (0); 1338 } 1339 1340 void 1341 tcp_setpersist(struct tcpcb *tp) 1342 { 1343 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1344 int tt; 1345 1346 tp->t_flags &= ~TF_PREVVALID; 1347 if (tcp_timer_active(tp, TT_REXMT)) 1348 panic("tcp_setpersist: retransmit pending"); 1349 /* 1350 * Start/restart persistance timer. 1351 */ 1352 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1353 TCPTV_PERSMIN, TCPTV_PERSMAX); 1354 tcp_timer_activate(tp, TT_PERSIST, tt); 1355 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1356 tp->t_rxtshift++; 1357 } 1358 1359 /* 1360 * Insert TCP options according to the supplied parameters to the place 1361 * optp in a consistent way. Can handle unaligned destinations. 1362 * 1363 * The order of the option processing is crucial for optimal packing and 1364 * alignment for the scarce option space. 1365 * 1366 * The optimal order for a SYN/SYN-ACK segment is: 1367 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1368 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1369 * 1370 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1371 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1372 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1373 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1374 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1375 */ 1376 int 1377 tcp_addoptions(struct tcpopt *to, u_char *optp) 1378 { 1379 u_int mask, optlen = 0; 1380 1381 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1382 if ((to->to_flags & mask) != mask) 1383 continue; 1384 if (optlen == TCP_MAXOLEN) 1385 break; 1386 switch (to->to_flags & mask) { 1387 case TOF_MSS: 1388 while (optlen % 4) { 1389 optlen += TCPOLEN_NOP; 1390 *optp++ = TCPOPT_NOP; 1391 } 1392 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1393 continue; 1394 optlen += TCPOLEN_MAXSEG; 1395 *optp++ = TCPOPT_MAXSEG; 1396 *optp++ = TCPOLEN_MAXSEG; 1397 to->to_mss = htons(to->to_mss); 1398 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1399 optp += sizeof(to->to_mss); 1400 break; 1401 case TOF_SCALE: 1402 while (!optlen || optlen % 2 != 1) { 1403 optlen += TCPOLEN_NOP; 1404 *optp++ = TCPOPT_NOP; 1405 } 1406 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1407 continue; 1408 optlen += TCPOLEN_WINDOW; 1409 *optp++ = TCPOPT_WINDOW; 1410 *optp++ = TCPOLEN_WINDOW; 1411 *optp++ = to->to_wscale; 1412 break; 1413 case TOF_SACKPERM: 1414 while (optlen % 2) { 1415 optlen += TCPOLEN_NOP; 1416 *optp++ = TCPOPT_NOP; 1417 } 1418 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1419 continue; 1420 optlen += TCPOLEN_SACK_PERMITTED; 1421 *optp++ = TCPOPT_SACK_PERMITTED; 1422 *optp++ = TCPOLEN_SACK_PERMITTED; 1423 break; 1424 case TOF_TS: 1425 while (!optlen || optlen % 4 != 2) { 1426 optlen += TCPOLEN_NOP; 1427 *optp++ = TCPOPT_NOP; 1428 } 1429 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1430 continue; 1431 optlen += TCPOLEN_TIMESTAMP; 1432 *optp++ = TCPOPT_TIMESTAMP; 1433 *optp++ = TCPOLEN_TIMESTAMP; 1434 to->to_tsval = htonl(to->to_tsval); 1435 to->to_tsecr = htonl(to->to_tsecr); 1436 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1437 optp += sizeof(to->to_tsval); 1438 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1439 optp += sizeof(to->to_tsecr); 1440 break; 1441 case TOF_SIGNATURE: 1442 { 1443 int siglen = TCPOLEN_SIGNATURE - 2; 1444 1445 while (!optlen || optlen % 4 != 2) { 1446 optlen += TCPOLEN_NOP; 1447 *optp++ = TCPOPT_NOP; 1448 } 1449 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1450 continue; 1451 optlen += TCPOLEN_SIGNATURE; 1452 *optp++ = TCPOPT_SIGNATURE; 1453 *optp++ = TCPOLEN_SIGNATURE; 1454 to->to_signature = optp; 1455 while (siglen--) 1456 *optp++ = 0; 1457 break; 1458 } 1459 case TOF_SACK: 1460 { 1461 int sackblks = 0; 1462 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1463 tcp_seq sack_seq; 1464 1465 while (!optlen || optlen % 4 != 2) { 1466 optlen += TCPOLEN_NOP; 1467 *optp++ = TCPOPT_NOP; 1468 } 1469 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1470 continue; 1471 optlen += TCPOLEN_SACKHDR; 1472 *optp++ = TCPOPT_SACK; 1473 sackblks = min(to->to_nsacks, 1474 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1475 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1476 while (sackblks--) { 1477 sack_seq = htonl(sack->start); 1478 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1479 optp += sizeof(sack_seq); 1480 sack_seq = htonl(sack->end); 1481 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1482 optp += sizeof(sack_seq); 1483 optlen += TCPOLEN_SACK; 1484 sack++; 1485 } 1486 TCPSTAT_INC(tcps_sack_send_blocks); 1487 break; 1488 } 1489 default: 1490 panic("%s: unknown TCP option type", __func__); 1491 break; 1492 } 1493 } 1494 1495 /* Terminate and pad TCP options to a 4 byte boundary. */ 1496 if (optlen % 4) { 1497 optlen += TCPOLEN_EOL; 1498 *optp++ = TCPOPT_EOL; 1499 } 1500 /* 1501 * According to RFC 793 (STD0007): 1502 * "The content of the header beyond the End-of-Option option 1503 * must be header padding (i.e., zero)." 1504 * and later: "The padding is composed of zeros." 1505 */ 1506 while (optlen % 4) { 1507 optlen += TCPOLEN_PAD; 1508 *optp++ = TCPOPT_PAD; 1509 } 1510 1511 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1512 return (optlen); 1513 } 1514