1 /* 2 * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved. 36 * 37 * License terms: all terms for the DragonFly license above plus the following: 38 * 39 * 4. All advertising materials mentioning features or use of this software 40 * must display the following acknowledgement: 41 * 42 * This product includes software developed by Jeffrey M. Hsu 43 * for the DragonFly Project. 44 * 45 * This requirement may be waived with permission from Jeffrey Hsu. 46 * This requirement will sunset and may be removed on July 8 2005, 47 * after which the standard DragonFly license (as shown above) will 48 * apply. 49 */ 50 51 /* 52 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 53 * The Regents of the University of California. All rights reserved. 54 * 55 * Redistribution and use in source and binary forms, with or without 56 * modification, are permitted provided that the following conditions 57 * are met: 58 * 1. Redistributions of source code must retain the above copyright 59 * notice, this list of conditions and the following disclaimer. 60 * 2. Redistributions in binary form must reproduce the above copyright 61 * notice, this list of conditions and the following disclaimer in the 62 * documentation and/or other materials provided with the distribution. 63 * 3. All advertising materials mentioning features or use of this software 64 * must display the following acknowledgement: 65 * This product includes software developed by the University of 66 * California, Berkeley and its contributors. 67 * 4. Neither the name of the University nor the names of its contributors 68 * may be used to endorse or promote products derived from this software 69 * without specific prior written permission. 70 * 71 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 72 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 73 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 74 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 75 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 76 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 77 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 78 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 79 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 80 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 81 * SUCH DAMAGE. 82 * 83 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 84 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $ 85 * $DragonFly: src/sys/netinet/tcp_output.c,v 1.16 2004/07/17 20:31:31 hsu Exp $ 86 */ 87 88 #include "opt_inet6.h" 89 #include "opt_ipsec.h" 90 #include "opt_tcpdebug.h" 91 92 #include <sys/param.h> 93 #include <sys/systm.h> 94 #include <sys/kernel.h> 95 #include <sys/sysctl.h> 96 #include <sys/mbuf.h> 97 #include <sys/domain.h> 98 #include <sys/protosw.h> 99 #include <sys/socket.h> 100 #include <sys/socketvar.h> 101 #include <sys/in_cksum.h> 102 #include <sys/thread.h> 103 #include <sys/globaldata.h> 104 105 #include <net/route.h> 106 107 #include <netinet/in.h> 108 #include <netinet/in_systm.h> 109 #include <netinet/ip.h> 110 #include <netinet/in_pcb.h> 111 #include <netinet/ip_var.h> 112 #include <netinet6/in6_pcb.h> 113 #include <netinet/ip6.h> 114 #include <netinet6/ip6_var.h> 115 #include <netinet/tcp.h> 116 #define TCPOUTFLAGS 117 #include <netinet/tcp_fsm.h> 118 #include <netinet/tcp_seq.h> 119 #include <netinet/tcp_timer.h> 120 #include <netinet/tcp_var.h> 121 #include <netinet/tcpip.h> 122 #ifdef TCPDEBUG 123 #include <netinet/tcp_debug.h> 124 #endif 125 126 #ifdef IPSEC 127 #include <netinet6/ipsec.h> 128 #endif /*IPSEC*/ 129 130 #ifdef FAST_IPSEC 131 #include <netipsec/ipsec.h> 132 #define IPSEC 133 #endif /*FAST_IPSEC*/ 134 135 #ifdef notyet 136 extern struct mbuf *m_copypack(); 137 #endif 138 139 int path_mtu_discovery = 1; 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 141 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 142 143 int ss_fltsz = 1; 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 145 &ss_fltsz, 1, "Slow start flight size"); 146 147 int ss_fltsz_local = 4; 148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 149 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 150 151 /* 152 * Tcp output routine: figure out what should be sent and send it. 153 */ 154 int 155 tcp_output(tp) 156 struct tcpcb *tp; 157 { 158 struct inpcb * const inp = tp->t_inpcb; 159 struct socket *so = inp->inp_socket; 160 long len, recvwin, sendwin; 161 int off, flags, error; 162 struct mbuf *m; 163 struct ip *ip = NULL; 164 struct ipovly *ipov = NULL; 165 struct tcphdr *th; 166 u_char opt[TCP_MAXOLEN]; 167 unsigned ipoptlen, optlen, hdrlen; 168 int idle, sendalot; 169 struct ip6_hdr *ip6 = NULL; 170 #ifdef INET6 171 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 172 #else 173 const boolean_t isipv6 = FALSE; 174 #endif 175 struct rmxp_tao *taop; 176 177 /* 178 * Determine length of data that should be transmitted, 179 * and flags that will be used. 180 * If there is some data or critical controls (SYN, RST) 181 * to send, then transmit; otherwise, investigate further. 182 */ 183 if ((tp->snd_max == tp->snd_una) && 184 (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 185 /* 186 * We have been idle for "a while" and no acks are 187 * expected to clock out any data we send -- 188 * slow start to get ack "clock" running again. 189 * 190 * Set the slow-start flight size depending on whether 191 * this is a local network or not. 192 */ 193 if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 194 (!isipv6 && in_localaddr(inp->inp_faddr))) 195 tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local; 196 else 197 tp->snd_cwnd = tp->t_maxseg * ss_fltsz; 198 } 199 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 200 if (idle && (tp->t_flags & TF_MORETOCOME)) 201 tp->t_flags |= TF_LASTIDLE; 202 else 203 tp->t_flags &= ~TF_LASTIDLE; 204 205 again: 206 sendalot = 0; 207 off = tp->snd_nxt - tp->snd_una; 208 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 209 sendwin = min(sendwin, tp->snd_bwnd); 210 211 flags = tcp_outflags[tp->t_state]; 212 /* 213 * Get standard flags, and add SYN or FIN if requested by 'hidden' 214 * state flags. 215 */ 216 if (tp->t_flags & TF_NEEDFIN) 217 flags |= TH_FIN; 218 if (tp->t_flags & TF_NEEDSYN) 219 flags |= TH_SYN; 220 221 /* 222 * If in persist timeout with window of 0, send 1 byte. 223 * Otherwise, if window is small but nonzero 224 * and timer expired, we will send what we can 225 * and go to transmit state. 226 */ 227 if (tp->t_flags & TF_FORCE) { 228 if (sendwin == 0) { 229 /* 230 * If we still have some data to send, then 231 * clear the FIN bit. Usually this would 232 * happen below when it realizes that we 233 * aren't sending all the data. However, 234 * if we have exactly 1 byte of unsent data, 235 * then it won't clear the FIN bit below, 236 * and if we are in persist state, we wind 237 * up sending the packet without recording 238 * that we sent the FIN bit. 239 * 240 * We can't just blindly clear the FIN bit, 241 * because if we don't have any more data 242 * to send then the probe will be the FIN 243 * itself. 244 */ 245 if (off < so->so_snd.sb_cc) 246 flags &= ~TH_FIN; 247 sendwin = 1; 248 } else { 249 callout_stop(tp->tt_persist); 250 tp->t_rxtshift = 0; 251 } 252 } 253 254 /* 255 * If snd_nxt == snd_max and we have transmitted a FIN, the 256 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 257 * a negative length. This can also occur when TCP opens up 258 * its congestion window while receiving additional duplicate 259 * acks after fast-retransmit because TCP will reset snd_nxt 260 * to snd_max after the fast-retransmit. 261 * 262 * In the normal retransmit-FIN-only case, however, snd_nxt will 263 * be set to snd_una, the offset will be 0, and the length may 264 * wind up 0. 265 */ 266 len = (long)ulmin(so->so_snd.sb_cc, sendwin) - off; 267 268 /* 269 * Lop off SYN bit if it has already been sent. However, if this 270 * is SYN-SENT state and if segment contains data and if we don't 271 * know that foreign host supports TAO, suppress sending segment. 272 */ 273 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 274 flags &= ~TH_SYN; 275 off--, len++; 276 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 277 ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL || 278 taop->tao_ccsent == 0)) 279 return 0; 280 } 281 282 /* 283 * Be careful not to send data and/or FIN on SYN segments 284 * in cases when no CC option will be sent. 285 * This measure is needed to prevent interoperability problems 286 * with not fully conformant TCP implementations. 287 */ 288 if ((flags & TH_SYN) && 289 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 290 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 291 len = 0; 292 flags &= ~TH_FIN; 293 } 294 295 if (len < 0) { 296 /* 297 * If FIN has been sent but not acked, 298 * but we haven't been called to retransmit, 299 * len will be < 0. Otherwise, window shrank 300 * after we sent into it. If window shrank to 0, 301 * cancel pending retransmit, pull snd_nxt back 302 * to (closed) window, and set the persist timer 303 * if it isn't already going. If the window didn't 304 * close completely, just wait for an ACK. 305 */ 306 len = 0; 307 if (sendwin == 0) { 308 callout_stop(tp->tt_rexmt); 309 tp->t_rxtshift = 0; 310 tp->snd_nxt = tp->snd_una; 311 if (!callout_active(tp->tt_persist)) 312 tcp_setpersist(tp); 313 } 314 } 315 316 /* 317 * len will be >= 0 after this point. Truncate to the maximum 318 * segment length and ensure that FIN is removed if the length 319 * no longer contains the last data byte. 320 */ 321 if (len > tp->t_maxseg) { 322 len = tp->t_maxseg; 323 sendalot = 1; 324 } 325 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 326 flags &= ~TH_FIN; 327 328 recvwin = sbspace(&so->so_rcv); 329 330 /* 331 * Sender silly window avoidance. We transmit under the following 332 * conditions when len is non-zero: 333 * 334 * - We have a full segment 335 * - This is the last buffer in a write()/send() and we are 336 * either idle or running NODELAY 337 * - we've timed out (e.g. persist timer) 338 * - we have more then 1/2 the maximum send window's worth of 339 * data (receiver may be limited the window size) 340 * - we need to retransmit 341 */ 342 if (len) { 343 if (len == tp->t_maxseg) 344 goto send; 345 /* 346 * NOTE! on localhost connections an 'ack' from the remote 347 * end may occur synchronously with the output and cause 348 * us to flush a buffer queued with moretocome. XXX 349 * 350 * note: the len + off check is almost certainly unnecessary. 351 */ 352 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 353 (idle || (tp->t_flags & TF_NODELAY)) && 354 len + off >= so->so_snd.sb_cc && 355 !(tp->t_flags & TF_NOPUSH)) { 356 goto send; 357 } 358 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 359 goto send; 360 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 361 goto send; 362 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 363 goto send; 364 } 365 366 /* 367 * Compare available window to amount of window 368 * known to peer (as advertised window less 369 * next expected input). If the difference is at least two 370 * max size segments, or at least 50% of the maximum possible 371 * window, then want to send a window update to peer. 372 */ 373 if (recvwin > 0) { 374 /* 375 * "adv" is the amount we can increase the window, 376 * taking into account that we are limited by 377 * TCP_MAXWIN << tp->rcv_scale. 378 */ 379 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 380 (tp->rcv_adv - tp->rcv_nxt); 381 382 if (adv >= (long) (2 * tp->t_maxseg)) 383 goto send; 384 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 385 goto send; 386 } 387 388 /* 389 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 390 * is also a catch-all for the retransmit timer timeout case. 391 */ 392 if (tp->t_flags & TF_ACKNOW) 393 goto send; 394 if ((flags & TH_RST) || 395 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 396 goto send; 397 if (SEQ_GT(tp->snd_up, tp->snd_una)) 398 goto send; 399 /* 400 * If our state indicates that FIN should be sent 401 * and we have not yet done so, then we need to send. 402 */ 403 if (flags & TH_FIN && 404 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 405 goto send; 406 407 /* 408 * TCP window updates are not reliable, rather a polling protocol 409 * using ``persist'' packets is used to insure receipt of window 410 * updates. The three ``states'' for the output side are: 411 * idle not doing retransmits or persists 412 * persisting to move a small or zero window 413 * (re)transmitting and thereby not persisting 414 * 415 * callout_active(tp->tt_persist) 416 * is true when we are in persist state. 417 * The TF_FORCE flag in tp->t_flags 418 * is set when we are called to send a persist packet. 419 * callout_active(tp->tt_rexmt) 420 * is set when we are retransmitting 421 * The output side is idle when both timers are zero. 422 * 423 * If send window is too small, there is data to transmit, and no 424 * retransmit or persist is pending, then go to persist state. 425 * If nothing happens soon, send when timer expires: 426 * if window is nonzero, transmit what we can, 427 * otherwise force out a byte. 428 */ 429 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 430 !callout_active(tp->tt_persist)) { 431 tp->t_rxtshift = 0; 432 tcp_setpersist(tp); 433 } 434 435 /* 436 * No reason to send a segment, just return. 437 */ 438 return (0); 439 440 send: 441 /* 442 * Before ESTABLISHED, force sending of initial options 443 * unless TCP set not to do any options. 444 * NOTE: we assume that the IP/TCP header plus TCP options 445 * always fit in a single mbuf, leaving room for a maximum 446 * link header, i.e. 447 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 448 */ 449 optlen = 0; 450 if (isipv6) 451 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 452 else 453 hdrlen = sizeof(struct tcpiphdr); 454 if (flags & TH_SYN) { 455 tp->snd_nxt = tp->iss; 456 if (!(tp->t_flags & TF_NOOPT)) { 457 u_short mss; 458 459 opt[0] = TCPOPT_MAXSEG; 460 opt[1] = TCPOLEN_MAXSEG; 461 mss = htons((u_short) tcp_mssopt(tp)); 462 (void)memcpy(opt + 2, &mss, sizeof(mss)); 463 optlen = TCPOLEN_MAXSEG; 464 465 if ((tp->t_flags & TF_REQ_SCALE) && 466 (!(flags & TH_ACK) || 467 (tp->t_flags & TF_RCVD_SCALE))) { 468 *((u_int32_t *)(opt + optlen)) = htonl( 469 TCPOPT_NOP << 24 | 470 TCPOPT_WINDOW << 16 | 471 TCPOLEN_WINDOW << 8 | 472 tp->request_r_scale); 473 optlen += 4; 474 } 475 } 476 } 477 478 /* 479 * Send a timestamp and echo-reply if this is a SYN and our side 480 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 481 * and our peer have sent timestamps in our SYN's. 482 */ 483 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 484 !(flags & TH_RST) && 485 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 486 u_int32_t *lp = (u_int32_t *)(opt + optlen); 487 488 /* Form timestamp option as shown in appendix A of RFC 1323. */ 489 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 490 *lp++ = htonl(ticks); 491 *lp = htonl(tp->ts_recent); 492 optlen += TCPOLEN_TSTAMP_APPA; 493 } 494 495 /* 496 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 497 * options are allowed (!TF_NOOPT) and it's not a RST. 498 */ 499 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 500 !(flags & TH_RST)) { 501 switch (flags & (TH_SYN|TH_ACK)) { 502 /* 503 * This is a normal ACK, send CC if we received CC before 504 * from our peer. 505 */ 506 case TH_ACK: 507 if (!(tp->t_flags & TF_RCVD_CC)) 508 break; 509 /*FALLTHROUGH*/ 510 511 /* 512 * We can only get here in T/TCP's SYN_SENT* state, when 513 * we're a sending a non-SYN segment without waiting for 514 * the ACK of our SYN. A check above assures that we only 515 * do this if our peer understands T/TCP. 516 */ 517 case 0: 518 opt[optlen++] = TCPOPT_NOP; 519 opt[optlen++] = TCPOPT_NOP; 520 opt[optlen++] = TCPOPT_CC; 521 opt[optlen++] = TCPOLEN_CC; 522 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 523 524 optlen += 4; 525 break; 526 527 /* 528 * This is our initial SYN, check whether we have to use 529 * CC or CC.new. 530 */ 531 case TH_SYN: 532 opt[optlen++] = TCPOPT_NOP; 533 opt[optlen++] = TCPOPT_NOP; 534 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 535 TCPOPT_CCNEW : TCPOPT_CC; 536 opt[optlen++] = TCPOLEN_CC; 537 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 538 optlen += 4; 539 break; 540 541 /* 542 * This is a SYN,ACK; send CC and CC.echo if we received 543 * CC from our peer. 544 */ 545 case (TH_SYN|TH_ACK): 546 if (tp->t_flags & TF_RCVD_CC) { 547 opt[optlen++] = TCPOPT_NOP; 548 opt[optlen++] = TCPOPT_NOP; 549 opt[optlen++] = TCPOPT_CC; 550 opt[optlen++] = TCPOLEN_CC; 551 *(u_int32_t *)&opt[optlen] = 552 htonl(tp->cc_send); 553 optlen += 4; 554 opt[optlen++] = TCPOPT_NOP; 555 opt[optlen++] = TCPOPT_NOP; 556 opt[optlen++] = TCPOPT_CCECHO; 557 opt[optlen++] = TCPOLEN_CC; 558 *(u_int32_t *)&opt[optlen] = 559 htonl(tp->cc_recv); 560 optlen += 4; 561 } 562 break; 563 } 564 } 565 566 hdrlen += optlen; 567 568 if (isipv6) 569 ipoptlen = ip6_optlen(inp); 570 else { 571 if (inp->inp_options) { 572 ipoptlen = inp->inp_options->m_len - 573 offsetof(struct ipoption, ipopt_list); 574 } else { 575 ipoptlen = 0; 576 } 577 } 578 #ifdef IPSEC 579 ipoptlen += ipsec_hdrsiz_tcp(tp); 580 #endif 581 582 /* 583 * Adjust data length if insertion of options will 584 * bump the packet length beyond the t_maxopd length. 585 * Clear the FIN bit because we cut off the tail of 586 * the segment. 587 */ 588 if (len + optlen + ipoptlen > tp->t_maxopd) { 589 /* 590 * If there is still more to send, don't close the connection. 591 */ 592 flags &= ~TH_FIN; 593 len = tp->t_maxopd - optlen - ipoptlen; 594 sendalot = 1; 595 } 596 597 #ifdef INET6 598 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 599 #else 600 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 601 #endif 602 603 /* 604 * Grab a header mbuf, attaching a copy of data to 605 * be transmitted, and initialize the header from 606 * the template for sends on this connection. 607 */ 608 if (len) { 609 if ((tp->t_flags & TF_FORCE) && len == 1) 610 tcpstat.tcps_sndprobe++; 611 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 612 tcpstat.tcps_sndrexmitpack++; 613 tcpstat.tcps_sndrexmitbyte += len; 614 } else { 615 tcpstat.tcps_sndpack++; 616 tcpstat.tcps_sndbyte += len; 617 } 618 #ifdef notyet 619 if ((m = m_copypack(so->so_snd.sb_mb, off, 620 (int)len, max_linkhdr + hdrlen)) == 0) { 621 error = ENOBUFS; 622 goto out; 623 } 624 /* 625 * m_copypack left space for our hdr; use it. 626 */ 627 m->m_len += hdrlen; 628 m->m_data -= hdrlen; 629 #else 630 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 631 if (m == NULL) { 632 error = ENOBUFS; 633 goto out; 634 } 635 #ifdef INET6 636 if (MHLEN < hdrlen + max_linkhdr) { 637 MCLGET(m, MB_DONTWAIT); 638 if (!(m->m_flags & M_EXT)) { 639 m_freem(m); 640 error = ENOBUFS; 641 goto out; 642 } 643 } 644 #endif 645 m->m_data += max_linkhdr; 646 m->m_len = hdrlen; 647 if (len <= MHLEN - hdrlen - max_linkhdr) { 648 m_copydata(so->so_snd.sb_mb, off, (int) len, 649 mtod(m, caddr_t) + hdrlen); 650 m->m_len += len; 651 } else { 652 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 653 if (m->m_next == 0) { 654 (void) m_free(m); 655 error = ENOBUFS; 656 goto out; 657 } 658 } 659 #endif 660 /* 661 * If we're sending everything we've got, set PUSH. 662 * (This will keep happy those implementations which only 663 * give data to the user when a buffer fills or 664 * a PUSH comes in.) 665 */ 666 if (off + len == so->so_snd.sb_cc) 667 flags |= TH_PUSH; 668 } else { 669 if (tp->t_flags & TF_ACKNOW) 670 tcpstat.tcps_sndacks++; 671 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 672 tcpstat.tcps_sndctrl++; 673 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 674 tcpstat.tcps_sndurg++; 675 else 676 tcpstat.tcps_sndwinup++; 677 678 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 679 if (m == NULL) { 680 error = ENOBUFS; 681 goto out; 682 } 683 if (isipv6 && 684 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 685 MH_ALIGN(m, hdrlen); 686 else 687 m->m_data += max_linkhdr; 688 m->m_len = hdrlen; 689 } 690 m->m_pkthdr.rcvif = (struct ifnet *)0; 691 if (isipv6) { 692 ip6 = mtod(m, struct ip6_hdr *); 693 th = (struct tcphdr *)(ip6 + 1); 694 tcp_fillheaders(tp, ip6, th); 695 } else { 696 ip = mtod(m, struct ip *); 697 ipov = (struct ipovly *)ip; 698 th = (struct tcphdr *)(ip + 1); 699 /* this picks up the pseudo header (w/o the length) */ 700 tcp_fillheaders(tp, ip, th); 701 } 702 703 /* 704 * Fill in fields, remembering maximum advertised 705 * window for use in delaying messages about window sizes. 706 * If resending a FIN, be sure not to use a new sequence number. 707 */ 708 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 709 tp->snd_nxt == tp->snd_max) 710 tp->snd_nxt--; 711 /* 712 * If we are doing retransmissions, then snd_nxt will 713 * not reflect the first unsent octet. For ACK only 714 * packets, we do not want the sequence number of the 715 * retransmitted packet, we want the sequence number 716 * of the next unsent octet. So, if there is no data 717 * (and no SYN or FIN), use snd_max instead of snd_nxt 718 * when filling in ti_seq. But if we are in persist 719 * state, snd_max might reflect one byte beyond the 720 * right edge of the window, so use snd_nxt in that 721 * case, since we know we aren't doing a retransmission. 722 * (retransmit and persist are mutually exclusive...) 723 */ 724 if (len || (flags & (TH_SYN|TH_FIN)) || callout_active(tp->tt_persist)) 725 th->th_seq = htonl(tp->snd_nxt); 726 else 727 th->th_seq = htonl(tp->snd_max); 728 th->th_ack = htonl(tp->rcv_nxt); 729 if (optlen) { 730 bcopy(opt, th + 1, optlen); 731 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 732 } 733 th->th_flags = flags; 734 /* 735 * Calculate receive window. Don't shrink window, 736 * but avoid silly window syndrome. 737 */ 738 if (recvwin < (long)(so->so_rcv.sb_hiwat / 4) && 739 recvwin < (long)tp->t_maxseg) 740 recvwin = 0; 741 if (recvwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 742 recvwin = (long)(tp->rcv_adv - tp->rcv_nxt); 743 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 744 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 745 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 746 747 /* 748 * Adjust the RXWIN0SENT flag - indicate that we have advertised 749 * a 0 window. This may cause the remote transmitter to stall. This 750 * flag tells soreceive() to disable delayed acknowledgements when 751 * draining the buffer. This can occur if the receiver is attempting 752 * to read more data then can be buffered prior to transmitting on 753 * the connection. 754 */ 755 if (recvwin == 0) 756 tp->t_flags |= TF_RXWIN0SENT; 757 else 758 tp->t_flags &= ~TF_RXWIN0SENT; 759 760 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 761 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 762 th->th_flags |= TH_URG; 763 } else { 764 /* 765 * If no urgent pointer to send, then we pull 766 * the urgent pointer to the left edge of the send window 767 * so that it doesn't drift into the send window on sequence 768 * number wraparound. 769 */ 770 tp->snd_up = tp->snd_una; /* drag it along */ 771 } 772 773 /* 774 * Put TCP length in extended header, and then 775 * checksum extended header and data. 776 */ 777 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 778 if (isipv6) { 779 /* 780 * ip6_plen is not need to be filled now, and will be filled 781 * in ip6_output. 782 */ 783 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 784 sizeof(struct tcphdr) + optlen + len); 785 } else { 786 m->m_pkthdr.csum_flags = CSUM_TCP; 787 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 788 if (len + optlen) 789 th->th_sum = in_addword(th->th_sum, 790 htons((u_short)(optlen + len))); 791 792 /* IP version must be set here for ipv4/ipv6 checking later */ 793 KASSERT(ip->ip_v == IPVERSION, 794 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 795 } 796 797 /* 798 * In transmit state, time the transmission and arrange for 799 * the retransmit. In persist state, just set snd_max. 800 */ 801 if (!(tp->t_flags & TF_FORCE) || !callout_active(tp->tt_persist)) { 802 tcp_seq startseq = tp->snd_nxt; 803 804 /* 805 * Advance snd_nxt over sequence space of this segment. 806 */ 807 if (flags & (TH_SYN|TH_FIN)) { 808 if (flags & TH_SYN) 809 tp->snd_nxt++; 810 if (flags & TH_FIN) { 811 tp->snd_nxt++; 812 tp->t_flags |= TF_SENTFIN; 813 } 814 } 815 tp->snd_nxt += len; 816 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 817 tp->snd_max = tp->snd_nxt; 818 /* 819 * Time this transmission if not a retransmission and 820 * not currently timing anything. 821 */ 822 if (tp->t_rtttime == 0) { 823 tp->t_rtttime = ticks; 824 tp->t_rtseq = startseq; 825 tcpstat.tcps_segstimed++; 826 } 827 } 828 829 /* 830 * Set retransmit timer if not currently set, 831 * and not doing a pure ack or a keep-alive probe. 832 * Initial value for retransmit timer is smoothed 833 * round-trip time + 2 * round-trip time variance. 834 * Initialize shift counter which is used for backoff 835 * of retransmit time. 836 */ 837 if (!callout_active(tp->tt_rexmt) && 838 tp->snd_nxt != tp->snd_una) { 839 if (callout_active(tp->tt_persist)) { 840 callout_stop(tp->tt_persist); 841 tp->t_rxtshift = 0; 842 } 843 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 844 tcp_timer_rexmt, tp); 845 } 846 } else { 847 /* 848 * Persist case, update snd_max but since we are in 849 * persist mode (no window) we do not update snd_nxt. 850 */ 851 int xlen = len; 852 if (flags & TH_SYN) 853 ++xlen; 854 if (flags & TH_FIN) { 855 ++xlen; 856 tp->t_flags |= TF_SENTFIN; 857 } 858 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 859 tp->snd_max = tp->snd_nxt + xlen; 860 } 861 862 #ifdef TCPDEBUG 863 /* 864 * Trace. 865 */ 866 if (so->so_options & SO_DEBUG) 867 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 868 #endif 869 870 /* 871 * Fill in IP length and desired time to live and 872 * send to IP level. There should be a better way 873 * to handle ttl and tos; we could keep them in 874 * the template, but need a way to checksum without them. 875 */ 876 /* 877 * m->m_pkthdr.len should have been set before cksum calcuration, 878 * because in6_cksum() need it. 879 */ 880 if (isipv6) { 881 /* 882 * we separately set hoplimit for every segment, since the 883 * user might want to change the value via setsockopt. 884 * Also, desired default hop limit might be changed via 885 * Neighbor Discovery. 886 */ 887 ip6->ip6_hlim = in6_selecthlim(inp, 888 (inp->in6p_route.ro_rt ? 889 inp->in6p_route.ro_rt->rt_ifp : NULL)); 890 891 /* TODO: IPv6 IP6TOS_ECT bit on */ 892 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route, 893 (so->so_options & SO_DONTROUTE), NULL, NULL, inp); 894 } else { 895 struct rtentry *rt; 896 ip->ip_len = m->m_pkthdr.len; 897 #ifdef INET6 898 if (INP_CHECK_SOCKAF(so, AF_INET6)) 899 ip->ip_ttl = in6_selecthlim(inp, 900 (inp->in6p_route.ro_rt ? 901 inp->in6p_route.ro_rt->rt_ifp : NULL)); 902 else 903 #endif 904 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 905 906 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 907 /* 908 * See if we should do MTU discovery. 909 * We do it only if the following are true: 910 * 1) we have a valid route to the destination 911 * 2) the MTU is not locked (if it is, 912 * then discovery has been disabled) 913 */ 914 if (path_mtu_discovery && 915 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) && 916 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 917 ip->ip_off |= IP_DF; 918 919 error = ip_output(m, inp->inp_options, &inp->inp_route, 920 (so->so_options & SO_DONTROUTE), NULL, inp); 921 } 922 if (error) { 923 924 /* 925 * We know that the packet was lost, so back out the 926 * sequence number advance, if any. 927 */ 928 if (!(tp->t_flags & TF_FORCE) || 929 !callout_active(tp->tt_persist)) { 930 /* 931 * No need to check for TH_FIN here because 932 * the TF_SENTFIN flag handles that case. 933 */ 934 if (!(flags & TH_SYN)) 935 tp->snd_nxt -= len; 936 } 937 938 out: 939 if (error == ENOBUFS) { 940 /* 941 * If we can't send, make sure there is something 942 * to get us going again later. Persist state 943 * is not necessarily right, but it is close enough. 944 */ 945 if (!callout_active(tp->tt_rexmt) && 946 !callout_active(tp->tt_persist)) { 947 tp->t_rxtshift = 0; 948 tcp_setpersist(tp); 949 } 950 tcp_quench(inp, 0); 951 return (0); 952 } 953 if (error == EMSGSIZE) { 954 /* 955 * ip_output() will have already fixed the route 956 * for us. tcp_mtudisc() will, as its last action, 957 * initiate retransmission, so it is important to 958 * not do so here. 959 */ 960 tcp_mtudisc(inp, 0); 961 return 0; 962 } 963 if ((error == EHOSTUNREACH || error == ENETDOWN) && 964 TCPS_HAVERCVDSYN(tp->t_state)) { 965 tp->t_softerror = error; 966 return (0); 967 } 968 return (error); 969 } 970 tcpstat.tcps_sndtotal++; 971 972 /* 973 * Data sent (as far as we can tell). 974 * If this advertises a larger window than any other segment, 975 * then remember the size of the advertised window. 976 * Any pending ACK has now been sent. 977 */ 978 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) 979 tp->rcv_adv = tp->rcv_nxt + recvwin; 980 tp->last_ack_sent = tp->rcv_nxt; 981 tp->t_flags &= ~TF_ACKNOW; 982 if (tcp_delack_enabled) 983 callout_stop(tp->tt_delack); 984 if (sendalot) 985 goto again; 986 return (0); 987 } 988 989 void 990 tcp_setpersist(tp) 991 struct tcpcb *tp; 992 { 993 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 994 int tt; 995 996 if (callout_active(tp->tt_rexmt)) 997 panic("tcp_setpersist: retransmit pending"); 998 /* 999 * Start/restart persistance timer. 1000 */ 1001 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1002 TCPTV_PERSMIN, TCPTV_PERSMAX); 1003 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1004 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1005 tp->t_rxtshift++; 1006 } 1007