1 /* 2 * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 4 * The Regents of the University of California. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. All advertising materials mentioning features or use of this software 15 * must display the following acknowledgement: 16 * This product includes software developed by the University of 17 * California, Berkeley and its contributors. 18 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 35 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $ 36 * $DragonFly: src/sys/netinet/tcp_output.c,v 1.14 2004/07/02 04:41:01 hsu Exp $ 37 */ 38 39 #include "opt_inet6.h" 40 #include "opt_ipsec.h" 41 #include "opt_tcpdebug.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/kernel.h> 46 #include <sys/sysctl.h> 47 #include <sys/mbuf.h> 48 #include <sys/domain.h> 49 #include <sys/protosw.h> 50 #include <sys/socket.h> 51 #include <sys/socketvar.h> 52 #include <sys/in_cksum.h> 53 #include <sys/thread.h> 54 #include <sys/globaldata.h> 55 56 #include <net/route.h> 57 58 #include <netinet/in.h> 59 #include <netinet/in_systm.h> 60 #include <netinet/ip.h> 61 #include <netinet/in_pcb.h> 62 #include <netinet/ip_var.h> 63 #include <netinet6/in6_pcb.h> 64 #include <netinet/ip6.h> 65 #include <netinet6/ip6_var.h> 66 #include <netinet/tcp.h> 67 #define TCPOUTFLAGS 68 #include <netinet/tcp_fsm.h> 69 #include <netinet/tcp_seq.h> 70 #include <netinet/tcp_timer.h> 71 #include <netinet/tcp_var.h> 72 #include <netinet/tcpip.h> 73 #ifdef TCPDEBUG 74 #include <netinet/tcp_debug.h> 75 #endif 76 77 #ifdef IPSEC 78 #include <netinet6/ipsec.h> 79 #endif /*IPSEC*/ 80 81 #ifdef FAST_IPSEC 82 #include <netipsec/ipsec.h> 83 #define IPSEC 84 #endif /*FAST_IPSEC*/ 85 86 #ifdef notyet 87 extern struct mbuf *m_copypack(); 88 #endif 89 90 int path_mtu_discovery = 1; 91 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 92 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 93 94 int ss_fltsz = 1; 95 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 96 &ss_fltsz, 1, "Slow start flight size"); 97 98 int ss_fltsz_local = 4; 99 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 100 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 101 102 int tcp_do_newreno = 1; 103 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno, 104 0, "Enable NewReno Algorithms"); 105 106 /* 107 * Tcp output routine: figure out what should be sent and send it. 108 */ 109 int 110 tcp_output(tp) 111 struct tcpcb *tp; 112 { 113 struct inpcb * const inp = tp->t_inpcb; 114 struct socket *so = inp->inp_socket; 115 long len, recvwin, sendwin; 116 int off, flags, error; 117 struct mbuf *m; 118 struct ip *ip = NULL; 119 struct ipovly *ipov = NULL; 120 struct tcphdr *th; 121 u_char opt[TCP_MAXOLEN]; 122 unsigned ipoptlen, optlen, hdrlen; 123 int idle, sendalot; 124 struct ip6_hdr *ip6 = NULL; 125 #ifdef INET6 126 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 127 #else 128 const boolean_t isipv6 = FALSE; 129 #endif 130 struct rmxp_tao *taop; 131 132 /* 133 * Determine length of data that should be transmitted, 134 * and flags that will be used. 135 * If there is some data or critical controls (SYN, RST) 136 * to send, then transmit; otherwise, investigate further. 137 */ 138 if ((tp->snd_max == tp->snd_una) && 139 (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 140 /* 141 * We have been idle for "a while" and no acks are 142 * expected to clock out any data we send -- 143 * slow start to get ack "clock" running again. 144 * 145 * Set the slow-start flight size depending on whether 146 * this is a local network or not. 147 */ 148 if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 149 (!isipv6 && in_localaddr(inp->inp_faddr))) 150 tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local; 151 else 152 tp->snd_cwnd = tp->t_maxseg * ss_fltsz; 153 } 154 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 155 if (idle && (tp->t_flags & TF_MORETOCOME)) 156 tp->t_flags |= TF_LASTIDLE; 157 else 158 tp->t_flags &= ~TF_LASTIDLE; 159 160 again: 161 sendalot = 0; 162 off = tp->snd_nxt - tp->snd_una; 163 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 164 sendwin = min(sendwin, tp->snd_bwnd); 165 166 flags = tcp_outflags[tp->t_state]; 167 /* 168 * Get standard flags, and add SYN or FIN if requested by 'hidden' 169 * state flags. 170 */ 171 if (tp->t_flags & TF_NEEDFIN) 172 flags |= TH_FIN; 173 if (tp->t_flags & TF_NEEDSYN) 174 flags |= TH_SYN; 175 176 /* 177 * If in persist timeout with window of 0, send 1 byte. 178 * Otherwise, if window is small but nonzero 179 * and timer expired, we will send what we can 180 * and go to transmit state. 181 */ 182 if (tp->t_flags & TF_FORCE) { 183 if (sendwin == 0) { 184 /* 185 * If we still have some data to send, then 186 * clear the FIN bit. Usually this would 187 * happen below when it realizes that we 188 * aren't sending all the data. However, 189 * if we have exactly 1 byte of unsent data, 190 * then it won't clear the FIN bit below, 191 * and if we are in persist state, we wind 192 * up sending the packet without recording 193 * that we sent the FIN bit. 194 * 195 * We can't just blindly clear the FIN bit, 196 * because if we don't have any more data 197 * to send then the probe will be the FIN 198 * itself. 199 */ 200 if (off < so->so_snd.sb_cc) 201 flags &= ~TH_FIN; 202 sendwin = 1; 203 } else { 204 callout_stop(tp->tt_persist); 205 tp->t_rxtshift = 0; 206 } 207 } 208 209 /* 210 * If snd_nxt == snd_max and we have transmitted a FIN, the 211 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 212 * a negative length. This can also occur when TCP opens up 213 * its congestion window while receiving additional duplicate 214 * acks after fast-retransmit because TCP will reset snd_nxt 215 * to snd_max after the fast-retransmit. 216 * 217 * In the normal retransmit-FIN-only case, however, snd_nxt will 218 * be set to snd_una, the offset will be 0, and the length may 219 * wind up 0. 220 */ 221 len = (long)ulmin(so->so_snd.sb_cc, sendwin) - off; 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 = tcp_gettaocache(&inp->inp_inc)) == NULL || 233 taop->tao_ccsent == 0)) 234 return 0; 235 } 236 237 /* 238 * Be careful not to send data and/or FIN on SYN segments 239 * in cases when no CC option will be sent. 240 * This measure is needed to prevent interoperability problems 241 * with not fully conformant TCP implementations. 242 */ 243 if ((flags & TH_SYN) && 244 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 245 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 246 len = 0; 247 flags &= ~TH_FIN; 248 } 249 250 if (len < 0) { 251 /* 252 * If FIN has been sent but not acked, 253 * but we haven't been called to retransmit, 254 * len will be < 0. Otherwise, window shrank 255 * after we sent into it. If window shrank to 0, 256 * cancel pending retransmit, pull snd_nxt back 257 * to (closed) window, and set the persist timer 258 * if it isn't already going. If the window didn't 259 * close completely, just wait for an ACK. 260 */ 261 len = 0; 262 if (sendwin == 0) { 263 callout_stop(tp->tt_rexmt); 264 tp->t_rxtshift = 0; 265 tp->snd_nxt = tp->snd_una; 266 if (!callout_active(tp->tt_persist)) 267 tcp_setpersist(tp); 268 } 269 } 270 271 /* 272 * len will be >= 0 after this point. Truncate to the maximum 273 * segment length and ensure that FIN is removed if the length 274 * no longer contains the last data byte. 275 */ 276 if (len > tp->t_maxseg) { 277 len = tp->t_maxseg; 278 sendalot = 1; 279 } 280 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 281 flags &= ~TH_FIN; 282 283 recvwin = sbspace(&so->so_rcv); 284 285 /* 286 * Sender silly window avoidance. We transmit under the following 287 * conditions when len is non-zero: 288 * 289 * - We have a full segment 290 * - This is the last buffer in a write()/send() and we are 291 * either idle or running NODELAY 292 * - we've timed out (e.g. persist timer) 293 * - we have more then 1/2 the maximum send window's worth of 294 * data (receiver may be limited the window size) 295 * - we need to retransmit 296 */ 297 if (len) { 298 if (len == tp->t_maxseg) 299 goto send; 300 /* 301 * NOTE! on localhost connections an 'ack' from the remote 302 * end may occur synchronously with the output and cause 303 * us to flush a buffer queued with moretocome. XXX 304 * 305 * note: the len + off check is almost certainly unnecessary. 306 */ 307 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 308 (idle || (tp->t_flags & TF_NODELAY)) && 309 len + off >= so->so_snd.sb_cc && 310 !(tp->t_flags & TF_NOPUSH)) { 311 goto send; 312 } 313 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 314 goto send; 315 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 316 goto send; 317 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 318 goto send; 319 } 320 321 /* 322 * Compare available window to amount of window 323 * known to peer (as advertised window less 324 * next expected input). If the difference is at least two 325 * max size segments, or at least 50% of the maximum possible 326 * window, then want to send a window update to peer. 327 */ 328 if (recvwin > 0) { 329 /* 330 * "adv" is the amount we can increase the window, 331 * taking into account that we are limited by 332 * TCP_MAXWIN << tp->rcv_scale. 333 */ 334 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 335 (tp->rcv_adv - tp->rcv_nxt); 336 337 if (adv >= (long) (2 * tp->t_maxseg)) 338 goto send; 339 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 340 goto send; 341 } 342 343 /* 344 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 345 * is also a catch-all for the retransmit timer timeout case. 346 */ 347 if (tp->t_flags & TF_ACKNOW) 348 goto send; 349 if ((flags & TH_RST) || 350 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 351 goto send; 352 if (SEQ_GT(tp->snd_up, tp->snd_una)) 353 goto send; 354 /* 355 * If our state indicates that FIN should be sent 356 * and we have not yet done so, then we need to send. 357 */ 358 if (flags & TH_FIN && 359 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 360 goto send; 361 362 /* 363 * TCP window updates are not reliable, rather a polling protocol 364 * using ``persist'' packets is used to insure receipt of window 365 * updates. The three ``states'' for the output side are: 366 * idle not doing retransmits or persists 367 * persisting to move a small or zero window 368 * (re)transmitting and thereby not persisting 369 * 370 * callout_active(tp->tt_persist) 371 * is true when we are in persist state. 372 * The TF_FORCE flag in tp->t_flags 373 * is set when we are called to send a persist packet. 374 * callout_active(tp->tt_rexmt) 375 * is set when we are retransmitting 376 * The output side is idle when both timers are zero. 377 * 378 * If send window is too small, there is data to transmit, and no 379 * retransmit or persist is pending, then go to persist state. 380 * If nothing happens soon, send when timer expires: 381 * if window is nonzero, transmit what we can, 382 * otherwise force out a byte. 383 */ 384 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 385 !callout_active(tp->tt_persist)) { 386 tp->t_rxtshift = 0; 387 tcp_setpersist(tp); 388 } 389 390 /* 391 * No reason to send a segment, just return. 392 */ 393 return (0); 394 395 send: 396 /* 397 * Before ESTABLISHED, force sending of initial options 398 * unless TCP set not to do any options. 399 * NOTE: we assume that the IP/TCP header plus TCP options 400 * always fit in a single mbuf, leaving room for a maximum 401 * link header, i.e. 402 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 403 */ 404 optlen = 0; 405 if (isipv6) 406 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 407 else 408 hdrlen = sizeof(struct tcpiphdr); 409 if (flags & TH_SYN) { 410 tp->snd_nxt = tp->iss; 411 if (!(tp->t_flags & TF_NOOPT)) { 412 u_short mss; 413 414 opt[0] = TCPOPT_MAXSEG; 415 opt[1] = TCPOLEN_MAXSEG; 416 mss = htons((u_short) tcp_mssopt(tp)); 417 (void)memcpy(opt + 2, &mss, sizeof(mss)); 418 optlen = TCPOLEN_MAXSEG; 419 420 if ((tp->t_flags & TF_REQ_SCALE) && 421 (!(flags & TH_ACK) || 422 (tp->t_flags & TF_RCVD_SCALE))) { 423 *((u_int32_t *)(opt + optlen)) = htonl( 424 TCPOPT_NOP << 24 | 425 TCPOPT_WINDOW << 16 | 426 TCPOLEN_WINDOW << 8 | 427 tp->request_r_scale); 428 optlen += 4; 429 } 430 } 431 } 432 433 /* 434 * Send a timestamp and echo-reply if this is a SYN and our side 435 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 436 * and our peer have sent timestamps in our SYN's. 437 */ 438 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 439 !(flags & TH_RST) && 440 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 441 u_int32_t *lp = (u_int32_t *)(opt + optlen); 442 443 /* Form timestamp option as shown in appendix A of RFC 1323. */ 444 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 445 *lp++ = htonl(ticks); 446 *lp = htonl(tp->ts_recent); 447 optlen += TCPOLEN_TSTAMP_APPA; 448 } 449 450 /* 451 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 452 * options are allowed (!TF_NOOPT) and it's not a RST. 453 */ 454 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 455 !(flags & TH_RST)) { 456 switch (flags & (TH_SYN|TH_ACK)) { 457 /* 458 * This is a normal ACK, send CC if we received CC before 459 * from our peer. 460 */ 461 case TH_ACK: 462 if (!(tp->t_flags & TF_RCVD_CC)) 463 break; 464 /*FALLTHROUGH*/ 465 466 /* 467 * We can only get here in T/TCP's SYN_SENT* state, when 468 * we're a sending a non-SYN segment without waiting for 469 * the ACK of our SYN. A check above assures that we only 470 * do this if our peer understands T/TCP. 471 */ 472 case 0: 473 opt[optlen++] = TCPOPT_NOP; 474 opt[optlen++] = TCPOPT_NOP; 475 opt[optlen++] = TCPOPT_CC; 476 opt[optlen++] = TCPOLEN_CC; 477 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 478 479 optlen += 4; 480 break; 481 482 /* 483 * This is our initial SYN, check whether we have to use 484 * CC or CC.new. 485 */ 486 case TH_SYN: 487 opt[optlen++] = TCPOPT_NOP; 488 opt[optlen++] = TCPOPT_NOP; 489 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 490 TCPOPT_CCNEW : TCPOPT_CC; 491 opt[optlen++] = TCPOLEN_CC; 492 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 493 optlen += 4; 494 break; 495 496 /* 497 * This is a SYN,ACK; send CC and CC.echo if we received 498 * CC from our peer. 499 */ 500 case (TH_SYN|TH_ACK): 501 if (tp->t_flags & TF_RCVD_CC) { 502 opt[optlen++] = TCPOPT_NOP; 503 opt[optlen++] = TCPOPT_NOP; 504 opt[optlen++] = TCPOPT_CC; 505 opt[optlen++] = TCPOLEN_CC; 506 *(u_int32_t *)&opt[optlen] = 507 htonl(tp->cc_send); 508 optlen += 4; 509 opt[optlen++] = TCPOPT_NOP; 510 opt[optlen++] = TCPOPT_NOP; 511 opt[optlen++] = TCPOPT_CCECHO; 512 opt[optlen++] = TCPOLEN_CC; 513 *(u_int32_t *)&opt[optlen] = 514 htonl(tp->cc_recv); 515 optlen += 4; 516 } 517 break; 518 } 519 } 520 521 hdrlen += optlen; 522 523 if (isipv6) 524 ipoptlen = ip6_optlen(inp); 525 else { 526 if (inp->inp_options) { 527 ipoptlen = inp->inp_options->m_len - 528 offsetof(struct ipoption, ipopt_list); 529 } else { 530 ipoptlen = 0; 531 } 532 } 533 #ifdef IPSEC 534 ipoptlen += ipsec_hdrsiz_tcp(tp); 535 #endif 536 537 /* 538 * Adjust data length if insertion of options will 539 * bump the packet length beyond the t_maxopd length. 540 * Clear the FIN bit because we cut off the tail of 541 * the segment. 542 */ 543 if (len + optlen + ipoptlen > tp->t_maxopd) { 544 /* 545 * If there is still more to send, don't close the connection. 546 */ 547 flags &= ~TH_FIN; 548 len = tp->t_maxopd - optlen - ipoptlen; 549 sendalot = 1; 550 } 551 552 #ifdef INET6 553 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 554 #else 555 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 556 #endif 557 558 /* 559 * Grab a header mbuf, attaching a copy of data to 560 * be transmitted, and initialize the header from 561 * the template for sends on this connection. 562 */ 563 if (len) { 564 if ((tp->t_flags & TF_FORCE) && len == 1) 565 tcpstat.tcps_sndprobe++; 566 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 567 tcpstat.tcps_sndrexmitpack++; 568 tcpstat.tcps_sndrexmitbyte += len; 569 } else { 570 tcpstat.tcps_sndpack++; 571 tcpstat.tcps_sndbyte += len; 572 } 573 #ifdef notyet 574 if ((m = m_copypack(so->so_snd.sb_mb, off, 575 (int)len, max_linkhdr + hdrlen)) == 0) { 576 error = ENOBUFS; 577 goto out; 578 } 579 /* 580 * m_copypack left space for our hdr; use it. 581 */ 582 m->m_len += hdrlen; 583 m->m_data -= hdrlen; 584 #else 585 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 586 if (m == NULL) { 587 error = ENOBUFS; 588 goto out; 589 } 590 #ifdef INET6 591 if (MHLEN < hdrlen + max_linkhdr) { 592 MCLGET(m, MB_DONTWAIT); 593 if (!(m->m_flags & M_EXT)) { 594 m_freem(m); 595 error = ENOBUFS; 596 goto out; 597 } 598 } 599 #endif 600 m->m_data += max_linkhdr; 601 m->m_len = hdrlen; 602 if (len <= MHLEN - hdrlen - max_linkhdr) { 603 m_copydata(so->so_snd.sb_mb, off, (int) len, 604 mtod(m, caddr_t) + hdrlen); 605 m->m_len += len; 606 } else { 607 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 608 if (m->m_next == 0) { 609 (void) m_free(m); 610 error = ENOBUFS; 611 goto out; 612 } 613 } 614 #endif 615 /* 616 * If we're sending everything we've got, set PUSH. 617 * (This will keep happy those implementations which only 618 * give data to the user when a buffer fills or 619 * a PUSH comes in.) 620 */ 621 if (off + len == so->so_snd.sb_cc) 622 flags |= TH_PUSH; 623 } else { 624 if (tp->t_flags & TF_ACKNOW) 625 tcpstat.tcps_sndacks++; 626 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 627 tcpstat.tcps_sndctrl++; 628 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 629 tcpstat.tcps_sndurg++; 630 else 631 tcpstat.tcps_sndwinup++; 632 633 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 634 if (m == NULL) { 635 error = ENOBUFS; 636 goto out; 637 } 638 if (isipv6 && 639 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 640 MH_ALIGN(m, hdrlen); 641 else 642 m->m_data += max_linkhdr; 643 m->m_len = hdrlen; 644 } 645 m->m_pkthdr.rcvif = (struct ifnet *)0; 646 if (isipv6) { 647 ip6 = mtod(m, struct ip6_hdr *); 648 th = (struct tcphdr *)(ip6 + 1); 649 tcp_fillheaders(tp, ip6, th); 650 } else { 651 ip = mtod(m, struct ip *); 652 ipov = (struct ipovly *)ip; 653 th = (struct tcphdr *)(ip + 1); 654 /* this picks up the pseudo header (w/o the length) */ 655 tcp_fillheaders(tp, ip, th); 656 } 657 658 /* 659 * Fill in fields, remembering maximum advertised 660 * window for use in delaying messages about window sizes. 661 * If resending a FIN, be sure not to use a new sequence number. 662 */ 663 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 664 tp->snd_nxt == tp->snd_max) 665 tp->snd_nxt--; 666 /* 667 * If we are doing retransmissions, then snd_nxt will 668 * not reflect the first unsent octet. For ACK only 669 * packets, we do not want the sequence number of the 670 * retransmitted packet, we want the sequence number 671 * of the next unsent octet. So, if there is no data 672 * (and no SYN or FIN), use snd_max instead of snd_nxt 673 * when filling in ti_seq. But if we are in persist 674 * state, snd_max might reflect one byte beyond the 675 * right edge of the window, so use snd_nxt in that 676 * case, since we know we aren't doing a retransmission. 677 * (retransmit and persist are mutually exclusive...) 678 */ 679 if (len || (flags & (TH_SYN|TH_FIN)) || callout_active(tp->tt_persist)) 680 th->th_seq = htonl(tp->snd_nxt); 681 else 682 th->th_seq = htonl(tp->snd_max); 683 th->th_ack = htonl(tp->rcv_nxt); 684 if (optlen) { 685 bcopy(opt, th + 1, optlen); 686 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 687 } 688 th->th_flags = flags; 689 /* 690 * Calculate receive window. Don't shrink window, 691 * but avoid silly window syndrome. 692 */ 693 if (recvwin < (long)(so->so_rcv.sb_hiwat / 4) && 694 recvwin < (long)tp->t_maxseg) 695 recvwin = 0; 696 if (recvwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 697 recvwin = (long)(tp->rcv_adv - tp->rcv_nxt); 698 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 699 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 700 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 701 702 /* 703 * Adjust the RXWIN0SENT flag - indicate that we have advertised 704 * a 0 window. This may cause the remote transmitter to stall. This 705 * flag tells soreceive() to disable delayed acknowledgements when 706 * draining the buffer. This can occur if the receiver is attempting 707 * to read more data then can be buffered prior to transmitting on 708 * the connection. 709 */ 710 if (recvwin == 0) 711 tp->t_flags |= TF_RXWIN0SENT; 712 else 713 tp->t_flags &= ~TF_RXWIN0SENT; 714 715 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 716 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 717 th->th_flags |= TH_URG; 718 } else { 719 /* 720 * If no urgent pointer to send, then we pull 721 * the urgent pointer to the left edge of the send window 722 * so that it doesn't drift into the send window on sequence 723 * number wraparound. 724 */ 725 tp->snd_up = tp->snd_una; /* drag it along */ 726 } 727 728 /* 729 * Put TCP length in extended header, and then 730 * checksum extended header and data. 731 */ 732 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 733 if (isipv6) { 734 /* 735 * ip6_plen is not need to be filled now, and will be filled 736 * in ip6_output. 737 */ 738 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 739 sizeof(struct tcphdr) + optlen + len); 740 } else { 741 m->m_pkthdr.csum_flags = CSUM_TCP; 742 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 743 if (len + optlen) 744 th->th_sum = in_addword(th->th_sum, 745 htons((u_short)(optlen + len))); 746 747 /* IP version must be set here for ipv4/ipv6 checking later */ 748 KASSERT(ip->ip_v == IPVERSION, 749 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 750 } 751 752 /* 753 * In transmit state, time the transmission and arrange for 754 * the retransmit. In persist state, just set snd_max. 755 */ 756 if (!(tp->t_flags & TF_FORCE) || !callout_active(tp->tt_persist)) { 757 tcp_seq startseq = tp->snd_nxt; 758 759 /* 760 * Advance snd_nxt over sequence space of this segment. 761 */ 762 if (flags & (TH_SYN|TH_FIN)) { 763 if (flags & TH_SYN) 764 tp->snd_nxt++; 765 if (flags & TH_FIN) { 766 tp->snd_nxt++; 767 tp->t_flags |= TF_SENTFIN; 768 } 769 } 770 tp->snd_nxt += len; 771 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 772 tp->snd_max = tp->snd_nxt; 773 /* 774 * Time this transmission if not a retransmission and 775 * not currently timing anything. 776 */ 777 if (tp->t_rtttime == 0) { 778 tp->t_rtttime = ticks; 779 tp->t_rtseq = startseq; 780 tcpstat.tcps_segstimed++; 781 } 782 } 783 784 /* 785 * Set retransmit timer if not currently set, 786 * and not doing a pure ack or a keep-alive probe. 787 * Initial value for retransmit timer is smoothed 788 * round-trip time + 2 * round-trip time variance. 789 * Initialize shift counter which is used for backoff 790 * of retransmit time. 791 */ 792 if (!callout_active(tp->tt_rexmt) && 793 tp->snd_nxt != tp->snd_una) { 794 if (callout_active(tp->tt_persist)) { 795 callout_stop(tp->tt_persist); 796 tp->t_rxtshift = 0; 797 } 798 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 799 tcp_timer_rexmt, tp); 800 } 801 } else { 802 /* 803 * Persist case, update snd_max but since we are in 804 * persist mode (no window) we do not update snd_nxt. 805 */ 806 int xlen = len; 807 if (flags & TH_SYN) 808 ++xlen; 809 if (flags & TH_FIN) { 810 ++xlen; 811 tp->t_flags |= TF_SENTFIN; 812 } 813 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 814 tp->snd_max = tp->snd_nxt + xlen; 815 } 816 817 #ifdef TCPDEBUG 818 /* 819 * Trace. 820 */ 821 if (so->so_options & SO_DEBUG) 822 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 823 #endif 824 825 /* 826 * Fill in IP length and desired time to live and 827 * send to IP level. There should be a better way 828 * to handle ttl and tos; we could keep them in 829 * the template, but need a way to checksum without them. 830 */ 831 /* 832 * m->m_pkthdr.len should have been set before cksum calcuration, 833 * because in6_cksum() need it. 834 */ 835 if (isipv6) { 836 /* 837 * we separately set hoplimit for every segment, since the 838 * user might want to change the value via setsockopt. 839 * Also, desired default hop limit might be changed via 840 * Neighbor Discovery. 841 */ 842 ip6->ip6_hlim = in6_selecthlim(inp, 843 (inp->in6p_route.ro_rt ? 844 inp->in6p_route.ro_rt->rt_ifp : NULL)); 845 846 /* TODO: IPv6 IP6TOS_ECT bit on */ 847 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route, 848 (so->so_options & SO_DONTROUTE), NULL, NULL, inp); 849 } else { 850 struct rtentry *rt; 851 ip->ip_len = m->m_pkthdr.len; 852 #ifdef INET6 853 if (INP_CHECK_SOCKAF(so, AF_INET6)) 854 ip->ip_ttl = in6_selecthlim(inp, 855 (inp->in6p_route.ro_rt ? 856 inp->in6p_route.ro_rt->rt_ifp : NULL)); 857 else 858 #endif 859 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 860 861 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 862 /* 863 * See if we should do MTU discovery. 864 * We do it only if the following are true: 865 * 1) we have a valid route to the destination 866 * 2) the MTU is not locked (if it is, 867 * then discovery has been disabled) 868 */ 869 if (path_mtu_discovery && 870 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) && 871 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 872 ip->ip_off |= IP_DF; 873 874 error = ip_output(m, inp->inp_options, &inp->inp_route, 875 (so->so_options & SO_DONTROUTE), NULL, inp); 876 } 877 if (error) { 878 879 /* 880 * We know that the packet was lost, so back out the 881 * sequence number advance, if any. 882 */ 883 if (!(tp->t_flags & TF_FORCE) || 884 !callout_active(tp->tt_persist)) { 885 /* 886 * No need to check for TH_FIN here because 887 * the TF_SENTFIN flag handles that case. 888 */ 889 if (!(flags & TH_SYN)) 890 tp->snd_nxt -= len; 891 } 892 893 out: 894 if (error == ENOBUFS) { 895 /* 896 * If we can't send, make sure there is something 897 * to get us going again later. Persist state 898 * is not necessarily right, but it is close enough. 899 */ 900 if (!callout_active(tp->tt_rexmt) && 901 !callout_active(tp->tt_persist)) { 902 tp->t_rxtshift = 0; 903 tcp_setpersist(tp); 904 } 905 tcp_quench(inp, 0); 906 return (0); 907 } 908 if (error == EMSGSIZE) { 909 /* 910 * ip_output() will have already fixed the route 911 * for us. tcp_mtudisc() will, as its last action, 912 * initiate retransmission, so it is important to 913 * not do so here. 914 */ 915 tcp_mtudisc(inp, 0); 916 return 0; 917 } 918 if ((error == EHOSTUNREACH || error == ENETDOWN) && 919 TCPS_HAVERCVDSYN(tp->t_state)) { 920 tp->t_softerror = error; 921 return (0); 922 } 923 return (error); 924 } 925 tcpstat.tcps_sndtotal++; 926 927 /* 928 * Data sent (as far as we can tell). 929 * If this advertises a larger window than any other segment, 930 * then remember the size of the advertised window. 931 * Any pending ACK has now been sent. 932 */ 933 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) 934 tp->rcv_adv = tp->rcv_nxt + recvwin; 935 tp->last_ack_sent = tp->rcv_nxt; 936 tp->t_flags &= ~TF_ACKNOW; 937 if (tcp_delack_enabled) 938 callout_stop(tp->tt_delack); 939 if (sendalot) 940 goto again; 941 return (0); 942 } 943 944 void 945 tcp_setpersist(tp) 946 struct tcpcb *tp; 947 { 948 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 949 int tt; 950 951 if (callout_active(tp->tt_rexmt)) 952 panic("tcp_setpersist: retransmit pending"); 953 /* 954 * Start/restart persistance timer. 955 */ 956 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 957 TCPTV_PERSMIN, TCPTV_PERSMAX); 958 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 959 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 960 tp->t_rxtshift++; 961 } 962