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 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 34 * $FreeBSD$ 35 */ 36 37 #include "opt_inet6.h" 38 #include "opt_ipsec.h" 39 #include "opt_tcpdebug.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/domain.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/route.h> 54 55 #include <netinet/in.h> 56 #include <netinet/in_systm.h> 57 #include <netinet/ip.h> 58 #include <netinet/in_pcb.h> 59 #include <netinet/ip_var.h> 60 #ifdef INET6 61 #include <netinet6/in6_pcb.h> 62 #include <netinet/ip6.h> 63 #include <netinet6/ip6_var.h> 64 #endif 65 #include <netinet/tcp.h> 66 #define TCPOUTFLAGS 67 #include <netinet/tcp_fsm.h> 68 #include <netinet/tcp_seq.h> 69 #include <netinet/tcp_timer.h> 70 #include <netinet/tcp_var.h> 71 #include <netinet/tcpip.h> 72 #ifdef TCPDEBUG 73 #include <netinet/tcp_debug.h> 74 #endif 75 76 #ifdef IPSEC 77 #include <netinet6/ipsec.h> 78 #endif /*IPSEC*/ 79 80 #include <machine/in_cksum.h> 81 82 #ifdef notyet 83 extern struct mbuf *m_copypack(); 84 #endif 85 86 static int path_mtu_discovery = 1; 87 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 88 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 89 90 int ss_fltsz = 1; 91 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 92 &ss_fltsz, 1, "Slow start flight size"); 93 94 int ss_fltsz_local = 4; 95 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 96 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 97 98 int tcp_do_newreno = 1; 99 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno, 100 0, "Enable NewReno Algorithms"); 101 /* 102 * Tcp output routine: figure out what should be sent and send it. 103 */ 104 int 105 tcp_output(tp) 106 register struct tcpcb *tp; 107 { 108 register struct socket *so = tp->t_inpcb->inp_socket; 109 register long len, win; 110 int off, flags, error; 111 register struct mbuf *m; 112 struct ip *ip = NULL; 113 register struct ipovly *ipov = NULL; 114 #ifdef INET6 115 struct ip6_hdr *ip6 = NULL; 116 #endif /* INET6 */ 117 register struct tcphdr *th; 118 u_char opt[TCP_MAXOLEN]; 119 unsigned ipoptlen, optlen, hdrlen; 120 int idle, sendalot; 121 #if 0 122 int maxburst = TCP_MAXBURST; 123 #endif 124 struct rmxp_tao *taop; 125 struct rmxp_tao tao_noncached; 126 #ifdef INET6 127 int isipv6; 128 #endif 129 130 #ifdef INET6 131 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 132 #endif 133 134 /* 135 * Determine length of data that should be transmitted, 136 * and flags that will be used. 137 * If there is some data or critical controls (SYN, RST) 138 * to send, then transmit; otherwise, investigate further. 139 */ 140 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 141 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 142 /* 143 * We have been idle for "a while" and no acks are 144 * expected to clock out any data we send -- 145 * slow start to get ack "clock" running again. 146 * 147 * Set the slow-start flight size depending on whether 148 * this is a local network or not. 149 */ 150 if ( 151 #ifdef INET6 152 (isipv6 && in6_localaddr(&tp->t_inpcb->in6p_faddr)) || 153 (!isipv6 && 154 #endif 155 in_localaddr(tp->t_inpcb->inp_faddr) 156 #ifdef INET6 157 ) 158 #endif 159 ) 160 tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local; 161 else 162 tp->snd_cwnd = tp->t_maxseg * ss_fltsz; 163 } 164 tp->t_flags &= ~TF_LASTIDLE; 165 if (idle) { 166 if (tp->t_flags & TF_MORETOCOME) { 167 tp->t_flags |= TF_LASTIDLE; 168 idle = 0; 169 } 170 } 171 again: 172 sendalot = 0; 173 off = tp->snd_nxt - tp->snd_una; 174 win = min(tp->snd_wnd, tp->snd_cwnd); 175 176 flags = tcp_outflags[tp->t_state]; 177 /* 178 * Get standard flags, and add SYN or FIN if requested by 'hidden' 179 * state flags. 180 */ 181 if (tp->t_flags & TF_NEEDFIN) 182 flags |= TH_FIN; 183 if (tp->t_flags & TF_NEEDSYN) 184 flags |= TH_SYN; 185 186 /* 187 * If in persist timeout with window of 0, send 1 byte. 188 * Otherwise, if window is small but nonzero 189 * and timer expired, we will send what we can 190 * and go to transmit state. 191 */ 192 if (tp->t_force) { 193 if (win == 0) { 194 /* 195 * If we still have some data to send, then 196 * clear the FIN bit. Usually this would 197 * happen below when it realizes that we 198 * aren't sending all the data. However, 199 * if we have exactly 1 byte of unsent data, 200 * then it won't clear the FIN bit below, 201 * and if we are in persist state, we wind 202 * up sending the packet without recording 203 * that we sent the FIN bit. 204 * 205 * We can't just blindly clear the FIN bit, 206 * because if we don't have any more data 207 * to send then the probe will be the FIN 208 * itself. 209 */ 210 if (off < so->so_snd.sb_cc) 211 flags &= ~TH_FIN; 212 win = 1; 213 } else { 214 callout_stop(tp->tt_persist); 215 tp->t_rxtshift = 0; 216 } 217 } 218 219 len = (long)ulmin(so->so_snd.sb_cc, win) - off; 220 221 if ((taop = tcp_gettaocache(&tp->t_inpcb->inp_inc)) == NULL) { 222 taop = &tao_noncached; 223 bzero(taop, sizeof(*taop)); 224 } 225 226 /* 227 * Lop off SYN bit if it has already been sent. However, if this 228 * is SYN-SENT state and if segment contains data and if we don't 229 * know that foreign host supports TAO, suppress sending segment. 230 */ 231 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 232 flags &= ~TH_SYN; 233 off--, len++; 234 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 235 taop->tao_ccsent == 0) 236 return 0; 237 } 238 239 /* 240 * Be careful not to send data and/or FIN on SYN segments 241 * in cases when no CC option will be sent. 242 * This measure is needed to prevent interoperability problems 243 * with not fully conformant TCP implementations. 244 */ 245 if ((flags & TH_SYN) && 246 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 247 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 248 len = 0; 249 flags &= ~TH_FIN; 250 } 251 252 if (len < 0) { 253 /* 254 * If FIN has been sent but not acked, 255 * but we haven't been called to retransmit, 256 * len will be -1. Otherwise, window shrank 257 * after we sent into it. If window shrank to 0, 258 * cancel pending retransmit, pull snd_nxt back 259 * to (closed) window, and set the persist timer 260 * if it isn't already going. If the window didn't 261 * close completely, just wait for an ACK. 262 */ 263 len = 0; 264 if (win == 0) { 265 callout_stop(tp->tt_rexmt); 266 tp->t_rxtshift = 0; 267 tp->snd_nxt = tp->snd_una; 268 if (!callout_active(tp->tt_persist)) 269 tcp_setpersist(tp); 270 } 271 } 272 if (len > tp->t_maxseg) { 273 len = tp->t_maxseg; 274 sendalot = 1; 275 } 276 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 277 flags &= ~TH_FIN; 278 279 win = sbspace(&so->so_rcv); 280 281 /* 282 * Sender silly window avoidance. We transmit under the following 283 * conditions when len is non-zero: 284 * 285 * - We have a full segment 286 * - This is the last buffer in a write()/send() and we are 287 * either idle or running NODELAY 288 * - we've timed out (e.g. persist timer) 289 * - we have more then 1/2 the maximum send window's worth of 290 * data (receiver may be limited the window size) 291 * - we need to retransmit 292 */ 293 if (len) { 294 if (len == tp->t_maxseg) 295 goto send; 296 /* 297 * NOTE! on localhost connections an 'ack' from the remote 298 * end may occur synchronously with the output and cause 299 * us to flush a buffer queued with moretocome. XXX 300 * 301 * note: the len + off check is almost certainly unnecessary. 302 */ 303 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 304 (idle || (tp->t_flags & TF_NODELAY)) && 305 len + off >= so->so_snd.sb_cc && 306 (tp->t_flags & TF_NOPUSH) == 0) { 307 goto send; 308 } 309 if (tp->t_force) /* typ. timeout case */ 310 goto send; 311 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 312 goto send; 313 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 314 goto send; 315 } 316 317 /* 318 * Compare available window to amount of window 319 * known to peer (as advertised window less 320 * next expected input). If the difference is at least two 321 * max size segments, or at least 50% of the maximum possible 322 * window, then want to send a window update to peer. 323 */ 324 if (win > 0) { 325 /* 326 * "adv" is the amount we can increase the window, 327 * taking into account that we are limited by 328 * TCP_MAXWIN << tp->rcv_scale. 329 */ 330 long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) - 331 (tp->rcv_adv - tp->rcv_nxt); 332 333 if (adv >= (long) (2 * tp->t_maxseg)) 334 goto send; 335 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 336 goto send; 337 } 338 339 /* 340 * Send if we owe peer an ACK. 341 */ 342 if (tp->t_flags & TF_ACKNOW) 343 goto send; 344 if ((flags & TH_RST) || 345 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 346 goto send; 347 if (SEQ_GT(tp->snd_up, tp->snd_una)) 348 goto send; 349 /* 350 * If our state indicates that FIN should be sent 351 * and we have not yet done so, or we're retransmitting the FIN, 352 * then we need to send. 353 */ 354 if (flags & TH_FIN && 355 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 356 goto send; 357 358 /* 359 * TCP window updates are not reliable, rather a polling protocol 360 * using ``persist'' packets is used to insure receipt of window 361 * updates. The three ``states'' for the output side are: 362 * idle not doing retransmits or persists 363 * persisting to move a small or zero window 364 * (re)transmitting and thereby not persisting 365 * 366 * callout_active(tp->tt_persist) 367 * is true when we are in persist state. 368 * tp->t_force 369 * is set when we are called to send a persist packet. 370 * callout_active(tp->tt_rexmt) 371 * is set when we are retransmitting 372 * The output side is idle when both timers are zero. 373 * 374 * If send window is too small, there is data to transmit, and no 375 * retransmit or persist is pending, then go to persist state. 376 * If nothing happens soon, send when timer expires: 377 * if window is nonzero, transmit what we can, 378 * otherwise force out a byte. 379 */ 380 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 381 !callout_active(tp->tt_persist)) { 382 tp->t_rxtshift = 0; 383 tcp_setpersist(tp); 384 } 385 386 /* 387 * No reason to send a segment, just return. 388 */ 389 return (0); 390 391 send: 392 /* 393 * Before ESTABLISHED, force sending of initial options 394 * unless TCP set not to do any options. 395 * NOTE: we assume that the IP/TCP header plus TCP options 396 * always fit in a single mbuf, leaving room for a maximum 397 * link header, i.e. 398 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 399 */ 400 optlen = 0; 401 #ifdef INET6 402 if (isipv6) 403 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 404 else 405 #endif 406 hdrlen = sizeof (struct tcpiphdr); 407 if (flags & TH_SYN) { 408 tp->snd_nxt = tp->iss; 409 if ((tp->t_flags & TF_NOOPT) == 0) { 410 u_short mss; 411 412 opt[0] = TCPOPT_MAXSEG; 413 opt[1] = TCPOLEN_MAXSEG; 414 mss = htons((u_short) tcp_mssopt(tp)); 415 (void)memcpy(opt + 2, &mss, sizeof(mss)); 416 optlen = TCPOLEN_MAXSEG; 417 418 if ((tp->t_flags & TF_REQ_SCALE) && 419 ((flags & TH_ACK) == 0 || 420 (tp->t_flags & TF_RCVD_SCALE))) { 421 *((u_int32_t *)(opt + optlen)) = htonl( 422 TCPOPT_NOP << 24 | 423 TCPOPT_WINDOW << 16 | 424 TCPOLEN_WINDOW << 8 | 425 tp->request_r_scale); 426 optlen += 4; 427 } 428 } 429 } 430 431 /* 432 * Send a timestamp and echo-reply if this is a SYN and our side 433 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 434 * and our peer have sent timestamps in our SYN's. 435 */ 436 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 437 (flags & TH_RST) == 0 && 438 ((flags & TH_ACK) == 0 || 439 (tp->t_flags & TF_RCVD_TSTMP))) { 440 u_int32_t *lp = (u_int32_t *)(opt + optlen); 441 442 /* Form timestamp option as shown in appendix A of RFC 1323. */ 443 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 444 *lp++ = htonl(ticks); 445 *lp = htonl(tp->ts_recent); 446 optlen += TCPOLEN_TSTAMP_APPA; 447 } 448 449 /* 450 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 451 * options are allowed (!TF_NOOPT) and it's not a RST. 452 */ 453 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 454 (flags & TH_RST) == 0) { 455 switch (flags & (TH_SYN|TH_ACK)) { 456 /* 457 * This is a normal ACK, send CC if we received CC before 458 * from our peer. 459 */ 460 case TH_ACK: 461 if (!(tp->t_flags & TF_RCVD_CC)) 462 break; 463 /*FALLTHROUGH*/ 464 465 /* 466 * We can only get here in T/TCP's SYN_SENT* state, when 467 * we're a sending a non-SYN segment without waiting for 468 * the ACK of our SYN. A check above assures that we only 469 * do this if our peer understands T/TCP. 470 */ 471 case 0: 472 opt[optlen++] = TCPOPT_NOP; 473 opt[optlen++] = TCPOPT_NOP; 474 opt[optlen++] = TCPOPT_CC; 475 opt[optlen++] = TCPOLEN_CC; 476 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 477 478 optlen += 4; 479 break; 480 481 /* 482 * This is our initial SYN, check whether we have to use 483 * CC or CC.new. 484 */ 485 case TH_SYN: 486 opt[optlen++] = TCPOPT_NOP; 487 opt[optlen++] = TCPOPT_NOP; 488 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 489 TCPOPT_CCNEW : TCPOPT_CC; 490 opt[optlen++] = TCPOLEN_CC; 491 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 492 optlen += 4; 493 break; 494 495 /* 496 * This is a SYN,ACK; send CC and CC.echo if we received 497 * CC from our peer. 498 */ 499 case (TH_SYN|TH_ACK): 500 if (tp->t_flags & TF_RCVD_CC) { 501 opt[optlen++] = TCPOPT_NOP; 502 opt[optlen++] = TCPOPT_NOP; 503 opt[optlen++] = TCPOPT_CC; 504 opt[optlen++] = TCPOLEN_CC; 505 *(u_int32_t *)&opt[optlen] = 506 htonl(tp->cc_send); 507 optlen += 4; 508 opt[optlen++] = TCPOPT_NOP; 509 opt[optlen++] = TCPOPT_NOP; 510 opt[optlen++] = TCPOPT_CCECHO; 511 opt[optlen++] = TCPOLEN_CC; 512 *(u_int32_t *)&opt[optlen] = 513 htonl(tp->cc_recv); 514 optlen += 4; 515 } 516 break; 517 } 518 } 519 520 hdrlen += optlen; 521 522 #ifdef INET6 523 if (isipv6) 524 ipoptlen = ip6_optlen(tp->t_inpcb); 525 else 526 #endif 527 { 528 if (tp->t_inpcb->inp_options) { 529 ipoptlen = tp->t_inpcb->inp_options->m_len - 530 offsetof(struct ipoption, ipopt_list); 531 } else { 532 ipoptlen = 0; 533 } 534 } 535 #ifdef IPSEC 536 ipoptlen += ipsec_hdrsiz_tcp(tp); 537 #endif 538 539 /* 540 * Adjust data length if insertion of options will 541 * bump the packet length beyond the t_maxopd length. 542 * Clear the FIN bit because we cut off the tail of 543 * the segment. 544 */ 545 if (len + optlen + ipoptlen > tp->t_maxopd) { 546 /* 547 * If there is still more to send, don't close the connection. 548 */ 549 flags &= ~TH_FIN; 550 len = tp->t_maxopd - optlen - ipoptlen; 551 sendalot = 1; 552 } 553 554 /*#ifdef DIAGNOSTIC*/ 555 #ifdef INET6 556 if (max_linkhdr + hdrlen > MCLBYTES) 557 panic("tcphdr too big"); 558 #else 559 if (max_linkhdr + hdrlen > MHLEN) 560 panic("tcphdr too big"); 561 #endif 562 /*#endif*/ 563 564 /* 565 * Grab a header mbuf, attaching a copy of data to 566 * be transmitted, and initialize the header from 567 * the template for sends on this connection. 568 */ 569 if (len) { 570 if (tp->t_force && len == 1) 571 tcpstat.tcps_sndprobe++; 572 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 573 tcpstat.tcps_sndrexmitpack++; 574 tcpstat.tcps_sndrexmitbyte += len; 575 } else { 576 tcpstat.tcps_sndpack++; 577 tcpstat.tcps_sndbyte += len; 578 } 579 #ifdef notyet 580 if ((m = m_copypack(so->so_snd.sb_mb, off, 581 (int)len, max_linkhdr + hdrlen)) == 0) { 582 error = ENOBUFS; 583 goto out; 584 } 585 /* 586 * m_copypack left space for our hdr; use it. 587 */ 588 m->m_len += hdrlen; 589 m->m_data -= hdrlen; 590 #else 591 MGETHDR(m, M_DONTWAIT, MT_HEADER); 592 if (m == NULL) { 593 error = ENOBUFS; 594 goto out; 595 } 596 #ifdef INET6 597 if (MHLEN < hdrlen + max_linkhdr) { 598 MCLGET(m, M_DONTWAIT); 599 if ((m->m_flags & M_EXT) == 0) { 600 m_freem(m); 601 error = ENOBUFS; 602 goto out; 603 } 604 } 605 #endif 606 m->m_data += max_linkhdr; 607 m->m_len = hdrlen; 608 if (len <= MHLEN - hdrlen - max_linkhdr) { 609 m_copydata(so->so_snd.sb_mb, off, (int) len, 610 mtod(m, caddr_t) + hdrlen); 611 m->m_len += len; 612 } else { 613 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 614 if (m->m_next == 0) { 615 (void) m_free(m); 616 error = ENOBUFS; 617 goto out; 618 } 619 } 620 #endif 621 /* 622 * If we're sending everything we've got, set PUSH. 623 * (This will keep happy those implementations which only 624 * give data to the user when a buffer fills or 625 * a PUSH comes in.) 626 */ 627 if (off + len == so->so_snd.sb_cc) 628 flags |= TH_PUSH; 629 } else { 630 if (tp->t_flags & TF_ACKNOW) 631 tcpstat.tcps_sndacks++; 632 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 633 tcpstat.tcps_sndctrl++; 634 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 635 tcpstat.tcps_sndurg++; 636 else 637 tcpstat.tcps_sndwinup++; 638 639 MGETHDR(m, M_DONTWAIT, MT_HEADER); 640 if (m == NULL) { 641 error = ENOBUFS; 642 goto out; 643 } 644 #ifdef INET6 645 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 646 MHLEN >= hdrlen) { 647 MH_ALIGN(m, hdrlen); 648 } else 649 #endif 650 m->m_data += max_linkhdr; 651 m->m_len = hdrlen; 652 } 653 m->m_pkthdr.rcvif = (struct ifnet *)0; 654 #ifdef INET6 655 if (isipv6) { 656 ip6 = mtod(m, struct ip6_hdr *); 657 th = (struct tcphdr *)(ip6 + 1); 658 tcp_fillheaders(tp, ip6, th); 659 } else 660 #endif /* INET6 */ 661 { 662 ip = mtod(m, struct ip *); 663 ipov = (struct ipovly *)ip; 664 th = (struct tcphdr *)(ip + 1); 665 /* this picks up the pseudo header (w/o the length) */ 666 tcp_fillheaders(tp, ip, th); 667 } 668 669 /* 670 * Fill in fields, remembering maximum advertised 671 * window for use in delaying messages about window sizes. 672 * If resending a FIN, be sure not to use a new sequence number. 673 */ 674 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 675 tp->snd_nxt == tp->snd_max) 676 tp->snd_nxt--; 677 /* 678 * If we are doing retransmissions, then snd_nxt will 679 * not reflect the first unsent octet. For ACK only 680 * packets, we do not want the sequence number of the 681 * retransmitted packet, we want the sequence number 682 * of the next unsent octet. So, if there is no data 683 * (and no SYN or FIN), use snd_max instead of snd_nxt 684 * when filling in ti_seq. But if we are in persist 685 * state, snd_max might reflect one byte beyond the 686 * right edge of the window, so use snd_nxt in that 687 * case, since we know we aren't doing a retransmission. 688 * (retransmit and persist are mutually exclusive...) 689 */ 690 if (len || (flags & (TH_SYN|TH_FIN)) 691 || callout_active(tp->tt_persist)) 692 th->th_seq = htonl(tp->snd_nxt); 693 else 694 th->th_seq = htonl(tp->snd_max); 695 th->th_ack = htonl(tp->rcv_nxt); 696 if (optlen) { 697 bcopy(opt, th + 1, optlen); 698 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 699 } 700 th->th_flags = flags; 701 /* 702 * Calculate receive window. Don't shrink window, 703 * but avoid silly window syndrome. 704 */ 705 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg) 706 win = 0; 707 if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) 708 win = (long)(tp->rcv_adv - tp->rcv_nxt); 709 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 710 win = (long)TCP_MAXWIN << tp->rcv_scale; 711 th->th_win = htons((u_short) (win>>tp->rcv_scale)); 712 713 714 /* 715 * Adjust the RXWIN0SENT flag - indicate that we have advertised 716 * a 0 window. This may cause the remote transmitter to stall. This 717 * flag tells soreceive() to disable delayed acknowledgements when 718 * draining the buffer. This can occur if the receiver is attempting 719 * to read more data then can be buffered prior to transmitting on 720 * the connection. 721 */ 722 if (win == 0) 723 tp->t_flags |= TF_RXWIN0SENT; 724 else 725 tp->t_flags &= ~TF_RXWIN0SENT; 726 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 727 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 728 th->th_flags |= TH_URG; 729 } else 730 /* 731 * If no urgent pointer to send, then we pull 732 * the urgent pointer to the left edge of the send window 733 * so that it doesn't drift into the send window on sequence 734 * number wraparound. 735 */ 736 tp->snd_up = tp->snd_una; /* drag it along */ 737 738 /* 739 * Put TCP length in extended header, and then 740 * checksum extended header and data. 741 */ 742 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 743 #ifdef INET6 744 if (isipv6) 745 /* 746 * ip6_plen is not need to be filled now, and will be filled 747 * in ip6_output. 748 */ 749 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 750 sizeof(struct tcphdr) + optlen + len); 751 else 752 #endif /* INET6 */ 753 { 754 m->m_pkthdr.csum_flags = CSUM_TCP; 755 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 756 if (len + optlen) 757 th->th_sum = in_addword(th->th_sum, 758 htons((u_short)(optlen + len))); 759 760 /* IP version must be set here for ipv4/ipv6 checking later */ 761 KASSERT(ip->ip_v == IPVERSION, 762 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 763 } 764 765 /* 766 * In transmit state, time the transmission and arrange for 767 * the retransmit. In persist state, just set snd_max. 768 */ 769 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 770 tcp_seq startseq = tp->snd_nxt; 771 772 /* 773 * Advance snd_nxt over sequence space of this segment. 774 */ 775 if (flags & (TH_SYN|TH_FIN)) { 776 if (flags & TH_SYN) 777 tp->snd_nxt++; 778 if (flags & TH_FIN) { 779 tp->snd_nxt++; 780 tp->t_flags |= TF_SENTFIN; 781 } 782 } 783 tp->snd_nxt += len; 784 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 785 tp->snd_max = tp->snd_nxt; 786 /* 787 * Time this transmission if not a retransmission and 788 * not currently timing anything. 789 */ 790 if (tp->t_rtttime == 0) { 791 tp->t_rtttime = ticks; 792 tp->t_rtseq = startseq; 793 tcpstat.tcps_segstimed++; 794 } 795 } 796 797 /* 798 * Set retransmit timer if not currently set, 799 * and not doing an ack or a keep-alive probe. 800 * Initial value for retransmit timer is smoothed 801 * round-trip time + 2 * round-trip time variance. 802 * Initialize shift counter which is used for backoff 803 * of retransmit time. 804 */ 805 if (!callout_active(tp->tt_rexmt) && 806 tp->snd_nxt != tp->snd_una) { 807 if (callout_active(tp->tt_persist)) { 808 callout_stop(tp->tt_persist); 809 tp->t_rxtshift = 0; 810 } 811 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 812 tcp_timer_rexmt, tp); 813 } 814 } else 815 if (SEQ_GT(tp->snd_nxt + len, tp->snd_max)) 816 tp->snd_max = tp->snd_nxt + len; 817 818 #ifdef TCPDEBUG 819 /* 820 * Trace. 821 */ 822 if (so->so_options & SO_DEBUG) 823 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 824 #endif 825 826 /* 827 * Fill in IP length and desired time to live and 828 * send to IP level. There should be a better way 829 * to handle ttl and tos; we could keep them in 830 * the template, but need a way to checksum without them. 831 */ 832 /* 833 * m->m_pkthdr.len should have been set before cksum calcuration, 834 * because in6_cksum() need it. 835 */ 836 #ifdef INET6 837 if (isipv6) { 838 /* 839 * we separately set hoplimit for every segment, since the 840 * user might want to change the value via setsockopt. 841 * Also, desired default hop limit might be changed via 842 * Neighbor Discovery. 843 */ 844 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, 845 tp->t_inpcb->in6p_route.ro_rt ? 846 tp->t_inpcb->in6p_route.ro_rt->rt_ifp 847 : NULL); 848 849 /* TODO: IPv6 IP6TOS_ECT bit on */ 850 #ifdef IPSEC 851 if (ipsec_setsocket(m, so) != 0) { 852 m_freem(m); 853 error = ENOBUFS; 854 goto out; 855 } 856 #endif /*IPSEC*/ 857 error = ip6_output(m, 858 tp->t_inpcb->in6p_outputopts, 859 &tp->t_inpcb->in6p_route, 860 (so->so_options & SO_DONTROUTE), NULL, NULL); 861 } else 862 #endif /* INET6 */ 863 { 864 struct rtentry *rt; 865 ip->ip_len = m->m_pkthdr.len; 866 #ifdef INET6 867 if (INP_CHECK_SOCKAF(so, AF_INET6)) 868 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, 869 tp->t_inpcb->in6p_route.ro_rt ? 870 tp->t_inpcb->in6p_route.ro_rt->rt_ifp 871 : NULL); 872 else 873 #endif /* INET6 */ 874 ip->ip_ttl = tp->t_inpcb->inp_ip_ttl; /* XXX */ 875 ip->ip_tos = tp->t_inpcb->inp_ip_tos; /* XXX */ 876 /* 877 * See if we should do MTU discovery. We do it only if the following 878 * are true: 879 * 1) we have a valid route to the destination 880 * 2) the MTU is not locked (if it is, then discovery has been 881 * disabled) 882 */ 883 if (path_mtu_discovery 884 && (rt = tp->t_inpcb->inp_route.ro_rt) 885 && rt->rt_flags & RTF_UP 886 && !(rt->rt_rmx.rmx_locks & RTV_MTU)) { 887 ip->ip_off |= IP_DF; 888 } 889 #ifdef IPSEC 890 ipsec_setsocket(m, so); 891 #endif /*IPSEC*/ 892 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 893 (so->so_options & SO_DONTROUTE), 0); 894 } 895 if (error) { 896 897 /* 898 * We know that the packet was lost, so back out the 899 * sequence number advance, if any. 900 */ 901 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 902 /* 903 * No need to check for TH_FIN here because 904 * the TF_SENTFIN flag handles that case. 905 */ 906 if ((flags & TH_SYN) == 0) 907 tp->snd_nxt -= len; 908 } 909 910 out: 911 if (error == ENOBUFS) { 912 if (!callout_active(tp->tt_rexmt) && 913 !callout_active(tp->tt_persist)) 914 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 915 tcp_timer_rexmt, tp); 916 tcp_quench(tp->t_inpcb, 0); 917 return (0); 918 } 919 if (error == EMSGSIZE) { 920 /* 921 * ip_output() will have already fixed the route 922 * for us. tcp_mtudisc() will, as its last action, 923 * initiate retransmission, so it is important to 924 * not do so here. 925 */ 926 tcp_mtudisc(tp->t_inpcb, 0); 927 return 0; 928 } 929 if ((error == EHOSTUNREACH || error == ENETDOWN) 930 && TCPS_HAVERCVDSYN(tp->t_state)) { 931 tp->t_softerror = error; 932 return (0); 933 } 934 return (error); 935 } 936 tcpstat.tcps_sndtotal++; 937 938 /* 939 * Data sent (as far as we can tell). 940 * If this advertises a larger window than any other segment, 941 * then remember the size of the advertised window. 942 * Any pending ACK has now been sent. 943 */ 944 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 945 tp->rcv_adv = tp->rcv_nxt + win; 946 tp->last_ack_sent = tp->rcv_nxt; 947 tp->t_flags &= ~TF_ACKNOW; 948 if (tcp_delack_enabled) 949 callout_stop(tp->tt_delack); 950 #if 0 951 /* 952 * This completely breaks TCP if newreno is turned on. What happens 953 * is that if delayed-acks are turned on on the receiver, this code 954 * on the transmitter effectively destroys the TCP window, forcing 955 * it to four packets (1.5Kx4 = 6K window). 956 */ 957 if (sendalot && (!tcp_do_newreno || --maxburst)) 958 goto again; 959 #endif 960 if (sendalot) 961 goto again; 962 return (0); 963 } 964 965 void 966 tcp_setpersist(tp) 967 register struct tcpcb *tp; 968 { 969 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 970 int tt; 971 972 if (callout_active(tp->tt_rexmt)) 973 panic("tcp_setpersist: retransmit pending"); 974 /* 975 * Start/restart persistance timer. 976 */ 977 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 978 TCPTV_PERSMIN, TCPTV_PERSMAX); 979 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 980 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 981 tp->t_rxtshift++; 982 } 983