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sys/netinet/tcp_output.c
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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 struct rmxp_tao tao; 133 #ifdef INET6 134 struct ip6_hdr *ip6 = NULL; 135 int isipv6; 136 137 bzero(&tao, sizeof(tao)); 138 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 139 #endif 140 141 INP_LOCK_ASSERT(tp->t_inpcb); 142 143 /* 144 * Determine length of data that should be transmitted, 145 * and flags that will be used. 146 * If there is some data or critical controls (SYN, RST) 147 * to send, then transmit; otherwise, investigate further. 148 */ 149 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 150 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 151 /* 152 * We have been idle for "a while" and no acks are 153 * expected to clock out any data we send -- 154 * slow start to get ack "clock" running again. 155 * 156 * Set the slow-start flight size depending on whether 157 * this is a local network or not. 158 */ 159 int ss = ss_fltsz; 160 #ifdef INET6 161 if (isipv6) { 162 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 163 ss = ss_fltsz_local; 164 } else 165 #endif /* INET6 */ 166 if (in_localaddr(tp->t_inpcb->inp_faddr)) 167 ss = ss_fltsz_local; 168 tp->snd_cwnd = tp->t_maxseg * ss; 169 } 170 tp->t_flags &= ~TF_LASTIDLE; 171 if (idle) { 172 if (tp->t_flags & TF_MORETOCOME) { 173 tp->t_flags |= TF_LASTIDLE; 174 idle = 0; 175 } 176 } 177 again: 178 /* 179 * If we've recently taken a timeout, snd_max will be greater than 180 * snd_nxt. There may be SACK information that allows us to avoid 181 * resending already delivered data. Adjust snd_nxt accordingly. 182 */ 183 if (tp->sack_enable && SEQ_LT(tp->snd_nxt, tp->snd_max)) 184 tcp_sack_adjust(tp); 185 sendalot = 0; 186 off = tp->snd_nxt - tp->snd_una; 187 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 188 sendwin = min(sendwin, tp->snd_bwnd); 189 190 flags = tcp_outflags[tp->t_state]; 191 /* 192 * Send any SACK-generated retransmissions. If we're explicitly trying 193 * to send out new data (when sendalot is 1), bypass this function. 194 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 195 * we're replacing a (future) new transmission with a retransmission 196 * now, and we previously incremented snd_cwnd in tcp_input(). 197 */ 198 /* 199 * Still in sack recovery , reset rxmit flag to zero. 200 */ 201 sack_rxmit = 0; 202 sack_bytes_rxmt = 0; 203 len = 0; 204 p = NULL; 205 if (tp->sack_enable && IN_FASTRECOVERY(tp) && 206 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 207 long cwin; 208 209 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 210 if (cwin < 0) 211 cwin = 0; 212 /* Do not retransmit SACK segments beyond snd_recover */ 213 if (SEQ_GT(p->end, tp->snd_recover)) { 214 /* 215 * (At least) part of sack hole extends beyond 216 * snd_recover. Check to see if we can rexmit data 217 * for this hole. 218 */ 219 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 220 /* 221 * Can't rexmit any more data for this hole. 222 * That data will be rexmitted in the next 223 * sack recovery episode, when snd_recover 224 * moves past p->rxmit. 225 */ 226 p = NULL; 227 goto after_sack_rexmit; 228 } else 229 /* Can rexmit part of the current hole */ 230 len = ((long)ulmin(cwin, 231 tp->snd_recover - p->rxmit)); 232 } else 233 len = ((long)ulmin(cwin, p->end - p->rxmit)); 234 off = p->rxmit - tp->snd_una; 235 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 236 __func__, off)); 237 if (len > 0) { 238 sack_rxmit = 1; 239 sendalot = 1; 240 tcpstat.tcps_sack_rexmits++; 241 tcpstat.tcps_sack_rexmit_bytes += 242 min(len, tp->t_maxseg); 243 } 244 } 245 after_sack_rexmit: 246 /* 247 * Get standard flags, and add SYN or FIN if requested by 'hidden' 248 * state flags. 249 */ 250 if (tp->t_flags & TF_NEEDFIN) 251 flags |= TH_FIN; 252 if (tp->t_flags & TF_NEEDSYN) 253 flags |= TH_SYN; 254 255 SOCKBUF_LOCK(&so->so_snd); 256 /* 257 * If in persist timeout with window of 0, send 1 byte. 258 * Otherwise, if window is small but nonzero 259 * and timer expired, we will send what we can 260 * and go to transmit state. 261 */ 262 if (tp->t_force) { 263 if (sendwin == 0) { 264 /* 265 * If we still have some data to send, then 266 * clear the FIN bit. Usually this would 267 * happen below when it realizes that we 268 * aren't sending all the data. However, 269 * if we have exactly 1 byte of unsent data, 270 * then it won't clear the FIN bit below, 271 * and if we are in persist state, we wind 272 * up sending the packet without recording 273 * that we sent the FIN bit. 274 * 275 * We can't just blindly clear the FIN bit, 276 * because if we don't have any more data 277 * to send then the probe will be the FIN 278 * itself. 279 */ 280 if (off < so->so_snd.sb_cc) 281 flags &= ~TH_FIN; 282 sendwin = 1; 283 } else { 284 callout_stop(tp->tt_persist); 285 tp->t_rxtshift = 0; 286 } 287 } 288 289 /* 290 * If snd_nxt == snd_max and we have transmitted a FIN, the 291 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 292 * a negative length. This can also occur when TCP opens up 293 * its congestion window while receiving additional duplicate 294 * acks after fast-retransmit because TCP will reset snd_nxt 295 * to snd_max after the fast-retransmit. 296 * 297 * In the normal retransmit-FIN-only case, however, snd_nxt will 298 * be set to snd_una, the offset will be 0, and the length may 299 * wind up 0. 300 * 301 * If sack_rxmit is true we are retransmitting from the scoreboard 302 * in which case len is already set. 303 */ 304 if (sack_rxmit == 0) { 305 if (sack_bytes_rxmt == 0) 306 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 307 else { 308 long cwin; 309 310 /* 311 * We are inside of a SACK recovery episode and are 312 * sending new data, having retransmitted all the 313 * data possible in the scoreboard. 314 */ 315 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 316 - off); 317 /* 318 * Don't remove this (len > 0) check ! 319 * We explicitly check for len > 0 here (although it 320 * isn't really necessary), to work around a gcc 321 * optimization issue - to force gcc to compute 322 * len above. Without this check, the computation 323 * of len is bungled by the optimizer. 324 */ 325 if (len > 0) { 326 cwin = tp->snd_cwnd - 327 (tp->snd_nxt - tp->sack_newdata) - 328 sack_bytes_rxmt; 329 if (cwin < 0) 330 cwin = 0; 331 len = lmin(len, cwin); 332 } 333 } 334 } 335 336 /* 337 * Lop off SYN bit if it has already been sent. However, if this 338 * is SYN-SENT state and if segment contains data and if we don't 339 * know that foreign host supports TAO, suppress sending segment. 340 */ 341 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 342 flags &= ~TH_SYN; 343 off--, len++; 344 if (tcp_do_rfc1644) 345 tcp_hc_gettao(&tp->t_inpcb->inp_inc, &tao); 346 if (len > 0 && tp->t_state == TCPS_SYN_SENT && 347 tao.tao_ccsent == 0) 348 goto just_return; 349 } 350 351 /* 352 * Be careful not to send data and/or FIN on SYN segments 353 * in cases when no CC option will be sent. 354 * This measure is needed to prevent interoperability problems 355 * with not fully conformant TCP implementations. 356 */ 357 if ((flags & TH_SYN) && 358 ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || 359 ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { 360 len = 0; 361 flags &= ~TH_FIN; 362 } 363 364 if (len < 0) { 365 /* 366 * If FIN has been sent but not acked, 367 * but we haven't been called to retransmit, 368 * len will be < 0. Otherwise, window shrank 369 * after we sent into it. If window shrank to 0, 370 * cancel pending retransmit, pull snd_nxt back 371 * to (closed) window, and set the persist timer 372 * if it isn't already going. If the window didn't 373 * close completely, just wait for an ACK. 374 */ 375 len = 0; 376 if (sendwin == 0) { 377 callout_stop(tp->tt_rexmt); 378 tp->t_rxtshift = 0; 379 tp->snd_nxt = tp->snd_una; 380 if (!callout_active(tp->tt_persist)) 381 tcp_setpersist(tp); 382 } 383 } 384 385 /* 386 * len will be >= 0 after this point. Truncate to the maximum 387 * segment length and ensure that FIN is removed if the length 388 * no longer contains the last data byte. 389 */ 390 if (len > tp->t_maxseg) { 391 len = tp->t_maxseg; 392 sendalot = 1; 393 } 394 if (sack_rxmit) { 395 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 396 flags &= ~TH_FIN; 397 } else { 398 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 399 flags &= ~TH_FIN; 400 } 401 402 recwin = sbspace(&so->so_rcv); 403 404 /* 405 * Sender silly window avoidance. We transmit under the following 406 * conditions when len is non-zero: 407 * 408 * - We have a full segment 409 * - This is the last buffer in a write()/send() and we are 410 * either idle or running NODELAY 411 * - we've timed out (e.g. persist timer) 412 * - we have more then 1/2 the maximum send window's worth of 413 * data (receiver may be limited the window size) 414 * - we need to retransmit 415 */ 416 if (len) { 417 if (len == tp->t_maxseg) 418 goto send; 419 /* 420 * NOTE! on localhost connections an 'ack' from the remote 421 * end may occur synchronously with the output and cause 422 * us to flush a buffer queued with moretocome. XXX 423 * 424 * note: the len + off check is almost certainly unnecessary. 425 */ 426 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 427 (idle || (tp->t_flags & TF_NODELAY)) && 428 len + off >= so->so_snd.sb_cc && 429 (tp->t_flags & TF_NOPUSH) == 0) { 430 goto send; 431 } 432 if (tp->t_force) /* typ. timeout case */ 433 goto send; 434 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 435 goto send; 436 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 437 goto send; 438 if (sack_rxmit) 439 goto send; 440 } 441 442 /* 443 * Compare available window to amount of window 444 * known to peer (as advertised window less 445 * next expected input). If the difference is at least two 446 * max size segments, or at least 50% of the maximum possible 447 * window, then want to send a window update to peer. 448 * Skip this if the connection is in T/TCP half-open state. 449 */ 450 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN)) { 451 /* 452 * "adv" is the amount we can increase the window, 453 * taking into account that we are limited by 454 * TCP_MAXWIN << tp->rcv_scale. 455 */ 456 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 457 (tp->rcv_adv - tp->rcv_nxt); 458 459 if (adv >= (long) (2 * tp->t_maxseg)) 460 goto send; 461 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 462 goto send; 463 } 464 465 /* 466 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 467 * is also a catch-all for the retransmit timer timeout case. 468 */ 469 if (tp->t_flags & TF_ACKNOW) 470 goto send; 471 if ((flags & TH_RST) || 472 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 473 goto send; 474 if (SEQ_GT(tp->snd_up, tp->snd_una)) 475 goto send; 476 /* 477 * If our state indicates that FIN should be sent 478 * and we have not yet done so, then we need to send. 479 */ 480 if (flags & TH_FIN && 481 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 482 goto send; 483 /* 484 * In SACK, it is possible for tcp_output to fail to send a segment 485 * after the retransmission timer has been turned off. Make sure 486 * that the retransmission timer is set. 487 */ 488 if (tp->sack_enable && SEQ_GT(tp->snd_max, tp->snd_una) && 489 !callout_active(tp->tt_rexmt) && 490 !callout_active(tp->tt_persist)) { 491 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 492 tcp_timer_rexmt, tp); 493 goto just_return; 494 } 495 /* 496 * TCP window updates are not reliable, rather a polling protocol 497 * using ``persist'' packets is used to insure receipt of window 498 * updates. The three ``states'' for the output side are: 499 * idle not doing retransmits or persists 500 * persisting to move a small or zero window 501 * (re)transmitting and thereby not persisting 502 * 503 * callout_active(tp->tt_persist) 504 * is true when we are in persist state. 505 * tp->t_force 506 * is set when we are called to send a persist packet. 507 * callout_active(tp->tt_rexmt) 508 * is set when we are retransmitting 509 * The output side is idle when both timers are zero. 510 * 511 * If send window is too small, there is data to transmit, and no 512 * retransmit or persist is pending, then go to persist state. 513 * If nothing happens soon, send when timer expires: 514 * if window is nonzero, transmit what we can, 515 * otherwise force out a byte. 516 */ 517 if (so->so_snd.sb_cc && !callout_active(tp->tt_rexmt) && 518 !callout_active(tp->tt_persist)) { 519 tp->t_rxtshift = 0; 520 tcp_setpersist(tp); 521 } 522 523 /* 524 * No reason to send a segment, just return. 525 */ 526 just_return: 527 SOCKBUF_UNLOCK(&so->so_snd); 528 return (0); 529 530 send: 531 SOCKBUF_LOCK_ASSERT(&so->so_snd); 532 /* 533 * Before ESTABLISHED, force sending of initial options 534 * unless TCP set not to do any options. 535 * NOTE: we assume that the IP/TCP header plus TCP options 536 * always fit in a single mbuf, leaving room for a maximum 537 * link header, i.e. 538 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 539 */ 540 optlen = 0; 541 #ifdef INET6 542 if (isipv6) 543 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 544 else 545 #endif 546 hdrlen = sizeof (struct tcpiphdr); 547 if (flags & TH_SYN) { 548 tp->snd_nxt = tp->iss; 549 if ((tp->t_flags & TF_NOOPT) == 0) { 550 u_short mss; 551 552 opt[0] = TCPOPT_MAXSEG; 553 opt[1] = TCPOLEN_MAXSEG; 554 mss = htons((u_short) tcp_mssopt(&tp->t_inpcb->inp_inc)); 555 (void)memcpy(opt + 2, &mss, sizeof(mss)); 556 optlen = TCPOLEN_MAXSEG; 557 558 /* 559 * If this is the first SYN of connection (not a SYN 560 * ACK), include SACK_PERMIT_HDR option. If this is a 561 * SYN ACK, include SACK_PERMIT_HDR option if peer has 562 * already done so. This is only for active connect, 563 * since the syncache takes care of the passive connect. 564 */ 565 if (tp->sack_enable && ((flags & TH_ACK) == 0 || 566 (tp->t_flags & TF_SACK_PERMIT))) { 567 *((u_int32_t *) (opt + optlen)) = 568 htonl(TCPOPT_SACK_PERMIT_HDR); 569 optlen += 4; 570 } 571 if ((tp->t_flags & TF_REQ_SCALE) && 572 ((flags & TH_ACK) == 0 || 573 (tp->t_flags & TF_RCVD_SCALE))) { 574 *((u_int32_t *)(opt + optlen)) = htonl( 575 TCPOPT_NOP << 24 | 576 TCPOPT_WINDOW << 16 | 577 TCPOLEN_WINDOW << 8 | 578 tp->request_r_scale); 579 optlen += 4; 580 } 581 } 582 } 583 584 /* 585 * Send a timestamp and echo-reply if this is a SYN and our side 586 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side 587 * and our peer have sent timestamps in our SYN's. 588 */ 589 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 590 (flags & TH_RST) == 0 && 591 ((flags & TH_ACK) == 0 || 592 (tp->t_flags & TF_RCVD_TSTMP))) { 593 u_int32_t *lp = (u_int32_t *)(opt + optlen); 594 595 /* Form timestamp option as shown in appendix A of RFC 1323. */ 596 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 597 *lp++ = htonl(ticks); 598 *lp = htonl(tp->ts_recent); 599 optlen += TCPOLEN_TSTAMP_APPA; 600 } 601 602 /* 603 * Send SACKs if necessary. This should be the last option processed. 604 * Only as many SACKs are sent as are permitted by the maximum options 605 * size. No more than three SACKs are sent. 606 */ 607 if (tp->sack_enable && tp->t_state == TCPS_ESTABLISHED && 608 (tp->t_flags & (TF_SACK_PERMIT|TF_NOOPT)) == TF_SACK_PERMIT && 609 tp->rcv_numsacks) { 610 u_int32_t *lp = (u_int32_t *)(opt + optlen); 611 u_int32_t *olp = lp++; 612 int count = 0; /* actual number of SACKs inserted */ 613 int maxsack = (MAX_TCPOPTLEN - (optlen + 4))/TCPOLEN_SACK; 614 615 tcpstat.tcps_sack_send_blocks++; 616 maxsack = min(maxsack, TCP_MAX_SACK); 617 for (i = 0; (i < tp->rcv_numsacks && count < maxsack); i++) { 618 struct sackblk sack = tp->sackblks[i]; 619 if (sack.start == 0 && sack.end == 0) 620 continue; 621 *lp++ = htonl(sack.start); 622 *lp++ = htonl(sack.end); 623 count++; 624 } 625 *olp = htonl(TCPOPT_SACK_HDR|(TCPOLEN_SACK*count+2)); 626 optlen += TCPOLEN_SACK*count + 4; /* including leading NOPs */ 627 } 628 /* 629 * Send `CC-family' options if our side wants to use them (TF_REQ_CC), 630 * options are allowed (!TF_NOOPT) and it's not a RST. 631 */ 632 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 633 (flags & TH_RST) == 0) { 634 switch (flags & (TH_SYN|TH_ACK)) { 635 /* 636 * This is a normal ACK, send CC if we received CC before 637 * from our peer. 638 */ 639 case TH_ACK: 640 if (!(tp->t_flags & TF_RCVD_CC)) 641 break; 642 /*FALLTHROUGH*/ 643 644 /* 645 * We can only get here in T/TCP's SYN_SENT* state, when 646 * we're a sending a non-SYN segment without waiting for 647 * the ACK of our SYN. A check above assures that we only 648 * do this if our peer understands T/TCP. 649 */ 650 case 0: 651 opt[optlen++] = TCPOPT_NOP; 652 opt[optlen++] = TCPOPT_NOP; 653 opt[optlen++] = TCPOPT_CC; 654 opt[optlen++] = TCPOLEN_CC; 655 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 656 657 optlen += 4; 658 break; 659 660 /* 661 * This is our initial SYN, check whether we have to use 662 * CC or CC.new. 663 */ 664 case TH_SYN: 665 opt[optlen++] = TCPOPT_NOP; 666 opt[optlen++] = TCPOPT_NOP; 667 opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? 668 TCPOPT_CCNEW : TCPOPT_CC; 669 opt[optlen++] = TCPOLEN_CC; 670 *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); 671 optlen += 4; 672 break; 673 674 /* 675 * This is a SYN,ACK; send CC and CC.echo if we received 676 * CC from our peer. 677 */ 678 case (TH_SYN|TH_ACK): 679 if (tp->t_flags & TF_RCVD_CC) { 680 opt[optlen++] = TCPOPT_NOP; 681 opt[optlen++] = TCPOPT_NOP; 682 opt[optlen++] = TCPOPT_CC; 683 opt[optlen++] = TCPOLEN_CC; 684 *(u_int32_t *)&opt[optlen] = 685 htonl(tp->cc_send); 686 optlen += 4; 687 opt[optlen++] = TCPOPT_NOP; 688 opt[optlen++] = TCPOPT_NOP; 689 opt[optlen++] = TCPOPT_CCECHO; 690 opt[optlen++] = TCPOLEN_CC; 691 *(u_int32_t *)&opt[optlen] = 692 htonl(tp->cc_recv); 693 optlen += 4; 694 } 695 break; 696 } 697 } 698 699 #ifdef TCP_SIGNATURE 700 #ifdef INET6 701 if (!isipv6) 702 #endif 703 if (tp->t_flags & TF_SIGNATURE) { 704 int i; 705 u_char *bp; 706 707 /* Initialize TCP-MD5 option (RFC2385) */ 708 bp = (u_char *)opt + optlen; 709 *bp++ = TCPOPT_SIGNATURE; 710 *bp++ = TCPOLEN_SIGNATURE; 711 sigoff = optlen + 2; 712 for (i = 0; i < TCP_SIGLEN; i++) 713 *bp++ = 0; 714 optlen += TCPOLEN_SIGNATURE; 715 716 /* Terminate options list and maintain 32-bit alignment. */ 717 *bp++ = TCPOPT_NOP; 718 *bp++ = TCPOPT_EOL; 719 optlen += 2; 720 } 721 #endif /* TCP_SIGNATURE */ 722 723 hdrlen += optlen; 724 725 #ifdef INET6 726 if (isipv6) 727 ipoptlen = ip6_optlen(tp->t_inpcb); 728 else 729 #endif 730 if (tp->t_inpcb->inp_options) 731 ipoptlen = tp->t_inpcb->inp_options->m_len - 732 offsetof(struct ipoption, ipopt_list); 733 else 734 ipoptlen = 0; 735 #ifdef IPSEC 736 ipoptlen += ipsec_hdrsiz_tcp(tp); 737 #endif 738 739 /* 740 * Adjust data length if insertion of options will 741 * bump the packet length beyond the t_maxopd length. 742 * Clear the FIN bit because we cut off the tail of 743 * the segment. 744 */ 745 if (len + optlen + ipoptlen > tp->t_maxopd) { 746 /* 747 * If there is still more to send, don't close the connection. 748 */ 749 flags &= ~TH_FIN; 750 len = tp->t_maxopd - optlen - ipoptlen; 751 sendalot = 1; 752 } 753 754 /*#ifdef DIAGNOSTIC*/ 755 #ifdef INET6 756 if (max_linkhdr + hdrlen > MCLBYTES) 757 #else 758 if (max_linkhdr + hdrlen > MHLEN) 759 #endif 760 panic("tcphdr too big"); 761 /*#endif*/ 762 763 /* 764 * Grab a header mbuf, attaching a copy of data to 765 * be transmitted, and initialize the header from 766 * the template for sends on this connection. 767 */ 768 if (len) { 769 if (tp->t_force && len == 1) 770 tcpstat.tcps_sndprobe++; 771 else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { 772 tcpstat.tcps_sndrexmitpack++; 773 tcpstat.tcps_sndrexmitbyte += len; 774 } else { 775 tcpstat.tcps_sndpack++; 776 tcpstat.tcps_sndbyte += len; 777 } 778 #ifdef notyet 779 if ((m = m_copypack(so->so_snd.sb_mb, off, 780 (int)len, max_linkhdr + hdrlen)) == 0) { 781 SOCKBUF_UNLOCK(&so->so_snd); 782 error = ENOBUFS; 783 goto out; 784 } 785 /* 786 * m_copypack left space for our hdr; use it. 787 */ 788 m->m_len += hdrlen; 789 m->m_data -= hdrlen; 790 #else 791 MGETHDR(m, M_DONTWAIT, MT_HEADER); 792 if (m == NULL) { 793 SOCKBUF_UNLOCK(&so->so_snd); 794 error = ENOBUFS; 795 goto out; 796 } 797 #ifdef INET6 798 if (MHLEN < hdrlen + max_linkhdr) { 799 MCLGET(m, M_DONTWAIT); 800 if ((m->m_flags & M_EXT) == 0) { 801 SOCKBUF_UNLOCK(&so->so_snd); 802 m_freem(m); 803 error = ENOBUFS; 804 goto out; 805 } 806 } 807 #endif 808 m->m_data += max_linkhdr; 809 m->m_len = hdrlen; 810 if (len <= MHLEN - hdrlen - max_linkhdr) { 811 m_copydata(so->so_snd.sb_mb, off, (int) len, 812 mtod(m, caddr_t) + hdrlen); 813 m->m_len += len; 814 } else { 815 m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); 816 if (m->m_next == 0) { 817 SOCKBUF_UNLOCK(&so->so_snd); 818 (void) m_free(m); 819 error = ENOBUFS; 820 goto out; 821 } 822 } 823 #endif 824 /* 825 * If we're sending everything we've got, set PUSH. 826 * (This will keep happy those implementations which only 827 * give data to the user when a buffer fills or 828 * a PUSH comes in.) 829 */ 830 if (off + len == so->so_snd.sb_cc) 831 flags |= TH_PUSH; 832 SOCKBUF_UNLOCK(&so->so_snd); 833 } else { 834 SOCKBUF_UNLOCK(&so->so_snd); 835 if (tp->t_flags & TF_ACKNOW) 836 tcpstat.tcps_sndacks++; 837 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 838 tcpstat.tcps_sndctrl++; 839 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 840 tcpstat.tcps_sndurg++; 841 else 842 tcpstat.tcps_sndwinup++; 843 844 MGETHDR(m, M_DONTWAIT, MT_HEADER); 845 if (m == NULL) { 846 error = ENOBUFS; 847 goto out; 848 } 849 #ifdef INET6 850 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 851 MHLEN >= hdrlen) { 852 MH_ALIGN(m, hdrlen); 853 } else 854 #endif 855 m->m_data += max_linkhdr; 856 m->m_len = hdrlen; 857 } 858 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 859 m->m_pkthdr.rcvif = (struct ifnet *)0; 860 #ifdef MAC 861 mac_create_mbuf_from_inpcb(tp->t_inpcb, m); 862 #endif 863 #ifdef INET6 864 if (isipv6) { 865 ip6 = mtod(m, struct ip6_hdr *); 866 th = (struct tcphdr *)(ip6 + 1); 867 tcpip_fillheaders(tp->t_inpcb, ip6, th); 868 } else 869 #endif /* INET6 */ 870 { 871 ip = mtod(m, struct ip *); 872 ipov = (struct ipovly *)ip; 873 th = (struct tcphdr *)(ip + 1); 874 tcpip_fillheaders(tp->t_inpcb, ip, th); 875 } 876 877 /* 878 * Fill in fields, remembering maximum advertised 879 * window for use in delaying messages about window sizes. 880 * If resending a FIN, be sure not to use a new sequence number. 881 */ 882 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 883 tp->snd_nxt == tp->snd_max) 884 tp->snd_nxt--; 885 /* 886 * If we are doing retransmissions, then snd_nxt will 887 * not reflect the first unsent octet. For ACK only 888 * packets, we do not want the sequence number of the 889 * retransmitted packet, we want the sequence number 890 * of the next unsent octet. So, if there is no data 891 * (and no SYN or FIN), use snd_max instead of snd_nxt 892 * when filling in ti_seq. But if we are in persist 893 * state, snd_max might reflect one byte beyond the 894 * right edge of the window, so use snd_nxt in that 895 * case, since we know we aren't doing a retransmission. 896 * (retransmit and persist are mutually exclusive...) 897 */ 898 if (sack_rxmit == 0) { 899 if (len || (flags & (TH_SYN|TH_FIN)) 900 || callout_active(tp->tt_persist)) 901 th->th_seq = htonl(tp->snd_nxt); 902 else 903 th->th_seq = htonl(tp->snd_max); 904 } else { 905 th->th_seq = htonl(p->rxmit); 906 p->rxmit += len; 907 } 908 th->th_ack = htonl(tp->rcv_nxt); 909 if (optlen) { 910 bcopy(opt, th + 1, optlen); 911 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 912 } 913 th->th_flags = flags; 914 /* 915 * Calculate receive window. Don't shrink window, 916 * but avoid silly window syndrome. 917 */ 918 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 919 recwin < (long)tp->t_maxseg) 920 recwin = 0; 921 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 922 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 923 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 924 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 925 th->th_win = htons((u_short) (recwin >> tp->rcv_scale)); 926 927 928 /* 929 * Adjust the RXWIN0SENT flag - indicate that we have advertised 930 * a 0 window. This may cause the remote transmitter to stall. This 931 * flag tells soreceive() to disable delayed acknowledgements when 932 * draining the buffer. This can occur if the receiver is attempting 933 * to read more data then can be buffered prior to transmitting on 934 * the connection. 935 */ 936 if (recwin == 0) 937 tp->t_flags |= TF_RXWIN0SENT; 938 else 939 tp->t_flags &= ~TF_RXWIN0SENT; 940 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 941 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 942 th->th_flags |= TH_URG; 943 } else 944 /* 945 * If no urgent pointer to send, then we pull 946 * the urgent pointer to the left edge of the send window 947 * so that it doesn't drift into the send window on sequence 948 * number wraparound. 949 */ 950 tp->snd_up = tp->snd_una; /* drag it along */ 951 952 #ifdef TCP_SIGNATURE 953 #ifdef INET6 954 if (!isipv6) 955 #endif 956 if (tp->t_flags & TF_SIGNATURE) 957 tcp_signature_compute(m, sizeof(struct ip), len, optlen, 958 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 959 #endif 960 961 /* 962 * Put TCP length in extended header, and then 963 * checksum extended header and data. 964 */ 965 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 966 #ifdef INET6 967 if (isipv6) 968 /* 969 * ip6_plen is not need to be filled now, and will be filled 970 * in ip6_output. 971 */ 972 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 973 sizeof(struct tcphdr) + optlen + len); 974 else 975 #endif /* INET6 */ 976 { 977 m->m_pkthdr.csum_flags = CSUM_TCP; 978 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 979 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 980 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 981 982 /* IP version must be set here for ipv4/ipv6 checking later */ 983 KASSERT(ip->ip_v == IPVERSION, 984 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 985 } 986 987 /* 988 * In transmit state, time the transmission and arrange for 989 * the retransmit. In persist state, just set snd_max. 990 */ 991 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 992 tcp_seq startseq = tp->snd_nxt; 993 994 /* 995 * Advance snd_nxt over sequence space of this segment. 996 */ 997 if (flags & (TH_SYN|TH_FIN)) { 998 if (flags & TH_SYN) 999 tp->snd_nxt++; 1000 if (flags & TH_FIN) { 1001 tp->snd_nxt++; 1002 tp->t_flags |= TF_SENTFIN; 1003 } 1004 } 1005 if (sack_rxmit) 1006 goto timer; 1007 tp->snd_nxt += len; 1008 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1009 tp->snd_max = tp->snd_nxt; 1010 /* 1011 * Time this transmission if not a retransmission and 1012 * not currently timing anything. 1013 */ 1014 if (tp->t_rtttime == 0) { 1015 tp->t_rtttime = ticks; 1016 tp->t_rtseq = startseq; 1017 tcpstat.tcps_segstimed++; 1018 } 1019 } 1020 1021 /* 1022 * Set retransmit timer if not currently set, 1023 * and not doing a pure ack or a keep-alive probe. 1024 * Initial value for retransmit timer is smoothed 1025 * round-trip time + 2 * round-trip time variance. 1026 * Initialize shift counter which is used for backoff 1027 * of retransmit time. 1028 */ 1029 timer: 1030 if (!callout_active(tp->tt_rexmt) && 1031 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1032 (tp->snd_nxt != tp->snd_una))) { 1033 if (callout_active(tp->tt_persist)) { 1034 callout_stop(tp->tt_persist); 1035 tp->t_rxtshift = 0; 1036 } 1037 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 1038 tcp_timer_rexmt, tp); 1039 } 1040 } else { 1041 /* 1042 * Persist case, update snd_max but since we are in 1043 * persist mode (no window) we do not update snd_nxt. 1044 */ 1045 int xlen = len; 1046 if (flags & TH_SYN) 1047 ++xlen; 1048 if (flags & TH_FIN) { 1049 ++xlen; 1050 tp->t_flags |= TF_SENTFIN; 1051 } 1052 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1053 tp->snd_max = tp->snd_nxt + len; 1054 } 1055 1056 #ifdef TCPDEBUG 1057 /* 1058 * Trace. 1059 */ 1060 if (so->so_options & SO_DEBUG) { 1061 u_short save = 0; 1062 #ifdef INET6 1063 if (!isipv6) 1064 #endif 1065 { 1066 save = ipov->ih_len; 1067 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1068 } 1069 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1070 #ifdef INET6 1071 if (!isipv6) 1072 #endif 1073 ipov->ih_len = save; 1074 } 1075 #endif 1076 1077 /* 1078 * Fill in IP length and desired time to live and 1079 * send to IP level. There should be a better way 1080 * to handle ttl and tos; we could keep them in 1081 * the template, but need a way to checksum without them. 1082 */ 1083 /* 1084 * m->m_pkthdr.len should have been set before cksum calcuration, 1085 * because in6_cksum() need it. 1086 */ 1087 #ifdef INET6 1088 if (isipv6) { 1089 /* 1090 * we separately set hoplimit for every segment, since the 1091 * user might want to change the value via setsockopt. 1092 * Also, desired default hop limit might be changed via 1093 * Neighbor Discovery. 1094 */ 1095 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1096 1097 /* TODO: IPv6 IP6TOS_ECT bit on */ 1098 error = ip6_output(m, 1099 tp->t_inpcb->in6p_outputopts, NULL, 1100 (so->so_options & SO_DONTROUTE), NULL, NULL, 1101 tp->t_inpcb); 1102 } else 1103 #endif /* INET6 */ 1104 { 1105 ip->ip_len = m->m_pkthdr.len; 1106 #ifdef INET6 1107 if (INP_CHECK_SOCKAF(so, AF_INET6)) 1108 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1109 #endif /* INET6 */ 1110 /* 1111 * If we do path MTU discovery, then we set DF on every packet. 1112 * This might not be the best thing to do according to RFC3390 1113 * Section 2. However the tcp hostcache migitates the problem 1114 * so it affects only the first tcp connection with a host. 1115 */ 1116 if (path_mtu_discovery) 1117 ip->ip_off |= IP_DF; 1118 1119 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1120 (so->so_options & SO_DONTROUTE), 0, tp->t_inpcb); 1121 } 1122 if (error) { 1123 1124 /* 1125 * We know that the packet was lost, so back out the 1126 * sequence number advance, if any. 1127 */ 1128 if (tp->t_force == 0 || !callout_active(tp->tt_persist)) { 1129 /* 1130 * No need to check for TH_FIN here because 1131 * the TF_SENTFIN flag handles that case. 1132 */ 1133 if ((flags & TH_SYN) == 0) { 1134 if (sack_rxmit) 1135 p->rxmit -= len; 1136 else 1137 tp->snd_nxt -= len; 1138 } 1139 } 1140 1141 out: 1142 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1143 if (error == ENOBUFS) { 1144 if (!callout_active(tp->tt_rexmt) && 1145 !callout_active(tp->tt_persist)) 1146 callout_reset(tp->tt_rexmt, tp->t_rxtcur, 1147 tcp_timer_rexmt, tp); 1148 tp->snd_cwnd = tp->t_maxseg; 1149 return (0); 1150 } 1151 if (error == EMSGSIZE) { 1152 /* 1153 * ip_output() will have already fixed the route 1154 * for us. tcp_mtudisc() will, as its last action, 1155 * initiate retransmission, so it is important to 1156 * not do so here. 1157 */ 1158 tcp_mtudisc(tp->t_inpcb, 0); 1159 return 0; 1160 } 1161 if ((error == EHOSTUNREACH || error == ENETDOWN) 1162 && TCPS_HAVERCVDSYN(tp->t_state)) { 1163 tp->t_softerror = error; 1164 return (0); 1165 } 1166 return (error); 1167 } 1168 tcpstat.tcps_sndtotal++; 1169 1170 /* 1171 * Data sent (as far as we can tell). 1172 * If this advertises a larger window than any other segment, 1173 * then remember the size of the advertised window. 1174 * Any pending ACK has now been sent. 1175 */ 1176 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1177 tp->rcv_adv = tp->rcv_nxt + recwin; 1178 tp->last_ack_sent = tp->rcv_nxt; 1179 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1180 if (callout_active(tp->tt_delack)) 1181 callout_stop(tp->tt_delack); 1182 #if 0 1183 /* 1184 * This completely breaks TCP if newreno is turned on. What happens 1185 * is that if delayed-acks are turned on on the receiver, this code 1186 * on the transmitter effectively destroys the TCP window, forcing 1187 * it to four packets (1.5Kx4 = 6K window). 1188 */ 1189 if (sendalot && (!tcp_do_newreno || --maxburst)) 1190 goto again; 1191 #endif 1192 if (sendalot) 1193 goto again; 1194 return (0); 1195 } 1196 1197 void 1198 tcp_setpersist(tp) 1199 register struct tcpcb *tp; 1200 { 1201 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1202 int tt; 1203 1204 if (callout_active(tp->tt_rexmt)) 1205 panic("tcp_setpersist: retransmit pending"); 1206 /* 1207 * Start/restart persistance timer. 1208 */ 1209 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1210 TCPTV_PERSMIN, TCPTV_PERSMAX); 1211 callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); 1212 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1213 tp->t_rxtshift++; 1214 }
Cache object: 88426c9e85896cf0c6ff0e78b0cb32db
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