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: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $ 35 * $DragonFly: src/sys/netinet/tcp_output.c,v 1.9 2004/02/14 21:12:39 dillon Exp $ 36 */ 37 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 #include "opt_tcpdebug.h" 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/kernel.h> 45 #include <sys/sysctl.h> 46 #include <sys/mbuf.h> 47 #include <sys/domain.h> 48 #include <sys/protosw.h> 49 #include <sys/socket.h> 50 #include <sys/socketvar.h> 51 #include <sys/in_cksum.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 #include <netinet6/in6_pcb.h> 61 #include <netinet/ip6.h> 62 #include <netinet6/ip6_var.h> 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 #ifdef FAST_IPSEC 79 #include <netipsec/ipsec.h> 80 #define IPSEC 81 #endif /*FAST_IPSEC*/ 82 83 #ifdef notyet 84 extern struct mbuf *m_copypack(); 85 #endif 86 87 int path_mtu_discovery = 1; 88 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 89 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 90 91 int ss_fltsz = 1; 92 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 93 &ss_fltsz, 1, "Slow start flight size"); 94 95 int ss_fltsz_local = 4; 96 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 97 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 98 99 int tcp_do_newreno = 1; 100 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno, 101 0, "Enable NewReno Algorithms"); 102 103 /* 104 * Tcp output routine: figure out what should be sent and send it. 105 */ 106 int 107 tcp_output(tp) 108 struct tcpcb *tp; 109 { 110 struct inpcb * const inp = tp->t_inpcb; 111 struct socket *so = inp->inp_socket; 112 long len, recvwin, sendwin; 113 int off, flags, error; 114 struct mbuf *m; 115 struct ip *ip = NULL; 116 struct ipovly *ipov = NULL; 117 struct tcphdr *th; 118 u_char opt[TCP_MAXOLEN]; 119 unsigned ipoptlen, optlen, hdrlen; 120 int idle, sendalot; 121 struct ip6_hdr *ip6 = NULL; 122 #ifdef INET6 123 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 124 #else 125 const boolean_t isipv6 = FALSE; 126 #endif 127 struct rmxp_tao *taop; 128 129 /* 130 * Determine length of data that should be transmitted, 131 * and flags that will be used. 132 * If there is some data or critical controls (SYN, RST) 133 * to send, then transmit; otherwise, investigate further. 134 */ 135 if ((tp->snd_max == tp->snd_una) && 136 (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 137 /* 138 * We have been idle for "a while" and no acks are 139 * expected to clock out any data we send -- 140 * slow start to get ack "clock" running again. 141 * 142 * Set the slow-start flight size depending on whether 143 * this is a local network or not. 144 */ 145 if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 146 (!isipv6 && in_localaddr(inp->inp_faddr))) 147 tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local; 148 else 149 tp->snd_cwnd = tp->t_maxseg * ss_fltsz; 150 } 151 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 152 if (idle && (tp->t_flags & TF_MORETOCOME)) 153 tp->t_flags |= TF_LASTIDLE; 154 else 155 tp->t_flags &= ~TF_LASTIDLE; 156 again: 157 sendalot = 0; 158 off = tp->snd_nxt - tp->snd_una; 159 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 160 sendwin = min(sendwin, tp->snd_bwnd); 161 162 flags = tcp_outflags[tp->t_state]; 163 /* 164 * Get standard flags, and add SYN or FIN if requested by 'hidden' 165 * state flags. 166 */ 167 if (tp->t_flags & TF_NEEDFIN) 168 flags |= TH_FIN; 169 if (tp->t_flags & TF_NEEDSYN) 170 flags |= TH_SYN; 171 172 /* 173 * If in persist timeout with window of 0, send 1 byte. 174 * Otherwise, if window is small but nonzero 175 * and timer expired, we will send what we can 176 * and go to transmit state. 177 */ 178 if (tp->t_force) { 179 if (sendwin == 0) { 180 /* 181 * If we still have some data to send, then 182 * clear the FIN bit. Usually this would 183 * happen below when it realizes that we 184 * aren't sending all the data. However, 185 * if we have exactly 1 byte of unsent data, 186 * then it won't clear the FIN bit below, 187 * and if we are in persist state, we wind 188 * up sending the packet without recording 189 * that we sent the FIN bit. 190 * 191 * We can't just blindly clear the FIN bit, 192 * because if we don't have any more data 193 * to send then the probe will be the FIN 194 * itself. 195 */ 196 if (off < so->so_snd.sb_cc) 197 flags &= ~TH_FIN; 198 sendwin = 1; 199 } else { 200 callout_stop(tp->tt_persist); 201 tp->t_rxtshift = 0; 202 } 203 } 204 205 /* 206 * If snd_nxt == snd_max and we have transmitted a FIN, the 207 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 208 * a negative length. This can also occur when TCP opens up 209 * its congestion window while receiving additional duplicate 210 * acks after fast-retransmit because TCP will reset snd_nxt 211 * to snd_max after the fast-retransmit. 212 * 213 * In the normal retransmit-FIN-only case, however, snd_nxt will 214 * be set to snd_una, the offset will be 0, and the length may 215 * wind up 0. 216 */ 217 len = (long)ulmin(so->so_snd.sb_cc, sendwin) - off; 218 219 /* 220 * Lop off SYN bit if it has already been sent. However, if this 221 * is SYN-SENT state and if segment contains data and if we don't 222 * know that foreign host supports TAO, suppress sending segment. 223 */ 224 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 225 flags &= ~TH_SYN; 226 off--, len++; 227 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 228 ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL || 229 taop->tao_ccsent == 0)) 230 return 0; 231 } 232 233 /* 234 * Be careful not to send data and/or FIN on SYN segments 235 * in cases when no CC option will be sent. 236 * This measure is needed to prevent interoperability problems 237 * with not fully conformant TCP implementations. 238 */ 239 if ((flags & TH_SYN) && 240 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 241 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 242 len = 0; 243 flags &= ~TH_FIN; 244 } 245 246 if (len < 0) { 247 /* 248 * If FIN has been sent but not acked, 249 * but we haven't been called to retransmit, 250 * len will be < 0. Otherwise, window shrank 251 * after we sent into it. If window shrank to 0, 252 * cancel pending retransmit, pull snd_nxt back 253 * to (closed) window, and set the persist timer 254 * if it isn't already going. If the window didn't 255 * close completely, just wait for an ACK. 256 */ 257 len = 0; 258 if (sendwin == 0) { 259 callout_stop(tp->tt_rexmt); 260 tp->t_rxtshift = 0; 261 tp->snd_nxt = tp->snd_una; 262 if (!callout_active(tp->tt_persist)) 263 tcp_setpersist(tp); 264 } 265 } 266 267 /* 268 * len will be >= 0 after this point. Truncate to the maximum 269 * segment length and ensure that FIN is removed if the length 270 * no longer contains the last data byte. 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 recvwin = 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)) { 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 (recvwin > 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(recvwin, (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 the peer an ACK, RST, SYN, or urgent data. ACKNOW 341 * is also a catch-all for the retransmit timer timeout case. 342 */ 343 if (tp->t_flags & TF_ACKNOW) 344 goto send; 345 if ((flags & TH_RST) || 346 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 347 goto send; 348 if (SEQ_GT(tp->snd_up, tp->snd_una)) 349 goto send; 350 /* 351 * If our state indicates that FIN should be sent 352 * and we have not yet done so, then we need to send. 353 */ 354 if (flags & TH_FIN && 355 (!(tp->t_flags & TF_SENTFIN) || 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 if (isipv6) 402 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 403 else 404 hdrlen = sizeof (struct tcpiphdr); 405 if (flags & TH_SYN) { 406 tp->snd_nxt = tp->iss; 407 if (!(tp->t_flags & TF_NOOPT)) { 408 u_short mss; 409 410 opt[0] = TCPOPT_MAXSEG; 411 opt[1] = TCPOLEN_MAXSEG; 412 mss = htons((u_short) tcp_mssopt(tp)); 413 (void)memcpy(opt + 2, &mss, sizeof(mss)); 414 optlen = TCPOLEN_MAXSEG; 415 416 if ((tp->t_flags & TF_REQ_SCALE) && 417 (!(flags & TH_ACK) || 418 (tp->t_flags & TF_RCVD_SCALE))) { 419 *((u_int32_t *)(opt + optlen)) = htonl( 420 TCPOPT_NOP << 24 | 421 TCPOPT_WINDOW << 16 | 422 TCPOLEN_WINDOW << 8 | 423 tp->request_r_scale); 424 optlen += 4; 425 } 426 } 427 } 428 429 /* 430 * Send a timestamp and echo-reply if this is a SYN and our side 431 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 432 * and our peer have sent timestamps in our SYN's. 433 */ 434 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 435 !(flags & TH_RST) && 436 (!(flags & TH_ACK) || (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)) { 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 if (isipv6) 520 ipoptlen = ip6_optlen(inp); 521 else { 522 if (inp->inp_options) { 523 ipoptlen = inp->inp_options->m_len - 524 offsetof(struct ipoption, ipopt_list); 525 } else { 526 ipoptlen = 0; 527 } 528 } 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 INET6 549 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 550 #else 551 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 552 #endif 553 554 /* 555 * Grab a header mbuf, attaching a copy of data to 556 * be transmitted, and initialize the header from 557 * the template for sends on this connection. 558 */ 559 if (len) { 560 if (tp->t_force && len == 1) 561 tcpstat.tcps_sndprobe++; 562 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 563 tcpstat.tcps_sndrexmitpack++; 564 tcpstat.tcps_sndrexmitbyte += len; 565 } else { 566 tcpstat.tcps_sndpack++; 567 tcpstat.tcps_sndbyte += len; 568 } 569 #ifdef notyet 570 if ((m = m_copypack(so->so_snd.sb_mb, off, 571 (int)len, max_linkhdr + hdrlen)) == 0) { 572 error = ENOBUFS; 573 goto out; 574 } 575 /* 576 * m_copypack left space for our hdr; use it. 577 */ 578 m->m_len += hdrlen; 579 m->m_data -= hdrlen; 580 #else 581 MGETHDR(m, M_DONTWAIT, MT_HEADER); 582 if (m == NULL) { 583 error = ENOBUFS; 584 goto out; 585 } 586 #ifdef INET6 587 if (MHLEN < hdrlen + max_linkhdr) { 588 MCLGET(m, M_DONTWAIT); 589 if (!(m->m_flags & M_EXT)) { 590 m_freem(m); 591 error = ENOBUFS; 592 goto out; 593 } 594 } 595 #endif 596 m->m_data += max_linkhdr; 597 m->m_len = hdrlen; 598 if (len <= MHLEN - hdrlen - max_linkhdr) { 599 m_copydata(so->so_snd.sb_mb, off, (int) len, 600 mtod(m, caddr_t) + hdrlen); 601 m->m_len += len; 602 } else { 603 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 604 if (m->m_next == 0) { 605 (void) m_free(m); 606 error = ENOBUFS; 607 goto out; 608 } 609 } 610 #endif 611 /* 612 * If we're sending everything we've got, set PUSH. 613 * (This will keep happy those implementations which only 614 * give data to the user when a buffer fills or 615 * a PUSH comes in.) 616 */ 617 if (off + len == so->so_snd.sb_cc) 618 flags |= TH_PUSH; 619 } else { 620 if (tp->t_flags & TF_ACKNOW) 621 tcpstat.tcps_sndacks++; 622 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 623 tcpstat.tcps_sndctrl++; 624 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 625 tcpstat.tcps_sndurg++; 626 else 627 tcpstat.tcps_sndwinup++; 628 629 MGETHDR(m, M_DONTWAIT, MT_HEADER); 630 if (m == NULL) { 631 error = ENOBUFS; 632 goto out; 633 } 634 if (isipv6 && 635 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 636 MH_ALIGN(m, hdrlen); 637 else 638 m->m_data += max_linkhdr; 639 m->m_len = hdrlen; 640 } 641 m->m_pkthdr.rcvif = (struct ifnet *)0; 642 if (isipv6) { 643 ip6 = mtod(m, struct ip6_hdr *); 644 th = (struct tcphdr *)(ip6 + 1); 645 tcp_fillheaders(tp, ip6, th); 646 } else { 647 ip = mtod(m, struct ip *); 648 ipov = (struct ipovly *)ip; 649 th = (struct tcphdr *)(ip + 1); 650 /* this picks up the pseudo header (w/o the length) */ 651 tcp_fillheaders(tp, ip, th); 652 } 653 654 /* 655 * Fill in fields, remembering maximum advertised 656 * window for use in delaying messages about window sizes. 657 * If resending a FIN, be sure not to use a new sequence number. 658 */ 659 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 660 tp->snd_nxt == tp->snd_max) 661 tp->snd_nxt--; 662 /* 663 * If we are doing retransmissions, then snd_nxt will 664 * not reflect the first unsent octet. For ACK only 665 * packets, we do not want the sequence number of the 666 * retransmitted packet, we want the sequence number 667 * of the next unsent octet. So, if there is no data 668 * (and no SYN or FIN), use snd_max instead of snd_nxt 669 * when filling in ti_seq. But if we are in persist 670 * state, snd_max might reflect one byte beyond the 671 * right edge of the window, so use snd_nxt in that 672 * case, since we know we aren't doing a retransmission. 673 * (retransmit and persist are mutually exclusive...) 674 */ 675 if (len || (flags & (TH_SYN|TH_FIN)) || callout_active(tp->tt_persist)) 676 th->th_seq = htonl(tp->snd_nxt); 677 else 678 th->th_seq = htonl(tp->snd_max); 679 th->th_ack = htonl(tp->rcv_nxt); 680 if (optlen) { 681 bcopy(opt, th + 1, optlen); 682 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 683 } 684 th->th_flags = flags; 685 /* 686 * Calculate receive window. Don't shrink window, 687 * but avoid silly window syndrome. 688 */ 689 if (recvwin < (long)(so->so_rcv.sb_hiwat / 4) && 690 recvwin < (long)tp->t_maxseg) 691 recvwin = 0; 692 if (recvwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 693 recvwin = (long)(tp->rcv_adv - tp->rcv_nxt); 694 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 695 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 696 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 697 698 /* 699 * Adjust the RXWIN0SENT flag - indicate that we have advertised 700 * a 0 window. This may cause the remote transmitter to stall. This 701 * flag tells soreceive() to disable delayed acknowledgements when 702 * draining the buffer. This can occur if the receiver is attempting 703 * to read more data then can be buffered prior to transmitting on 704 * the connection. 705 */ 706 if (recvwin == 0) 707 tp->t_flags |= TF_RXWIN0SENT; 708 else 709 tp->t_flags &= ~TF_RXWIN0SENT; 710 711 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 712 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 713 th->th_flags |= TH_URG; 714 } else 715 /* 716 * If no urgent pointer to send, then we pull 717 * the urgent pointer to the left edge of the send window 718 * so that it doesn't drift into the send window on sequence 719 * number wraparound. 720 */ 721 tp->snd_up = tp->snd_una; /* drag it along */ 722 723 /* 724 * Put TCP length in extended header, and then 725 * checksum extended header and data. 726 */ 727 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 728 if (isipv6) { 729 /* 730 * ip6_plen is not need to be filled now, and will be filled 731 * in ip6_output. 732 */ 733 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 734 sizeof(struct tcphdr) + optlen + len); 735 } else { 736 m->m_pkthdr.csum_flags = CSUM_TCP; 737 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 738 if (len + optlen) 739 th->th_sum = in_addword(th->th_sum, 740 htons((u_short)(optlen + len))); 741 742 /* IP version must be set here for ipv4/ipv6 checking later */ 743 KASSERT(ip->ip_v == IPVERSION, 744 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 745 } 746 747 /* 748 * In transmit state, time the transmission and arrange for 749 * the retransmit. In persist state, just set snd_max. 750 */ 751 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 752 tcp_seq startseq = tp->snd_nxt; 753 754 /* 755 * Advance snd_nxt over sequence space of this segment. 756 */ 757 if (flags & (TH_SYN|TH_FIN)) { 758 if (flags & TH_SYN) 759 tp->snd_nxt++; 760 if (flags & TH_FIN) { 761 tp->snd_nxt++; 762 tp->t_flags |= TF_SENTFIN; 763 } 764 } 765 tp->snd_nxt += len; 766 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 767 tp->snd_max = tp->snd_nxt; 768 /* 769 * Time this transmission if not a retransmission and 770 * not currently timing anything. 771 */ 772 if (tp->t_rtttime == 0) { 773 tp->t_rtttime = ticks; 774 tp->t_rtseq = startseq; 775 tcpstat.tcps_segstimed++; 776 } 777 } 778 779 /* 780 * Set retransmit timer if not currently set, 781 * and not doing a pure ack or a keep-alive probe. 782 * Initial value for retransmit timer is smoothed 783 * round-trip time + 2 * round-trip time variance. 784 * Initialize shift counter which is used for backoff 785 * of retransmit time. 786 */ 787 if (!callout_active(tp->tt_rexmt) && 788 tp->snd_nxt != tp->snd_una) { 789 if (callout_active(tp->tt_persist)) { 790 callout_stop(tp->tt_persist); 791 tp->t_rxtshift = 0; 792 } 793 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 794 tcp_timer_rexmt, tp); 795 } 796 } else { 797 /* 798 * Persist case, update snd_max but since we are in 799 * persist mode (no window) we do not update snd_nxt. 800 */ 801 int xlen = len; 802 if (flags & TH_SYN) 803 ++xlen; 804 if (flags & TH_FIN) { 805 ++xlen; 806 tp->t_flags |= TF_SENTFIN; 807 } 808 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 809 tp->snd_max = tp->snd_nxt + xlen; 810 } 811 812 #ifdef TCPDEBUG 813 /* 814 * Trace. 815 */ 816 if (so->so_options & SO_DEBUG) 817 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 818 #endif 819 820 /* 821 * Fill in IP length and desired time to live and 822 * send to IP level. There should be a better way 823 * to handle ttl and tos; we could keep them in 824 * the template, but need a way to checksum without them. 825 */ 826 /* 827 * m->m_pkthdr.len should have been set before cksum calcuration, 828 * because in6_cksum() need it. 829 */ 830 if (isipv6) { 831 /* 832 * we separately set hoplimit for every segment, since the 833 * user might want to change the value via setsockopt. 834 * Also, desired default hop limit might be changed via 835 * Neighbor Discovery. 836 */ 837 ip6->ip6_hlim = in6_selecthlim(inp, 838 (inp->in6p_route.ro_rt ? 839 inp->in6p_route.ro_rt->rt_ifp : NULL)); 840 841 /* TODO: IPv6 IP6TOS_ECT bit on */ 842 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route, 843 (so->so_options & SO_DONTROUTE), NULL, NULL, inp); 844 } else { 845 struct rtentry *rt; 846 ip->ip_len = m->m_pkthdr.len; 847 #ifdef INET6 848 if (INP_CHECK_SOCKAF(so, AF_INET6)) 849 ip->ip_ttl = in6_selecthlim(inp, 850 (inp->in6p_route.ro_rt ? 851 inp->in6p_route.ro_rt->rt_ifp : NULL)); 852 else 853 #endif 854 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 855 856 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 857 /* 858 * See if we should do MTU discovery. 859 * We do it only if the following are true: 860 * 1) we have a valid route to the destination 861 * 2) the MTU is not locked (if it is, 862 * then discovery has been disabled) 863 */ 864 if (path_mtu_discovery && 865 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) && 866 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 867 ip->ip_off |= IP_DF; 868 869 error = ip_output(m, inp->inp_options, &inp->inp_route, 870 (so->so_options & SO_DONTROUTE), NULL, inp); 871 } 872 if (error) { 873 874 /* 875 * We know that the packet was lost, so back out the 876 * sequence number advance, if any. 877 */ 878 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 879 /* 880 * No need to check for TH_FIN here because 881 * the TF_SENTFIN flag handles that case. 882 */ 883 if (!(flags & TH_SYN)) 884 tp->snd_nxt -= len; 885 } 886 887 out: 888 if (error == ENOBUFS) { 889 /* 890 * If we can't send, make sure there is something 891 * to get us going again later. Persist state 892 * is not necessarily right, but it is close enough. 893 */ 894 if (!callout_active(tp->tt_rexmt) && 895 !callout_active(tp->tt_persist)) { 896 tp->t_rxtshift = 0; 897 tcp_setpersist(tp); 898 } 899 tcp_quench(inp, 0); 900 return (0); 901 } 902 if (error == EMSGSIZE) { 903 /* 904 * ip_output() will have already fixed the route 905 * for us. tcp_mtudisc() will, as its last action, 906 * initiate retransmission, so it is important to 907 * not do so here. 908 */ 909 tcp_mtudisc(inp, 0); 910 return 0; 911 } 912 if ((error == EHOSTUNREACH || error == ENETDOWN) && 913 TCPS_HAVERCVDSYN(tp->t_state)) { 914 tp->t_softerror = error; 915 return (0); 916 } 917 return (error); 918 } 919 tcpstat.tcps_sndtotal++; 920 921 /* 922 * Data sent (as far as we can tell). 923 * If this advertises a larger window than any other segment, 924 * then remember the size of the advertised window. 925 * Any pending ACK has now been sent. 926 */ 927 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) 928 tp->rcv_adv = tp->rcv_nxt + recvwin; 929 tp->last_ack_sent = tp->rcv_nxt; 930 tp->t_flags &= ~TF_ACKNOW; 931 if (tcp_delack_enabled) 932 callout_stop(tp->tt_delack); 933 if (sendalot) 934 goto again; 935 return (0); 936 } 937 938 void 939 tcp_setpersist(tp) 940 struct tcpcb *tp; 941 { 942 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 943 int tt; 944 945 if (callout_active(tp->tt_rexmt)) 946 panic("tcp_setpersist: retransmit pending"); 947 /* 948 * Start/restart persistance timer. 949 */ 950 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 951 TCPTV_PERSMIN, TCPTV_PERSMAX); 952 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 953 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 954 tp->t_rxtshift++; 955 } 956