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