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_mac.h" 40 #include "opt_tcpdebug.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/domain.h> 45 #include <sys/kernel.h> 46 #include <sys/lock.h> 47 #include <sys/mac.h> 48 #include <sys/mbuf.h> 49 #include <sys/mutex.h> 50 #include <sys/protosw.h> 51 #include <sys/socket.h> 52 #include <sys/socketvar.h> 53 #include <sys/sysctl.h> 54 55 #include <net/route.h> 56 57 #include <netinet/in.h> 58 #include <netinet/in_systm.h> 59 #include <netinet/ip.h> 60 #include <netinet/in_pcb.h> 61 #include <netinet/ip_var.h> 62 #ifdef INET6 63 #include <netinet6/in6_pcb.h> 64 #include <netinet/ip6.h> 65 #include <netinet6/ip6_var.h> 66 #endif 67 #include <netinet/tcp.h> 68 #define TCPOUTFLAGS 69 #include <netinet/tcp_fsm.h> 70 #include <netinet/tcp_seq.h> 71 #include <netinet/tcp_timer.h> 72 #include <netinet/tcp_var.h> 73 #include <netinet/tcpip.h> 74 #ifdef TCPDEBUG 75 #include <netinet/tcp_debug.h> 76 #endif 77 78 #ifdef IPSEC 79 #include <netinet6/ipsec.h> 80 #endif /*IPSEC*/ 81 82 #include <machine/in_cksum.h> 83 84 #ifdef notyet 85 extern struct mbuf *m_copypack(); 86 #endif 87 88 int path_mtu_discovery = 1; 89 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 90 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 91 92 int ss_fltsz = 1; 93 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 94 &ss_fltsz, 1, "Slow start flight size"); 95 96 int ss_fltsz_local = 4; 97 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 98 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 99 100 int tcp_do_newreno = 1; 101 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno, 102 0, "Enable NewReno Algorithms"); 103 /* 104 * Tcp output routine: figure out what should be sent and send it. 105 */ 106 int 107 tcp_output(struct tcpcb *tp) 108 { 109 struct socket *so = tp->t_inpcb->inp_socket; 110 long len, win; 111 int off, flags, error; 112 struct mbuf *m; 113 struct ip *ip = NULL; 114 struct ipovly *ipov = NULL; 115 struct tcphdr *th; 116 u_char opt[TCP_MAXOLEN]; 117 unsigned ipoptlen, optlen, hdrlen; 118 int idle, sendalot; 119 #if 0 120 int maxburst = TCP_MAXBURST; 121 #endif 122 struct rmxp_tao *taop; 123 struct rmxp_tao tao_noncached; 124 #ifdef INET6 125 struct ip6_hdr *ip6 = NULL; 126 int isipv6; 127 128 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 129 #endif 130 131 mtx_assert(&tp->t_inpcb->inp_mtx, MA_OWNED); 132 133 /* 134 * Determine length of data that should be transmitted, 135 * and flags that will be used. 136 * If there is some data or critical controls (SYN, RST) 137 * to send, then transmit; otherwise, investigate further. 138 */ 139 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 140 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 141 /* 142 * We have been idle for "a while" and no acks are 143 * expected to clock out any data we send -- 144 * slow start to get ack "clock" running again. 145 * 146 * Set the slow-start flight size depending on whether 147 * this is a local network or not. 148 */ 149 int ss = ss_fltsz; 150 #ifdef INET6 151 if (isipv6) { 152 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 153 ss = ss_fltsz_local; 154 } else 155 #endif /* INET6 */ 156 if (in_localaddr(tp->t_inpcb->inp_faddr)) 157 ss = ss_fltsz_local; 158 tp->snd_cwnd = tp->t_maxseg * ss; 159 } 160 tp->t_flags &= ~TF_LASTIDLE; 161 if (idle) { 162 if (tp->t_flags & TF_MORETOCOME) { 163 tp->t_flags |= TF_LASTIDLE; 164 idle = 0; 165 } 166 } 167 again: 168 sendalot = 0; 169 off = tp->snd_nxt - tp->snd_una; 170 win = min(tp->snd_wnd, tp->snd_cwnd); 171 win = min(win, tp->snd_bwnd); 172 173 flags = tcp_outflags[tp->t_state]; 174 /* 175 * Get standard flags, and add SYN or FIN if requested by 'hidden' 176 * state flags. 177 */ 178 if (tp->t_flags & TF_NEEDFIN) 179 flags |= TH_FIN; 180 if (tp->t_flags & TF_NEEDSYN) 181 flags |= TH_SYN; 182 183 /* 184 * If in persist timeout with window of 0, send 1 byte. 185 * Otherwise, if window is small but nonzero 186 * and timer expired, we will send what we can 187 * and go to transmit state. 188 */ 189 if (tp->t_force) { 190 if (win == 0) { 191 /* 192 * If we still have some data to send, then 193 * clear the FIN bit. Usually this would 194 * happen below when it realizes that we 195 * aren't sending all the data. However, 196 * if we have exactly 1 byte of unsent data, 197 * then it won't clear the FIN bit below, 198 * and if we are in persist state, we wind 199 * up sending the packet without recording 200 * that we sent the FIN bit. 201 * 202 * We can't just blindly clear the FIN bit, 203 * because if we don't have any more data 204 * to send then the probe will be the FIN 205 * itself. 206 */ 207 if (off < so->so_snd.sb_cc) 208 flags &= ~TH_FIN; 209 win = 1; 210 } else { 211 callout_stop(tp->tt_persist); 212 tp->t_rxtshift = 0; 213 } 214 } 215 216 len = (long)ulmin(so->so_snd.sb_cc, win) - off; 217 218 if ((taop = tcp_gettaocache(&tp->t_inpcb->inp_inc)) == NULL) { 219 taop = &tao_noncached; 220 bzero(taop, sizeof(*taop)); 221 } 222 223 /* 224 * Lop off SYN bit if it has already been sent. However, if this 225 * is SYN-SENT state and if segment contains data and if we don't 226 * know that foreign host supports TAO, suppress sending segment. 227 */ 228 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 229 flags &= ~TH_SYN; 230 off--, len++; 231 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 232 taop->tao_ccsent == 0) 233 return 0; 234 } 235 236 /* 237 * Be careful not to send data and/or FIN on SYN segments 238 * in cases when no CC option will be sent. 239 * This measure is needed to prevent interoperability problems 240 * with not fully conformant TCP implementations. 241 */ 242 if ((flags & TH_SYN) && 243 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 244 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 245 len = 0; 246 flags &= ~TH_FIN; 247 } 248 249 if (len < 0) { 250 /* 251 * If FIN has been sent but not acked, 252 * but we haven't been called to retransmit, 253 * len will be -1. Otherwise, window shrank 254 * after we sent into it. If window shrank to 0, 255 * cancel pending retransmit, pull snd_nxt back 256 * to (closed) window, and set the persist timer 257 * if it isn't already going. If the window didn't 258 * close completely, just wait for an ACK. 259 */ 260 len = 0; 261 if (win == 0) { 262 callout_stop(tp->tt_rexmt); 263 tp->t_rxtshift = 0; 264 tp->snd_nxt = tp->snd_una; 265 if (!callout_active(tp->tt_persist)) 266 tcp_setpersist(tp); 267 } 268 } 269 if (len > tp->t_maxseg) { 270 len = tp->t_maxseg; 271 sendalot = 1; 272 } 273 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 274 flags &= ~TH_FIN; 275 276 win = sbspace(&so->so_rcv); 277 278 /* 279 * Sender silly window avoidance. We transmit under the following 280 * conditions when len is non-zero: 281 * 282 * - We have a full segment 283 * - This is the last buffer in a write()/send() and we are 284 * either idle or running NODELAY 285 * - we've timed out (e.g. persist timer) 286 * - we have more then 1/2 the maximum send window's worth of 287 * data (receiver may be limited the window size) 288 * - we need to retransmit 289 */ 290 if (len) { 291 if (len == tp->t_maxseg) 292 goto send; 293 /* 294 * NOTE! on localhost connections an 'ack' from the remote 295 * end may occur synchronously with the output and cause 296 * us to flush a buffer queued with moretocome. XXX 297 * 298 * note: the len + off check is almost certainly unnecessary. 299 */ 300 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 301 (idle || (tp->t_flags & TF_NODELAY)) && 302 len + off >= so->so_snd.sb_cc && 303 (tp->t_flags & TF_NOPUSH) == 0) { 304 goto send; 305 } 306 if (tp->t_force) /* typ. timeout case */ 307 goto send; 308 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 309 goto send; 310 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 311 goto send; 312 } 313 314 /* 315 * Compare available window to amount of window 316 * known to peer (as advertised window less 317 * next expected input). If the difference is at least two 318 * max size segments, or at least 50% of the maximum possible 319 * window, then want to send a window update to peer. 320 */ 321 if (win > 0) { 322 /* 323 * "adv" is the amount we can increase the window, 324 * taking into account that we are limited by 325 * TCP_MAXWIN << tp->rcv_scale. 326 */ 327 long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) - 328 (tp->rcv_adv - tp->rcv_nxt); 329 330 if (adv >= (long) (2 * tp->t_maxseg)) 331 goto send; 332 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 333 goto send; 334 } 335 336 /* 337 * Send if we owe peer an ACK. 338 */ 339 if (tp->t_flags & TF_ACKNOW) 340 goto send; 341 if ((flags & TH_RST) || 342 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 343 goto send; 344 if (SEQ_GT(tp->snd_up, tp->snd_una)) 345 goto send; 346 /* 347 * If our state indicates that FIN should be sent 348 * and we have not yet done so, or we're retransmitting the FIN, 349 * then we need to send. 350 */ 351 if (flags & TH_FIN && 352 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 353 goto send; 354 355 /* 356 * TCP window updates are not reliable, rather a polling protocol 357 * using ``persist'' packets is used to insure receipt of window 358 * updates. The three ``states'' for the output side are: 359 * idle not doing retransmits or persists 360 * persisting to move a small or zero window 361 * (re)transmitting and thereby not persisting 362 * 363 * callout_active(tp->tt_persist) 364 * is true when we are in persist state. 365 * tp->t_force 366 * is set when we are called to send a persist packet. 367 * callout_active(tp->tt_rexmt) 368 * is set when we are retransmitting 369 * The output side is idle when both timers are zero. 370 * 371 * If send window is too small, there is data to transmit, and no 372 * retransmit or persist is pending, then go to persist state. 373 * If nothing happens soon, send when timer expires: 374 * if window is nonzero, transmit what we can, 375 * otherwise force out a byte. 376 */ 377 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 378 !callout_active(tp->tt_persist)) { 379 tp->t_rxtshift = 0; 380 tcp_setpersist(tp); 381 } 382 383 /* 384 * No reason to send a segment, just return. 385 */ 386 return (0); 387 388 send: 389 /* 390 * Before ESTABLISHED, force sending of initial options 391 * unless TCP set not to do any options. 392 * NOTE: we assume that the IP/TCP header plus TCP options 393 * always fit in a single mbuf, leaving room for a maximum 394 * link header, i.e. 395 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 396 */ 397 optlen = 0; 398 #ifdef INET6 399 if (isipv6) 400 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 401 else 402 #endif 403 hdrlen = sizeof (struct tcpiphdr); 404 if (flags & TH_SYN) { 405 tp->snd_nxt = tp->iss; 406 if ((tp->t_flags & TF_NOOPT) == 0) { 407 u_short mss; 408 409 opt[0] = TCPOPT_MAXSEG; 410 opt[1] = TCPOLEN_MAXSEG; 411 mss = htons((u_short) tcp_mssopt(tp)); 412 (void)memcpy(opt + 2, &mss, sizeof(mss)); 413 optlen = TCPOLEN_MAXSEG; 414 415 if ((tp->t_flags & TF_REQ_SCALE) && 416 ((flags & TH_ACK) == 0 || 417 (tp->t_flags & TF_RCVD_SCALE))) { 418 *((u_int32_t *)(opt + optlen)) = htonl( 419 TCPOPT_NOP << 24 | 420 TCPOPT_WINDOW << 16 | 421 TCPOLEN_WINDOW << 8 | 422 tp->request_r_scale); 423 optlen += 4; 424 } 425 } 426 } 427 428 /* 429 * Send a timestamp and echo-reply if this is a SYN and our side 430 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 431 * and our peer have sent timestamps in our SYN's. 432 */ 433 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 434 (flags & TH_RST) == 0 && 435 ((flags & TH_ACK) == 0 || 436 (tp->t_flags & TF_RCVD_TSTMP))) { 437 u_int32_t *lp = (u_int32_t *)(opt + optlen); 438 439 /* Form timestamp option as shown in appendix A of RFC 1323. */ 440 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 441 *lp++ = htonl(ticks); 442 *lp = htonl(tp->ts_recent); 443 optlen += TCPOLEN_TSTAMP_APPA; 444 } 445 446 /* 447 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 448 * options are allowed (!TF_NOOPT) and it's not a RST. 449 */ 450 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 451 (flags & TH_RST) == 0) { 452 switch (flags & (TH_SYN|TH_ACK)) { 453 /* 454 * This is a normal ACK, send CC if we received CC before 455 * from our peer. 456 */ 457 case TH_ACK: 458 if (!(tp->t_flags & TF_RCVD_CC)) 459 break; 460 /*FALLTHROUGH*/ 461 462 /* 463 * We can only get here in T/TCP's SYN_SENT* state, when 464 * we're a sending a non-SYN segment without waiting for 465 * the ACK of our SYN. A check above assures that we only 466 * do this if our peer understands T/TCP. 467 */ 468 case 0: 469 opt[optlen++] = TCPOPT_NOP; 470 opt[optlen++] = TCPOPT_NOP; 471 opt[optlen++] = TCPOPT_CC; 472 opt[optlen++] = TCPOLEN_CC; 473 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 474 475 optlen += 4; 476 break; 477 478 /* 479 * This is our initial SYN, check whether we have to use 480 * CC or CC.new. 481 */ 482 case TH_SYN: 483 opt[optlen++] = TCPOPT_NOP; 484 opt[optlen++] = TCPOPT_NOP; 485 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 486 TCPOPT_CCNEW : TCPOPT_CC; 487 opt[optlen++] = TCPOLEN_CC; 488 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 489 optlen += 4; 490 break; 491 492 /* 493 * This is a SYN,ACK; send CC and CC.echo if we received 494 * CC from our peer. 495 */ 496 case (TH_SYN|TH_ACK): 497 if (tp->t_flags & TF_RCVD_CC) { 498 opt[optlen++] = TCPOPT_NOP; 499 opt[optlen++] = TCPOPT_NOP; 500 opt[optlen++] = TCPOPT_CC; 501 opt[optlen++] = TCPOLEN_CC; 502 *(u_int32_t *)&opt[optlen] = 503 htonl(tp->cc_send); 504 optlen += 4; 505 opt[optlen++] = TCPOPT_NOP; 506 opt[optlen++] = TCPOPT_NOP; 507 opt[optlen++] = TCPOPT_CCECHO; 508 opt[optlen++] = TCPOLEN_CC; 509 *(u_int32_t *)&opt[optlen] = 510 htonl(tp->cc_recv); 511 optlen += 4; 512 } 513 break; 514 } 515 } 516 517 hdrlen += optlen; 518 519 #ifdef INET6 520 if (isipv6) 521 ipoptlen = ip6_optlen(tp->t_inpcb); 522 else 523 #endif 524 if (tp->t_inpcb->inp_options) 525 ipoptlen = tp->t_inpcb->inp_options->m_len - 526 offsetof(struct ipoption, ipopt_list); 527 else 528 ipoptlen = 0; 529 #ifdef IPSEC 530 ipoptlen += ipsec_hdrsiz_tcp(tp); 531 #endif 532 533 /* 534 * Adjust data length if insertion of options will 535 * bump the packet length beyond the t_maxopd length. 536 * Clear the FIN bit because we cut off the tail of 537 * the segment. 538 */ 539 if (len + optlen + ipoptlen > tp->t_maxopd) { 540 /* 541 * If there is still more to send, don't close the connection. 542 */ 543 flags &= ~TH_FIN; 544 len = tp->t_maxopd - optlen - ipoptlen; 545 sendalot = 1; 546 } 547 548 /*#ifdef DIAGNOSTIC*/ 549 #ifdef INET6 550 if (max_linkhdr + hdrlen > MCLBYTES) 551 #else 552 if (max_linkhdr + hdrlen > MHLEN) 553 #endif 554 panic("tcphdr too big"); 555 /*#endif*/ 556 557 /* 558 * Grab a header mbuf, attaching a copy of data to 559 * be transmitted, and initialize the header from 560 * the template for sends on this connection. 561 */ 562 if (len) { 563 if (tp->t_force && len == 1) 564 tcpstat.tcps_sndprobe++; 565 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 566 tcpstat.tcps_sndrexmitpack++; 567 tcpstat.tcps_sndrexmitbyte += len; 568 } else { 569 tcpstat.tcps_sndpack++; 570 tcpstat.tcps_sndbyte += len; 571 } 572 #ifdef notyet 573 if ((m = m_copypack(so->so_snd.sb_mb, off, 574 (int)len, max_linkhdr + hdrlen)) == 0) { 575 error = ENOBUFS; 576 goto out; 577 } 578 /* 579 * m_copypack left space for our hdr; use it. 580 */ 581 m->m_len += hdrlen; 582 m->m_data -= hdrlen; 583 #else 584 MGETHDR(m, M_DONTWAIT, MT_HEADER); 585 if (m == NULL) { 586 error = ENOBUFS; 587 goto out; 588 } 589 #ifdef INET6 590 if (MHLEN < hdrlen + max_linkhdr) { 591 MCLGET(m, M_DONTWAIT); 592 if ((m->m_flags & M_EXT) == 0) { 593 m_freem(m); 594 error = ENOBUFS; 595 goto out; 596 } 597 } 598 #endif 599 m->m_data += max_linkhdr; 600 m->m_len = hdrlen; 601 if (len <= MHLEN - hdrlen - max_linkhdr) { 602 m_copydata(so->so_snd.sb_mb, off, (int) len, 603 mtod(m, caddr_t) + hdrlen); 604 m->m_len += len; 605 } else { 606 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 607 if (m->m_next == 0) { 608 (void) m_free(m); 609 error = ENOBUFS; 610 goto out; 611 } 612 } 613 #endif 614 /* 615 * If we're sending everything we've got, set PUSH. 616 * (This will keep happy those implementations which only 617 * give data to the user when a buffer fills or 618 * a PUSH comes in.) 619 */ 620 if (off + len == so->so_snd.sb_cc) 621 flags |= TH_PUSH; 622 } else { 623 if (tp->t_flags & TF_ACKNOW) 624 tcpstat.tcps_sndacks++; 625 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 626 tcpstat.tcps_sndctrl++; 627 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 628 tcpstat.tcps_sndurg++; 629 else 630 tcpstat.tcps_sndwinup++; 631 632 MGETHDR(m, M_DONTWAIT, MT_HEADER); 633 if (m == NULL) { 634 error = ENOBUFS; 635 goto out; 636 } 637 #ifdef INET6 638 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 639 MHLEN >= hdrlen) { 640 MH_ALIGN(m, hdrlen); 641 } else 642 #endif 643 m->m_data += max_linkhdr; 644 m->m_len = hdrlen; 645 } 646 m->m_pkthdr.rcvif = (struct ifnet *)0; 647 #ifdef MAC 648 mac_create_mbuf_from_socket(so, m); 649 #endif 650 #ifdef INET6 651 if (isipv6) { 652 ip6 = mtod(m, struct ip6_hdr *); 653 th = (struct tcphdr *)(ip6 + 1); 654 tcp_fillheaders(tp, ip6, th); 655 } else 656 #endif /* INET6 */ 657 { 658 ip = mtod(m, struct ip *); 659 ipov = (struct ipovly *)ip; 660 th = (struct tcphdr *)(ip + 1); 661 /* this picks up the pseudo header (w/o the length) */ 662 tcp_fillheaders(tp, ip, th); 663 } 664 665 /* 666 * Fill in fields, remembering maximum advertised 667 * window for use in delaying messages about window sizes. 668 * If resending a FIN, be sure not to use a new sequence number. 669 */ 670 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 671 tp->snd_nxt == tp->snd_max) 672 tp->snd_nxt--; 673 /* 674 * If we are doing retransmissions, then snd_nxt will 675 * not reflect the first unsent octet. For ACK only 676 * packets, we do not want the sequence number of the 677 * retransmitted packet, we want the sequence number 678 * of the next unsent octet. So, if there is no data 679 * (and no SYN or FIN), use snd_max instead of snd_nxt 680 * when filling in ti_seq. But if we are in persist 681 * state, snd_max might reflect one byte beyond the 682 * right edge of the window, so use snd_nxt in that 683 * case, since we know we aren't doing a retransmission. 684 * (retransmit and persist are mutually exclusive...) 685 */ 686 if (len || (flags & (TH_SYN|TH_FIN)) 687 || callout_active(tp->tt_persist)) 688 th->th_seq = htonl(tp->snd_nxt); 689 else 690 th->th_seq = htonl(tp->snd_max); 691 th->th_ack = htonl(tp->rcv_nxt); 692 if (optlen) { 693 bcopy(opt, th + 1, optlen); 694 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 695 } 696 th->th_flags = flags; 697 /* 698 * Calculate receive window. Don't shrink window, 699 * but avoid silly window syndrome. 700 */ 701 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg) 702 win = 0; 703 if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) 704 win = (long)(tp->rcv_adv - tp->rcv_nxt); 705 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 706 win = (long)TCP_MAXWIN << tp->rcv_scale; 707 th->th_win = htons((u_short) (win>>tp->rcv_scale)); 708 709 710 /* 711 * Adjust the RXWIN0SENT flag - indicate that we have advertised 712 * a 0 window. This may cause the remote transmitter to stall. This 713 * flag tells soreceive() to disable delayed acknowledgements when 714 * draining the buffer. This can occur if the receiver is attempting 715 * to read more data then can be buffered prior to transmitting on 716 * the connection. 717 */ 718 if (win == 0) 719 tp->t_flags |= TF_RXWIN0SENT; 720 else 721 tp->t_flags &= ~TF_RXWIN0SENT; 722 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 723 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 724 th->th_flags |= TH_URG; 725 } else 726 /* 727 * If no urgent pointer to send, then we pull 728 * the urgent pointer to the left edge of the send window 729 * so that it doesn't drift into the send window on sequence 730 * number wraparound. 731 */ 732 tp->snd_up = tp->snd_una; /* drag it along */ 733 734 /* 735 * Put TCP length in extended header, and then 736 * checksum extended header and data. 737 */ 738 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 739 #ifdef INET6 740 if (isipv6) 741 /* 742 * ip6_plen is not need to be filled now, and will be filled 743 * in ip6_output. 744 */ 745 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 746 sizeof(struct tcphdr) + optlen + len); 747 else 748 #endif /* INET6 */ 749 { 750 m->m_pkthdr.csum_flags = CSUM_TCP; 751 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 752 if (len + optlen) 753 th->th_sum = in_addword(th->th_sum, 754 htons((u_short)(optlen + len))); 755 756 /* IP version must be set here for ipv4/ipv6 checking later */ 757 KASSERT(ip->ip_v == IPVERSION, 758 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 759 } 760 761 /* 762 * In transmit state, time the transmission and arrange for 763 * the retransmit. In persist state, just set snd_max. 764 */ 765 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 766 tcp_seq startseq = tp->snd_nxt; 767 768 /* 769 * Advance snd_nxt over sequence space of this segment. 770 */ 771 if (flags & (TH_SYN|TH_FIN)) { 772 if (flags & TH_SYN) 773 tp->snd_nxt++; 774 if (flags & TH_FIN) { 775 tp->snd_nxt++; 776 tp->t_flags |= TF_SENTFIN; 777 } 778 } 779 tp->snd_nxt += len; 780 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 781 tp->snd_max = tp->snd_nxt; 782 /* 783 * Time this transmission if not a retransmission and 784 * not currently timing anything. 785 */ 786 if (tp->t_rtttime == 0) { 787 tp->t_rtttime = ticks; 788 tp->t_rtseq = startseq; 789 tcpstat.tcps_segstimed++; 790 } 791 } 792 793 /* 794 * Set retransmit timer if not currently set, 795 * and not doing an ack or a keep-alive probe. 796 * Initial value for retransmit timer is smoothed 797 * round-trip time + 2 * round-trip time variance. 798 * Initialize shift counter which is used for backoff 799 * of retransmit time. 800 */ 801 if (!callout_active(tp->tt_rexmt) && 802 tp->snd_nxt != tp->snd_una) { 803 if (callout_active(tp->tt_persist)) { 804 callout_stop(tp->tt_persist); 805 tp->t_rxtshift = 0; 806 } 807 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 808 tcp_timer_rexmt, tp); 809 } 810 } else 811 if (SEQ_GT(tp->snd_nxt + len, tp->snd_max)) 812 tp->snd_max = tp->snd_nxt + len; 813 814 #ifdef TCPDEBUG 815 /* 816 * Trace. 817 */ 818 if (so->so_options & SO_DEBUG) 819 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 820 #endif 821 822 /* 823 * Fill in IP length and desired time to live and 824 * send to IP level. There should be a better way 825 * to handle ttl and tos; we could keep them in 826 * the template, but need a way to checksum without them. 827 */ 828 /* 829 * m->m_pkthdr.len should have been set before cksum calcuration, 830 * because in6_cksum() need it. 831 */ 832 #ifdef INET6 833 if (isipv6) { 834 /* 835 * we separately set hoplimit for every segment, since the 836 * user might want to change the value via setsockopt. 837 * Also, desired default hop limit might be changed via 838 * Neighbor Discovery. 839 */ 840 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, 841 tp->t_inpcb->in6p_route.ro_rt ? 842 tp->t_inpcb->in6p_route.ro_rt->rt_ifp 843 : NULL); 844 845 /* TODO: IPv6 IP6TOS_ECT bit on */ 846 #ifdef IPSEC 847 if (ipsec_setsocket(m, so) != 0) { 848 m_freem(m); 849 error = ENOBUFS; 850 goto out; 851 } 852 #endif /*IPSEC*/ 853 error = ip6_output(m, 854 tp->t_inpcb->in6p_outputopts, 855 &tp->t_inpcb->in6p_route, 856 (so->so_options & SO_DONTROUTE), NULL, NULL); 857 } else 858 #endif /* INET6 */ 859 { 860 struct rtentry *rt; 861 ip->ip_len = m->m_pkthdr.len; 862 #ifdef INET6 863 if (INP_CHECK_SOCKAF(so, AF_INET6)) 864 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, 865 tp->t_inpcb->in6p_route.ro_rt ? 866 tp->t_inpcb->in6p_route.ro_rt->rt_ifp 867 : NULL); 868 else 869 #endif /* INET6 */ 870 ip->ip_ttl = tp->t_inpcb->inp_ip_ttl; /* XXX */ 871 ip->ip_tos = tp->t_inpcb->inp_ip_tos; /* XXX */ 872 /* 873 * See if we should do MTU discovery. We do it only if the following 874 * are true: 875 * 1) we have a valid route to the destination 876 * 2) the MTU is not locked (if it is, then discovery has been 877 * disabled) 878 */ 879 if (path_mtu_discovery 880 && (rt = tp->t_inpcb->inp_route.ro_rt) 881 && rt->rt_flags & RTF_UP 882 && !(rt->rt_rmx.rmx_locks & RTV_MTU)) { 883 ip->ip_off |= IP_DF; 884 } 885 #ifdef IPSEC 886 ipsec_setsocket(m, so); 887 #endif /*IPSEC*/ 888 error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, 889 (so->so_options & SO_DONTROUTE), 0); 890 } 891 if (error) { 892 893 /* 894 * We know that the packet was lost, so back out the 895 * sequence number advance, if any. 896 */ 897 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 898 /* 899 * No need to check for TH_FIN here because 900 * the TF_SENTFIN flag handles that case. 901 */ 902 if ((flags & TH_SYN) == 0) 903 tp->snd_nxt -= len; 904 } 905 906 out: 907 if (error == ENOBUFS) { 908 if (!callout_active(tp->tt_rexmt) && 909 !callout_active(tp->tt_persist)) 910 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 911 tcp_timer_rexmt, tp); 912 tcp_quench(tp->t_inpcb, 0); 913 return (0); 914 } 915 if (error == EMSGSIZE) { 916 /* 917 * ip_output() will have already fixed the route 918 * for us. tcp_mtudisc() will, as its last action, 919 * initiate retransmission, so it is important to 920 * not do so here. 921 */ 922 tcp_mtudisc(tp->t_inpcb, 0); 923 return 0; 924 } 925 if ((error == EHOSTUNREACH || error == ENETDOWN) 926 && TCPS_HAVERCVDSYN(tp->t_state)) { 927 tp->t_softerror = error; 928 return (0); 929 } 930 return (error); 931 } 932 tcpstat.tcps_sndtotal++; 933 934 /* 935 * Data sent (as far as we can tell). 936 * If this advertises a larger window than any other segment, 937 * then remember the size of the advertised window. 938 * Any pending ACK has now been sent. 939 */ 940 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 941 tp->rcv_adv = tp->rcv_nxt + win; 942 tp->last_ack_sent = tp->rcv_nxt; 943 tp->t_flags &= ~TF_ACKNOW; 944 if (tcp_delack_enabled) 945 callout_stop(tp->tt_delack); 946 #if 0 947 /* 948 * This completely breaks TCP if newreno is turned on. What happens 949 * is that if delayed-acks are turned on on the receiver, this code 950 * on the transmitter effectively destroys the TCP window, forcing 951 * it to four packets (1.5Kx4 = 6K window). 952 */ 953 if (sendalot && (!tcp_do_newreno || --maxburst)) 954 goto again; 955 #endif 956 if (sendalot) 957 goto again; 958 return (0); 959 } 960 961 void 962 tcp_setpersist(tp) 963 register struct tcpcb *tp; 964 { 965 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 966 int tt; 967 968 if (callout_active(tp->tt_rexmt)) 969 panic("tcp_setpersist: retransmit pending"); 970 /* 971 * Start/restart persistance timer. 972 */ 973 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 974 TCPTV_PERSMIN, TCPTV_PERSMAX); 975 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 976 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 977 tp->t_rxtshift++; 978 } 979