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