1 /* 2 * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved. 36 * 37 * License terms: all terms for the DragonFly license above plus the following: 38 * 39 * 4. All advertising materials mentioning features or use of this software 40 * must display the following acknowledgement: 41 * 42 * This product includes software developed by Jeffrey M. Hsu 43 * for the DragonFly Project. 44 * 45 * This requirement may be waived with permission from Jeffrey Hsu. 46 * This requirement will sunset and may be removed on July 8 2005, 47 * after which the standard DragonFly license (as shown above) will 48 * apply. 49 */ 50 51 /* 52 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 53 * The Regents of the University of California. All rights reserved. 54 * 55 * Redistribution and use in source and binary forms, with or without 56 * modification, are permitted provided that the following conditions 57 * are met: 58 * 1. Redistributions of source code must retain the above copyright 59 * notice, this list of conditions and the following disclaimer. 60 * 2. Redistributions in binary form must reproduce the above copyright 61 * notice, this list of conditions and the following disclaimer in the 62 * documentation and/or other materials provided with the distribution. 63 * 3. All advertising materials mentioning features or use of this software 64 * must display the following acknowledgement: 65 * This product includes software developed by the University of 66 * California, Berkeley and its contributors. 67 * 4. Neither the name of the University nor the names of its contributors 68 * may be used to endorse or promote products derived from this software 69 * without specific prior written permission. 70 * 71 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 72 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 73 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 74 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 75 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 76 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 77 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 78 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 79 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 80 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 81 * SUCH DAMAGE. 82 * 83 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 84 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $ 85 * $DragonFly: src/sys/netinet/tcp_output.c,v 1.18 2004/08/08 06:33:24 hsu Exp $ 86 */ 87 88 #include "opt_inet6.h" 89 #include "opt_ipsec.h" 90 #include "opt_tcpdebug.h" 91 92 #include <sys/param.h> 93 #include <sys/systm.h> 94 #include <sys/kernel.h> 95 #include <sys/sysctl.h> 96 #include <sys/mbuf.h> 97 #include <sys/domain.h> 98 #include <sys/protosw.h> 99 #include <sys/socket.h> 100 #include <sys/socketvar.h> 101 #include <sys/in_cksum.h> 102 #include <sys/thread.h> 103 #include <sys/globaldata.h> 104 105 #include <net/route.h> 106 107 #include <netinet/in.h> 108 #include <netinet/in_systm.h> 109 #include <netinet/ip.h> 110 #include <netinet/in_pcb.h> 111 #include <netinet/ip_var.h> 112 #include <netinet6/in6_pcb.h> 113 #include <netinet/ip6.h> 114 #include <netinet6/ip6_var.h> 115 #include <netinet/tcp.h> 116 #define TCPOUTFLAGS 117 #include <netinet/tcp_fsm.h> 118 #include <netinet/tcp_seq.h> 119 #include <netinet/tcp_timer.h> 120 #include <netinet/tcp_var.h> 121 #include <netinet/tcpip.h> 122 #ifdef TCPDEBUG 123 #include <netinet/tcp_debug.h> 124 #endif 125 126 #ifdef IPSEC 127 #include <netinet6/ipsec.h> 128 #endif /*IPSEC*/ 129 130 #ifdef FAST_IPSEC 131 #include <netipsec/ipsec.h> 132 #define IPSEC 133 #endif /*FAST_IPSEC*/ 134 135 #ifdef notyet 136 extern struct mbuf *m_copypack(); 137 #endif 138 139 int path_mtu_discovery = 1; 140 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 141 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 142 143 int ss_fltsz = 1; 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 145 &ss_fltsz, 1, "Slow start flight size"); 146 147 int ss_fltsz_local = 4; 148 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 149 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 150 151 static int avoid_pure_win_update = 1; 152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, avoid_pure_win_update, CTLFLAG_RW, 153 &avoid_pure_win_update, 1, "Avoid pure window updates when possible"); 154 155 /* 156 * Tcp output routine: figure out what should be sent and send it. 157 */ 158 int 159 tcp_output(tp) 160 struct tcpcb *tp; 161 { 162 struct inpcb * const inp = tp->t_inpcb; 163 struct socket *so = inp->inp_socket; 164 long len, recvwin, sendwin; 165 int off, flags, error; 166 struct mbuf *m; 167 struct ip *ip = NULL; 168 struct ipovly *ipov = NULL; 169 struct tcphdr *th; 170 u_char opt[TCP_MAXOLEN]; 171 unsigned ipoptlen, optlen, hdrlen; 172 int idle; 173 boolean_t sendalot; 174 struct ip6_hdr *ip6 = NULL; 175 #ifdef INET6 176 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; 177 #else 178 const boolean_t isipv6 = FALSE; 179 #endif 180 struct rmxp_tao *taop; 181 182 /* 183 * Determine length of data that should be transmitted, 184 * and flags that will be used. 185 * If there is some data or critical controls (SYN, RST) 186 * to send, then transmit; otherwise, investigate further. 187 */ 188 if ((tp->snd_max == tp->snd_una) && 189 (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 190 /* 191 * We have been idle for "a while" and no acks are 192 * expected to clock out any data we send -- 193 * slow start to get ack "clock" running again. 194 * 195 * Set the slow-start flight size depending on whether 196 * this is a local network or not. 197 */ 198 if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 199 (!isipv6 && in_localaddr(inp->inp_faddr))) 200 tp->snd_cwnd = tp->t_maxseg * ss_fltsz_local; 201 else 202 tp->snd_cwnd = tp->t_maxseg * ss_fltsz; 203 } 204 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 205 if (idle && (tp->t_flags & TF_MORETOCOME)) 206 tp->t_flags |= TF_LASTIDLE; 207 else 208 tp->t_flags &= ~TF_LASTIDLE; 209 210 again: 211 sendalot = FALSE; 212 off = tp->snd_nxt - tp->snd_una; 213 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 214 sendwin = min(sendwin, tp->snd_bwnd); 215 216 flags = tcp_outflags[tp->t_state]; 217 /* 218 * Get standard flags, and add SYN or FIN if requested by 'hidden' 219 * state flags. 220 */ 221 if (tp->t_flags & TF_NEEDFIN) 222 flags |= TH_FIN; 223 if (tp->t_flags & TF_NEEDSYN) 224 flags |= TH_SYN; 225 226 /* 227 * If in persist timeout with window of 0, send 1 byte. 228 * Otherwise, if window is small but nonzero 229 * and timer expired, we will send what we can 230 * and go to transmit state. 231 */ 232 if (tp->t_flags & TF_FORCE) { 233 if (sendwin == 0) { 234 /* 235 * If we still have some data to send, then 236 * clear the FIN bit. Usually this would 237 * happen below when it realizes that we 238 * aren't sending all the data. However, 239 * if we have exactly 1 byte of unsent data, 240 * then it won't clear the FIN bit below, 241 * and if we are in persist state, we wind 242 * up sending the packet without recording 243 * that we sent the FIN bit. 244 * 245 * We can't just blindly clear the FIN bit, 246 * because if we don't have any more data 247 * to send then the probe will be the FIN 248 * itself. 249 */ 250 if (off < so->so_snd.sb_cc) 251 flags &= ~TH_FIN; 252 sendwin = 1; 253 } else { 254 callout_stop(tp->tt_persist); 255 tp->t_rxtshift = 0; 256 } 257 } 258 259 /* 260 * If snd_nxt == snd_max and we have transmitted a FIN, the 261 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 262 * a negative length. This can also occur when TCP opens up 263 * its congestion window while receiving additional duplicate 264 * acks after fast-retransmit because TCP will reset snd_nxt 265 * to snd_max after the fast-retransmit. 266 * 267 * In the normal retransmit-FIN-only case, however, snd_nxt will 268 * be set to snd_una, the offset will be 0, and the length may 269 * wind up 0. 270 */ 271 len = (long)ulmin(so->so_snd.sb_cc, sendwin) - off; 272 273 /* 274 * Lop off SYN bit if it has already been sent. However, if this 275 * is SYN-SENT state and if segment contains data and if we don't 276 * know that foreign host supports TAO, suppress sending segment. 277 */ 278 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 279 flags &= ~TH_SYN; 280 off--, len++; 281 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 282 ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL || 283 taop->tao_ccsent == 0)) 284 return 0; 285 } 286 287 /* 288 * Be careful not to send data and/or FIN on SYN segments 289 * in cases when no CC option will be sent. 290 * This measure is needed to prevent interoperability problems 291 * with not fully conformant TCP implementations. 292 */ 293 if ((flags & TH_SYN) && 294 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 295 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 296 len = 0; 297 flags &= ~TH_FIN; 298 } 299 300 if (len < 0) { 301 /* 302 * If FIN has been sent but not acked, 303 * but we haven't been called to retransmit, 304 * len will be < 0. Otherwise, window shrank 305 * after we sent into it. If window shrank to 0, 306 * cancel pending retransmit, pull snd_nxt back 307 * to (closed) window, and set the persist timer 308 * if it isn't already going. If the window didn't 309 * close completely, just wait for an ACK. 310 */ 311 len = 0; 312 if (sendwin == 0) { 313 callout_stop(tp->tt_rexmt); 314 tp->t_rxtshift = 0; 315 tp->snd_nxt = tp->snd_una; 316 if (!callout_active(tp->tt_persist)) 317 tcp_setpersist(tp); 318 } 319 } 320 321 /* 322 * len will be >= 0 after this point. Truncate to the maximum 323 * segment length and ensure that FIN is removed if the length 324 * no longer contains the last data byte. 325 */ 326 if (len > tp->t_maxseg) { 327 len = tp->t_maxseg; 328 sendalot = TRUE; 329 } 330 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 331 flags &= ~TH_FIN; 332 333 recvwin = sbspace(&so->so_rcv); 334 335 /* 336 * Sender silly window avoidance. We transmit under the following 337 * conditions when len is non-zero: 338 * 339 * - We have a full segment 340 * - This is the last buffer in a write()/send() and we are 341 * either idle or running NODELAY 342 * - we've timed out (e.g. persist timer) 343 * - we have more then 1/2 the maximum send window's worth of 344 * data (receiver may be limited the window size) 345 * - we need to retransmit 346 */ 347 if (len) { 348 if (len == tp->t_maxseg) 349 goto send; 350 /* 351 * NOTE! on localhost connections an 'ack' from the remote 352 * end may occur synchronously with the output and cause 353 * us to flush a buffer queued with moretocome. XXX 354 * 355 * note: the len + off check is almost certainly unnecessary. 356 */ 357 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 358 (idle || (tp->t_flags & TF_NODELAY)) && 359 len + off >= so->so_snd.sb_cc && 360 !(tp->t_flags & TF_NOPUSH)) { 361 goto send; 362 } 363 if (tp->t_flags & TF_FORCE) /* typ. timeout case */ 364 goto send; 365 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 366 goto send; 367 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 368 goto send; 369 } 370 371 /* 372 * Compare available window to amount of window 373 * known to peer (as advertised window less 374 * next expected input). If the difference is at least two 375 * max size segments, or at least 50% of the maximum possible 376 * window, then want to send a window update to peer. 377 */ 378 if (recvwin > 0) { 379 /* 380 * "adv" is the amount we can increase the window, 381 * taking into account that we are limited by 382 * TCP_MAXWIN << tp->rcv_scale. 383 */ 384 long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - 385 (tp->rcv_adv - tp->rcv_nxt); 386 387 /* 388 * This ack case typically occurs when the user has drained 389 * the TCP socket buffer sufficiently to warrent an ack 390 * containing a 'pure window update'... that is, an ack that 391 * ONLY updates the tcp window. 392 * 393 * It is unclear why we would need to do a pure window update 394 * past 2 segments if we are going to do one at 1/2 the high 395 * water mark anyway, especially since under normal conditions 396 * the user program will drain the socket buffer quickly. 397 * The 2-segment pure window update will often add a large 398 * number of extra, unnecessary acks to the stream. 399 * 400 * avoid_pure_win_update now defaults to 1. 401 */ 402 if (avoid_pure_win_update == 0) { 403 if (adv >= (long) (2 * tp->t_maxseg)) 404 goto send; 405 } 406 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 407 goto send; 408 } 409 410 /* 411 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 412 * is also a catch-all for the retransmit timer timeout case. 413 */ 414 if (tp->t_flags & TF_ACKNOW) 415 goto send; 416 if ((flags & TH_RST) || 417 ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) 418 goto send; 419 if (SEQ_GT(tp->snd_up, tp->snd_una)) 420 goto send; 421 /* 422 * If our state indicates that FIN should be sent 423 * and we have not yet done so, then we need to send. 424 */ 425 if (flags & TH_FIN && 426 (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) 427 goto send; 428 429 /* 430 * TCP window updates are not reliable, rather a polling protocol 431 * using ``persist'' packets is used to insure receipt of window 432 * updates. The three ``states'' for the output side are: 433 * idle not doing retransmits or persists 434 * persisting to move a small or zero window 435 * (re)transmitting and thereby not persisting 436 * 437 * callout_active(tp->tt_persist) 438 * is true when we are in persist state. 439 * The TF_FORCE flag in tp->t_flags 440 * is set when we are called to send a persist packet. 441 * callout_active(tp->tt_rexmt) 442 * is set when we are retransmitting 443 * The output side is idle when both timers are zero. 444 * 445 * If send window is too small, there is data to transmit, and no 446 * retransmit or persist is pending, then go to persist state. 447 * If nothing happens soon, send when timer expires: 448 * if window is nonzero, transmit what we can, 449 * otherwise force out a byte. 450 */ 451 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 452 !callout_active(tp->tt_persist)) { 453 tp->t_rxtshift = 0; 454 tcp_setpersist(tp); 455 } 456 457 /* 458 * No reason to send a segment, just return. 459 */ 460 return (0); 461 462 send: 463 /* 464 * Before ESTABLISHED, force sending of initial options 465 * unless TCP set not to do any options. 466 * NOTE: we assume that the IP/TCP header plus TCP options 467 * always fit in a single mbuf, leaving room for a maximum 468 * link header, i.e. 469 * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES 470 */ 471 optlen = 0; 472 if (isipv6) 473 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 474 else 475 hdrlen = sizeof(struct tcpiphdr); 476 if (flags & TH_SYN) { 477 tp->snd_nxt = tp->iss; 478 if (!(tp->t_flags & TF_NOOPT)) { 479 u_short mss; 480 481 opt[0] = TCPOPT_MAXSEG; 482 opt[1] = TCPOLEN_MAXSEG; 483 mss = htons((u_short) tcp_mssopt(tp)); 484 (void)memcpy(opt + 2, &mss, sizeof(mss)); 485 optlen = TCPOLEN_MAXSEG; 486 487 if ((tp->t_flags & TF_REQ_SCALE) && 488 (!(flags & TH_ACK) || 489 (tp->t_flags & TF_RCVD_SCALE))) { 490 *((u_int32_t *)(opt + optlen)) = htonl( 491 TCPOPT_NOP << 24 | 492 TCPOPT_WINDOW << 16 | 493 TCPOLEN_WINDOW << 8 | 494 tp->request_r_scale); 495 optlen += 4; 496 } 497 } 498 } 499 500 /* 501 * Send a timestamp and echo-reply if this is a SYN and our side 502 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 503 * and our peer have sent timestamps in our SYN's. 504 */ 505 if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && 506 !(flags & TH_RST) && 507 (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { 508 u_int32_t *lp = (u_int32_t *)(opt + optlen); 509 510 /* Form timestamp option as shown in appendix A of RFC 1323. */ 511 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 512 *lp++ = htonl(ticks); 513 *lp = htonl(tp->ts_recent); 514 optlen += TCPOLEN_TSTAMP_APPA; 515 } 516 517 /* 518 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 519 * options are allowed (!TF_NOOPT) and it's not a RST. 520 */ 521 if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC && 522 !(flags & TH_RST)) { 523 switch (flags & (TH_SYN | TH_ACK)) { 524 /* 525 * This is a normal ACK, send CC if we received CC before 526 * from our peer. 527 */ 528 case TH_ACK: 529 if (!(tp->t_flags & TF_RCVD_CC)) 530 break; 531 /*FALLTHROUGH*/ 532 533 /* 534 * We can only get here in T/TCP's SYN_SENT* state, when 535 * we're a sending a non-SYN segment without waiting for 536 * the ACK of our SYN. A check above assures that we only 537 * do this if our peer understands T/TCP. 538 */ 539 case 0: 540 opt[optlen++] = TCPOPT_NOP; 541 opt[optlen++] = TCPOPT_NOP; 542 opt[optlen++] = TCPOPT_CC; 543 opt[optlen++] = TCPOLEN_CC; 544 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 545 optlen += 4; 546 break; 547 548 /* 549 * This is our initial SYN, check whether we have to use 550 * CC or CC.new. 551 */ 552 case TH_SYN: 553 opt[optlen++] = TCPOPT_NOP; 554 opt[optlen++] = TCPOPT_NOP; 555 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 556 TCPOPT_CCNEW : TCPOPT_CC; 557 opt[optlen++] = TCPOLEN_CC; 558 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 559 optlen += 4; 560 break; 561 562 /* 563 * This is a SYN,ACK; send CC and CC.echo if we received 564 * CC from our peer. 565 */ 566 case (TH_SYN | TH_ACK): 567 if (tp->t_flags & TF_RCVD_CC) { 568 opt[optlen++] = TCPOPT_NOP; 569 opt[optlen++] = TCPOPT_NOP; 570 opt[optlen++] = TCPOPT_CC; 571 opt[optlen++] = TCPOLEN_CC; 572 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 573 optlen += 4; 574 opt[optlen++] = TCPOPT_NOP; 575 opt[optlen++] = TCPOPT_NOP; 576 opt[optlen++] = TCPOPT_CCECHO; 577 opt[optlen++] = TCPOLEN_CC; 578 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_recv); 579 optlen += 4; 580 } 581 break; 582 } 583 } 584 585 hdrlen += optlen; 586 587 if (isipv6) { 588 ipoptlen = ip6_optlen(inp); 589 } else { 590 if (inp->inp_options) { 591 ipoptlen = inp->inp_options->m_len - 592 offsetof(struct ipoption, ipopt_list); 593 } else { 594 ipoptlen = 0; 595 } 596 } 597 #ifdef IPSEC 598 ipoptlen += ipsec_hdrsiz_tcp(tp); 599 #endif 600 601 /* 602 * Adjust data length if insertion of options will 603 * bump the packet length beyond the t_maxopd length. 604 * Clear the FIN bit because we cut off the tail of 605 * the segment. 606 */ 607 if (len + optlen + ipoptlen > tp->t_maxopd) { 608 /* 609 * If there is still more to send, don't close the connection. 610 */ 611 flags &= ~TH_FIN; 612 len = tp->t_maxopd - optlen - ipoptlen; 613 sendalot = TRUE; 614 } 615 616 #ifdef INET6 617 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); 618 #else 619 KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); 620 #endif 621 622 /* 623 * Grab a header mbuf, attaching a copy of data to 624 * be transmitted, and initialize the header from 625 * the template for sends on this connection. 626 */ 627 if (len) { 628 if ((tp->t_flags & TF_FORCE) && len == 1) 629 tcpstat.tcps_sndprobe++; 630 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 631 tcpstat.tcps_sndrexmitpack++; 632 tcpstat.tcps_sndrexmitbyte += len; 633 } else { 634 tcpstat.tcps_sndpack++; 635 tcpstat.tcps_sndbyte += len; 636 } 637 #ifdef notyet 638 if ((m = m_copypack(so->so_snd.sb_mb, off, (int)len, 639 max_linkhdr + hdrlen)) == NULL) { 640 error = ENOBUFS; 641 goto out; 642 } 643 /* 644 * m_copypack left space for our hdr; use it. 645 */ 646 m->m_len += hdrlen; 647 m->m_data -= hdrlen; 648 #else 649 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 650 if (m == NULL) { 651 error = ENOBUFS; 652 goto out; 653 } 654 #ifdef INET6 655 if (MHLEN < hdrlen + max_linkhdr) { 656 MCLGET(m, MB_DONTWAIT); 657 if (!(m->m_flags & M_EXT)) { 658 m_freem(m); 659 error = ENOBUFS; 660 goto out; 661 } 662 } 663 #endif 664 m->m_data += max_linkhdr; 665 m->m_len = hdrlen; 666 if (len <= MHLEN - hdrlen - max_linkhdr) { 667 m_copydata(so->so_snd.sb_mb, off, (int) len, 668 mtod(m, caddr_t) + hdrlen); 669 m->m_len += len; 670 } else { 671 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 672 if (m->m_next == NULL) { 673 (void) m_free(m); 674 error = ENOBUFS; 675 goto out; 676 } 677 } 678 #endif 679 /* 680 * If we're sending everything we've got, set PUSH. 681 * (This will keep happy those implementations which only 682 * give data to the user when a buffer fills or 683 * a PUSH comes in.) 684 */ 685 if (off + len == so->so_snd.sb_cc) 686 flags |= TH_PUSH; 687 } else { 688 if (tp->t_flags & TF_ACKNOW) 689 tcpstat.tcps_sndacks++; 690 else if (flags & (TH_SYN | TH_FIN | TH_RST)) 691 tcpstat.tcps_sndctrl++; 692 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 693 tcpstat.tcps_sndurg++; 694 else 695 tcpstat.tcps_sndwinup++; 696 697 MGETHDR(m, MB_DONTWAIT, MT_HEADER); 698 if (m == NULL) { 699 error = ENOBUFS; 700 goto out; 701 } 702 if (isipv6 && 703 (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) 704 MH_ALIGN(m, hdrlen); 705 else 706 m->m_data += max_linkhdr; 707 m->m_len = hdrlen; 708 } 709 m->m_pkthdr.rcvif = (struct ifnet *)0; 710 if (isipv6) { 711 ip6 = mtod(m, struct ip6_hdr *); 712 th = (struct tcphdr *)(ip6 + 1); 713 tcp_fillheaders(tp, ip6, th); 714 } else { 715 ip = mtod(m, struct ip *); 716 ipov = (struct ipovly *)ip; 717 th = (struct tcphdr *)(ip + 1); 718 /* this picks up the pseudo header (w/o the length) */ 719 tcp_fillheaders(tp, ip, th); 720 } 721 722 /* 723 * Fill in fields, remembering maximum advertised 724 * window for use in delaying messages about window sizes. 725 * If resending a FIN, be sure not to use a new sequence number. 726 */ 727 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 728 tp->snd_nxt == tp->snd_max) 729 tp->snd_nxt--; 730 /* 731 * If we are doing retransmissions, then snd_nxt will 732 * not reflect the first unsent octet. For ACK only 733 * packets, we do not want the sequence number of the 734 * retransmitted packet, we want the sequence number 735 * of the next unsent octet. So, if there is no data 736 * (and no SYN or FIN), use snd_max instead of snd_nxt 737 * when filling in ti_seq. But if we are in persist 738 * state, snd_max might reflect one byte beyond the 739 * right edge of the window, so use snd_nxt in that 740 * case, since we know we aren't doing a retransmission. 741 * (retransmit and persist are mutually exclusive...) 742 */ 743 if (len || (flags & (TH_SYN|TH_FIN)) || callout_active(tp->tt_persist)) 744 th->th_seq = htonl(tp->snd_nxt); 745 else 746 th->th_seq = htonl(tp->snd_max); 747 th->th_ack = htonl(tp->rcv_nxt); 748 if (optlen) { 749 bcopy(opt, th + 1, optlen); 750 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; 751 } 752 th->th_flags = flags; 753 /* 754 * Calculate receive window. Don't shrink window, 755 * but avoid silly window syndrome. 756 */ 757 if (recvwin < (long)(so->so_rcv.sb_hiwat / 4) && 758 recvwin < (long)tp->t_maxseg) 759 recvwin = 0; 760 if (recvwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 761 recvwin = (long)(tp->rcv_adv - tp->rcv_nxt); 762 if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) 763 recvwin = (long)TCP_MAXWIN << tp->rcv_scale; 764 th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); 765 766 /* 767 * Adjust the RXWIN0SENT flag - indicate that we have advertised 768 * a 0 window. This may cause the remote transmitter to stall. This 769 * flag tells soreceive() to disable delayed acknowledgements when 770 * draining the buffer. This can occur if the receiver is attempting 771 * to read more data then can be buffered prior to transmitting on 772 * the connection. 773 */ 774 if (recvwin == 0) 775 tp->t_flags |= TF_RXWIN0SENT; 776 else 777 tp->t_flags &= ~TF_RXWIN0SENT; 778 779 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 780 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 781 th->th_flags |= TH_URG; 782 } else { 783 /* 784 * If no urgent pointer to send, then we pull 785 * the urgent pointer to the left edge of the send window 786 * so that it doesn't drift into the send window on sequence 787 * number wraparound. 788 */ 789 tp->snd_up = tp->snd_una; /* drag it along */ 790 } 791 792 /* 793 * Put TCP length in extended header, and then 794 * checksum extended header and data. 795 */ 796 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 797 if (isipv6) { 798 /* 799 * ip6_plen is not need to be filled now, and will be filled 800 * in ip6_output. 801 */ 802 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 803 sizeof(struct tcphdr) + optlen + len); 804 } else { 805 m->m_pkthdr.csum_flags = CSUM_TCP; 806 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 807 if (len + optlen) 808 th->th_sum = in_addword(th->th_sum, 809 htons((u_short)(optlen + len))); 810 811 /* IP version must be set here for ipv4/ipv6 checking later */ 812 KASSERT(ip->ip_v == IPVERSION, 813 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 814 } 815 816 /* 817 * In transmit state, time the transmission and arrange for 818 * the retransmit. In persist state, just set snd_max. 819 */ 820 if (!(tp->t_flags & TF_FORCE) || !callout_active(tp->tt_persist)) { 821 tcp_seq startseq = tp->snd_nxt; 822 823 /* 824 * Advance snd_nxt over sequence space of this segment. 825 */ 826 if (flags & (TH_SYN | TH_FIN)) { 827 if (flags & TH_SYN) 828 tp->snd_nxt++; 829 if (flags & TH_FIN) { 830 tp->snd_nxt++; 831 tp->t_flags |= TF_SENTFIN; 832 } 833 } 834 tp->snd_nxt += len; 835 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 836 tp->snd_max = tp->snd_nxt; 837 /* 838 * Time this transmission if not a retransmission and 839 * not currently timing anything. 840 */ 841 if (tp->t_rtttime == 0) { 842 tp->t_rtttime = ticks; 843 tp->t_rtseq = startseq; 844 tcpstat.tcps_segstimed++; 845 } 846 } 847 848 /* 849 * Set retransmit timer if not currently set, 850 * and not doing a pure ack or a keep-alive probe. 851 * Initial value for retransmit timer is smoothed 852 * round-trip time + 2 * round-trip time variance. 853 * Initialize shift counter which is used for backoff 854 * of retransmit time. 855 */ 856 if (!callout_active(tp->tt_rexmt) && 857 tp->snd_nxt != tp->snd_una) { 858 if (callout_active(tp->tt_persist)) { 859 callout_stop(tp->tt_persist); 860 tp->t_rxtshift = 0; 861 } 862 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 863 tcp_timer_rexmt, tp); 864 } 865 } else { 866 /* 867 * Persist case, update snd_max but since we are in 868 * persist mode (no window) we do not update snd_nxt. 869 */ 870 int xlen = len; 871 if (flags & TH_SYN) 872 ++xlen; 873 if (flags & TH_FIN) { 874 ++xlen; 875 tp->t_flags |= TF_SENTFIN; 876 } 877 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 878 tp->snd_max = tp->snd_nxt + xlen; 879 } 880 881 #ifdef TCPDEBUG 882 /* 883 * Trace. 884 */ 885 if (so->so_options & SO_DEBUG) 886 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 887 #endif 888 889 /* 890 * Fill in IP length and desired time to live and 891 * send to IP level. There should be a better way 892 * to handle ttl and tos; we could keep them in 893 * the template, but need a way to checksum without them. 894 */ 895 /* 896 * m->m_pkthdr.len should have been set before cksum calcuration, 897 * because in6_cksum() need it. 898 */ 899 if (isipv6) { 900 /* 901 * we separately set hoplimit for every segment, since the 902 * user might want to change the value via setsockopt. 903 * Also, desired default hop limit might be changed via 904 * Neighbor Discovery. 905 */ 906 ip6->ip6_hlim = in6_selecthlim(inp, 907 (inp->in6p_route.ro_rt ? 908 inp->in6p_route.ro_rt->rt_ifp : NULL)); 909 910 /* TODO: IPv6 IP6TOS_ECT bit on */ 911 error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route, 912 (so->so_options & SO_DONTROUTE), NULL, NULL, inp); 913 } else { 914 struct rtentry *rt; 915 ip->ip_len = m->m_pkthdr.len; 916 #ifdef INET6 917 if (INP_CHECK_SOCKAF(so, AF_INET6)) 918 ip->ip_ttl = in6_selecthlim(inp, 919 (inp->in6p_route.ro_rt ? 920 inp->in6p_route.ro_rt->rt_ifp : NULL)); 921 else 922 #endif 923 ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ 924 925 ip->ip_tos = inp->inp_ip_tos; /* XXX */ 926 /* 927 * See if we should do MTU discovery. 928 * We do it only if the following are true: 929 * 1) we have a valid route to the destination 930 * 2) the MTU is not locked (if it is, 931 * then discovery has been disabled) 932 */ 933 if (path_mtu_discovery && 934 (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) && 935 !(rt->rt_rmx.rmx_locks & RTV_MTU)) 936 ip->ip_off |= IP_DF; 937 938 error = ip_output(m, inp->inp_options, &inp->inp_route, 939 (so->so_options & SO_DONTROUTE), NULL, inp); 940 } 941 if (error) { 942 943 /* 944 * We know that the packet was lost, so back out the 945 * sequence number advance, if any. 946 */ 947 if (!(tp->t_flags & TF_FORCE) || 948 !callout_active(tp->tt_persist)) { 949 /* 950 * No need to check for TH_FIN here because 951 * the TF_SENTFIN flag handles that case. 952 */ 953 if (!(flags & TH_SYN)) 954 tp->snd_nxt -= len; 955 } 956 957 out: 958 if (error == ENOBUFS) { 959 /* 960 * If we can't send, make sure there is something 961 * to get us going again later. Persist state 962 * is not necessarily right, but it is close enough. 963 */ 964 if (!callout_active(tp->tt_rexmt) && 965 !callout_active(tp->tt_persist)) { 966 tp->t_rxtshift = 0; 967 tcp_setpersist(tp); 968 } 969 tcp_quench(inp, 0); 970 return (0); 971 } 972 if (error == EMSGSIZE) { 973 /* 974 * ip_output() will have already fixed the route 975 * for us. tcp_mtudisc() will, as its last action, 976 * initiate retransmission, so it is important to 977 * not do so here. 978 */ 979 tcp_mtudisc(inp, 0); 980 return 0; 981 } 982 if ((error == EHOSTUNREACH || error == ENETDOWN) && 983 TCPS_HAVERCVDSYN(tp->t_state)) { 984 tp->t_softerror = error; 985 return (0); 986 } 987 return (error); 988 } 989 tcpstat.tcps_sndtotal++; 990 991 /* 992 * Data sent (as far as we can tell). 993 * If this advertises a larger window than any other segment, 994 * then remember the size of the advertised window. 995 * Any pending ACK has now been sent. 996 */ 997 if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) 998 tp->rcv_adv = tp->rcv_nxt + recvwin; 999 tp->last_ack_sent = tp->rcv_nxt; 1000 tp->t_flags &= ~TF_ACKNOW; 1001 if (tcp_delack_enabled) 1002 callout_stop(tp->tt_delack); 1003 if (sendalot) 1004 goto again; 1005 return (0); 1006 } 1007 1008 void 1009 tcp_setpersist(tp) 1010 struct tcpcb *tp; 1011 { 1012 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1013 int tt; 1014 1015 if (callout_active(tp->tt_rexmt)) 1016 panic("tcp_setpersist: retransmit pending"); 1017 /* 1018 * Start/restart persistance timer. 1019 */ 1020 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1021 TCPTV_PERSMIN, TCPTV_PERSMAX); 1022 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1023 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1024 tp->t_rxtshift++; 1025 } 1026