Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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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 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_mac.h" 39 #include "opt_tcpdebug.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/domain.h> 44 #include <sys/kernel.h> 45 #include <sys/lock.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 #include <netinet/ip_options.h> 61 #ifdef INET6 62 #include <netinet6/in6_pcb.h> 63 #include <netinet/ip6.h> 64 #include <netinet6/ip6_var.h> 65 #endif 66 #include <netinet/tcp.h> 67 #define TCPOUTFLAGS 68 #include <netinet/tcp_fsm.h> 69 #include <netinet/tcp_seq.h> 70 #include <netinet/tcp_timer.h> 71 #include <netinet/tcp_var.h> 72 #include <netinet/tcpip.h> 73 #ifdef TCPDEBUG 74 #include <netinet/tcp_debug.h> 75 #endif 76 77 #ifdef IPSEC 78 #include <netipsec/ipsec.h> 79 #endif /*IPSEC*/ 80 81 #include <machine/in_cksum.h> 82 83 #include <security/mac/mac_framework.h> 84 85 #ifdef notyet 86 extern struct mbuf *m_copypack(); 87 #endif 88 89 int path_mtu_discovery = 1; 90 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 91 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 92 93 int ss_fltsz = 1; 94 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 95 &ss_fltsz, 1, "Slow start flight size"); 96 97 int ss_fltsz_local = 4; 98 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 99 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 100 101 int tcp_do_newreno = 1; 102 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, 103 &tcp_do_newreno, 0, "Enable NewReno Algorithms"); 104 105 int tcp_do_tso = 1; 106 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 107 &tcp_do_tso, 0, "Enable TCP Segmentation Offload"); 108 109 int tcp_do_autosndbuf = 1; 110 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 111 &tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing"); 112 113 int tcp_autosndbuf_inc = 8*1024; 114 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 115 &tcp_autosndbuf_inc, 0, "Incrementor step size of automatic send buffer"); 116 117 int tcp_autosndbuf_max = 256*1024; 118 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 119 &tcp_autosndbuf_max, 0, "Max size of automatic send buffer"); 120 121 122 /* 123 * Tcp output routine: figure out what should be sent and send it. 124 */ 125 int 126 tcp_output(struct tcpcb *tp) 127 { 128 struct socket *so = tp->t_inpcb->inp_socket; 129 long len, recwin, sendwin; 130 int off, flags, error, rw; 131 struct mbuf *m; 132 struct ip *ip = NULL; 133 struct ipovly *ipov = NULL; 134 struct tcphdr *th; 135 u_char opt[TCP_MAXOLEN]; 136 unsigned ipoptlen, optlen, hdrlen; 137 #ifdef IPSEC 138 unsigned ipsec_optlen = 0; 139 #endif 140 int idle, sendalot; 141 int sack_rxmit, sack_bytes_rxmt; 142 struct sackhole *p; 143 int tso; 144 struct tcpopt to; 145 #if 0 146 int maxburst = TCP_MAXBURST; 147 #endif 148 #ifdef INET6 149 struct ip6_hdr *ip6 = NULL; 150 int isipv6; 151 152 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 153 #endif 154 155 INP_WLOCK_ASSERT(tp->t_inpcb); 156 157 /* 158 * Determine length of data that should be transmitted, 159 * and flags that will be used. 160 * If there is some data or critical controls (SYN, RST) 161 * to send, then transmit; otherwise, investigate further. 162 */ 163 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 164 if (idle && (ticks - (int)tp->t_rcvtime) >= tp->t_rxtcur) { 165 /* 166 * If we've been idle for more than one retransmit 167 * timeout the old congestion window is no longer 168 * current and we have to reduce it to the restart 169 * window before we can transmit again. 170 * 171 * The restart window is the initial window or the last 172 * CWND, whichever is smaller. 173 * 174 * This is done to prevent us from flooding the path with 175 * a full CWND at wirespeed, overloading router and switch 176 * buffers along the way. 177 * 178 * See RFC5681 Section 4.1. "Restarting Idle Connections". 179 */ 180 if (tcp_do_rfc3390) 181 rw = min(4 * tp->t_maxseg, 182 max(2 * tp->t_maxseg, 4380)); 183 #ifdef INET6 184 else if ((isipv6 ? in6_localaddr(&tp->t_inpcb->in6p_faddr) : 185 in_localaddr(tp->t_inpcb->inp_faddr))) 186 #else 187 else if (in_localaddr(tp->t_inpcb->inp_faddr)) 188 #endif 189 rw = ss_fltsz_local * tp->t_maxseg; 190 else 191 rw = ss_fltsz * tp->t_maxseg; 192 193 tp->snd_cwnd = min(rw, tp->snd_cwnd); 194 } 195 tp->t_flags &= ~TF_LASTIDLE; 196 if (idle) { 197 if (tp->t_flags & TF_MORETOCOME) { 198 tp->t_flags |= TF_LASTIDLE; 199 idle = 0; 200 } 201 } 202 again: 203 /* 204 * If we've recently taken a timeout, snd_max will be greater than 205 * snd_nxt. There may be SACK information that allows us to avoid 206 * resending already delivered data. Adjust snd_nxt accordingly. 207 */ 208 if ((tp->t_flags & TF_SACK_PERMIT) && 209 SEQ_LT(tp->snd_nxt, tp->snd_max)) 210 tcp_sack_adjust(tp); 211 sendalot = 0; 212 tso = 0; 213 off = tp->snd_nxt - tp->snd_una; 214 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 215 sendwin = min(sendwin, tp->snd_bwnd); 216 217 flags = tcp_outflags[tp->t_state]; 218 /* 219 * Send any SACK-generated retransmissions. If we're explicitly trying 220 * to send out new data (when sendalot is 1), bypass this function. 221 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 222 * we're replacing a (future) new transmission with a retransmission 223 * now, and we previously incremented snd_cwnd in tcp_input(). 224 */ 225 /* 226 * Still in sack recovery , reset rxmit flag to zero. 227 */ 228 sack_rxmit = 0; 229 sack_bytes_rxmt = 0; 230 len = 0; 231 p = NULL; 232 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp) && 233 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 234 long cwin; 235 236 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 237 if (cwin < 0) 238 cwin = 0; 239 /* Do not retransmit SACK segments beyond snd_recover */ 240 if (SEQ_GT(p->end, tp->snd_recover)) { 241 /* 242 * (At least) part of sack hole extends beyond 243 * snd_recover. Check to see if we can rexmit data 244 * for this hole. 245 */ 246 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 247 /* 248 * Can't rexmit any more data for this hole. 249 * That data will be rexmitted in the next 250 * sack recovery episode, when snd_recover 251 * moves past p->rxmit. 252 */ 253 p = NULL; 254 goto after_sack_rexmit; 255 } else 256 /* Can rexmit part of the current hole */ 257 len = ((long)ulmin(cwin, 258 tp->snd_recover - p->rxmit)); 259 } else 260 len = ((long)ulmin(cwin, p->end - p->rxmit)); 261 off = p->rxmit - tp->snd_una; 262 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 263 __func__, off)); 264 if (len > 0) { 265 sack_rxmit = 1; 266 sendalot = 1; 267 tcpstat.tcps_sack_rexmits++; 268 tcpstat.tcps_sack_rexmit_bytes += 269 min(len, tp->t_maxseg); 270 } 271 } 272 after_sack_rexmit: 273 /* 274 * Get standard flags, and add SYN or FIN if requested by 'hidden' 275 * state flags. 276 */ 277 if (tp->t_flags & TF_NEEDFIN) 278 flags |= TH_FIN; 279 if (tp->t_flags & TF_NEEDSYN) 280 flags |= TH_SYN; 281 282 SOCKBUF_LOCK(&so->so_snd); 283 /* 284 * If in persist timeout with window of 0, send 1 byte. 285 * Otherwise, if window is small but nonzero 286 * and timer expired, we will send what we can 287 * and go to transmit state. 288 */ 289 if (tp->t_flags & TF_FORCEDATA) { 290 if (sendwin == 0) { 291 /* 292 * If we still have some data to send, then 293 * clear the FIN bit. Usually this would 294 * happen below when it realizes that we 295 * aren't sending all the data. However, 296 * if we have exactly 1 byte of unsent data, 297 * then it won't clear the FIN bit below, 298 * and if we are in persist state, we wind 299 * up sending the packet without recording 300 * that we sent the FIN bit. 301 * 302 * We can't just blindly clear the FIN bit, 303 * because if we don't have any more data 304 * to send then the probe will be the FIN 305 * itself. 306 */ 307 if (off < so->so_snd.sb_cc) 308 flags &= ~TH_FIN; 309 sendwin = 1; 310 } else { 311 tcp_timer_activate(tp, TT_PERSIST, 0); 312 tp->t_rxtshift = 0; 313 } 314 } 315 316 /* 317 * If snd_nxt == snd_max and we have transmitted a FIN, the 318 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 319 * a negative length. This can also occur when TCP opens up 320 * its congestion window while receiving additional duplicate 321 * acks after fast-retransmit because TCP will reset snd_nxt 322 * to snd_max after the fast-retransmit. 323 * 324 * In the normal retransmit-FIN-only case, however, snd_nxt will 325 * be set to snd_una, the offset will be 0, and the length may 326 * wind up 0. 327 * 328 * If sack_rxmit is true we are retransmitting from the scoreboard 329 * in which case len is already set. 330 */ 331 if (sack_rxmit == 0) { 332 if (sack_bytes_rxmt == 0) 333 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 334 else { 335 long cwin; 336 337 /* 338 * We are inside of a SACK recovery episode and are 339 * sending new data, having retransmitted all the 340 * data possible in the scoreboard. 341 */ 342 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 343 - off); 344 /* 345 * Don't remove this (len > 0) check ! 346 * We explicitly check for len > 0 here (although it 347 * isn't really necessary), to work around a gcc 348 * optimization issue - to force gcc to compute 349 * len above. Without this check, the computation 350 * of len is bungled by the optimizer. 351 */ 352 if (len > 0) { 353 cwin = tp->snd_cwnd - 354 (tp->snd_nxt - tp->sack_newdata) - 355 sack_bytes_rxmt; 356 if (cwin < 0) 357 cwin = 0; 358 len = lmin(len, cwin); 359 } 360 } 361 } 362 363 /* 364 * Lop off SYN bit if it has already been sent. However, if this 365 * is SYN-SENT state and if segment contains data and if we don't 366 * know that foreign host supports TAO, suppress sending segment. 367 */ 368 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 369 if (tp->t_state != TCPS_SYN_RECEIVED) 370 flags &= ~TH_SYN; 371 off--, len++; 372 } 373 374 /* 375 * Be careful not to send data and/or FIN on SYN segments. 376 * This measure is needed to prevent interoperability problems 377 * with not fully conformant TCP implementations. 378 */ 379 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 380 len = 0; 381 flags &= ~TH_FIN; 382 } 383 384 if (len < 0) { 385 /* 386 * If FIN has been sent but not acked, 387 * but we haven't been called to retransmit, 388 * len will be < 0. Otherwise, window shrank 389 * after we sent into it. If window shrank to 0, 390 * cancel pending retransmit, pull snd_nxt back 391 * to (closed) window, and set the persist timer 392 * if it isn't already going. If the window didn't 393 * close completely, just wait for an ACK. 394 */ 395 len = 0; 396 if (sendwin == 0) { 397 tcp_timer_activate(tp, TT_REXMT, 0); 398 tp->t_rxtshift = 0; 399 tp->snd_nxt = tp->snd_una; 400 if (!tcp_timer_active(tp, TT_PERSIST)) 401 tcp_setpersist(tp); 402 } 403 } 404 405 /* len will be >= 0 after this point. */ 406 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 407 408 /* 409 * Automatic sizing of send socket buffer. Often the send buffer 410 * size is not optimally adjusted to the actual network conditions 411 * at hand (delay bandwidth product). Setting the buffer size too 412 * small limits throughput on links with high bandwidth and high 413 * delay (eg. trans-continental/oceanic links). Setting the 414 * buffer size too big consumes too much real kernel memory, 415 * especially with many connections on busy servers. 416 * 417 * The criteria to step up the send buffer one notch are: 418 * 1. receive window of remote host is larger than send buffer 419 * (with a fudge factor of 5/4th); 420 * 2. send buffer is filled to 7/8th with data (so we actually 421 * have data to make use of it); 422 * 3. send buffer fill has not hit maximal automatic size; 423 * 4. our send window (slow start and cogestion controlled) is 424 * larger than sent but unacknowledged data in send buffer. 425 * 426 * The remote host receive window scaling factor may limit the 427 * growing of the send buffer before it reaches its allowed 428 * maximum. 429 * 430 * It scales directly with slow start or congestion window 431 * and does at most one step per received ACK. This fast 432 * scaling has the drawback of growing the send buffer beyond 433 * what is strictly necessary to make full use of a given 434 * delay*bandwith product. However testing has shown this not 435 * to be much of an problem. At worst we are trading wasting 436 * of available bandwith (the non-use of it) for wasting some 437 * socket buffer memory. 438 * 439 * TODO: Shrink send buffer during idle periods together 440 * with congestion window. Requires another timer. Has to 441 * wait for upcoming tcp timer rewrite. 442 */ 443 if (tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 444 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 445 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 446 so->so_snd.sb_cc < tcp_autosndbuf_max && 447 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 448 if (!sbreserve_locked(&so->so_snd, 449 min(so->so_snd.sb_hiwat + tcp_autosndbuf_inc, 450 tcp_autosndbuf_max), so, curthread)) 451 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 452 } 453 } 454 455 /* 456 * Truncate to the maximum segment length or enable TCP Segmentation 457 * Offloading (if supported by hardware) and ensure that FIN is removed 458 * if the length no longer contains the last data byte. 459 * 460 * TSO may only be used if we are in a pure bulk sending state. The 461 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 462 * IP options prevent using TSO. With TSO the TCP header is the same 463 * (except for the sequence number) for all generated packets. This 464 * makes it impossible to transmit any options which vary per generated 465 * segment or packet. 466 * 467 * The length of TSO bursts is limited to TCP_MAXWIN. That limit and 468 * removal of FIN (if not already catched here) are handled later after 469 * the exact length of the TCP options are known. 470 */ 471 #ifdef IPSEC 472 /* 473 * Pre-calculate here as we save another lookup into the darknesses 474 * of IPsec that way and can actually decide if TSO is ok. 475 */ 476 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 477 #endif 478 if (len > tp->t_maxseg) { 479 if ((tp->t_flags & TF_TSO) && tcp_do_tso && 480 ((tp->t_flags & TF_SIGNATURE) == 0) && 481 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 482 tp->t_inpcb->inp_options == NULL && 483 tp->t_inpcb->in6p_options == NULL 484 #ifdef IPSEC 485 && ipsec_optlen == 0 486 #endif 487 ) { 488 tso = 1; 489 } else { 490 len = tp->t_maxseg; 491 sendalot = 1; 492 } 493 } 494 495 if (sack_rxmit) { 496 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 497 flags &= ~TH_FIN; 498 } else { 499 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 500 flags &= ~TH_FIN; 501 } 502 503 recwin = sbspace(&so->so_rcv); 504 505 /* 506 * Sender silly window avoidance. We transmit under the following 507 * conditions when len is non-zero: 508 * 509 * - We have a full segment (or more with TSO) 510 * - This is the last buffer in a write()/send() and we are 511 * either idle or running NODELAY 512 * - we've timed out (e.g. persist timer) 513 * - we have more then 1/2 the maximum send window's worth of 514 * data (receiver may be limited the window size) 515 * - we need to retransmit 516 */ 517 if (len) { 518 if (len >= tp->t_maxseg) 519 goto send; 520 /* 521 * NOTE! on localhost connections an 'ack' from the remote 522 * end may occur synchronously with the output and cause 523 * us to flush a buffer queued with moretocome. XXX 524 * 525 * note: the len + off check is almost certainly unnecessary. 526 */ 527 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 528 (idle || (tp->t_flags & TF_NODELAY)) && 529 len + off >= so->so_snd.sb_cc && 530 (tp->t_flags & TF_NOPUSH) == 0) { 531 goto send; 532 } 533 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 534 goto send; 535 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 536 goto send; 537 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 538 goto send; 539 if (sack_rxmit) 540 goto send; 541 } 542 543 /* 544 * Compare available window to amount of window 545 * known to peer (as advertised window less 546 * next expected input). If the difference is at least two 547 * max size segments, or at least 50% of the maximum possible 548 * window, then want to send a window update to peer. 549 * Skip this if the connection is in T/TCP half-open state. 550 * Don't send pure window updates when the peer has closed 551 * the connection and won't ever send more data. 552 */ 553 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 554 !TCPS_HAVERCVDFIN(tp->t_state)) { 555 /* 556 * "adv" is the amount we can increase the window, 557 * taking into account that we are limited by 558 * TCP_MAXWIN << tp->rcv_scale. 559 */ 560 long adv; 561 int oldwin; 562 563 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale); 564 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 565 oldwin = (tp->rcv_adv - tp->rcv_nxt); 566 adv -= oldwin; 567 } else 568 oldwin = 0; 569 570 /* 571 * If the new window size ends up being the same as the old 572 * size when it is scaled, then don't force a window update. 573 */ 574 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale) 575 goto dontupdate; 576 if (adv >= (long) (2 * tp->t_maxseg)) 577 goto send; 578 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 579 goto send; 580 } 581 dontupdate: 582 583 /* 584 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 585 * is also a catch-all for the retransmit timer timeout case. 586 */ 587 if (tp->t_flags & TF_ACKNOW) 588 goto send; 589 if ((flags & TH_RST) || 590 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 591 goto send; 592 if (SEQ_GT(tp->snd_up, tp->snd_una)) 593 goto send; 594 /* 595 * If our state indicates that FIN should be sent 596 * and we have not yet done so, then we need to send. 597 */ 598 if (flags & TH_FIN && 599 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 600 goto send; 601 /* 602 * In SACK, it is possible for tcp_output to fail to send a segment 603 * after the retransmission timer has been turned off. Make sure 604 * that the retransmission timer is set. 605 */ 606 if ((tp->t_flags & TF_SACK_PERMIT) && 607 SEQ_GT(tp->snd_max, tp->snd_una) && 608 !tcp_timer_active(tp, TT_REXMT) && 609 !tcp_timer_active(tp, TT_PERSIST)) { 610 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 611 goto just_return; 612 } 613 /* 614 * TCP window updates are not reliable, rather a polling protocol 615 * using ``persist'' packets is used to insure receipt of window 616 * updates. The three ``states'' for the output side are: 617 * idle not doing retransmits or persists 618 * persisting to move a small or zero window 619 * (re)transmitting and thereby not persisting 620 * 621 * tcp_timer_active(tp, TT_PERSIST) 622 * is true when we are in persist state. 623 * (tp->t_flags & TF_FORCEDATA) 624 * is set when we are called to send a persist packet. 625 * tcp_timer_active(tp, TT_REXMT) 626 * is set when we are retransmitting 627 * The output side is idle when both timers are zero. 628 * 629 * If send window is too small, there is data to transmit, and no 630 * retransmit or persist is pending, then go to persist state. 631 * If nothing happens soon, send when timer expires: 632 * if window is nonzero, transmit what we can, 633 * otherwise force out a byte. 634 */ 635 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 636 !tcp_timer_active(tp, TT_PERSIST)) { 637 tp->t_rxtshift = 0; 638 tcp_setpersist(tp); 639 } 640 641 /* 642 * No reason to send a segment, just return. 643 */ 644 just_return: 645 SOCKBUF_UNLOCK(&so->so_snd); 646 return (0); 647 648 send: 649 SOCKBUF_LOCK_ASSERT(&so->so_snd); 650 /* 651 * Before ESTABLISHED, force sending of initial options 652 * unless TCP set not to do any options. 653 * NOTE: we assume that the IP/TCP header plus TCP options 654 * always fit in a single mbuf, leaving room for a maximum 655 * link header, i.e. 656 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 657 */ 658 optlen = 0; 659 #ifdef INET6 660 if (isipv6) 661 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 662 else 663 #endif 664 hdrlen = sizeof (struct tcpiphdr); 665 666 /* 667 * Compute options for segment. 668 * We only have to care about SYN and established connection 669 * segments. Options for SYN-ACK segments are handled in TCP 670 * syncache. 671 */ 672 if ((tp->t_flags & TF_NOOPT) == 0) { 673 to.to_flags = 0; 674 /* Maximum segment size. */ 675 if (flags & TH_SYN) { 676 tp->snd_nxt = tp->iss; 677 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 678 to.to_flags |= TOF_MSS; 679 } 680 /* Window scaling. */ 681 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 682 to.to_wscale = tp->request_r_scale; 683 to.to_flags |= TOF_SCALE; 684 } 685 /* Timestamps. */ 686 if ((tp->t_flags & TF_RCVD_TSTMP) || 687 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 688 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 689 to.to_tsecr = tp->ts_recent; 690 to.to_flags |= TOF_TS; 691 /* Set receive buffer autosizing timestamp. */ 692 if (tp->rfbuf_ts == 0 && 693 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 694 tp->rfbuf_ts = tcp_ts_getticks(); 695 } 696 /* Selective ACK's. */ 697 if (tp->t_flags & TF_SACK_PERMIT) { 698 if (flags & TH_SYN) 699 to.to_flags |= TOF_SACKPERM; 700 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 701 (tp->t_flags & TF_SACK_PERMIT) && 702 tp->rcv_numsacks > 0) { 703 to.to_flags |= TOF_SACK; 704 to.to_nsacks = tp->rcv_numsacks; 705 to.to_sacks = (u_char *)tp->sackblks; 706 } 707 } 708 #ifdef TCP_SIGNATURE 709 /* TCP-MD5 (RFC2385). */ 710 if (tp->t_flags & TF_SIGNATURE) 711 to.to_flags |= TOF_SIGNATURE; 712 #endif /* TCP_SIGNATURE */ 713 714 /* Processing the options. */ 715 hdrlen += optlen = tcp_addoptions(&to, opt); 716 } 717 718 #ifdef INET6 719 if (isipv6) 720 ipoptlen = ip6_optlen(tp->t_inpcb); 721 else 722 #endif 723 if (tp->t_inpcb->inp_options) 724 ipoptlen = tp->t_inpcb->inp_options->m_len - 725 offsetof(struct ipoption, ipopt_list); 726 else 727 ipoptlen = 0; 728 #ifdef IPSEC 729 ipoptlen += ipsec_optlen; 730 #endif 731 732 /* 733 * Adjust data length if insertion of options will 734 * bump the packet length beyond the t_maxopd length. 735 * Clear the FIN bit because we cut off the tail of 736 * the segment. 737 * 738 * When doing TSO limit a burst to TCP_MAXWIN minus the 739 * IP, TCP and Options length to keep ip->ip_len from 740 * overflowing. Prevent the last segment from being 741 * fractional thus making them all equal sized and set 742 * the flag to continue sending. TSO is disabled when 743 * IP options or IPSEC are present. 744 */ 745 if (len + optlen + ipoptlen > tp->t_maxopd) { 746 flags &= ~TH_FIN; 747 if (tso) { 748 if (len > TCP_MAXWIN - hdrlen - optlen) { 749 len = TCP_MAXWIN - hdrlen - optlen; 750 len = len - (len % (tp->t_maxopd - optlen)); 751 sendalot = 1; 752 } else if (tp->t_flags & TF_NEEDFIN) 753 sendalot = 1; 754 } else { 755 len = tp->t_maxopd - optlen - ipoptlen; 756 sendalot = 1; 757 } 758 } 759 760 /*#ifdef DIAGNOSTIC*/ 761 #ifdef INET6 762 if (max_linkhdr + hdrlen > MCLBYTES) 763 #else 764 if (max_linkhdr + hdrlen > MHLEN) 765 #endif 766 panic("tcphdr too big"); 767 /*#endif*/ 768 769 /* 770 * This KASSERT is here to catch edge cases at a well defined place. 771 * Before, those had triggered (random) panic conditions further down. 772 */ 773 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 774 775 /* 776 * Grab a header mbuf, attaching a copy of data to 777 * be transmitted, and initialize the header from 778 * the template for sends on this connection. 779 */ 780 if (len) { 781 struct mbuf *mb; 782 u_int moff; 783 784 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 785 tcpstat.tcps_sndprobe++; 786 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 787 tcpstat.tcps_sndrexmitpack++; 788 tcpstat.tcps_sndrexmitbyte += len; 789 } else { 790 tcpstat.tcps_sndpack++; 791 tcpstat.tcps_sndbyte += len; 792 } 793 #ifdef notyet 794 if ((m = m_copypack(so->so_snd.sb_mb, off, 795 (int)len, max_linkhdr + hdrlen)) == 0) { 796 SOCKBUF_UNLOCK(&so->so_snd); 797 error = ENOBUFS; 798 goto out; 799 } 800 /* 801 * m_copypack left space for our hdr; use it. 802 */ 803 m->m_len += hdrlen; 804 m->m_data -= hdrlen; 805 #else 806 MGETHDR(m, M_DONTWAIT, MT_DATA); 807 if (m == NULL) { 808 SOCKBUF_UNLOCK(&so->so_snd); 809 error = ENOBUFS; 810 goto out; 811 } 812 #ifdef INET6 813 if (MHLEN < hdrlen + max_linkhdr) { 814 MCLGET(m, M_DONTWAIT); 815 if ((m->m_flags & M_EXT) == 0) { 816 SOCKBUF_UNLOCK(&so->so_snd); 817 m_freem(m); 818 error = ENOBUFS; 819 goto out; 820 } 821 } 822 #endif 823 m->m_data += max_linkhdr; 824 m->m_len = hdrlen; 825 826 /* 827 * Start the m_copy functions from the closest mbuf 828 * to the offset in the socket buffer chain. 829 */ 830 mb = sbsndptr(&so->so_snd, off, len, &moff); 831 832 if (len <= MHLEN - hdrlen - max_linkhdr) { 833 m_copydata(mb, moff, (int)len, 834 mtod(m, caddr_t) + hdrlen); 835 m->m_len += len; 836 } else { 837 m->m_next = m_copy(mb, moff, (int)len); 838 if (m->m_next == NULL) { 839 SOCKBUF_UNLOCK(&so->so_snd); 840 (void) m_free(m); 841 error = ENOBUFS; 842 goto out; 843 } 844 } 845 #endif 846 /* 847 * If we're sending everything we've got, set PUSH. 848 * (This will keep happy those implementations which only 849 * give data to the user when a buffer fills or 850 * a PUSH comes in.) 851 */ 852 if (off + len == so->so_snd.sb_cc) 853 flags |= TH_PUSH; 854 SOCKBUF_UNLOCK(&so->so_snd); 855 } else { 856 SOCKBUF_UNLOCK(&so->so_snd); 857 if (tp->t_flags & TF_ACKNOW) 858 tcpstat.tcps_sndacks++; 859 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 860 tcpstat.tcps_sndctrl++; 861 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 862 tcpstat.tcps_sndurg++; 863 else 864 tcpstat.tcps_sndwinup++; 865 866 MGETHDR(m, M_DONTWAIT, MT_DATA); 867 if (m == NULL) { 868 error = ENOBUFS; 869 goto out; 870 } 871 #ifdef INET6 872 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 873 MHLEN >= hdrlen) { 874 MH_ALIGN(m, hdrlen); 875 } else 876 #endif 877 m->m_data += max_linkhdr; 878 m->m_len = hdrlen; 879 } 880 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 881 m->m_pkthdr.rcvif = (struct ifnet *)0; 882 #ifdef MAC 883 mac_create_mbuf_from_inpcb(tp->t_inpcb, m); 884 #endif 885 #ifdef INET6 886 if (isipv6) { 887 ip6 = mtod(m, struct ip6_hdr *); 888 th = (struct tcphdr *)(ip6 + 1); 889 tcpip_fillheaders(tp->t_inpcb, ip6, th); 890 } else 891 #endif /* INET6 */ 892 { 893 ip = mtod(m, struct ip *); 894 ipov = (struct ipovly *)ip; 895 th = (struct tcphdr *)(ip + 1); 896 tcpip_fillheaders(tp->t_inpcb, ip, th); 897 } 898 899 /* 900 * Fill in fields, remembering maximum advertised 901 * window for use in delaying messages about window sizes. 902 * If resending a FIN, be sure not to use a new sequence number. 903 */ 904 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 905 tp->snd_nxt == tp->snd_max) 906 tp->snd_nxt--; 907 /* 908 * If we are doing retransmissions, then snd_nxt will 909 * not reflect the first unsent octet. For ACK only 910 * packets, we do not want the sequence number of the 911 * retransmitted packet, we want the sequence number 912 * of the next unsent octet. So, if there is no data 913 * (and no SYN or FIN), use snd_max instead of snd_nxt 914 * when filling in ti_seq. But if we are in persist 915 * state, snd_max might reflect one byte beyond the 916 * right edge of the window, so use snd_nxt in that 917 * case, since we know we aren't doing a retransmission. 918 * (retransmit and persist are mutually exclusive...) 919 */ 920 if (sack_rxmit == 0) { 921 if (len || (flags & (TH_SYN|TH_FIN)) || 922 tcp_timer_active(tp, TT_PERSIST)) 923 th->th_seq = htonl(tp->snd_nxt); 924 else 925 th->th_seq = htonl(tp->snd_max); 926 } else { 927 th->th_seq = htonl(p->rxmit); 928 p->rxmit += len; 929 tp->sackhint.sack_bytes_rexmit += len; 930 } 931 th->th_ack = htonl(tp->rcv_nxt); 932 if (optlen) { 933 bcopy(opt, th + 1, optlen); 934 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 935 } 936 th->th_flags = flags; 937 /* 938 * Calculate receive window. Don't shrink window, 939 * but avoid silly window syndrome. 940 */ 941 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 942 recwin < (long)tp->t_maxseg) 943 recwin = 0; 944 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 945 recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 946 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 947 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 948 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 949 950 /* 951 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 952 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 953 * case is handled in syncache. 954 */ 955 if (flags & TH_SYN) 956 th->th_win = htons((u_short) 957 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 958 else 959 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 960 961 /* 962 * Adjust the RXWIN0SENT flag - indicate that we have advertised 963 * a 0 window. This may cause the remote transmitter to stall. This 964 * flag tells soreceive() to disable delayed acknowledgements when 965 * draining the buffer. This can occur if the receiver is attempting 966 * to read more data then can be buffered prior to transmitting on 967 * the connection. 968 */ 969 if (th->th_win == 0) 970 tp->t_flags |= TF_RXWIN0SENT; 971 else 972 tp->t_flags &= ~TF_RXWIN0SENT; 973 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 974 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 975 th->th_flags |= TH_URG; 976 } else 977 /* 978 * If no urgent pointer to send, then we pull 979 * the urgent pointer to the left edge of the send window 980 * so that it doesn't drift into the send window on sequence 981 * number wraparound. 982 */ 983 tp->snd_up = tp->snd_una; /* drag it along */ 984 985 #ifdef TCP_SIGNATURE 986 if (tp->t_flags & TF_SIGNATURE) { 987 int sigoff = to.to_signature - opt; 988 tcp_signature_compute(m, 0, len, optlen, 989 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 990 } 991 #endif 992 993 /* 994 * Put TCP length in extended header, and then 995 * checksum extended header and data. 996 */ 997 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 998 #ifdef INET6 999 if (isipv6) 1000 /* 1001 * ip6_plen is not need to be filled now, and will be filled 1002 * in ip6_output. 1003 */ 1004 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 1005 sizeof(struct tcphdr) + optlen + len); 1006 else 1007 #endif /* INET6 */ 1008 { 1009 m->m_pkthdr.csum_flags = CSUM_TCP; 1010 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1011 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1012 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1013 1014 /* IP version must be set here for ipv4/ipv6 checking later */ 1015 KASSERT(ip->ip_v == IPVERSION, 1016 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1017 } 1018 1019 /* 1020 * Enable TSO and specify the size of the segments. 1021 * The TCP pseudo header checksum is always provided. 1022 * XXX: Fixme: This is currently not the case for IPv6. 1023 */ 1024 if (tso) { 1025 KASSERT(len > tp->t_maxopd - optlen, 1026 ("%s: len <= tso_segsz", __func__)); 1027 m->m_pkthdr.csum_flags |= CSUM_TSO; 1028 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1029 } 1030 1031 /* 1032 * In transmit state, time the transmission and arrange for 1033 * the retransmit. In persist state, just set snd_max. 1034 */ 1035 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1036 !tcp_timer_active(tp, TT_PERSIST)) { 1037 tcp_seq startseq = tp->snd_nxt; 1038 1039 /* 1040 * Advance snd_nxt over sequence space of this segment. 1041 */ 1042 if (flags & (TH_SYN|TH_FIN)) { 1043 if (flags & TH_SYN) 1044 tp->snd_nxt++; 1045 if (flags & TH_FIN) { 1046 tp->snd_nxt++; 1047 tp->t_flags |= TF_SENTFIN; 1048 } 1049 } 1050 if (sack_rxmit) 1051 goto timer; 1052 tp->snd_nxt += len; 1053 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1054 tp->snd_max = tp->snd_nxt; 1055 /* 1056 * Time this transmission if not a retransmission and 1057 * not currently timing anything. 1058 */ 1059 if (tp->t_rtttime == 0) { 1060 tp->t_rtttime = ticks; 1061 tp->t_rtseq = startseq; 1062 tcpstat.tcps_segstimed++; 1063 } 1064 } 1065 1066 /* 1067 * Set retransmit timer if not currently set, 1068 * and not doing a pure ack or a keep-alive probe. 1069 * Initial value for retransmit timer is smoothed 1070 * round-trip time + 2 * round-trip time variance. 1071 * Initialize shift counter which is used for backoff 1072 * of retransmit time. 1073 */ 1074 timer: 1075 if (!tcp_timer_active(tp, TT_REXMT) && 1076 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1077 (tp->snd_nxt != tp->snd_una))) { 1078 if (tcp_timer_active(tp, TT_PERSIST)) { 1079 tcp_timer_activate(tp, TT_PERSIST, 0); 1080 tp->t_rxtshift = 0; 1081 } 1082 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1083 } 1084 } else { 1085 /* 1086 * Persist case, update snd_max but since we are in 1087 * persist mode (no window) we do not update snd_nxt. 1088 */ 1089 int xlen = len; 1090 if (flags & TH_SYN) 1091 ++xlen; 1092 if (flags & TH_FIN) { 1093 ++xlen; 1094 tp->t_flags |= TF_SENTFIN; 1095 } 1096 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1097 tp->snd_max = tp->snd_nxt + len; 1098 } 1099 1100 #ifdef TCPDEBUG 1101 /* 1102 * Trace. 1103 */ 1104 if (so->so_options & SO_DEBUG) { 1105 u_short save = 0; 1106 #ifdef INET6 1107 if (!isipv6) 1108 #endif 1109 { 1110 save = ipov->ih_len; 1111 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1112 } 1113 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1114 #ifdef INET6 1115 if (!isipv6) 1116 #endif 1117 ipov->ih_len = save; 1118 } 1119 #endif 1120 1121 /* 1122 * Fill in IP length and desired time to live and 1123 * send to IP level. There should be a better way 1124 * to handle ttl and tos; we could keep them in 1125 * the template, but need a way to checksum without them. 1126 */ 1127 /* 1128 * m->m_pkthdr.len should have been set before cksum calcuration, 1129 * because in6_cksum() need it. 1130 */ 1131 #ifdef INET6 1132 if (isipv6) { 1133 /* 1134 * we separately set hoplimit for every segment, since the 1135 * user might want to change the value via setsockopt. 1136 * Also, desired default hop limit might be changed via 1137 * Neighbor Discovery. 1138 */ 1139 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1140 1141 /* TODO: IPv6 IP6TOS_ECT bit on */ 1142 error = ip6_output(m, 1143 tp->t_inpcb->in6p_outputopts, NULL, 1144 ((so->so_options & SO_DONTROUTE) ? 1145 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1146 } else 1147 #endif /* INET6 */ 1148 { 1149 ip->ip_len = m->m_pkthdr.len; 1150 #ifdef INET6 1151 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1152 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1153 #endif /* INET6 */ 1154 /* 1155 * If we do path MTU discovery, then we set DF on every packet. 1156 * This might not be the best thing to do according to RFC3390 1157 * Section 2. However the tcp hostcache migitates the problem 1158 * so it affects only the first tcp connection with a host. 1159 * 1160 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1161 */ 1162 if (path_mtu_discovery && tp->t_maxopd > tcp_minmss) 1163 ip->ip_off |= IP_DF; 1164 1165 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1166 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1167 tp->t_inpcb); 1168 } 1169 if (error) { 1170 1171 /* 1172 * We know that the packet was lost, so back out the 1173 * sequence number advance, if any. 1174 * 1175 * If the error is EPERM the packet got blocked by the 1176 * local firewall. Normally we should terminate the 1177 * connection but the blocking may have been spurious 1178 * due to a firewall reconfiguration cycle. So we treat 1179 * it like a packet loss and let the retransmit timer and 1180 * timeouts do their work over time. 1181 * XXX: It is a POLA question whether calling tcp_drop right 1182 * away would be the really correct behavior instead. 1183 */ 1184 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1185 !tcp_timer_active(tp, TT_PERSIST)) && 1186 ((flags & TH_SYN) == 0) && 1187 (error != EPERM)) { 1188 if (sack_rxmit) { 1189 p->rxmit -= len; 1190 tp->sackhint.sack_bytes_rexmit -= len; 1191 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1192 ("sackhint bytes rtx >= 0")); 1193 } else 1194 tp->snd_nxt -= len; 1195 } 1196 out: 1197 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1198 switch (error) { 1199 case EPERM: 1200 tp->t_softerror = error; 1201 return (error); 1202 case ENOBUFS: 1203 if (!tcp_timer_active(tp, TT_REXMT) && 1204 !tcp_timer_active(tp, TT_PERSIST)) 1205 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1206 tp->snd_cwnd = tp->t_maxseg; 1207 return (0); 1208 case EMSGSIZE: 1209 /* 1210 * For some reason the interface we used initially 1211 * to send segments changed to another or lowered 1212 * its MTU. 1213 * 1214 * tcp_mtudisc() will find out the new MTU and as 1215 * its last action, initiate retransmission, so it 1216 * is important to not do so here. 1217 * 1218 * If TSO was active we either got an interface 1219 * without TSO capabilits or TSO was turned off. 1220 * Disable it for this connection as too and 1221 * immediatly retry with MSS sized segments generated 1222 * by this function. 1223 */ 1224 if (tso) 1225 tp->t_flags &= ~TF_TSO; 1226 tcp_mtudisc(tp->t_inpcb, 0); 1227 return (0); 1228 case EHOSTDOWN: 1229 case EHOSTUNREACH: 1230 case ENETDOWN: 1231 case ENETUNREACH: 1232 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1233 tp->t_softerror = error; 1234 return (0); 1235 } 1236 /* FALLTHROUGH */ 1237 default: 1238 return (error); 1239 } 1240 } 1241 tcpstat.tcps_sndtotal++; 1242 1243 /* 1244 * Data sent (as far as we can tell). 1245 * If this advertises a larger window than any other segment, 1246 * then remember the size of the advertised window. 1247 * Any pending ACK has now been sent. 1248 */ 1249 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1250 tp->rcv_adv = tp->rcv_nxt + recwin; 1251 tp->last_ack_sent = tp->rcv_nxt; 1252 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1253 if (tcp_timer_active(tp, TT_DELACK)) 1254 tcp_timer_activate(tp, TT_DELACK, 0); 1255 #if 0 1256 /* 1257 * This completely breaks TCP if newreno is turned on. What happens 1258 * is that if delayed-acks are turned on on the receiver, this code 1259 * on the transmitter effectively destroys the TCP window, forcing 1260 * it to four packets (1.5Kx4 = 6K window). 1261 */ 1262 if (sendalot && (!tcp_do_newreno || --maxburst)) 1263 goto again; 1264 #endif 1265 if (sendalot) 1266 goto again; 1267 return (0); 1268 } 1269 1270 void 1271 tcp_setpersist(struct tcpcb *tp) 1272 { 1273 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1274 int tt; 1275 1276 tp->t_flags &= ~TF_PREVVALID; 1277 if (tcp_timer_active(tp, TT_REXMT)) 1278 panic("tcp_setpersist: retransmit pending"); 1279 /* 1280 * Start/restart persistance timer. 1281 */ 1282 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1283 TCPTV_PERSMIN, TCPTV_PERSMAX); 1284 tcp_timer_activate(tp, TT_PERSIST, tt); 1285 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1286 tp->t_rxtshift++; 1287 } 1288 1289 /* 1290 * Insert TCP options according to the supplied parameters to the place 1291 * optp in a consistent way. Can handle unaligned destinations. 1292 * 1293 * The order of the option processing is crucial for optimal packing and 1294 * alignment for the scarce option space. 1295 * 1296 * The optimal order for a SYN/SYN-ACK segment is: 1297 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1298 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1299 * 1300 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1301 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1302 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1303 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1304 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1305 */ 1306 int 1307 tcp_addoptions(struct tcpopt *to, u_char *optp) 1308 { 1309 u_int mask, optlen = 0; 1310 1311 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1312 if ((to->to_flags & mask) != mask) 1313 continue; 1314 if (optlen == TCP_MAXOLEN) 1315 break; 1316 switch (to->to_flags & mask) { 1317 case TOF_MSS: 1318 while (optlen % 4) { 1319 optlen += TCPOLEN_NOP; 1320 *optp++ = TCPOPT_NOP; 1321 } 1322 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1323 continue; 1324 optlen += TCPOLEN_MAXSEG; 1325 *optp++ = TCPOPT_MAXSEG; 1326 *optp++ = TCPOLEN_MAXSEG; 1327 to->to_mss = htons(to->to_mss); 1328 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1329 optp += sizeof(to->to_mss); 1330 break; 1331 case TOF_SCALE: 1332 while (!optlen || optlen % 2 != 1) { 1333 optlen += TCPOLEN_NOP; 1334 *optp++ = TCPOPT_NOP; 1335 } 1336 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1337 continue; 1338 optlen += TCPOLEN_WINDOW; 1339 *optp++ = TCPOPT_WINDOW; 1340 *optp++ = TCPOLEN_WINDOW; 1341 *optp++ = to->to_wscale; 1342 break; 1343 case TOF_SACKPERM: 1344 while (optlen % 2) { 1345 optlen += TCPOLEN_NOP; 1346 *optp++ = TCPOPT_NOP; 1347 } 1348 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1349 continue; 1350 optlen += TCPOLEN_SACK_PERMITTED; 1351 *optp++ = TCPOPT_SACK_PERMITTED; 1352 *optp++ = TCPOLEN_SACK_PERMITTED; 1353 break; 1354 case TOF_TS: 1355 while (!optlen || optlen % 4 != 2) { 1356 optlen += TCPOLEN_NOP; 1357 *optp++ = TCPOPT_NOP; 1358 } 1359 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1360 continue; 1361 optlen += TCPOLEN_TIMESTAMP; 1362 *optp++ = TCPOPT_TIMESTAMP; 1363 *optp++ = TCPOLEN_TIMESTAMP; 1364 to->to_tsval = htonl(to->to_tsval); 1365 to->to_tsecr = htonl(to->to_tsecr); 1366 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1367 optp += sizeof(to->to_tsval); 1368 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1369 optp += sizeof(to->to_tsecr); 1370 break; 1371 case TOF_SIGNATURE: 1372 { 1373 int siglen = TCPOLEN_SIGNATURE - 2; 1374 1375 while (!optlen || optlen % 4 != 2) { 1376 optlen += TCPOLEN_NOP; 1377 *optp++ = TCPOPT_NOP; 1378 } 1379 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1380 continue; 1381 optlen += TCPOLEN_SIGNATURE; 1382 *optp++ = TCPOPT_SIGNATURE; 1383 *optp++ = TCPOLEN_SIGNATURE; 1384 to->to_signature = optp; 1385 while (siglen--) 1386 *optp++ = 0; 1387 break; 1388 } 1389 case TOF_SACK: 1390 { 1391 int sackblks = 0; 1392 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1393 tcp_seq sack_seq; 1394 1395 while (!optlen || optlen % 4 != 2) { 1396 optlen += TCPOLEN_NOP; 1397 *optp++ = TCPOPT_NOP; 1398 } 1399 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1400 continue; 1401 optlen += TCPOLEN_SACKHDR; 1402 *optp++ = TCPOPT_SACK; 1403 sackblks = min(to->to_nsacks, 1404 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1405 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1406 while (sackblks--) { 1407 sack_seq = htonl(sack->start); 1408 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1409 optp += sizeof(sack_seq); 1410 sack_seq = htonl(sack->end); 1411 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1412 optp += sizeof(sack_seq); 1413 optlen += TCPOLEN_SACK; 1414 sack++; 1415 } 1416 tcpstat.tcps_sack_send_blocks++; 1417 break; 1418 } 1419 default: 1420 panic("%s: unknown TCP option type", __func__); 1421 break; 1422 } 1423 } 1424 1425 /* Terminate and pad TCP options to a 4 byte boundary. */ 1426 if (optlen % 4) { 1427 optlen += TCPOLEN_EOL; 1428 *optp++ = TCPOPT_EOL; 1429 } 1430 /* 1431 * According to RFC 793 (STD0007): 1432 * "The content of the header beyond the End-of-Option option 1433 * must be header padding (i.e., zero)." 1434 * and later: "The padding is composed of zeros." 1435 */ 1436 while (optlen % 4) { 1437 optlen += TCPOLEN_PAD; 1438 *optp++ = TCPOPT_PAD; 1439 } 1440 1441 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1442 return (optlen); 1443 }
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