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 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 30 * $FreeBSD$ 31 */ 32 33 #include "opt_inet.h" 34 #include "opt_inet6.h" 35 #include "opt_ipsec.h" 36 #include "opt_mac.h" 37 #include "opt_tcpdebug.h" 38 #include "opt_tcp_sack.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/domain.h> 43 #include <sys/kernel.h> 44 #include <sys/lock.h> 45 #include <sys/mac.h> 46 #include <sys/mbuf.h> 47 #include <sys/mutex.h> 48 #include <sys/protosw.h> 49 #include <sys/socket.h> 50 #include <sys/socketvar.h> 51 #include <sys/sysctl.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 #ifdef INET6 61 #include <netinet6/in6_pcb.h> 62 #include <netinet/ip6.h> 63 #include <netinet6/ip6_var.h> 64 #endif 65 #include <netinet/tcp.h> 66 #define TCPOUTFLAGS 67 #include <netinet/tcp_fsm.h> 68 #include <netinet/tcp_seq.h> 69 #include <netinet/tcp_timer.h> 70 #include <netinet/tcp_var.h> 71 #include <netinet/tcpip.h> 72 #ifdef TCPDEBUG 73 #include <netinet/tcp_debug.h> 74 #endif 75 76 #ifdef IPSEC 77 #include <netinet6/ipsec.h> 78 #endif /*IPSEC*/ 79 80 #ifdef FAST_IPSEC 81 #include <netipsec/ipsec.h> 82 #define IPSEC 83 #endif /*FAST_IPSEC*/ 84 85 #include <machine/in_cksum.h> 86 87 #ifdef notyet 88 extern struct mbuf *m_copypack(); 89 #endif 90 91 int path_mtu_discovery = 1; 92 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 93 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 94 95 int ss_fltsz = 1; 96 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 97 &ss_fltsz, 1, "Slow start flight size"); 98 99 int ss_fltsz_local = 4; 100 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 101 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 102 103 int tcp_do_newreno = 1; 104 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno, 105 0, "Enable NewReno Algorithms"); 106 107 /* 108 * Tcp output routine: figure out what should be sent and send it. 109 */ 110 int 111 tcp_output(struct tcpcb *tp) 112 { 113 struct socket *so = tp->t_inpcb->inp_socket; 114 long len, recwin, sendwin; 115 int off, flags, error; 116 #ifdef TCP_SIGNATURE 117 int sigoff = 0; 118 #endif 119 struct mbuf *m; 120 struct ip *ip = NULL; 121 struct ipovly *ipov = NULL; 122 struct tcphdr *th; 123 u_char opt[TCP_MAXOLEN]; 124 unsigned ipoptlen, optlen, hdrlen; 125 int idle, sendalot; 126 int i, sack_rxmit; 127 struct sackhole *p; 128 #if 0 129 int maxburst = TCP_MAXBURST; 130 #endif 131 struct rmxp_tao tao; 132 #ifdef INET6 133 struct ip6_hdr *ip6 = NULL; 134 int isipv6; 135 136 bzero(&tao, sizeof(tao)); 137 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 138 #endif 139 140 INP_LOCK_ASSERT(tp->t_inpcb); 141 142 /* 143 * Determine length of data that should be transmitted, 144 * and flags that will be used. 145 * If there is some data or critical controls (SYN, RST) 146 * to send, then transmit; otherwise, investigate further. 147 */ 148 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 149 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 150 /* 151 * We have been idle for "a while" and no acks are 152 * expected to clock out any data we send -- 153 * slow start to get ack "clock" running again. 154 * 155 * Set the slow-start flight size depending on whether 156 * this is a local network or not. 157 */ 158 int ss = ss_fltsz; 159 #ifdef INET6 160 if (isipv6) { 161 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 162 ss = ss_fltsz_local; 163 } else 164 #endif /* INET6 */ 165 if (in_localaddr(tp->t_inpcb->inp_faddr)) 166 ss = ss_fltsz_local; 167 tp->snd_cwnd = tp->t_maxseg * ss; 168 } 169 tp->t_flags &= ~TF_LASTIDLE; 170 if (idle) { 171 if (tp->t_flags & TF_MORETOCOME) { 172 tp->t_flags |= TF_LASTIDLE; 173 idle = 0; 174 } 175 } 176 again: 177 /* 178 * If we've recently taken a timeout, snd_max will be greater than 179 * snd_nxt. There may be SACK information that allows us to avoid 180 * resending already delivered data. Adjust snd_nxt accordingly. 181 */ 182 if (tp->sack_enable && SEQ_LT(tp->snd_nxt, tp->snd_max)) 183 tcp_sack_adjust(tp); 184 sendalot = 0; 185 off = tp->snd_nxt - tp->snd_una; 186 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 187 sendwin = min(sendwin, tp->snd_bwnd); 188 189 flags = tcp_outflags[tp->t_state]; 190 /* 191 * Send any SACK-generated retransmissions. If we're explicitly trying 192 * to send out new data (when sendalot is 1), bypass this function. 193 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 194 * we're replacing a (future) new transmission with a retransmission 195 * now, and we previously incremented snd_cwnd in tcp_input(). 196 */ 197 /* 198 * Still in sack recovery , reset rxmit flag to zero. 199 */ 200 sack_rxmit = 0; 201 len = 0; 202 p = NULL; 203 if (tp->sack_enable && IN_FASTRECOVERY(tp) && 204 (p = tcp_sack_output(tp))) { 205 sack_rxmit = 1; 206 sendalot = 1; 207 off = p->rxmit - tp->snd_una; 208 KASSERT(tp->snd_cwnd >= 0,("%s: CWIN is negative: %ld", __func__, tp->snd_cwnd)); 209 /* Do not retransmit SACK segments beyond snd_recover */ 210 if (SEQ_GT(p->end, tp->snd_recover)) 211 len = min(tp->snd_cwnd, tp->snd_recover - p->rxmit); 212 else 213 len = min(tp->snd_cwnd, p->end - p->rxmit); 214 if (len > 0) { 215 tcpstat.tcps_sack_rexmits++; 216 tcpstat.tcps_sack_rexmit_bytes += 217 min(len, tp->t_maxseg); 218 } 219 } 220 /* 221 * Get standard flags, and add SYN or FIN if requested by 'hidden' 222 * state flags. 223 */ 224 if (tp->t_flags & TF_NEEDFIN) 225 flags |= TH_FIN; 226 if (tp->t_flags & TF_NEEDSYN) 227 flags |= TH_SYN; 228 229 /* 230 * If in persist timeout with window of 0, send 1 byte. 231 * Otherwise, if window is small but nonzero 232 * and timer expired, we will send what we can 233 * and go to transmit state. 234 */ 235 if (tp->t_force) { 236 if (sendwin == 0) { 237 /* 238 * If we still have some data to send, then 239 * clear the FIN bit. Usually this would 240 * happen below when it realizes that we 241 * aren't sending all the data. However, 242 * if we have exactly 1 byte of unsent data, 243 * then it won't clear the FIN bit below, 244 * and if we are in persist state, we wind 245 * up sending the packet without recording 246 * that we sent the FIN bit. 247 * 248 * We can't just blindly clear the FIN bit, 249 * because if we don't have any more data 250 * to send then the probe will be the FIN 251 * itself. 252 */ 253 if (off < so->so_snd.sb_cc) 254 flags &= ~TH_FIN; 255 sendwin = 1; 256 } else { 257 callout_stop(tp->tt_persist); 258 tp->t_rxtshift = 0; 259 } 260 } 261 262 /* 263 * If snd_nxt == snd_max and we have transmitted a FIN, the 264 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 265 * a negative length. This can also occur when TCP opens up 266 * its congestion window while receiving additional duplicate 267 * acks after fast-retransmit because TCP will reset snd_nxt 268 * to snd_max after the fast-retransmit. 269 * 270 * In the normal retransmit-FIN-only case, however, snd_nxt will 271 * be set to snd_una, the offset will be 0, and the length may 272 * wind up 0. 273 * 274 * If sack_rxmit is true we are retransmitting from the scoreboard 275 * in which case len is already set. 276 */ 277 if (!sack_rxmit) 278 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 279 280 /* 281 * Lop off SYN bit if it has already been sent. However, if this 282 * is SYN-SENT state and if segment contains data and if we don't 283 * know that foreign host supports TAO, suppress sending segment. 284 */ 285 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 286 flags &= ~TH_SYN; 287 off--, len++; 288 if (tcp_do_rfc1644) 289 tcp_hc_gettao(&tp->t_inpcb->inp_inc, &tao); 290 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 291 tao.tao_ccsent == 0) 292 return 0; 293 } 294 295 /* 296 * Be careful not to send data and/or FIN on SYN segments 297 * in cases when no CC option will be sent. 298 * This measure is needed to prevent interoperability problems 299 * with not fully conformant TCP implementations. 300 */ 301 if ((flags & TH_SYN) && 302 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 303 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 304 len = 0; 305 flags &= ~TH_FIN; 306 } 307 308 if (len < 0) { 309 /* 310 * If FIN has been sent but not acked, 311 * but we haven't been called to retransmit, 312 * len will be < 0. Otherwise, window shrank 313 * after we sent into it. If window shrank to 0, 314 * cancel pending retransmit, pull snd_nxt back 315 * to (closed) window, and set the persist timer 316 * if it isn't already going. If the window didn't 317 * close completely, just wait for an ACK. 318 */ 319 len = 0; 320 if (sendwin == 0) { 321 callout_stop(tp->tt_rexmt); 322 tp->t_rxtshift = 0; 323 tp->snd_nxt = tp->snd_una; 324 if (!callout_active(tp->tt_persist)) 325 tcp_setpersist(tp); 326 } 327 } 328 329 /* 330 * len will be >= 0 after this point. Truncate to the maximum 331 * segment length and ensure that FIN is removed if the length 332 * no longer contains the last data byte. 333 */ 334 if (len > tp->t_maxseg) { 335 len = tp->t_maxseg; 336 sendalot = 1; 337 } 338 if (off + len < so->so_snd.sb_cc) 339 flags &= ~TH_FIN; 340 341 recwin = sbspace(&so->so_rcv); 342 343 /* 344 * Sender silly window avoidance. We transmit under the following 345 * conditions when len is non-zero: 346 * 347 * - We have a full segment 348 * - This is the last buffer in a write()/send() and we are 349 * either idle or running NODELAY 350 * - we've timed out (e.g. persist timer) 351 * - we have more then 1/2 the maximum send window's worth of 352 * data (receiver may be limited the window size) 353 * - we need to retransmit 354 */ 355 if (len) { 356 if (len == tp->t_maxseg) 357 goto send; 358 /* 359 * NOTE! on localhost connections an 'ack' from the remote 360 * end may occur synchronously with the output and cause 361 * us to flush a buffer queued with moretocome. XXX 362 * 363 * note: the len + off check is almost certainly unnecessary. 364 */ 365 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 366 (idle || (tp->t_flags & TF_NODELAY)) && 367 len + off >= so->so_snd.sb_cc && 368 (tp->t_flags & TF_NOPUSH) == 0) { 369 goto send; 370 } 371 if (tp->t_force) /* typ. timeout case */ 372 goto send; 373 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 374 goto send; 375 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 376 goto send; 377 if (sack_rxmit) 378 goto send; 379 } 380 381 /* 382 * Compare available window to amount of window 383 * known to peer (as advertised window less 384 * next expected input). If the difference is at least two 385 * max size segments, or at least 50% of the maximum possible 386 * window, then want to send a window update to peer. 387 * Skip this if the connection is in T/TCP half-open state. 388 */ 389 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN)) { 390 /* 391 * "adv" is the amount we can increase the window, 392 * taking into account that we are limited by 393 * TCP_MAXWIN << tp->rcv_scale. 394 */ 395 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 396 (tp->rcv_adv - tp->rcv_nxt); 397 398 if (adv >= (long) (2 * tp->t_maxseg)) 399 goto send; 400 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 401 goto send; 402 } 403 404 /* 405 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 406 * is also a catch-all for the retransmit timer timeout case. 407 */ 408 if (tp->t_flags & TF_ACKNOW) 409 goto send; 410 if ((flags & TH_RST) || 411 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 412 goto send; 413 if (SEQ_GT(tp->snd_up, tp->snd_una)) 414 goto send; 415 /* 416 * If our state indicates that FIN should be sent 417 * and we have not yet done so, then we need to send. 418 */ 419 if (flags & TH_FIN && 420 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 421 goto send; 422 /* 423 * In SACK, it is possible for tcp_output to fail to send a segment 424 * after the retransmission timer has been turned off. Make sure 425 * that the retransmission timer is set. 426 */ 427 if (tp->sack_enable && SEQ_GT(tp->snd_max, tp->snd_una) && 428 !callout_active(tp->tt_rexmt) && 429 !callout_active(tp->tt_persist)) { 430 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 431 tcp_timer_rexmt, tp); 432 return (0); 433 } 434 /* 435 * TCP window updates are not reliable, rather a polling protocol 436 * using ``persist'' packets is used to insure receipt of window 437 * updates. The three ``states'' for the output side are: 438 * idle not doing retransmits or persists 439 * persisting to move a small or zero window 440 * (re)transmitting and thereby not persisting 441 * 442 * callout_active(tp->tt_persist) 443 * is true when we are in persist state. 444 * tp->t_force 445 * is set when we are called to send a persist packet. 446 * callout_active(tp->tt_rexmt) 447 * is set when we are retransmitting 448 * The output side is idle when both timers are zero. 449 * 450 * If send window is too small, there is data to transmit, and no 451 * retransmit or persist is pending, then go to persist state. 452 * If nothing happens soon, send when timer expires: 453 * if window is nonzero, transmit what we can, 454 * otherwise force out a byte. 455 */ 456 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 457 !callout_active(tp->tt_persist)) { 458 tp->t_rxtshift = 0; 459 tcp_setpersist(tp); 460 } 461 462 /* 463 * No reason to send a segment, just return. 464 */ 465 return (0); 466 467 send: 468 /* 469 * Before ESTABLISHED, force sending of initial options 470 * unless TCP set not to do any options. 471 * NOTE: we assume that the IP/TCP header plus TCP options 472 * always fit in a single mbuf, leaving room for a maximum 473 * link header, i.e. 474 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 475 */ 476 optlen = 0; 477 #ifdef INET6 478 if (isipv6) 479 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 480 else 481 #endif 482 hdrlen = sizeof (struct tcpiphdr); 483 if (flags & TH_SYN) { 484 tp->snd_nxt = tp->iss; 485 if ((tp->t_flags & TF_NOOPT) == 0) { 486 u_short mss; 487 488 opt[0] = TCPOPT_MAXSEG; 489 opt[1] = TCPOLEN_MAXSEG; 490 mss = htons((u_short) tcp_mssopt(&tp->t_inpcb->inp_inc)); 491 (void)memcpy(opt + 2, &mss, sizeof(mss)); 492 optlen = TCPOLEN_MAXSEG; 493 494 /* 495 * If this is the first SYN of connection (not a SYN 496 * ACK), include SACK_PERMIT_HDR option. If this is a 497 * SYN ACK, include SACK_PERMIT_HDR option if peer has 498 * already done so. This is only for active connect, 499 * since the syncache takes care of the passive connect. 500 */ 501 if (tp->sack_enable && ((flags & TH_ACK) == 0 || 502 (tp->t_flags & TF_SACK_PERMIT))) { 503 *((u_int32_t *) (opt + optlen)) = 504 htonl(TCPOPT_SACK_PERMIT_HDR); 505 optlen += 4; 506 } 507 if ((tp->t_flags & TF_REQ_SCALE) && 508 ((flags & TH_ACK) == 0 || 509 (tp->t_flags & TF_RCVD_SCALE))) { 510 *((u_int32_t *)(opt + optlen)) = htonl( 511 TCPOPT_NOP << 24 | 512 TCPOPT_WINDOW << 16 | 513 TCPOLEN_WINDOW << 8 | 514 tp->request_r_scale); 515 optlen += 4; 516 } 517 } 518 } 519 520 /* 521 * Send a timestamp and echo-reply if this is a SYN and our side 522 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 523 * and our peer have sent timestamps in our SYN's. 524 */ 525 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 526 (flags & TH_RST) == 0 && 527 ((flags & TH_ACK) == 0 || 528 (tp->t_flags & TF_RCVD_TSTMP))) { 529 u_int32_t *lp = (u_int32_t *)(opt + optlen); 530 531 /* Form timestamp option as shown in appendix A of RFC 1323. */ 532 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 533 *lp++ = htonl(ticks); 534 *lp = htonl(tp->ts_recent); 535 optlen += TCPOLEN_TSTAMP_APPA; 536 } 537 538 /* 539 * Send SACKs if necessary. This should be the last option processed. 540 * Only as many SACKs are sent as are permitted by the maximum options 541 * size. No more than three SACKs are sent. 542 */ 543 if (tp->sack_enable && tp->t_state == TCPS_ESTABLISHED && 544 (tp->t_flags & (TF_SACK_PERMIT|TF_NOOPT)) == TF_SACK_PERMIT && 545 tp->rcv_numsacks) { 546 u_int32_t *lp = (u_int32_t *)(opt + optlen); 547 u_int32_t *olp = lp++; 548 int count = 0; /* actual number of SACKs inserted */ 549 int maxsack = (MAX_TCPOPTLEN - (optlen + 4))/TCPOLEN_SACK; 550 551 tcpstat.tcps_sack_send_blocks++; 552 maxsack = min(maxsack, TCP_MAX_SACK); 553 for (i = 0; (i < tp->rcv_numsacks && count < maxsack); i++) { 554 struct sackblk sack = tp->sackblks[i]; 555 if (sack.start == 0 && sack.end == 0) 556 continue; 557 *lp++ = htonl(sack.start); 558 *lp++ = htonl(sack.end); 559 count++; 560 } 561 *olp = htonl(TCPOPT_SACK_HDR|(TCPOLEN_SACK*count+2)); 562 optlen += TCPOLEN_SACK*count + 4; /* including leading NOPs */ 563 } 564 /* 565 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 566 * options are allowed (!TF_NOOPT) and it's not a RST. 567 */ 568 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 569 (flags & TH_RST) == 0) { 570 switch (flags & (TH_SYN|TH_ACK)) { 571 /* 572 * This is a normal ACK, send CC if we received CC before 573 * from our peer. 574 */ 575 case TH_ACK: 576 if (!(tp->t_flags & TF_RCVD_CC)) 577 break; 578 /*FALLTHROUGH*/ 579 580 /* 581 * We can only get here in T/TCP's SYN_SENT* state, when 582 * we're a sending a non-SYN segment without waiting for 583 * the ACK of our SYN. A check above assures that we only 584 * do this if our peer understands T/TCP. 585 */ 586 case 0: 587 opt[optlen++] = TCPOPT_NOP; 588 opt[optlen++] = TCPOPT_NOP; 589 opt[optlen++] = TCPOPT_CC; 590 opt[optlen++] = TCPOLEN_CC; 591 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 592 593 optlen += 4; 594 break; 595 596 /* 597 * This is our initial SYN, check whether we have to use 598 * CC or CC.new. 599 */ 600 case TH_SYN: 601 opt[optlen++] = TCPOPT_NOP; 602 opt[optlen++] = TCPOPT_NOP; 603 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 604 TCPOPT_CCNEW : TCPOPT_CC; 605 opt[optlen++] = TCPOLEN_CC; 606 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 607 optlen += 4; 608 break; 609 610 /* 611 * This is a SYN,ACK; send CC and CC.echo if we received 612 * CC from our peer. 613 */ 614 case (TH_SYN|TH_ACK): 615 if (tp->t_flags & TF_RCVD_CC) { 616 opt[optlen++] = TCPOPT_NOP; 617 opt[optlen++] = TCPOPT_NOP; 618 opt[optlen++] = TCPOPT_CC; 619 opt[optlen++] = TCPOLEN_CC; 620 *(u_int32_t *)&opt[optlen] = 621 htonl(tp->cc_send); 622 optlen += 4; 623 opt[optlen++] = TCPOPT_NOP; 624 opt[optlen++] = TCPOPT_NOP; 625 opt[optlen++] = TCPOPT_CCECHO; 626 opt[optlen++] = TCPOLEN_CC; 627 *(u_int32_t *)&opt[optlen] = 628 htonl(tp->cc_recv); 629 optlen += 4; 630 } 631 break; 632 } 633 } 634 635 #ifdef TCP_SIGNATURE 636 #ifdef INET6 637 if (!isipv6) 638 #endif 639 if (tp->t_flags & TF_SIGNATURE) { 640 int i; 641 u_char *bp; 642 643 /* Initialize TCP-MD5 option (RFC2385) */ 644 bp = (u_char *)opt + optlen; 645 *bp++ = TCPOPT_SIGNATURE; 646 *bp++ = TCPOLEN_SIGNATURE; 647 sigoff = optlen + 2; 648 for (i = 0; i < TCP_SIGLEN; i++) 649 *bp++ = 0; 650 optlen += TCPOLEN_SIGNATURE; 651 652 /* Terminate options list and maintain 32-bit alignment. */ 653 *bp++ = TCPOPT_NOP; 654 *bp++ = TCPOPT_EOL; 655 optlen += 2; 656 } 657 #endif /* TCP_SIGNATURE */ 658 659 hdrlen += optlen; 660 661 #ifdef INET6 662 if (isipv6) 663 ipoptlen = ip6_optlen(tp->t_inpcb); 664 else 665 #endif 666 if (tp->t_inpcb->inp_options) 667 ipoptlen = tp->t_inpcb->inp_options->m_len - 668 offsetof(struct ipoption, ipopt_list); 669 else 670 ipoptlen = 0; 671 #ifdef IPSEC 672 ipoptlen += ipsec_hdrsiz_tcp(tp); 673 #endif 674 675 /* 676 * Adjust data length if insertion of options will 677 * bump the packet length beyond the t_maxopd length. 678 * Clear the FIN bit because we cut off the tail of 679 * the segment. 680 */ 681 if (len + optlen + ipoptlen > tp->t_maxopd) { 682 /* 683 * If there is still more to send, don't close the connection. 684 */ 685 flags &= ~TH_FIN; 686 len = tp->t_maxopd - optlen - ipoptlen; 687 sendalot = 1; 688 } 689 690 /*#ifdef DIAGNOSTIC*/ 691 #ifdef INET6 692 if (max_linkhdr + hdrlen > MCLBYTES) 693 #else 694 if (max_linkhdr + hdrlen > MHLEN) 695 #endif 696 panic("tcphdr too big"); 697 /*#endif*/ 698 699 /* 700 * Grab a header mbuf, attaching a copy of data to 701 * be transmitted, and initialize the header from 702 * the template for sends on this connection. 703 */ 704 if (len) { 705 if (tp->t_force && len == 1) 706 tcpstat.tcps_sndprobe++; 707 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 708 tcpstat.tcps_sndrexmitpack++; 709 tcpstat.tcps_sndrexmitbyte += len; 710 } else { 711 tcpstat.tcps_sndpack++; 712 tcpstat.tcps_sndbyte += len; 713 } 714 #ifdef notyet 715 if ((m = m_copypack(so->so_snd.sb_mb, off, 716 (int)len, max_linkhdr + hdrlen)) == 0) { 717 error = ENOBUFS; 718 goto out; 719 } 720 /* 721 * m_copypack left space for our hdr; use it. 722 */ 723 m->m_len += hdrlen; 724 m->m_data -= hdrlen; 725 #else 726 MGETHDR(m, M_DONTWAIT, MT_HEADER); 727 if (m == NULL) { 728 error = ENOBUFS; 729 goto out; 730 } 731 #ifdef INET6 732 if (MHLEN < hdrlen + max_linkhdr) { 733 MCLGET(m, M_DONTWAIT); 734 if ((m->m_flags & M_EXT) == 0) { 735 m_freem(m); 736 error = ENOBUFS; 737 goto out; 738 } 739 } 740 #endif 741 m->m_data += max_linkhdr; 742 m->m_len = hdrlen; 743 if (len <= MHLEN - hdrlen - max_linkhdr) { 744 m_copydata(so->so_snd.sb_mb, off, (int) len, 745 mtod(m, caddr_t) + hdrlen); 746 m->m_len += len; 747 } else { 748 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 749 if (m->m_next == 0) { 750 (void) m_free(m); 751 error = ENOBUFS; 752 goto out; 753 } 754 } 755 #endif 756 /* 757 * If we're sending everything we've got, set PUSH. 758 * (This will keep happy those implementations which only 759 * give data to the user when a buffer fills or 760 * a PUSH comes in.) 761 */ 762 if (off + len == so->so_snd.sb_cc) 763 flags |= TH_PUSH; 764 } else { 765 if (tp->t_flags & TF_ACKNOW) 766 tcpstat.tcps_sndacks++; 767 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 768 tcpstat.tcps_sndctrl++; 769 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 770 tcpstat.tcps_sndurg++; 771 else 772 tcpstat.tcps_sndwinup++; 773 774 MGETHDR(m, M_DONTWAIT, MT_HEADER); 775 if (m == NULL) { 776 error = ENOBUFS; 777 goto out; 778 } 779 #ifdef INET6 780 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 781 MHLEN >= hdrlen) { 782 MH_ALIGN(m, hdrlen); 783 } else 784 #endif 785 m->m_data += max_linkhdr; 786 m->m_len = hdrlen; 787 } 788 m->m_pkthdr.rcvif = (struct ifnet *)0; 789 #ifdef MAC 790 mac_create_mbuf_from_inpcb(tp->t_inpcb, m); 791 #endif 792 #ifdef INET6 793 if (isipv6) { 794 ip6 = mtod(m, struct ip6_hdr *); 795 th = (struct tcphdr *)(ip6 + 1); 796 tcpip_fillheaders(tp->t_inpcb, ip6, th); 797 } else 798 #endif /* INET6 */ 799 { 800 ip = mtod(m, struct ip *); 801 ipov = (struct ipovly *)ip; 802 th = (struct tcphdr *)(ip + 1); 803 tcpip_fillheaders(tp->t_inpcb, ip, th); 804 } 805 806 /* 807 * Fill in fields, remembering maximum advertised 808 * window for use in delaying messages about window sizes. 809 * If resending a FIN, be sure not to use a new sequence number. 810 */ 811 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 812 tp->snd_nxt == tp->snd_max) 813 tp->snd_nxt--; 814 /* 815 * If we are doing retransmissions, then snd_nxt will 816 * not reflect the first unsent octet. For ACK only 817 * packets, we do not want the sequence number of the 818 * retransmitted packet, we want the sequence number 819 * of the next unsent octet. So, if there is no data 820 * (and no SYN or FIN), use snd_max instead of snd_nxt 821 * when filling in ti_seq. But if we are in persist 822 * state, snd_max might reflect one byte beyond the 823 * right edge of the window, so use snd_nxt in that 824 * case, since we know we aren't doing a retransmission. 825 * (retransmit and persist are mutually exclusive...) 826 */ 827 if (len || (flags & (TH_SYN|TH_FIN)) 828 || callout_active(tp->tt_persist)) 829 th->th_seq = htonl(tp->snd_nxt); 830 else 831 th->th_seq = htonl(tp->snd_max); 832 if (sack_rxmit) { 833 th->th_seq = htonl(p->rxmit); 834 p->rxmit += len; 835 } 836 th->th_ack = htonl(tp->rcv_nxt); 837 if (optlen) { 838 bcopy(opt, th + 1, optlen); 839 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 840 } 841 th->th_flags = flags; 842 /* 843 * Calculate receive window. Don't shrink window, 844 * but avoid silly window syndrome. 845 */ 846 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 847 recwin < (long)tp->t_maxseg) 848 recwin = 0; 849 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 850 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 851 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 852 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 853 th->th_win = htons((u_short) (recwin >> tp->rcv_scale)); 854 855 856 /* 857 * Adjust the RXWIN0SENT flag - indicate that we have advertised 858 * a 0 window. This may cause the remote transmitter to stall. This 859 * flag tells soreceive() to disable delayed acknowledgements when 860 * draining the buffer. This can occur if the receiver is attempting 861 * to read more data then can be buffered prior to transmitting on 862 * the connection. 863 */ 864 if (recwin == 0) 865 tp->t_flags |= TF_RXWIN0SENT; 866 else 867 tp->t_flags &= ~TF_RXWIN0SENT; 868 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 869 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 870 th->th_flags |= TH_URG; 871 } else 872 /* 873 * If no urgent pointer to send, then we pull 874 * the urgent pointer to the left edge of the send window 875 * so that it doesn't drift into the send window on sequence 876 * number wraparound. 877 */ 878 tp->snd_up = tp->snd_una; /* drag it along */ 879 880 #ifdef TCP_SIGNATURE 881 #ifdef INET6 882 if (!isipv6) 883 #endif 884 if (tp->t_flags & TF_SIGNATURE) 885 tcp_signature_compute(m, sizeof(struct ip), len, optlen, 886 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 887 #endif 888 889 /* 890 * Put TCP length in extended header, and then 891 * checksum extended header and data. 892 */ 893 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 894 #ifdef INET6 895 if (isipv6) 896 /* 897 * ip6_plen is not need to be filled now, and will be filled 898 * in ip6_output. 899 */ 900 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 901 sizeof(struct tcphdr) + optlen + len); 902 else 903 #endif /* INET6 */ 904 { 905 m->m_pkthdr.csum_flags = CSUM_TCP; 906 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 907 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 908 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 909 910 /* IP version must be set here for ipv4/ipv6 checking later */ 911 KASSERT(ip->ip_v == IPVERSION, 912 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 913 } 914 915 /* 916 * In transmit state, time the transmission and arrange for 917 * the retransmit. In persist state, just set snd_max. 918 */ 919 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 920 tcp_seq startseq = tp->snd_nxt; 921 922 /* 923 * Advance snd_nxt over sequence space of this segment. 924 */ 925 if (flags & (TH_SYN|TH_FIN)) { 926 if (flags & TH_SYN) 927 tp->snd_nxt++; 928 if (flags & TH_FIN) { 929 tp->snd_nxt++; 930 tp->t_flags |= TF_SENTFIN; 931 } 932 } 933 if (tp->sack_enable && sack_rxmit && (p->rxmit != tp->snd_nxt)) 934 goto timer; 935 tp->snd_nxt += len; 936 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 937 tp->snd_max = tp->snd_nxt; 938 /* 939 * Time this transmission if not a retransmission and 940 * not currently timing anything. 941 */ 942 if (tp->t_rtttime == 0) { 943 tp->t_rtttime = ticks; 944 tp->t_rtseq = startseq; 945 tcpstat.tcps_segstimed++; 946 } 947 } 948 949 /* 950 * Set retransmit timer if not currently set, 951 * and not doing a pure ack or a keep-alive probe. 952 * Initial value for retransmit timer is smoothed 953 * round-trip time + 2 * round-trip time variance. 954 * Initialize shift counter which is used for backoff 955 * of retransmit time. 956 */ 957 timer: 958 if (tp->sack_enable && sack_rxmit && 959 !callout_active(tp->tt_rexmt) && 960 tp->snd_nxt != tp->snd_max) { 961 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 962 tcp_timer_rexmt, tp); 963 if (callout_active(tp->tt_persist)) { 964 callout_stop(tp->tt_persist); 965 tp->t_rxtshift = 0; 966 } 967 } 968 if (!callout_active(tp->tt_rexmt) && 969 tp->snd_nxt != tp->snd_una) { 970 if (callout_active(tp->tt_persist)) { 971 callout_stop(tp->tt_persist); 972 tp->t_rxtshift = 0; 973 } 974 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 975 tcp_timer_rexmt, tp); 976 } 977 } else { 978 /* 979 * Persist case, update snd_max but since we are in 980 * persist mode (no window) we do not update snd_nxt. 981 */ 982 int xlen = len; 983 if (flags & TH_SYN) 984 ++xlen; 985 if (flags & TH_FIN) { 986 ++xlen; 987 tp->t_flags |= TF_SENTFIN; 988 } 989 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 990 tp->snd_max = tp->snd_nxt + len; 991 } 992 993 #ifdef TCPDEBUG 994 /* 995 * Trace. 996 */ 997 if (so->so_options & SO_DEBUG) { 998 u_short save = 0; 999 #ifdef INET6 1000 if (!isipv6) 1001 #endif 1002 { 1003 save = ipov->ih_len; 1004 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1005 } 1006 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1007 #ifdef INET6 1008 if (!isipv6) 1009 #endif 1010 ipov->ih_len = save; 1011 } 1012 #endif 1013 1014 /* 1015 * Fill in IP length and desired time to live and 1016 * send to IP level. There should be a better way 1017 * to handle ttl and tos; we could keep them in 1018 * the template, but need a way to checksum without them. 1019 */ 1020 /* 1021 * m->m_pkthdr.len should have been set before cksum calcuration, 1022 * because in6_cksum() need it. 1023 */ 1024 #ifdef INET6 1025 if (isipv6) { 1026 /* 1027 * we separately set hoplimit for every segment, since the 1028 * user might want to change the value via setsockopt. 1029 * Also, desired default hop limit might be changed via 1030 * Neighbor Discovery. 1031 */ 1032 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1033 1034 /* TODO: IPv6 IP6TOS_ECT bit on */ 1035 error = ip6_output(m, 1036 tp->t_inpcb->in6p_outputopts, NULL, 1037 (so->so_options & SO_DONTROUTE), NULL, NULL, 1038 tp->t_inpcb); 1039 } else 1040 #endif /* INET6 */ 1041 { 1042 ip->ip_len = m->m_pkthdr.len; 1043 #ifdef INET6 1044 if (INP_CHECK_SOCKAF(so, AF_INET6)) 1045 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1046 #endif /* INET6 */ 1047 /* 1048 * If we do path MTU discovery, then we set DF on every packet. 1049 * This might not be the best thing to do according to RFC3390 1050 * Section 2. However the tcp hostcache migitates the problem 1051 * so it affects only the first tcp connection with a host. 1052 */ 1053 if (path_mtu_discovery) 1054 ip->ip_off |= IP_DF; 1055 1056 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1057 (so->so_options & SO_DONTROUTE), 0, tp->t_inpcb); 1058 } 1059 if (error) { 1060 1061 /* 1062 * We know that the packet was lost, so back out the 1063 * sequence number advance, if any. 1064 */ 1065 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 1066 /* 1067 * No need to check for TH_FIN here because 1068 * the TF_SENTFIN flag handles that case. 1069 */ 1070 if ((flags & TH_SYN) == 0) 1071 tp->snd_nxt -= len; 1072 } 1073 1074 out: 1075 if (error == ENOBUFS) { 1076 if (!callout_active(tp->tt_rexmt) && 1077 !callout_active(tp->tt_persist)) 1078 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 1079 tcp_timer_rexmt, tp); 1080 tcp_quench(tp->t_inpcb, 0); 1081 return (0); 1082 } 1083 if (error == EMSGSIZE) { 1084 /* 1085 * ip_output() will have already fixed the route 1086 * for us. tcp_mtudisc() will, as its last action, 1087 * initiate retransmission, so it is important to 1088 * not do so here. 1089 */ 1090 tcp_mtudisc(tp->t_inpcb, 0); 1091 return 0; 1092 } 1093 if ((error == EHOSTUNREACH || error == ENETDOWN) 1094 && TCPS_HAVERCVDSYN(tp->t_state)) { 1095 tp->t_softerror = error; 1096 return (0); 1097 } 1098 return (error); 1099 } 1100 tcpstat.tcps_sndtotal++; 1101 1102 /* 1103 * Data sent (as far as we can tell). 1104 * If this advertises a larger window than any other segment, 1105 * then remember the size of the advertised window. 1106 * Any pending ACK has now been sent. 1107 */ 1108 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1109 tp->rcv_adv = tp->rcv_nxt + recwin; 1110 tp->last_ack_sent = tp->rcv_nxt; 1111 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1112 if (callout_active(tp->tt_delack)) 1113 callout_stop(tp->tt_delack); 1114 #if 0 1115 /* 1116 * This completely breaks TCP if newreno is turned on. What happens 1117 * is that if delayed-acks are turned on on the receiver, this code 1118 * on the transmitter effectively destroys the TCP window, forcing 1119 * it to four packets (1.5Kx4 = 6K window). 1120 */ 1121 if (sendalot && (!tcp_do_newreno || --maxburst)) 1122 goto again; 1123 #endif 1124 if (sendalot) 1125 goto again; 1126 return (0); 1127 } 1128 1129 void 1130 tcp_setpersist(tp) 1131 register struct tcpcb *tp; 1132 { 1133 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1134 int tt; 1135 1136 if (callout_active(tp->tt_rexmt)) 1137 panic("tcp_setpersist: retransmit pending"); 1138 /* 1139 * Start/restart persistance timer. 1140 */ 1141 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1142 TCPTV_PERSMIN, TCPTV_PERSMAX); 1143 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1144 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1145 tp->t_rxtshift++; 1146 } 1147