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