1 /* $OpenBSD: tcp_output.c,v 1.123 2017/10/25 12:38:21 job Exp $ */ 2 /* $NetBSD: tcp_output.c,v 1.16 1997/06/03 16:17:09 kml Exp $ */ 3 4 /* 5 * Copyright (c) 1982, 1986, 1988, 1990, 1993 6 * The Regents of the University of California. All rights reserved. 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 University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)COPYRIGHT 1.1 (NRL) 17 January 1995 33 * 34 * NRL grants permission for redistribution and use in source and binary 35 * forms, with or without modification, of the software and documentation 36 * created at NRL provided that the following conditions are met: 37 * 38 * 1. Redistributions of source code must retain the above copyright 39 * notice, this list of conditions and the following disclaimer. 40 * 2. Redistributions in binary form must reproduce the above copyright 41 * notice, this list of conditions and the following disclaimer in the 42 * documentation and/or other materials provided with the distribution. 43 * 3. All advertising materials mentioning features or use of this software 44 * must display the following acknowledgements: 45 * This product includes software developed by the University of 46 * California, Berkeley and its contributors. 47 * This product includes software developed at the Information 48 * Technology Division, US Naval Research Laboratory. 49 * 4. Neither the name of the NRL nor the names of its contributors 50 * may be used to endorse or promote products derived from this software 51 * without specific prior written permission. 52 * 53 * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS 54 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 55 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 56 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR 57 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 58 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 59 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 60 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 61 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 62 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 63 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 64 * 65 * The views and conclusions contained in the software and documentation 66 * are those of the authors and should not be interpreted as representing 67 * official policies, either expressed or implied, of the US Naval 68 * Research Laboratory (NRL). 69 */ 70 71 #include "pf.h" 72 73 #include <sys/param.h> 74 #include <sys/systm.h> 75 #include <sys/mbuf.h> 76 #include <sys/protosw.h> 77 #include <sys/socket.h> 78 #include <sys/socketvar.h> 79 #include <sys/kernel.h> 80 81 #include <net/route.h> 82 83 #include <netinet/in.h> 84 #include <netinet/ip.h> 85 #include <netinet/in_pcb.h> 86 #include <netinet/ip_var.h> 87 #include <netinet/tcp.h> 88 #define TCPOUTFLAGS 89 #include <netinet/tcp_fsm.h> 90 #include <netinet/tcp_seq.h> 91 #include <netinet/tcp_timer.h> 92 #include <netinet/tcp_var.h> 93 #include <netinet/tcp_debug.h> 94 95 #ifdef notyet 96 extern struct mbuf *m_copypack(); 97 #endif 98 99 extern int tcprexmtthresh; 100 101 #ifdef TCP_SACK_DEBUG 102 void tcp_print_holes(struct tcpcb *tp); 103 104 void 105 tcp_print_holes(struct tcpcb *tp) 106 { 107 struct sackhole *p = tp->snd_holes; 108 if (p == NULL) 109 return; 110 printf("Hole report: start--end dups rxmit\n"); 111 while (p) { 112 printf("%x--%x d %d r %x\n", p->start, p->end, p->dups, 113 p->rxmit); 114 p = p->next; 115 } 116 printf("\n"); 117 } 118 #endif /* TCP_SACK_DEBUG */ 119 120 /* 121 * Returns pointer to a sackhole if there are any pending retransmissions; 122 * NULL otherwise. 123 */ 124 struct sackhole * 125 tcp_sack_output(struct tcpcb *tp) 126 { 127 struct sackhole *p; 128 129 if (!tp->sack_enable) 130 return (NULL); 131 p = tp->snd_holes; 132 while (p) { 133 if (p->dups >= tcprexmtthresh && SEQ_LT(p->rxmit, p->end)) { 134 if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */ 135 p = p->next; 136 continue; 137 } 138 #ifdef TCP_SACK_DEBUG 139 if (p) 140 tcp_print_holes(tp); 141 #endif 142 return (p); 143 } 144 p = p->next; 145 } 146 return (NULL); 147 } 148 149 /* 150 * After a timeout, the SACK list may be rebuilt. This SACK information 151 * should be used to avoid retransmitting SACKed data. This function 152 * traverses the SACK list to see if snd_nxt should be moved forward. 153 */ 154 155 void 156 tcp_sack_adjust(struct tcpcb *tp) 157 { 158 struct sackhole *cur = tp->snd_holes; 159 if (cur == NULL) 160 return; /* No holes */ 161 if (SEQ_GEQ(tp->snd_nxt, tp->rcv_lastsack)) 162 return; /* We're already beyond any SACKed blocks */ 163 /* 164 * Two cases for which we want to advance snd_nxt: 165 * i) snd_nxt lies between end of one hole and beginning of another 166 * ii) snd_nxt lies between end of last hole and rcv_lastsack 167 */ 168 while (cur->next) { 169 if (SEQ_LT(tp->snd_nxt, cur->end)) 170 return; 171 if (SEQ_GEQ(tp->snd_nxt, cur->next->start)) 172 cur = cur->next; 173 else { 174 tp->snd_nxt = cur->next->start; 175 return; 176 } 177 } 178 if (SEQ_LT(tp->snd_nxt, cur->end)) 179 return; 180 tp->snd_nxt = tp->rcv_lastsack; 181 return; 182 } 183 184 /* 185 * Tcp output routine: figure out what should be sent and send it. 186 */ 187 int 188 tcp_output(struct tcpcb *tp) 189 { 190 struct socket *so = tp->t_inpcb->inp_socket; 191 long len, win, txmaxseg; 192 int off, flags, error; 193 struct mbuf *m; 194 struct tcphdr *th; 195 u_int32_t optbuf[howmany(MAX_TCPOPTLEN, sizeof(u_int32_t))]; 196 u_char *opt = (u_char *)optbuf; 197 unsigned int optlen, hdrlen, packetlen; 198 int idle, sendalot = 0; 199 int i, sack_rxmit = 0; 200 struct sackhole *p; 201 int maxburst = TCP_MAXBURST; 202 #ifdef TCP_SIGNATURE 203 unsigned int sigoff; 204 #endif /* TCP_SIGNATURE */ 205 #ifdef TCP_ECN 206 int needect; 207 #endif 208 209 if (tp->t_flags & TF_BLOCKOUTPUT) { 210 tp->t_flags |= TF_NEEDOUTPUT; 211 return (0); 212 } else 213 tp->t_flags &= ~TF_NEEDOUTPUT; 214 215 #if defined(TCP_SIGNATURE) && defined(DIAGNOSTIC) 216 if (tp->sack_enable && (tp->t_flags & TF_SIGNATURE)) 217 return (EINVAL); 218 #endif /* defined(TCP_SIGNATURE) && defined(DIAGNOSTIC) */ 219 220 /* 221 * Determine length of data that should be transmitted, 222 * and flags that will be used. 223 * If there is some data or critical controls (SYN, RST) 224 * to send, then transmit; otherwise, investigate further. 225 */ 226 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 227 if (idle && (tcp_now - tp->t_rcvtime) >= tp->t_rxtcur) 228 /* 229 * We have been idle for "a while" and no acks are 230 * expected to clock out any data we send -- 231 * slow start to get ack "clock" running again. 232 */ 233 tp->snd_cwnd = 2 * tp->t_maxseg; 234 235 /* remember 'idle' for next invocation of tcp_output */ 236 if (idle && soissending(so)) { 237 tp->t_flags |= TF_LASTIDLE; 238 idle = 0; 239 } else 240 tp->t_flags &= ~TF_LASTIDLE; 241 242 again: 243 /* 244 * If we've recently taken a timeout, snd_max will be greater than 245 * snd_nxt. There may be SACK information that allows us to avoid 246 * resending already delivered data. Adjust snd_nxt accordingly. 247 */ 248 if (tp->sack_enable && SEQ_LT(tp->snd_nxt, tp->snd_max)) 249 tcp_sack_adjust(tp); 250 off = tp->snd_nxt - tp->snd_una; 251 win = ulmin(tp->snd_wnd, tp->snd_cwnd); 252 253 flags = tcp_outflags[tp->t_state]; 254 255 /* 256 * Send any SACK-generated retransmissions. If we're explicitly trying 257 * to send out new data (when sendalot is 1), bypass this function. 258 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 259 * we're replacing a (future) new transmission with a retransmission 260 * now, and we previously incremented snd_cwnd in tcp_input(). 261 */ 262 if (tp->sack_enable && !sendalot) { 263 if (tp->t_dupacks >= tcprexmtthresh && 264 (p = tcp_sack_output(tp))) { 265 off = p->rxmit - tp->snd_una; 266 sack_rxmit = 1; 267 /* Coalesce holes into a single retransmission */ 268 len = min(tp->t_maxseg, p->end - p->rxmit); 269 if (SEQ_LT(tp->snd_una, tp->snd_last)) 270 tp->snd_cwnd -= tp->t_maxseg; 271 } 272 } 273 274 sendalot = 0; 275 /* 276 * If in persist timeout with window of 0, send 1 byte. 277 * Otherwise, if window is small but nonzero 278 * and timer expired, we will send what we can 279 * and go to transmit state. 280 */ 281 if (tp->t_force) { 282 if (win == 0) { 283 /* 284 * If we still have some data to send, then 285 * clear the FIN bit. Usually this would 286 * happen below when it realizes that we 287 * aren't sending all the data. However, 288 * if we have exactly 1 byte of unset data, 289 * then it won't clear the FIN bit below, 290 * and if we are in persist state, we wind 291 * up sending the packet without recording 292 * that we sent the FIN bit. 293 * 294 * We can't just blindly clear the FIN bit, 295 * because if we don't have any more data 296 * to send then the probe will be the FIN 297 * itself. 298 */ 299 if (off < so->so_snd.sb_cc) 300 flags &= ~TH_FIN; 301 win = 1; 302 } else { 303 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 304 tp->t_rxtshift = 0; 305 } 306 } 307 308 if (!sack_rxmit) { 309 len = ulmin(so->so_snd.sb_cc, win) - off; 310 } 311 312 if (len < 0) { 313 /* 314 * If FIN has been sent but not acked, 315 * but we haven't been called to retransmit, 316 * len will be -1. Otherwise, window shrank 317 * after we sent into it. If window shrank to 0, 318 * cancel pending retransmit, pull snd_nxt back 319 * to (closed) window, and set the persist timer 320 * if it isn't already going. If the window didn't 321 * close completely, just wait for an ACK. 322 */ 323 len = 0; 324 if (win == 0) { 325 TCP_TIMER_DISARM(tp, TCPT_REXMT); 326 tp->t_rxtshift = 0; 327 tp->snd_nxt = tp->snd_una; 328 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) 329 tcp_setpersist(tp); 330 } 331 } 332 333 /* 334 * Never send more than half a buffer full. This insures that we can 335 * always keep 2 packets on the wire, no matter what SO_SNDBUF is, and 336 * therefore acks will never be delayed unless we run out of data to 337 * transmit. 338 */ 339 txmaxseg = ulmin(so->so_snd.sb_hiwat / 2, tp->t_maxseg); 340 341 if (len > txmaxseg) { 342 len = txmaxseg; 343 sendalot = 1; 344 } 345 if (off + len < so->so_snd.sb_cc) 346 flags &= ~TH_FIN; 347 348 win = sbspace(so, &so->so_rcv); 349 350 /* 351 * Sender silly window avoidance. If connection is idle 352 * and can send all data, a maximum segment, 353 * at least a maximum default-size segment do it, 354 * or are forced, do it; otherwise don't bother. 355 * If peer's buffer is tiny, then send 356 * when window is at least half open. 357 * If retransmitting (possibly after persist timer forced us 358 * to send into a small window), then must resend. 359 */ 360 if (len) { 361 if (len == txmaxseg) 362 goto send; 363 if ((idle || (tp->t_flags & TF_NODELAY)) && 364 len + off >= so->so_snd.sb_cc && !soissending(so) && 365 (tp->t_flags & TF_NOPUSH) == 0) 366 goto send; 367 if (tp->t_force) 368 goto send; 369 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 370 goto send; 371 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 372 goto send; 373 if (sack_rxmit) 374 goto send; 375 } 376 377 /* 378 * Compare available window to amount of window 379 * known to peer (as advertised window less 380 * next expected input). If the difference is at least two 381 * max size segments, or at least 50% of the maximum possible 382 * window, then want to send a window update to peer. 383 */ 384 if (win > 0) { 385 /* 386 * "adv" is the amount we can increase the window, 387 * taking into account that we are limited by 388 * TCP_MAXWIN << tp->rcv_scale. 389 */ 390 long adv = lmin(win, (long)TCP_MAXWIN << tp->rcv_scale) - 391 (tp->rcv_adv - tp->rcv_nxt); 392 393 if (adv >= (long) (2 * tp->t_maxseg)) 394 goto send; 395 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 396 goto send; 397 } 398 399 /* 400 * Send if we owe peer an ACK. 401 */ 402 if (tp->t_flags & TF_ACKNOW) 403 goto send; 404 if (flags & (TH_SYN|TH_RST)) 405 goto send; 406 if (SEQ_GT(tp->snd_up, tp->snd_una)) 407 goto send; 408 /* 409 * If our state indicates that FIN should be sent 410 * and we have not yet done so, or we're retransmitting the FIN, 411 * then we need to send. 412 */ 413 if (flags & TH_FIN && 414 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 415 goto send; 416 /* 417 * In SACK, it is possible for tcp_output to fail to send a segment 418 * after the retransmission timer has been turned off. Make sure 419 * that the retransmission timer is set. 420 */ 421 if (SEQ_GT(tp->snd_max, tp->snd_una) && 422 TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 423 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 424 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 425 return (0); 426 } 427 428 /* 429 * TCP window updates are not reliable, rather a polling protocol 430 * using ``persist'' packets is used to insure receipt of window 431 * updates. The three ``states'' for the output side are: 432 * idle not doing retransmits or persists 433 * persisting to move a small or zero window 434 * (re)transmitting and thereby not persisting 435 * 436 * tp->t_timer[TCPT_PERSIST] 437 * is set when we are in persist state. 438 * tp->t_force 439 * is set when we are called to send a persist packet. 440 * tp->t_timer[TCPT_REXMT] 441 * is set when we are retransmitting 442 * The output side is idle when both timers are zero. 443 * 444 * If send window is too small, there is data to transmit, and no 445 * retransmit or persist is pending, then go to persist state. 446 * If nothing happens soon, send when timer expires: 447 * if window is nonzero, transmit what we can, 448 * otherwise force out a byte. 449 */ 450 if (so->so_snd.sb_cc && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 451 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 452 tp->t_rxtshift = 0; 453 tcp_setpersist(tp); 454 } 455 456 /* 457 * No reason to send a segment, just return. 458 */ 459 return (0); 460 461 send: 462 /* 463 * Before ESTABLISHED, force sending of initial options 464 * unless TCP set not to do any options. 465 * NOTE: we assume that the IP/TCP header plus TCP options 466 * always fit in a single mbuf, leaving room for a maximum 467 * link header, i.e. 468 * max_linkhdr + sizeof(network header) + sizeof(struct tcphdr + 469 * optlen <= MHLEN 470 */ 471 optlen = 0; 472 473 switch (tp->pf) { 474 case 0: /*default to PF_INET*/ 475 case PF_INET: 476 hdrlen = sizeof(struct ip) + sizeof(struct tcphdr); 477 break; 478 #ifdef INET6 479 case PF_INET6: 480 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 481 break; 482 #endif /* INET6 */ 483 default: 484 return (EPFNOSUPPORT); 485 } 486 487 if (flags & TH_SYN) { 488 tp->snd_nxt = tp->iss; 489 if ((tp->t_flags & TF_NOOPT) == 0) { 490 u_int16_t mss; 491 492 opt[0] = TCPOPT_MAXSEG; 493 opt[1] = 4; 494 mss = htons((u_int16_t) tcp_mss(tp, 0)); 495 memcpy(opt + 2, &mss, sizeof(mss)); 496 optlen = 4; 497 498 if (flags & TH_ACK) 499 tcp_mss_update(tp); 500 /* 501 * If this is the first SYN of connection (not a SYN 502 * ACK), include SACK_PERMIT_HDR option. If this is a 503 * SYN ACK, include SACK_PERMIT_HDR option if peer has 504 * already done so. 505 */ 506 if (tp->sack_enable && ((flags & TH_ACK) == 0 || 507 (tp->t_flags & TF_SACK_PERMIT))) { 508 *((u_int32_t *) (opt + optlen)) = 509 htonl(TCPOPT_SACK_PERMIT_HDR); 510 optlen += 4; 511 } 512 if ((tp->t_flags & TF_REQ_SCALE) && 513 ((flags & TH_ACK) == 0 || 514 (tp->t_flags & TF_RCVD_SCALE))) { 515 *((u_int32_t *) (opt + optlen)) = htonl( 516 TCPOPT_NOP << 24 | 517 TCPOPT_WINDOW << 16 | 518 TCPOLEN_WINDOW << 8 | 519 tp->request_r_scale); 520 optlen += 4; 521 } 522 } 523 } 524 525 /* 526 * Send a timestamp and echo-reply if this is a SYN and our side 527 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 528 * and our peer have sent timestamps in our SYN's. 529 */ 530 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 531 (flags & TH_RST) == 0 && 532 ((flags & (TH_SYN|TH_ACK)) == TH_SYN || 533 (tp->t_flags & TF_RCVD_TSTMP))) { 534 u_int32_t *lp = (u_int32_t *)(opt + optlen); 535 536 /* Form timestamp option as shown in appendix A of RFC 1323. */ 537 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 538 *lp++ = htonl(tcp_now + tp->ts_modulate); 539 *lp = htonl(tp->ts_recent); 540 optlen += TCPOLEN_TSTAMP_APPA; 541 542 /* Set receive buffer autosizing timestamp. */ 543 if (tp->rfbuf_ts == 0) 544 tp->rfbuf_ts = tcp_now; 545 546 } 547 548 #ifdef TCP_SIGNATURE 549 if (tp->t_flags & TF_SIGNATURE) { 550 u_int8_t *bp = (u_int8_t *)(opt + optlen); 551 552 /* Send signature option */ 553 *(bp++) = TCPOPT_SIGNATURE; 554 *(bp++) = TCPOLEN_SIGNATURE; 555 sigoff = optlen + 2; 556 557 { 558 unsigned int i; 559 560 for (i = 0; i < 16; i++) 561 *(bp++) = 0; 562 } 563 564 565 /* Pad options list to the next 32 bit boundary and 566 * terminate it. 567 */ 568 *bp++ = TCPOPT_NOP; 569 *bp++ = TCPOPT_NOP; 570 571 optlen += TCPOLEN_SIGLEN; 572 } 573 #endif /* TCP_SIGNATURE */ 574 575 /* 576 * Send SACKs if necessary. This should be the last option processed. 577 * Only as many SACKs are sent as are permitted by the maximum options 578 * size. No more than three SACKs are sent. 579 */ 580 if (tp->sack_enable && tp->t_state == TCPS_ESTABLISHED && 581 (tp->t_flags & (TF_SACK_PERMIT|TF_NOOPT)) == TF_SACK_PERMIT && 582 tp->rcv_numsacks) { 583 u_int32_t *lp = (u_int32_t *)(opt + optlen); 584 u_int32_t *olp = lp++; 585 int count = 0; /* actual number of SACKs inserted */ 586 int maxsack = (MAX_TCPOPTLEN - (optlen + 4))/TCPOLEN_SACK; 587 588 tcpstat_inc(tcps_sack_snd_opts); 589 maxsack = min(maxsack, TCP_MAX_SACK); 590 for (i = 0; (i < tp->rcv_numsacks && count < maxsack); i++) { 591 struct sackblk sack = tp->sackblks[i]; 592 if (sack.start == 0 && sack.end == 0) 593 continue; 594 *lp++ = htonl(sack.start); 595 *lp++ = htonl(sack.end); 596 count++; 597 } 598 *olp = htonl(TCPOPT_SACK_HDR|(TCPOLEN_SACK*count+2)); 599 optlen += TCPOLEN_SACK*count + 4; /* including leading NOPs */ 600 } 601 602 #ifdef DIAGNOSTIC 603 if (optlen > MAX_TCPOPTLEN) 604 panic("tcp_output: options too long"); 605 #endif /* DIAGNOSTIC */ 606 607 hdrlen += optlen; 608 609 /* 610 * Adjust data length if insertion of options will 611 * bump the packet length beyond the t_maxopd length. 612 */ 613 if (len > tp->t_maxopd - optlen) { 614 len = tp->t_maxopd - optlen; 615 sendalot = 1; 616 flags &= ~TH_FIN; 617 } 618 619 #ifdef DIAGNOSTIC 620 if (max_linkhdr + hdrlen > MCLBYTES) 621 panic("tcphdr too big"); 622 #endif 623 624 /* 625 * Grab a header mbuf, attaching a copy of data to 626 * be transmitted, and initialize the header from 627 * the template for sends on this connection. 628 */ 629 if (len) { 630 if (tp->t_force && len == 1) 631 tcpstat_inc(tcps_sndprobe); 632 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 633 tcpstat_pkt(tcps_sndrexmitpack, tcps_sndrexmitbyte, 634 len); 635 } else { 636 tcpstat_pkt(tcps_sndpack, tcps_sndbyte, len); 637 } 638 #ifdef notyet 639 if ((m = m_copypack(so->so_snd.sb_mb, off, 640 (int)len, max_linkhdr + hdrlen)) == 0) { 641 error = ENOBUFS; 642 goto out; 643 } 644 /* 645 * m_copypack left space for our hdr; use it. 646 */ 647 m->m_len += hdrlen; 648 m->m_data -= hdrlen; 649 #else 650 MGETHDR(m, M_DONTWAIT, MT_HEADER); 651 if (m != NULL && max_linkhdr + hdrlen > MHLEN) { 652 MCLGET(m, M_DONTWAIT); 653 if ((m->m_flags & M_EXT) == 0) { 654 m_freem(m); 655 m = NULL; 656 } 657 } 658 if (m == NULL) { 659 error = ENOBUFS; 660 goto out; 661 } 662 m->m_data += max_linkhdr; 663 m->m_len = hdrlen; 664 if (len <= M_TRAILINGSPACE(m)) { 665 m_copydata(so->so_snd.sb_mb, off, (int) len, 666 mtod(m, caddr_t) + hdrlen); 667 m->m_len += len; 668 } else { 669 m->m_next = m_copym(so->so_snd.sb_mb, off, (int) len, 670 M_NOWAIT); 671 if (m->m_next == 0) { 672 (void) m_free(m); 673 error = ENOBUFS; 674 goto out; 675 } 676 } 677 if (so->so_snd.sb_mb->m_flags & M_PKTHDR) 678 m->m_pkthdr.ph_loopcnt = 679 so->so_snd.sb_mb->m_pkthdr.ph_loopcnt; 680 #endif 681 /* 682 * If we're sending everything we've got, set PUSH. 683 * (This will keep happy those implementations which only 684 * give data to the user when a buffer fills or 685 * a PUSH comes in.) 686 */ 687 if (off + len == so->so_snd.sb_cc && !soissending(so)) 688 flags |= TH_PUSH; 689 } else { 690 if (tp->t_flags & TF_ACKNOW) 691 tcpstat_inc(tcps_sndacks); 692 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 693 tcpstat_inc(tcps_sndctrl); 694 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 695 tcpstat_inc(tcps_sndurg); 696 else 697 tcpstat_inc(tcps_sndwinup); 698 699 MGETHDR(m, M_DONTWAIT, MT_HEADER); 700 if (m != NULL && max_linkhdr + hdrlen > MHLEN) { 701 MCLGET(m, M_DONTWAIT); 702 if ((m->m_flags & M_EXT) == 0) { 703 m_freem(m); 704 m = NULL; 705 } 706 } 707 if (m == NULL) { 708 error = ENOBUFS; 709 goto out; 710 } 711 m->m_data += max_linkhdr; 712 m->m_len = hdrlen; 713 } 714 m->m_pkthdr.ph_ifidx = 0; 715 m->m_pkthdr.len = hdrlen + len; 716 717 if (!tp->t_template) 718 panic("tcp_output"); 719 #ifdef DIAGNOSTIC 720 if (tp->t_template->m_len != hdrlen - optlen) 721 panic("tcp_output: template len != hdrlen - optlen"); 722 #endif /* DIAGNOSTIC */ 723 memcpy(mtod(m, caddr_t), mtod(tp->t_template, caddr_t), 724 tp->t_template->m_len); 725 th = (struct tcphdr *)(mtod(m, caddr_t) + tp->t_template->m_len - 726 sizeof(struct tcphdr)); 727 728 /* 729 * Fill in fields, remembering maximum advertised 730 * window for use in delaying messages about window sizes. 731 * If resending a FIN, be sure not to use a new sequence number. 732 */ 733 if ((flags & TH_FIN) && (tp->t_flags & TF_SENTFIN) && 734 (tp->snd_nxt == tp->snd_max)) 735 tp->snd_nxt--; 736 /* 737 * If we are doing retransmissions, then snd_nxt will 738 * not reflect the first unsent octet. For ACK only 739 * packets, we do not want the sequence number of the 740 * retransmitted packet, we want the sequence number 741 * of the next unsent octet. So, if there is no data 742 * (and no SYN or FIN), use snd_max instead of snd_nxt 743 * when filling in ti_seq. But if we are in persist 744 * state, snd_max might reflect one byte beyond the 745 * right edge of the window, so use snd_nxt in that 746 * case, since we know we aren't doing a retransmission. 747 * (retransmit and persist are mutually exclusive...) 748 */ 749 if (len || (flags & (TH_SYN|TH_FIN)) || TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) 750 th->th_seq = htonl(tp->snd_nxt); 751 else 752 th->th_seq = htonl(tp->snd_max); 753 754 if (sack_rxmit) { 755 /* 756 * If sendalot was turned on (due to option stuffing), turn it 757 * off. Properly set th_seq field. Advance the ret'x pointer 758 * by len. 759 */ 760 if (sendalot) 761 sendalot = 0; 762 th->th_seq = htonl(p->rxmit); 763 p->rxmit += len; 764 tcpstat_pkt(tcps_sack_rexmits, tcps_sack_rexmit_bytes, len); 765 } 766 767 th->th_ack = htonl(tp->rcv_nxt); 768 if (optlen) { 769 memcpy(th + 1, opt, optlen); 770 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 771 } 772 #ifdef TCP_ECN 773 if (tcp_do_ecn) { 774 /* 775 * if we have received congestion experienced segs, 776 * set ECE bit. 777 */ 778 if (tp->t_flags & TF_RCVD_CE) { 779 flags |= TH_ECE; 780 tcpstat_inc(tcps_ecn_sndece); 781 } 782 if (!(tp->t_flags & TF_DISABLE_ECN)) { 783 /* 784 * if this is a SYN seg, set ECE and CWR. 785 * set only ECE for SYN-ACK if peer supports ECN. 786 */ 787 if ((flags & (TH_SYN|TH_ACK)) == TH_SYN) 788 flags |= (TH_ECE|TH_CWR); 789 else if ((tp->t_flags & TF_ECN_PERMIT) && 790 (flags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) 791 flags |= TH_ECE; 792 } 793 /* 794 * if we have reduced the congestion window, notify 795 * the peer by setting CWR bit. 796 */ 797 if ((tp->t_flags & TF_ECN_PERMIT) && 798 (tp->t_flags & TF_SEND_CWR)) { 799 flags |= TH_CWR; 800 tp->t_flags &= ~TF_SEND_CWR; 801 tcpstat_inc(tcps_ecn_sndcwr); 802 } 803 } 804 #endif 805 th->th_flags = flags; 806 807 /* 808 * Calculate receive window. Don't shrink window, 809 * but avoid silly window syndrome. 810 */ 811 if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg) 812 win = 0; 813 if (win > (long)TCP_MAXWIN << tp->rcv_scale) 814 win = (long)TCP_MAXWIN << tp->rcv_scale; 815 if (win < (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt)) 816 win = (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt); 817 if (flags & TH_RST) 818 win = 0; 819 th->th_win = htons((u_int16_t) (win>>tp->rcv_scale)); 820 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 821 u_int32_t urp = tp->snd_up - tp->snd_nxt; 822 if (urp > IP_MAXPACKET) 823 urp = IP_MAXPACKET; 824 th->th_urp = htons((u_int16_t)urp); 825 th->th_flags |= TH_URG; 826 } else 827 /* 828 * If no urgent pointer to send, then we pull 829 * the urgent pointer to the left edge of the send window 830 * so that it doesn't drift into the send window on sequence 831 * number wraparound. 832 */ 833 tp->snd_up = tp->snd_una; /* drag it along */ 834 835 #ifdef TCP_SIGNATURE 836 if (tp->t_flags & TF_SIGNATURE) { 837 int iphlen; 838 union sockaddr_union src, dst; 839 struct tdb *tdb; 840 841 bzero(&src, sizeof(union sockaddr_union)); 842 bzero(&dst, sizeof(union sockaddr_union)); 843 844 switch (tp->pf) { 845 case 0: /*default to PF_INET*/ 846 case AF_INET: 847 iphlen = sizeof(struct ip); 848 src.sa.sa_len = sizeof(struct sockaddr_in); 849 src.sa.sa_family = AF_INET; 850 src.sin.sin_addr = mtod(m, struct ip *)->ip_src; 851 dst.sa.sa_len = sizeof(struct sockaddr_in); 852 dst.sa.sa_family = AF_INET; 853 dst.sin.sin_addr = mtod(m, struct ip *)->ip_dst; 854 break; 855 #ifdef INET6 856 case AF_INET6: 857 iphlen = sizeof(struct ip6_hdr); 858 src.sa.sa_len = sizeof(struct sockaddr_in6); 859 src.sa.sa_family = AF_INET6; 860 src.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_src; 861 dst.sa.sa_len = sizeof(struct sockaddr_in6); 862 dst.sa.sa_family = AF_INET6; 863 dst.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst; 864 break; 865 #endif /* INET6 */ 866 } 867 868 tdb = gettdbbysrcdst(rtable_l2(tp->t_inpcb->inp_rtableid), 869 0, &src, &dst, IPPROTO_TCP); 870 if (tdb == NULL) { 871 m_freem(m); 872 return (EPERM); 873 } 874 875 if (tcp_signature(tdb, tp->pf, m, th, iphlen, 0, 876 mtod(m, caddr_t) + hdrlen - optlen + sigoff) < 0) { 877 m_freem(m); 878 return (EINVAL); 879 } 880 } 881 #endif /* TCP_SIGNATURE */ 882 883 /* Defer checksumming until later (ip_output() or hardware) */ 884 m->m_pkthdr.csum_flags |= M_TCP_CSUM_OUT; 885 886 /* 887 * In transmit state, time the transmission and arrange for 888 * the retransmit. In persist state, just set snd_max. 889 */ 890 if (tp->t_force == 0 || TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 891 tcp_seq startseq = tp->snd_nxt; 892 893 /* 894 * Advance snd_nxt over sequence space of this segment. 895 */ 896 if (flags & (TH_SYN|TH_FIN)) { 897 if (flags & TH_SYN) 898 tp->snd_nxt++; 899 if (flags & TH_FIN) { 900 tp->snd_nxt++; 901 tp->t_flags |= TF_SENTFIN; 902 } 903 } 904 if (tp->sack_enable) { 905 if (sack_rxmit && (p->rxmit != tp->snd_nxt)) { 906 goto timer; 907 } 908 } 909 tp->snd_nxt += len; 910 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 911 tp->snd_max = tp->snd_nxt; 912 /* 913 * Time this transmission if not a retransmission and 914 * not currently timing anything. 915 */ 916 if (tp->t_rtttime == 0) { 917 tp->t_rtttime = tcp_now; 918 tp->t_rtseq = startseq; 919 tcpstat_inc(tcps_segstimed); 920 } 921 } 922 923 /* 924 * Set retransmit timer if not currently set, 925 * and not doing an ack or a keep-alive probe. 926 * Initial value for retransmit timer is smoothed 927 * round-trip time + 2 * round-trip time variance. 928 * Initialize shift counter which is used for backoff 929 * of retransmit time. 930 */ 931 timer: 932 if (tp->sack_enable && sack_rxmit && 933 TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 934 tp->snd_nxt != tp->snd_max) { 935 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 936 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) { 937 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 938 tp->t_rxtshift = 0; 939 } 940 } 941 942 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 943 tp->snd_nxt != tp->snd_una) { 944 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 945 if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) { 946 TCP_TIMER_DISARM(tp, TCPT_PERSIST); 947 tp->t_rxtshift = 0; 948 } 949 } 950 951 if (len == 0 && so->so_snd.sb_cc && 952 TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && 953 TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 954 /* 955 * Avoid a situation where we do not set persist timer 956 * after a zero window condition. For example: 957 * 1) A -> B: packet with enough data to fill the window 958 * 2) B -> A: ACK for #1 + new data (0 window 959 * advertisement) 960 * 3) A -> B: ACK for #2, 0 len packet 961 * 962 * In this case, A will not activate the persist timer, 963 * because it chose to send a packet. Unless tcp_output 964 * is called for some other reason (delayed ack timer, 965 * another input packet from B, socket syscall), A will 966 * not send zero window probes. 967 * 968 * So, if you send a 0-length packet, but there is data 969 * in the socket buffer, and neither the rexmt or 970 * persist timer is already set, then activate the 971 * persist timer. 972 */ 973 tp->t_rxtshift = 0; 974 tcp_setpersist(tp); 975 } 976 } else 977 if (SEQ_GT(tp->snd_nxt + len, tp->snd_max)) 978 tp->snd_max = tp->snd_nxt + len; 979 980 tcp_update_sndspace(tp); 981 982 /* 983 * Trace. 984 */ 985 if (so->so_options & SO_DEBUG) 986 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, caddr_t), 0, 987 len); 988 989 /* 990 * Fill in IP length and desired time to live and 991 * send to IP level. There should be a better way 992 * to handle ttl and tos; we could keep them in 993 * the template, but need a way to checksum without them. 994 */ 995 996 #ifdef TCP_ECN 997 /* 998 * if peer is ECN capable, set the ECT bit in the IP header. 999 * but don't set ECT for a pure ack, a retransmit or a window probe. 1000 */ 1001 needect = 0; 1002 if (tcp_do_ecn && (tp->t_flags & TF_ECN_PERMIT)) { 1003 if (len == 0 || SEQ_LT(tp->snd_nxt, tp->snd_max) || 1004 (tp->t_force && len == 1)) { 1005 /* don't set ECT */ 1006 } else { 1007 needect = 1; 1008 tcpstat_inc(tcps_ecn_sndect); 1009 } 1010 } 1011 #endif 1012 1013 /* force routing table */ 1014 m->m_pkthdr.ph_rtableid = tp->t_inpcb->inp_rtableid; 1015 1016 #if NPF > 0 1017 m->m_pkthdr.pf.inp = tp->t_inpcb; 1018 #endif 1019 1020 switch (tp->pf) { 1021 case 0: /*default to PF_INET*/ 1022 case AF_INET: 1023 { 1024 struct ip *ip; 1025 1026 ip = mtod(m, struct ip *); 1027 ip->ip_len = htons(m->m_pkthdr.len); 1028 packetlen = m->m_pkthdr.len; 1029 ip->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl; 1030 ip->ip_tos = tp->t_inpcb->inp_ip.ip_tos; 1031 #ifdef TCP_ECN 1032 if (needect) 1033 ip->ip_tos |= IPTOS_ECN_ECT0; 1034 #endif 1035 } 1036 error = ip_output(m, tp->t_inpcb->inp_options, 1037 &tp->t_inpcb->inp_route, 1038 (ip_mtudisc ? IP_MTUDISC : 0), NULL, tp->t_inpcb, 0); 1039 break; 1040 #ifdef INET6 1041 case AF_INET6: 1042 { 1043 struct ip6_hdr *ip6; 1044 1045 ip6 = mtod(m, struct ip6_hdr *); 1046 ip6->ip6_plen = m->m_pkthdr.len - 1047 sizeof(struct ip6_hdr); 1048 packetlen = m->m_pkthdr.len; 1049 ip6->ip6_nxt = IPPROTO_TCP; 1050 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb); 1051 #ifdef TCP_ECN 1052 if (needect) 1053 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1054 #endif 1055 } 1056 error = ip6_output(m, tp->t_inpcb->inp_outputopts6, 1057 &tp->t_inpcb->inp_route6, 1058 0, NULL, tp->t_inpcb); 1059 break; 1060 #endif /* INET6 */ 1061 } 1062 1063 if (error) { 1064 out: 1065 if (error == ENOBUFS) { 1066 /* 1067 * If the interface queue is full, or IP cannot 1068 * get an mbuf, trigger TCP slow start. 1069 */ 1070 tp->snd_cwnd = tp->t_maxseg; 1071 return (0); 1072 } 1073 if (error == EMSGSIZE) { 1074 /* 1075 * ip_output() will have already fixed the route 1076 * for us. tcp_mtudisc() will, as its last action, 1077 * initiate retransmission, so it is important to 1078 * not do so here. 1079 */ 1080 tcp_mtudisc(tp->t_inpcb, -1); 1081 return (0); 1082 } 1083 if (error == EACCES) /* translate pf(4) error for userland */ 1084 error = EHOSTUNREACH; 1085 if ((error == EHOSTUNREACH || error == ENETDOWN) && 1086 TCPS_HAVERCVDSYN(tp->t_state)) { 1087 tp->t_softerror = error; 1088 return (0); 1089 } 1090 1091 /* Restart the delayed ACK timer, if necessary. */ 1092 if (tp->t_flags & TF_DELACK) 1093 TCP_RESTART_DELACK(tp); 1094 1095 return (error); 1096 } 1097 1098 if (packetlen > tp->t_pmtud_mtu_sent) 1099 tp->t_pmtud_mtu_sent = packetlen; 1100 1101 tcpstat_inc(tcps_sndtotal); 1102 if (tp->t_flags & TF_DELACK) 1103 tcpstat_inc(tcps_delack); 1104 1105 /* 1106 * Data sent (as far as we can tell). 1107 * If this advertises a larger window than any other segment, 1108 * then remember the size of the advertised window. 1109 * Any pending ACK has now been sent. 1110 */ 1111 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 1112 tp->rcv_adv = tp->rcv_nxt + win; 1113 tp->last_ack_sent = tp->rcv_nxt; 1114 tp->t_flags &= ~TF_ACKNOW; 1115 TCP_CLEAR_DELACK(tp); 1116 if (sendalot && --maxburst) 1117 goto again; 1118 return (0); 1119 } 1120 1121 void 1122 tcp_setpersist(struct tcpcb *tp) 1123 { 1124 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> (1 + TCP_RTT_BASE_SHIFT); 1125 int nticks; 1126 1127 if (TCP_TIMER_ISARMED(tp, TCPT_REXMT)) 1128 panic("tcp_output REXMT"); 1129 /* 1130 * Start/restart persistence timer. 1131 */ 1132 if (t < tp->t_rttmin) 1133 t = tp->t_rttmin; 1134 TCPT_RANGESET(nticks, t * tcp_backoff[tp->t_rxtshift], 1135 TCPTV_PERSMIN, TCPTV_PERSMAX); 1136 TCP_TIMER_ARM(tp, TCPT_PERSIST, nticks); 1137 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1138 tp->t_rxtshift++; 1139 } 1140