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 KASSERT(tp->snd_cwnd >= 0, 206 ("%s: CWIN is negative : %ld", __func__, tp->snd_cwnd)); 207 /* Do not retransmit SACK segments beyond snd_recover */ 208 if (SEQ_GT(p->end, tp->snd_recover)) { 209 /* 210 * (At least) part of sack hole extends beyond 211 * snd_recover. Check to see if we can rexmit data 212 * for this hole. 213 */ 214 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 215 /* 216 * Can't rexmit any more data for this hole. 217 * That data will be rexmitted in the next 218 * sack recovery episode, when snd_recover 219 * moves past p->rxmit. 220 */ 221 p = NULL; 222 goto after_sack_rexmit; 223 } else 224 /* Can rexmit part of the current hole */ 225 len = ((long)ulmin(tp->snd_cwnd, 226 tp->snd_recover - p->rxmit)); 227 } else 228 len = ((long)ulmin(tp->snd_cwnd, p->end - p->rxmit)); 229 sack_rxmit = 1; 230 sendalot = 1; 231 off = p->rxmit - tp->snd_una; 232 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 233 __func__, off)); 234 if (len > 0) { 235 tcpstat.tcps_sack_rexmits++; 236 tcpstat.tcps_sack_rexmit_bytes += 237 min(len, tp->t_maxseg); 238 } 239 } 240 after_sack_rexmit: 241 /* 242 * Get standard flags, and add SYN or FIN if requested by 'hidden' 243 * state flags. 244 */ 245 if (tp->t_flags & TF_NEEDFIN) 246 flags |= TH_FIN; 247 if (tp->t_flags & TF_NEEDSYN) 248 flags |= TH_SYN; 249 250 /* 251 * If in persist timeout with window of 0, send 1 byte. 252 * Otherwise, if window is small but nonzero 253 * and timer expired, we will send what we can 254 * and go to transmit state. 255 */ 256 if (tp->t_force) { 257 if (sendwin == 0) { 258 /* 259 * If we still have some data to send, then 260 * clear the FIN bit. Usually this would 261 * happen below when it realizes that we 262 * aren't sending all the data. However, 263 * if we have exactly 1 byte of unsent data, 264 * then it won't clear the FIN bit below, 265 * and if we are in persist state, we wind 266 * up sending the packet without recording 267 * that we sent the FIN bit. 268 * 269 * We can't just blindly clear the FIN bit, 270 * because if we don't have any more data 271 * to send then the probe will be the FIN 272 * itself. 273 */ 274 if (off < so->so_snd.sb_cc) 275 flags &= ~TH_FIN; 276 sendwin = 1; 277 } else { 278 callout_stop(tp->tt_persist); 279 tp->t_rxtshift = 0; 280 } 281 } 282 283 /* 284 * If snd_nxt == snd_max and we have transmitted a FIN, the 285 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 286 * a negative length. This can also occur when TCP opens up 287 * its congestion window while receiving additional duplicate 288 * acks after fast-retransmit because TCP will reset snd_nxt 289 * to snd_max after the fast-retransmit. 290 * 291 * In the normal retransmit-FIN-only case, however, snd_nxt will 292 * be set to snd_una, the offset will be 0, and the length may 293 * wind up 0. 294 * 295 * If sack_rxmit is true we are retransmitting from the scoreboard 296 * in which case len is already set. 297 */ 298 if (!sack_rxmit) 299 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 300 301 /* 302 * Lop off SYN bit if it has already been sent. However, if this 303 * is SYN-SENT state and if segment contains data and if we don't 304 * know that foreign host supports TAO, suppress sending segment. 305 */ 306 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 307 flags &= ~TH_SYN; 308 off--, len++; 309 if (tcp_do_rfc1644) 310 tcp_hc_gettao(&tp->t_inpcb->inp_inc, &tao); 311 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 312 tao.tao_ccsent == 0) 313 return 0; 314 } 315 316 /* 317 * Be careful not to send data and/or FIN on SYN segments 318 * in cases when no CC option will be sent. 319 * This measure is needed to prevent interoperability problems 320 * with not fully conformant TCP implementations. 321 */ 322 if ((flags & TH_SYN) && 323 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 324 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 325 len = 0; 326 flags &= ~TH_FIN; 327 } 328 329 if (len < 0) { 330 /* 331 * If FIN has been sent but not acked, 332 * but we haven't been called to retransmit, 333 * len will be < 0. Otherwise, window shrank 334 * after we sent into it. If window shrank to 0, 335 * cancel pending retransmit, pull snd_nxt back 336 * to (closed) window, and set the persist timer 337 * if it isn't already going. If the window didn't 338 * close completely, just wait for an ACK. 339 */ 340 len = 0; 341 if (sendwin == 0) { 342 callout_stop(tp->tt_rexmt); 343 tp->t_rxtshift = 0; 344 tp->snd_nxt = tp->snd_una; 345 if (!callout_active(tp->tt_persist)) 346 tcp_setpersist(tp); 347 } 348 } 349 350 /* 351 * len will be >= 0 after this point. Truncate to the maximum 352 * segment length and ensure that FIN is removed if the length 353 * no longer contains the last data byte. 354 */ 355 if (len > tp->t_maxseg) { 356 len = tp->t_maxseg; 357 sendalot = 1; 358 } 359 if (off + len < so->so_snd.sb_cc) 360 flags &= ~TH_FIN; 361 362 recwin = sbspace(&so->so_rcv); 363 364 /* 365 * Sender silly window avoidance. We transmit under the following 366 * conditions when len is non-zero: 367 * 368 * - We have a full segment 369 * - This is the last buffer in a write()/send() and we are 370 * either idle or running NODELAY 371 * - we've timed out (e.g. persist timer) 372 * - we have more then 1/2 the maximum send window's worth of 373 * data (receiver may be limited the window size) 374 * - we need to retransmit 375 */ 376 if (len) { 377 if (len == tp->t_maxseg) 378 goto send; 379 /* 380 * NOTE! on localhost connections an 'ack' from the remote 381 * end may occur synchronously with the output and cause 382 * us to flush a buffer queued with moretocome. XXX 383 * 384 * note: the len + off check is almost certainly unnecessary. 385 */ 386 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 387 (idle || (tp->t_flags & TF_NODELAY)) && 388 len + off >= so->so_snd.sb_cc && 389 (tp->t_flags & TF_NOPUSH) == 0) { 390 goto send; 391 } 392 if (tp->t_force) /* typ. timeout case */ 393 goto send; 394 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 395 goto send; 396 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 397 goto send; 398 if (sack_rxmit) 399 goto send; 400 } 401 402 /* 403 * Compare available window to amount of window 404 * known to peer (as advertised window less 405 * next expected input). If the difference is at least two 406 * max size segments, or at least 50% of the maximum possible 407 * window, then want to send a window update to peer. 408 * Skip this if the connection is in T/TCP half-open state. 409 */ 410 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN)) { 411 /* 412 * "adv" is the amount we can increase the window, 413 * taking into account that we are limited by 414 * TCP_MAXWIN << tp->rcv_scale. 415 */ 416 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 417 (tp->rcv_adv - tp->rcv_nxt); 418 419 if (adv >= (long) (2 * tp->t_maxseg)) 420 goto send; 421 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 422 goto send; 423 } 424 425 /* 426 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 427 * is also a catch-all for the retransmit timer timeout case. 428 */ 429 if (tp->t_flags & TF_ACKNOW) 430 goto send; 431 if ((flags & TH_RST) || 432 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 433 goto send; 434 if (SEQ_GT(tp->snd_up, tp->snd_una)) 435 goto send; 436 /* 437 * If our state indicates that FIN should be sent 438 * and we have not yet done so, then we need to send. 439 */ 440 if (flags & TH_FIN && 441 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 442 goto send; 443 /* 444 * In SACK, it is possible for tcp_output to fail to send a segment 445 * after the retransmission timer has been turned off. Make sure 446 * that the retransmission timer is set. 447 */ 448 if (tp->sack_enable && SEQ_GT(tp->snd_max, tp->snd_una) && 449 !callout_active(tp->tt_rexmt) && 450 !callout_active(tp->tt_persist)) { 451 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 452 tcp_timer_rexmt, tp); 453 return (0); 454 } 455 /* 456 * TCP window updates are not reliable, rather a polling protocol 457 * using ``persist'' packets is used to insure receipt of window 458 * updates. The three ``states'' for the output side are: 459 * idle not doing retransmits or persists 460 * persisting to move a small or zero window 461 * (re)transmitting and thereby not persisting 462 * 463 * callout_active(tp->tt_persist) 464 * is true when we are in persist state. 465 * tp->t_force 466 * is set when we are called to send a persist packet. 467 * callout_active(tp->tt_rexmt) 468 * is set when we are retransmitting 469 * The output side is idle when both timers are zero. 470 * 471 * If send window is too small, there is data to transmit, and no 472 * retransmit or persist is pending, then go to persist state. 473 * If nothing happens soon, send when timer expires: 474 * if window is nonzero, transmit what we can, 475 * otherwise force out a byte. 476 */ 477 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 478 !callout_active(tp->tt_persist)) { 479 tp->t_rxtshift = 0; 480 tcp_setpersist(tp); 481 } 482 483 /* 484 * No reason to send a segment, just return. 485 */ 486 return (0); 487 488 send: 489 /* 490 * Before ESTABLISHED, force sending of initial options 491 * unless TCP set not to do any options. 492 * NOTE: we assume that the IP/TCP header plus TCP options 493 * always fit in a single mbuf, leaving room for a maximum 494 * link header, i.e. 495 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 496 */ 497 optlen = 0; 498 #ifdef INET6 499 if (isipv6) 500 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 501 else 502 #endif 503 hdrlen = sizeof (struct tcpiphdr); 504 if (flags & TH_SYN) { 505 tp->snd_nxt = tp->iss; 506 if ((tp->t_flags & TF_NOOPT) == 0) { 507 u_short mss; 508 509 opt[0] = TCPOPT_MAXSEG; 510 opt[1] = TCPOLEN_MAXSEG; 511 mss = htons((u_short) tcp_mssopt(&tp->t_inpcb->inp_inc)); 512 (void)memcpy(opt + 2, &mss, sizeof(mss)); 513 optlen = TCPOLEN_MAXSEG; 514 515 /* 516 * If this is the first SYN of connection (not a SYN 517 * ACK), include SACK_PERMIT_HDR option. If this is a 518 * SYN ACK, include SACK_PERMIT_HDR option if peer has 519 * already done so. This is only for active connect, 520 * since the syncache takes care of the passive connect. 521 */ 522 if (tp->sack_enable && ((flags & TH_ACK) == 0 || 523 (tp->t_flags & TF_SACK_PERMIT))) { 524 *((u_int32_t *) (opt + optlen)) = 525 htonl(TCPOPT_SACK_PERMIT_HDR); 526 optlen += 4; 527 } 528 if ((tp->t_flags & TF_REQ_SCALE) && 529 ((flags & TH_ACK) == 0 || 530 (tp->t_flags & TF_RCVD_SCALE))) { 531 *((u_int32_t *)(opt + optlen)) = htonl( 532 TCPOPT_NOP << 24 | 533 TCPOPT_WINDOW << 16 | 534 TCPOLEN_WINDOW << 8 | 535 tp->request_r_scale); 536 optlen += 4; 537 } 538 } 539 } 540 541 /* 542 * Send a timestamp and echo-reply if this is a SYN and our side 543 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 544 * and our peer have sent timestamps in our SYN's. 545 */ 546 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 547 (flags & TH_RST) == 0 && 548 ((flags & TH_ACK) == 0 || 549 (tp->t_flags & TF_RCVD_TSTMP))) { 550 u_int32_t *lp = (u_int32_t *)(opt + optlen); 551 552 /* Form timestamp option as shown in appendix A of RFC 1323. */ 553 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 554 *lp++ = htonl(ticks); 555 *lp = htonl(tp->ts_recent); 556 optlen += TCPOLEN_TSTAMP_APPA; 557 } 558 559 /* 560 * Send SACKs if necessary. This should be the last option processed. 561 * Only as many SACKs are sent as are permitted by the maximum options 562 * size. No more than three SACKs are sent. 563 */ 564 if (tp->sack_enable && tp->t_state == TCPS_ESTABLISHED && 565 (tp->t_flags & (TF_SACK_PERMIT|TF_NOOPT)) == TF_SACK_PERMIT && 566 tp->rcv_numsacks) { 567 u_int32_t *lp = (u_int32_t *)(opt + optlen); 568 u_int32_t *olp = lp++; 569 int count = 0; /* actual number of SACKs inserted */ 570 int maxsack = (MAX_TCPOPTLEN - (optlen + 4))/TCPOLEN_SACK; 571 572 tcpstat.tcps_sack_send_blocks++; 573 maxsack = min(maxsack, TCP_MAX_SACK); 574 for (i = 0; (i < tp->rcv_numsacks && count < maxsack); i++) { 575 struct sackblk sack = tp->sackblks[i]; 576 if (sack.start == 0 && sack.end == 0) 577 continue; 578 *lp++ = htonl(sack.start); 579 *lp++ = htonl(sack.end); 580 count++; 581 } 582 *olp = htonl(TCPOPT_SACK_HDR|(TCPOLEN_SACK*count+2)); 583 optlen += TCPOLEN_SACK*count + 4; /* including leading NOPs */ 584 } 585 /* 586 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 587 * options are allowed (!TF_NOOPT) and it's not a RST. 588 */ 589 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 590 (flags & TH_RST) == 0) { 591 switch (flags & (TH_SYN|TH_ACK)) { 592 /* 593 * This is a normal ACK, send CC if we received CC before 594 * from our peer. 595 */ 596 case TH_ACK: 597 if (!(tp->t_flags & TF_RCVD_CC)) 598 break; 599 /*FALLTHROUGH*/ 600 601 /* 602 * We can only get here in T/TCP's SYN_SENT* state, when 603 * we're a sending a non-SYN segment without waiting for 604 * the ACK of our SYN. A check above assures that we only 605 * do this if our peer understands T/TCP. 606 */ 607 case 0: 608 opt[optlen++] = TCPOPT_NOP; 609 opt[optlen++] = TCPOPT_NOP; 610 opt[optlen++] = TCPOPT_CC; 611 opt[optlen++] = TCPOLEN_CC; 612 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 613 614 optlen += 4; 615 break; 616 617 /* 618 * This is our initial SYN, check whether we have to use 619 * CC or CC.new. 620 */ 621 case TH_SYN: 622 opt[optlen++] = TCPOPT_NOP; 623 opt[optlen++] = TCPOPT_NOP; 624 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 625 TCPOPT_CCNEW : TCPOPT_CC; 626 opt[optlen++] = TCPOLEN_CC; 627 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 628 optlen += 4; 629 break; 630 631 /* 632 * This is a SYN,ACK; send CC and CC.echo if we received 633 * CC from our peer. 634 */ 635 case (TH_SYN|TH_ACK): 636 if (tp->t_flags & TF_RCVD_CC) { 637 opt[optlen++] = TCPOPT_NOP; 638 opt[optlen++] = TCPOPT_NOP; 639 opt[optlen++] = TCPOPT_CC; 640 opt[optlen++] = TCPOLEN_CC; 641 *(u_int32_t *)&opt[optlen] = 642 htonl(tp->cc_send); 643 optlen += 4; 644 opt[optlen++] = TCPOPT_NOP; 645 opt[optlen++] = TCPOPT_NOP; 646 opt[optlen++] = TCPOPT_CCECHO; 647 opt[optlen++] = TCPOLEN_CC; 648 *(u_int32_t *)&opt[optlen] = 649 htonl(tp->cc_recv); 650 optlen += 4; 651 } 652 break; 653 } 654 } 655 656 #ifdef TCP_SIGNATURE 657 #ifdef INET6 658 if (!isipv6) 659 #endif 660 if (tp->t_flags & TF_SIGNATURE) { 661 int i; 662 u_char *bp; 663 664 /* Initialize TCP-MD5 option (RFC2385) */ 665 bp = (u_char *)opt + optlen; 666 *bp++ = TCPOPT_SIGNATURE; 667 *bp++ = TCPOLEN_SIGNATURE; 668 sigoff = optlen + 2; 669 for (i = 0; i < TCP_SIGLEN; i++) 670 *bp++ = 0; 671 optlen += TCPOLEN_SIGNATURE; 672 673 /* Terminate options list and maintain 32-bit alignment. */ 674 *bp++ = TCPOPT_NOP; 675 *bp++ = TCPOPT_EOL; 676 optlen += 2; 677 } 678 #endif /* TCP_SIGNATURE */ 679 680 hdrlen += optlen; 681 682 #ifdef INET6 683 if (isipv6) 684 ipoptlen = ip6_optlen(tp->t_inpcb); 685 else 686 #endif 687 if (tp->t_inpcb->inp_options) 688 ipoptlen = tp->t_inpcb->inp_options->m_len - 689 offsetof(struct ipoption, ipopt_list); 690 else 691 ipoptlen = 0; 692 #ifdef IPSEC 693 ipoptlen += ipsec_hdrsiz_tcp(tp); 694 #endif 695 696 /* 697 * Adjust data length if insertion of options will 698 * bump the packet length beyond the t_maxopd length. 699 * Clear the FIN bit because we cut off the tail of 700 * the segment. 701 */ 702 if (len + optlen + ipoptlen > tp->t_maxopd) { 703 /* 704 * If there is still more to send, don't close the connection. 705 */ 706 flags &= ~TH_FIN; 707 len = tp->t_maxopd - optlen - ipoptlen; 708 sendalot = 1; 709 } 710 711 /*#ifdef DIAGNOSTIC*/ 712 #ifdef INET6 713 if (max_linkhdr + hdrlen > MCLBYTES) 714 #else 715 if (max_linkhdr + hdrlen > MHLEN) 716 #endif 717 panic("tcphdr too big"); 718 /*#endif*/ 719 720 /* 721 * Grab a header mbuf, attaching a copy of data to 722 * be transmitted, and initialize the header from 723 * the template for sends on this connection. 724 */ 725 if (len) { 726 if (tp->t_force && len == 1) 727 tcpstat.tcps_sndprobe++; 728 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 729 tcpstat.tcps_sndrexmitpack++; 730 tcpstat.tcps_sndrexmitbyte += len; 731 } else { 732 tcpstat.tcps_sndpack++; 733 tcpstat.tcps_sndbyte += len; 734 } 735 #ifdef notyet 736 if ((m = m_copypack(so->so_snd.sb_mb, off, 737 (int)len, max_linkhdr + hdrlen)) == 0) { 738 error = ENOBUFS; 739 goto out; 740 } 741 /* 742 * m_copypack left space for our hdr; use it. 743 */ 744 m->m_len += hdrlen; 745 m->m_data -= hdrlen; 746 #else 747 MGETHDR(m, M_DONTWAIT, MT_HEADER); 748 if (m == NULL) { 749 error = ENOBUFS; 750 goto out; 751 } 752 #ifdef INET6 753 if (MHLEN < hdrlen + max_linkhdr) { 754 MCLGET(m, M_DONTWAIT); 755 if ((m->m_flags & M_EXT) == 0) { 756 m_freem(m); 757 error = ENOBUFS; 758 goto out; 759 } 760 } 761 #endif 762 m->m_data += max_linkhdr; 763 m->m_len = hdrlen; 764 if (len <= MHLEN - hdrlen - max_linkhdr) { 765 m_copydata(so->so_snd.sb_mb, off, (int) len, 766 mtod(m, caddr_t) + hdrlen); 767 m->m_len += len; 768 } else { 769 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 770 if (m->m_next == 0) { 771 (void) m_free(m); 772 error = ENOBUFS; 773 goto out; 774 } 775 } 776 #endif 777 /* 778 * If we're sending everything we've got, set PUSH. 779 * (This will keep happy those implementations which only 780 * give data to the user when a buffer fills or 781 * a PUSH comes in.) 782 */ 783 if (off + len == so->so_snd.sb_cc) 784 flags |= TH_PUSH; 785 } else { 786 if (tp->t_flags & TF_ACKNOW) 787 tcpstat.tcps_sndacks++; 788 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 789 tcpstat.tcps_sndctrl++; 790 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 791 tcpstat.tcps_sndurg++; 792 else 793 tcpstat.tcps_sndwinup++; 794 795 MGETHDR(m, M_DONTWAIT, MT_HEADER); 796 if (m == NULL) { 797 error = ENOBUFS; 798 goto out; 799 } 800 #ifdef INET6 801 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 802 MHLEN >= hdrlen) { 803 MH_ALIGN(m, hdrlen); 804 } else 805 #endif 806 m->m_data += max_linkhdr; 807 m->m_len = hdrlen; 808 } 809 m->m_pkthdr.rcvif = (struct ifnet *)0; 810 #ifdef MAC 811 mac_create_mbuf_from_inpcb(tp->t_inpcb, m); 812 #endif 813 #ifdef INET6 814 if (isipv6) { 815 ip6 = mtod(m, struct ip6_hdr *); 816 th = (struct tcphdr *)(ip6 + 1); 817 tcpip_fillheaders(tp->t_inpcb, ip6, th); 818 } else 819 #endif /* INET6 */ 820 { 821 ip = mtod(m, struct ip *); 822 ipov = (struct ipovly *)ip; 823 th = (struct tcphdr *)(ip + 1); 824 tcpip_fillheaders(tp->t_inpcb, ip, th); 825 } 826 827 /* 828 * Fill in fields, remembering maximum advertised 829 * window for use in delaying messages about window sizes. 830 * If resending a FIN, be sure not to use a new sequence number. 831 */ 832 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 833 tp->snd_nxt == tp->snd_max) 834 tp->snd_nxt--; 835 /* 836 * If we are doing retransmissions, then snd_nxt will 837 * not reflect the first unsent octet. For ACK only 838 * packets, we do not want the sequence number of the 839 * retransmitted packet, we want the sequence number 840 * of the next unsent octet. So, if there is no data 841 * (and no SYN or FIN), use snd_max instead of snd_nxt 842 * when filling in ti_seq. But if we are in persist 843 * state, snd_max might reflect one byte beyond the 844 * right edge of the window, so use snd_nxt in that 845 * case, since we know we aren't doing a retransmission. 846 * (retransmit and persist are mutually exclusive...) 847 */ 848 if (len || (flags & (TH_SYN|TH_FIN)) 849 || callout_active(tp->tt_persist)) 850 th->th_seq = htonl(tp->snd_nxt); 851 else 852 th->th_seq = htonl(tp->snd_max); 853 if (sack_rxmit) { 854 th->th_seq = htonl(p->rxmit); 855 p->rxmit += len; 856 } 857 th->th_ack = htonl(tp->rcv_nxt); 858 if (optlen) { 859 bcopy(opt, th + 1, optlen); 860 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 861 } 862 th->th_flags = flags; 863 /* 864 * Calculate receive window. Don't shrink window, 865 * but avoid silly window syndrome. 866 */ 867 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 868 recwin < (long)tp->t_maxseg) 869 recwin = 0; 870 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 871 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 872 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 873 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 874 th->th_win = htons((u_short) (recwin >> tp->rcv_scale)); 875 876 877 /* 878 * Adjust the RXWIN0SENT flag - indicate that we have advertised 879 * a 0 window. This may cause the remote transmitter to stall. This 880 * flag tells soreceive() to disable delayed acknowledgements when 881 * draining the buffer. This can occur if the receiver is attempting 882 * to read more data then can be buffered prior to transmitting on 883 * the connection. 884 */ 885 if (recwin == 0) 886 tp->t_flags |= TF_RXWIN0SENT; 887 else 888 tp->t_flags &= ~TF_RXWIN0SENT; 889 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 890 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 891 th->th_flags |= TH_URG; 892 } else 893 /* 894 * If no urgent pointer to send, then we pull 895 * the urgent pointer to the left edge of the send window 896 * so that it doesn't drift into the send window on sequence 897 * number wraparound. 898 */ 899 tp->snd_up = tp->snd_una; /* drag it along */ 900 901 #ifdef TCP_SIGNATURE 902 #ifdef INET6 903 if (!isipv6) 904 #endif 905 if (tp->t_flags & TF_SIGNATURE) 906 tcp_signature_compute(m, sizeof(struct ip), len, optlen, 907 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 908 #endif 909 910 /* 911 * Put TCP length in extended header, and then 912 * checksum extended header and data. 913 */ 914 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 915 #ifdef INET6 916 if (isipv6) 917 /* 918 * ip6_plen is not need to be filled now, and will be filled 919 * in ip6_output. 920 */ 921 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 922 sizeof(struct tcphdr) + optlen + len); 923 else 924 #endif /* INET6 */ 925 { 926 m->m_pkthdr.csum_flags = CSUM_TCP; 927 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 928 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 929 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 930 931 /* IP version must be set here for ipv4/ipv6 checking later */ 932 KASSERT(ip->ip_v == IPVERSION, 933 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 934 } 935 936 /* 937 * In transmit state, time the transmission and arrange for 938 * the retransmit. In persist state, just set snd_max. 939 */ 940 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 941 tcp_seq startseq = tp->snd_nxt; 942 943 /* 944 * Advance snd_nxt over sequence space of this segment. 945 */ 946 if (flags & (TH_SYN|TH_FIN)) { 947 if (flags & TH_SYN) 948 tp->snd_nxt++; 949 if (flags & TH_FIN) { 950 tp->snd_nxt++; 951 tp->t_flags |= TF_SENTFIN; 952 } 953 } 954 if (tp->sack_enable && sack_rxmit && (p->rxmit != tp->snd_nxt)) 955 goto timer; 956 tp->snd_nxt += len; 957 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 958 tp->snd_max = tp->snd_nxt; 959 /* 960 * Time this transmission if not a retransmission and 961 * not currently timing anything. 962 */ 963 if (tp->t_rtttime == 0) { 964 tp->t_rtttime = ticks; 965 tp->t_rtseq = startseq; 966 tcpstat.tcps_segstimed++; 967 } 968 } 969 970 /* 971 * Set retransmit timer if not currently set, 972 * and not doing a pure ack or a keep-alive probe. 973 * Initial value for retransmit timer is smoothed 974 * round-trip time + 2 * round-trip time variance. 975 * Initialize shift counter which is used for backoff 976 * of retransmit time. 977 */ 978 timer: 979 if (tp->sack_enable && sack_rxmit && 980 !callout_active(tp->tt_rexmt) && 981 tp->snd_nxt != tp->snd_max) { 982 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 983 tcp_timer_rexmt, tp); 984 if (callout_active(tp->tt_persist)) { 985 callout_stop(tp->tt_persist); 986 tp->t_rxtshift = 0; 987 } 988 } 989 if (!callout_active(tp->tt_rexmt) && 990 tp->snd_nxt != tp->snd_una) { 991 if (callout_active(tp->tt_persist)) { 992 callout_stop(tp->tt_persist); 993 tp->t_rxtshift = 0; 994 } 995 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 996 tcp_timer_rexmt, tp); 997 } 998 } else { 999 /* 1000 * Persist case, update snd_max but since we are in 1001 * persist mode (no window) we do not update snd_nxt. 1002 */ 1003 int xlen = len; 1004 if (flags & TH_SYN) 1005 ++xlen; 1006 if (flags & TH_FIN) { 1007 ++xlen; 1008 tp->t_flags |= TF_SENTFIN; 1009 } 1010 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1011 tp->snd_max = tp->snd_nxt + len; 1012 } 1013 1014 #ifdef TCPDEBUG 1015 /* 1016 * Trace. 1017 */ 1018 if (so->so_options & SO_DEBUG) { 1019 u_short save = 0; 1020 #ifdef INET6 1021 if (!isipv6) 1022 #endif 1023 { 1024 save = ipov->ih_len; 1025 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1026 } 1027 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1028 #ifdef INET6 1029 if (!isipv6) 1030 #endif 1031 ipov->ih_len = save; 1032 } 1033 #endif 1034 1035 /* 1036 * Fill in IP length and desired time to live and 1037 * send to IP level. There should be a better way 1038 * to handle ttl and tos; we could keep them in 1039 * the template, but need a way to checksum without them. 1040 */ 1041 /* 1042 * m->m_pkthdr.len should have been set before cksum calcuration, 1043 * because in6_cksum() need it. 1044 */ 1045 #ifdef INET6 1046 if (isipv6) { 1047 /* 1048 * we separately set hoplimit for every segment, since the 1049 * user might want to change the value via setsockopt. 1050 * Also, desired default hop limit might be changed via 1051 * Neighbor Discovery. 1052 */ 1053 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1054 1055 /* TODO: IPv6 IP6TOS_ECT bit on */ 1056 error = ip6_output(m, 1057 tp->t_inpcb->in6p_outputopts, NULL, 1058 (so->so_options & SO_DONTROUTE), NULL, NULL, 1059 tp->t_inpcb); 1060 } else 1061 #endif /* INET6 */ 1062 { 1063 ip->ip_len = m->m_pkthdr.len; 1064 #ifdef INET6 1065 if (INP_CHECK_SOCKAF(so, AF_INET6)) 1066 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1067 #endif /* INET6 */ 1068 /* 1069 * If we do path MTU discovery, then we set DF on every packet. 1070 * This might not be the best thing to do according to RFC3390 1071 * Section 2. However the tcp hostcache migitates the problem 1072 * so it affects only the first tcp connection with a host. 1073 */ 1074 if (path_mtu_discovery) 1075 ip->ip_off |= IP_DF; 1076 1077 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1078 (so->so_options & SO_DONTROUTE), 0, tp->t_inpcb); 1079 } 1080 if (error) { 1081 1082 /* 1083 * We know that the packet was lost, so back out the 1084 * sequence number advance, if any. 1085 */ 1086 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 1087 /* 1088 * No need to check for TH_FIN here because 1089 * the TF_SENTFIN flag handles that case. 1090 */ 1091 if ((flags & TH_SYN) == 0) 1092 tp->snd_nxt -= len; 1093 } 1094 1095 out: 1096 if (error == ENOBUFS) { 1097 if (!callout_active(tp->tt_rexmt) && 1098 !callout_active(tp->tt_persist)) 1099 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 1100 tcp_timer_rexmt, tp); 1101 tcp_quench(tp->t_inpcb, 0); 1102 return (0); 1103 } 1104 if (error == EMSGSIZE) { 1105 /* 1106 * ip_output() will have already fixed the route 1107 * for us. tcp_mtudisc() will, as its last action, 1108 * initiate retransmission, so it is important to 1109 * not do so here. 1110 */ 1111 tcp_mtudisc(tp->t_inpcb, 0); 1112 return 0; 1113 } 1114 if ((error == EHOSTUNREACH || error == ENETDOWN) 1115 && TCPS_HAVERCVDSYN(tp->t_state)) { 1116 tp->t_softerror = error; 1117 return (0); 1118 } 1119 return (error); 1120 } 1121 tcpstat.tcps_sndtotal++; 1122 1123 /* 1124 * Data sent (as far as we can tell). 1125 * If this advertises a larger window than any other segment, 1126 * then remember the size of the advertised window. 1127 * Any pending ACK has now been sent. 1128 */ 1129 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1130 tp->rcv_adv = tp->rcv_nxt + recwin; 1131 tp->last_ack_sent = tp->rcv_nxt; 1132 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1133 if (callout_active(tp->tt_delack)) 1134 callout_stop(tp->tt_delack); 1135 #if 0 1136 /* 1137 * This completely breaks TCP if newreno is turned on. What happens 1138 * is that if delayed-acks are turned on on the receiver, this code 1139 * on the transmitter effectively destroys the TCP window, forcing 1140 * it to four packets (1.5Kx4 = 6K window). 1141 */ 1142 if (sendalot && (!tcp_do_newreno || --maxburst)) 1143 goto again; 1144 #endif 1145 if (sendalot) 1146 goto again; 1147 return (0); 1148 } 1149 1150 void 1151 tcp_setpersist(tp) 1152 register struct tcpcb *tp; 1153 { 1154 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1155 int tt; 1156 1157 if (callout_active(tp->tt_rexmt)) 1158 panic("tcp_setpersist: retransmit pending"); 1159 /* 1160 * Start/restart persistance timer. 1161 */ 1162 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1163 TCPTV_PERSMIN, TCPTV_PERSMAX); 1164 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1165 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1166 tp->t_rxtshift++; 1167 } 1168