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