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 #include <sys/vimage.h> 53 54 #include <net/route.h> 55 56 #include <netinet/in.h> 57 #include <netinet/in_systm.h> 58 #include <netinet/ip.h> 59 #include <netinet/in_pcb.h> 60 #include <netinet/ip_var.h> 61 #include <netinet/ip_options.h> 62 #ifdef INET6 63 #include <netinet6/in6_pcb.h> 64 #include <netinet/ip6.h> 65 #include <netinet6/ip6_var.h> 66 #endif 67 #include <netinet/tcp.h> 68 #define TCPOUTFLAGS 69 #include <netinet/tcp_fsm.h> 70 #include <netinet/tcp_seq.h> 71 #include <netinet/tcp_timer.h> 72 #include <netinet/tcp_var.h> 73 #include <netinet/tcpip.h> 74 #ifdef TCPDEBUG 75 #include <netinet/tcp_debug.h> 76 #endif 77 78 #ifdef IPSEC 79 #include <netipsec/ipsec.h> 80 #endif /*IPSEC*/ 81 82 #include <machine/in_cksum.h> 83 84 #include <security/mac/mac_framework.h> 85 86 #ifdef notyet 87 extern struct mbuf *m_copypack(); 88 #endif 89 90 int path_mtu_discovery = 1; 91 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 92 &path_mtu_discovery, 1, "Enable Path MTU Discovery"); 93 94 int ss_fltsz = 1; 95 SYSCTL_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 96 &ss_fltsz, 1, "Slow start flight size"); 97 98 int ss_fltsz_local = 4; 99 SYSCTL_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, CTLFLAG_RW, 100 &ss_fltsz_local, 1, "Slow start flight size for local networks"); 101 102 int tcp_do_newreno = 1; 103 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, 104 &tcp_do_newreno, 0, "Enable NewReno Algorithms"); 105 106 int tcp_do_tso = 1; 107 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 108 &tcp_do_tso, 0, "Enable TCP Segmentation Offload"); 109 110 int tcp_do_autosndbuf = 1; 111 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 112 &tcp_do_autosndbuf, 0, "Enable automatic send buffer sizing"); 113 114 int tcp_autosndbuf_inc = 8*1024; 115 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 116 &tcp_autosndbuf_inc, 0, "Incrementor step size of automatic send buffer"); 117 118 int tcp_autosndbuf_max = 256*1024; 119 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 120 &tcp_autosndbuf_max, 0, "Max size of automatic send buffer"); 121 122 123 /* 124 * Tcp output routine: figure out what should be sent and send it. 125 */ 126 int 127 tcp_output(struct tcpcb *tp) 128 { 129 struct socket *so = tp->t_inpcb->inp_socket; 130 long len, recwin, sendwin; 131 int off, flags, error; 132 struct mbuf *m; 133 struct ip *ip = NULL; 134 struct ipovly *ipov = NULL; 135 struct tcphdr *th; 136 u_char opt[TCP_MAXOLEN]; 137 unsigned ipoptlen, optlen, hdrlen; 138 #ifdef IPSEC 139 unsigned ipsec_optlen = 0; 140 #endif 141 int idle, sendalot; 142 int sack_rxmit, sack_bytes_rxmt; 143 struct sackhole *p; 144 int tso = 0; 145 struct tcpopt to; 146 #if 0 147 int maxburst = TCP_MAXBURST; 148 #endif 149 #ifdef INET6 150 struct ip6_hdr *ip6 = NULL; 151 int isipv6; 152 153 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 154 #endif 155 156 INP_WLOCK_ASSERT(tp->t_inpcb); 157 158 /* 159 * Determine length of data that should be transmitted, 160 * and flags that will be used. 161 * If there is some data or critical controls (SYN, RST) 162 * to send, then transmit; otherwise, investigate further. 163 */ 164 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 165 if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { 166 /* 167 * We have been idle for "a while" and no acks are 168 * expected to clock out any data we send -- 169 * slow start to get ack "clock" running again. 170 * 171 * Set the slow-start flight size depending on whether 172 * this is a local network or not. 173 */ 174 int ss = V_ss_fltsz; 175 #ifdef INET6 176 if (isipv6) { 177 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 178 ss = V_ss_fltsz_local; 179 } else 180 #endif /* INET6 */ 181 if (in_localaddr(tp->t_inpcb->inp_faddr)) 182 ss = V_ss_fltsz_local; 183 tp->snd_cwnd = tp->t_maxseg * ss; 184 } 185 tp->t_flags &= ~TF_LASTIDLE; 186 if (idle) { 187 if (tp->t_flags & TF_MORETOCOME) { 188 tp->t_flags |= TF_LASTIDLE; 189 idle = 0; 190 } 191 } 192 again: 193 /* 194 * If we've recently taken a timeout, snd_max will be greater than 195 * snd_nxt. There may be SACK information that allows us to avoid 196 * resending already delivered data. Adjust snd_nxt accordingly. 197 */ 198 if ((tp->t_flags & TF_SACK_PERMIT) && 199 SEQ_LT(tp->snd_nxt, tp->snd_max)) 200 tcp_sack_adjust(tp); 201 sendalot = 0; 202 off = tp->snd_nxt - tp->snd_una; 203 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 204 sendwin = min(sendwin, tp->snd_bwnd); 205 206 flags = tcp_outflags[tp->t_state]; 207 /* 208 * Send any SACK-generated retransmissions. If we're explicitly trying 209 * to send out new data (when sendalot is 1), bypass this function. 210 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 211 * we're replacing a (future) new transmission with a retransmission 212 * now, and we previously incremented snd_cwnd in tcp_input(). 213 */ 214 /* 215 * Still in sack recovery , reset rxmit flag to zero. 216 */ 217 sack_rxmit = 0; 218 sack_bytes_rxmt = 0; 219 len = 0; 220 p = NULL; 221 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp) && 222 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 223 long cwin; 224 225 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 226 if (cwin < 0) 227 cwin = 0; 228 /* Do not retransmit SACK segments beyond snd_recover */ 229 if (SEQ_GT(p->end, tp->snd_recover)) { 230 /* 231 * (At least) part of sack hole extends beyond 232 * snd_recover. Check to see if we can rexmit data 233 * for this hole. 234 */ 235 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 236 /* 237 * Can't rexmit any more data for this hole. 238 * That data will be rexmitted in the next 239 * sack recovery episode, when snd_recover 240 * moves past p->rxmit. 241 */ 242 p = NULL; 243 goto after_sack_rexmit; 244 } else 245 /* Can rexmit part of the current hole */ 246 len = ((long)ulmin(cwin, 247 tp->snd_recover - p->rxmit)); 248 } else 249 len = ((long)ulmin(cwin, p->end - p->rxmit)); 250 off = p->rxmit - tp->snd_una; 251 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 252 __func__, off)); 253 if (len > 0) { 254 sack_rxmit = 1; 255 sendalot = 1; 256 V_tcpstat.tcps_sack_rexmits++; 257 V_tcpstat.tcps_sack_rexmit_bytes += 258 min(len, tp->t_maxseg); 259 } 260 } 261 after_sack_rexmit: 262 /* 263 * Get standard flags, and add SYN or FIN if requested by 'hidden' 264 * state flags. 265 */ 266 if (tp->t_flags & TF_NEEDFIN) 267 flags |= TH_FIN; 268 if (tp->t_flags & TF_NEEDSYN) 269 flags |= TH_SYN; 270 271 SOCKBUF_LOCK(&so->so_snd); 272 /* 273 * If in persist timeout with window of 0, send 1 byte. 274 * Otherwise, if window is small but nonzero 275 * and timer expired, we will send what we can 276 * and go to transmit state. 277 */ 278 if (tp->t_flags & TF_FORCEDATA) { 279 if (sendwin == 0) { 280 /* 281 * If we still have some data to send, then 282 * clear the FIN bit. Usually this would 283 * happen below when it realizes that we 284 * aren't sending all the data. However, 285 * if we have exactly 1 byte of unsent data, 286 * then it won't clear the FIN bit below, 287 * and if we are in persist state, we wind 288 * up sending the packet without recording 289 * that we sent the FIN bit. 290 * 291 * We can't just blindly clear the FIN bit, 292 * because if we don't have any more data 293 * to send then the probe will be the FIN 294 * itself. 295 */ 296 if (off < so->so_snd.sb_cc) 297 flags &= ~TH_FIN; 298 sendwin = 1; 299 } else { 300 tcp_timer_activate(tp, TT_PERSIST, 0); 301 tp->t_rxtshift = 0; 302 } 303 } 304 305 /* 306 * If snd_nxt == snd_max and we have transmitted a FIN, the 307 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 308 * a negative length. This can also occur when TCP opens up 309 * its congestion window while receiving additional duplicate 310 * acks after fast-retransmit because TCP will reset snd_nxt 311 * to snd_max after the fast-retransmit. 312 * 313 * In the normal retransmit-FIN-only case, however, snd_nxt will 314 * be set to snd_una, the offset will be 0, and the length may 315 * wind up 0. 316 * 317 * If sack_rxmit is true we are retransmitting from the scoreboard 318 * in which case len is already set. 319 */ 320 if (sack_rxmit == 0) { 321 if (sack_bytes_rxmt == 0) 322 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 323 else { 324 long cwin; 325 326 /* 327 * We are inside of a SACK recovery episode and are 328 * sending new data, having retransmitted all the 329 * data possible in the scoreboard. 330 */ 331 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 332 - off); 333 /* 334 * Don't remove this (len > 0) check ! 335 * We explicitly check for len > 0 here (although it 336 * isn't really necessary), to work around a gcc 337 * optimization issue - to force gcc to compute 338 * len above. Without this check, the computation 339 * of len is bungled by the optimizer. 340 */ 341 if (len > 0) { 342 cwin = tp->snd_cwnd - 343 (tp->snd_nxt - tp->sack_newdata) - 344 sack_bytes_rxmt; 345 if (cwin < 0) 346 cwin = 0; 347 len = lmin(len, cwin); 348 } 349 } 350 } 351 352 /* 353 * Lop off SYN bit if it has already been sent. However, if this 354 * is SYN-SENT state and if segment contains data and if we don't 355 * know that foreign host supports TAO, suppress sending segment. 356 */ 357 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 358 if (tp->t_state != TCPS_SYN_RECEIVED) 359 flags &= ~TH_SYN; 360 off--, len++; 361 } 362 363 /* 364 * Be careful not to send data and/or FIN on SYN segments. 365 * This measure is needed to prevent interoperability problems 366 * with not fully conformant TCP implementations. 367 */ 368 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 369 len = 0; 370 flags &= ~TH_FIN; 371 } 372 373 if (len < 0) { 374 /* 375 * If FIN has been sent but not acked, 376 * but we haven't been called to retransmit, 377 * len will be < 0. Otherwise, window shrank 378 * after we sent into it. If window shrank to 0, 379 * cancel pending retransmit, pull snd_nxt back 380 * to (closed) window, and set the persist timer 381 * if it isn't already going. If the window didn't 382 * close completely, just wait for an ACK. 383 */ 384 len = 0; 385 if (sendwin == 0) { 386 tcp_timer_activate(tp, TT_REXMT, 0); 387 tp->t_rxtshift = 0; 388 tp->snd_nxt = tp->snd_una; 389 if (!tcp_timer_active(tp, TT_PERSIST)) 390 tcp_setpersist(tp); 391 } 392 } 393 394 /* len will be >= 0 after this point. */ 395 KASSERT(len >= 0, ("%s: len < 0", __func__)); 396 397 /* 398 * Automatic sizing of send socket buffer. Often the send buffer 399 * size is not optimally adjusted to the actual network conditions 400 * at hand (delay bandwidth product). Setting the buffer size too 401 * small limits throughput on links with high bandwidth and high 402 * delay (eg. trans-continental/oceanic links). Setting the 403 * buffer size too big consumes too much real kernel memory, 404 * especially with many connections on busy servers. 405 * 406 * The criteria to step up the send buffer one notch are: 407 * 1. receive window of remote host is larger than send buffer 408 * (with a fudge factor of 5/4th); 409 * 2. send buffer is filled to 7/8th with data (so we actually 410 * have data to make use of it); 411 * 3. send buffer fill has not hit maximal automatic size; 412 * 4. our send window (slow start and cogestion controlled) is 413 * larger than sent but unacknowledged data in send buffer. 414 * 415 * The remote host receive window scaling factor may limit the 416 * growing of the send buffer before it reaches its allowed 417 * maximum. 418 * 419 * It scales directly with slow start or congestion window 420 * and does at most one step per received ACK. This fast 421 * scaling has the drawback of growing the send buffer beyond 422 * what is strictly necessary to make full use of a given 423 * delay*bandwith product. However testing has shown this not 424 * to be much of an problem. At worst we are trading wasting 425 * of available bandwith (the non-use of it) for wasting some 426 * socket buffer memory. 427 * 428 * TODO: Shrink send buffer during idle periods together 429 * with congestion window. Requires another timer. Has to 430 * wait for upcoming tcp timer rewrite. 431 */ 432 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 433 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 434 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 435 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 436 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 437 if (!sbreserve_locked(&so->so_snd, 438 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 439 V_tcp_autosndbuf_max), so, curthread)) 440 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 441 } 442 } 443 444 /* 445 * Truncate to the maximum segment length or enable TCP Segmentation 446 * Offloading (if supported by hardware) and ensure that FIN is removed 447 * if the length no longer contains the last data byte. 448 * 449 * TSO may only be used if we are in a pure bulk sending state. The 450 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 451 * IP options prevent using TSO. With TSO the TCP header is the same 452 * (except for the sequence number) for all generated packets. This 453 * makes it impossible to transmit any options which vary per generated 454 * segment or packet. 455 * 456 * The length of TSO bursts is limited to TCP_MAXWIN. That limit and 457 * removal of FIN (if not already catched here) are handled later after 458 * the exact length of the TCP options are known. 459 */ 460 #ifdef IPSEC 461 /* 462 * Pre-calculate here as we save another lookup into the darknesses 463 * of IPsec that way and can actually decide if TSO is ok. 464 */ 465 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 466 #endif 467 if (len > tp->t_maxseg) { 468 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && 469 ((tp->t_flags & TF_SIGNATURE) == 0) && 470 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 471 tp->t_inpcb->inp_options == NULL && 472 tp->t_inpcb->in6p_options == NULL 473 #ifdef IPSEC 474 && ipsec_optlen == 0 475 #endif 476 ) { 477 tso = 1; 478 } else { 479 len = tp->t_maxseg; 480 sendalot = 1; 481 tso = 0; 482 } 483 } 484 if (sack_rxmit) { 485 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 486 flags &= ~TH_FIN; 487 } else { 488 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 489 flags &= ~TH_FIN; 490 } 491 492 recwin = sbspace(&so->so_rcv); 493 494 /* 495 * Sender silly window avoidance. We transmit under the following 496 * conditions when len is non-zero: 497 * 498 * - We have a full segment (or more with TSO) 499 * - This is the last buffer in a write()/send() and we are 500 * either idle or running NODELAY 501 * - we've timed out (e.g. persist timer) 502 * - we have more then 1/2 the maximum send window's worth of 503 * data (receiver may be limited the window size) 504 * - we need to retransmit 505 */ 506 if (len) { 507 if (len >= tp->t_maxseg) 508 goto send; 509 /* 510 * NOTE! on localhost connections an 'ack' from the remote 511 * end may occur synchronously with the output and cause 512 * us to flush a buffer queued with moretocome. XXX 513 * 514 * note: the len + off check is almost certainly unnecessary. 515 */ 516 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 517 (idle || (tp->t_flags & TF_NODELAY)) && 518 len + off >= so->so_snd.sb_cc && 519 (tp->t_flags & TF_NOPUSH) == 0) { 520 goto send; 521 } 522 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 523 goto send; 524 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 525 goto send; 526 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 527 goto send; 528 if (sack_rxmit) 529 goto send; 530 } 531 532 /* 533 * Compare available window to amount of window 534 * known to peer (as advertised window less 535 * next expected input). If the difference is at least two 536 * max size segments, or at least 50% of the maximum possible 537 * window, then want to send a window update to peer. 538 * Skip this if the connection is in T/TCP half-open state. 539 * Don't send pure window updates when the peer has closed 540 * the connection and won't ever send more data. 541 */ 542 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 543 !TCPS_HAVERCVDFIN(tp->t_state)) { 544 /* 545 * "adv" is the amount we can increase the window, 546 * taking into account that we are limited by 547 * TCP_MAXWIN << tp->rcv_scale. 548 */ 549 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 550 (tp->rcv_adv - tp->rcv_nxt); 551 552 if (adv >= (long) (2 * tp->t_maxseg)) 553 goto send; 554 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 555 goto send; 556 } 557 558 /* 559 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 560 * is also a catch-all for the retransmit timer timeout case. 561 */ 562 if (tp->t_flags & TF_ACKNOW) 563 goto send; 564 if ((flags & TH_RST) || 565 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 566 goto send; 567 if (SEQ_GT(tp->snd_up, tp->snd_una)) 568 goto send; 569 /* 570 * If our state indicates that FIN should be sent 571 * and we have not yet done so, then we need to send. 572 */ 573 if (flags & TH_FIN && 574 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 575 goto send; 576 /* 577 * In SACK, it is possible for tcp_output to fail to send a segment 578 * after the retransmission timer has been turned off. Make sure 579 * that the retransmission timer is set. 580 */ 581 if ((tp->t_flags & TF_SACK_PERMIT) && 582 SEQ_GT(tp->snd_max, tp->snd_una) && 583 !tcp_timer_active(tp, TT_REXMT) && 584 !tcp_timer_active(tp, TT_PERSIST)) { 585 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 586 goto just_return; 587 } 588 /* 589 * TCP window updates are not reliable, rather a polling protocol 590 * using ``persist'' packets is used to insure receipt of window 591 * updates. The three ``states'' for the output side are: 592 * idle not doing retransmits or persists 593 * persisting to move a small or zero window 594 * (re)transmitting and thereby not persisting 595 * 596 * tcp_timer_active(tp, TT_PERSIST) 597 * is true when we are in persist state. 598 * (tp->t_flags & TF_FORCEDATA) 599 * is set when we are called to send a persist packet. 600 * tcp_timer_active(tp, TT_REXMT) 601 * is set when we are retransmitting 602 * The output side is idle when both timers are zero. 603 * 604 * If send window is too small, there is data to transmit, and no 605 * retransmit or persist is pending, then go to persist state. 606 * If nothing happens soon, send when timer expires: 607 * if window is nonzero, transmit what we can, 608 * otherwise force out a byte. 609 */ 610 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 611 !tcp_timer_active(tp, TT_PERSIST)) { 612 tp->t_rxtshift = 0; 613 tcp_setpersist(tp); 614 } 615 616 /* 617 * No reason to send a segment, just return. 618 */ 619 just_return: 620 SOCKBUF_UNLOCK(&so->so_snd); 621 return (0); 622 623 send: 624 SOCKBUF_LOCK_ASSERT(&so->so_snd); 625 /* 626 * Before ESTABLISHED, force sending of initial options 627 * unless TCP set not to do any options. 628 * NOTE: we assume that the IP/TCP header plus TCP options 629 * always fit in a single mbuf, leaving room for a maximum 630 * link header, i.e. 631 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 632 */ 633 optlen = 0; 634 #ifdef INET6 635 if (isipv6) 636 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 637 else 638 #endif 639 hdrlen = sizeof (struct tcpiphdr); 640 641 /* 642 * Compute options for segment. 643 * We only have to care about SYN and established connection 644 * segments. Options for SYN-ACK segments are handled in TCP 645 * syncache. 646 */ 647 if ((tp->t_flags & TF_NOOPT) == 0) { 648 to.to_flags = 0; 649 /* Maximum segment size. */ 650 if (flags & TH_SYN) { 651 tp->snd_nxt = tp->iss; 652 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 653 to.to_flags |= TOF_MSS; 654 } 655 /* Window scaling. */ 656 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 657 to.to_wscale = tp->request_r_scale; 658 to.to_flags |= TOF_SCALE; 659 } 660 /* Timestamps. */ 661 if ((tp->t_flags & TF_RCVD_TSTMP) || 662 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 663 to.to_tsval = ticks + tp->ts_offset; 664 to.to_tsecr = tp->ts_recent; 665 to.to_flags |= TOF_TS; 666 /* Set receive buffer autosizing timestamp. */ 667 if (tp->rfbuf_ts == 0 && 668 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 669 tp->rfbuf_ts = ticks; 670 } 671 /* Selective ACK's. */ 672 if (tp->t_flags & TF_SACK_PERMIT) { 673 if (flags & TH_SYN) 674 to.to_flags |= TOF_SACKPERM; 675 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 676 (tp->t_flags & TF_SACK_PERMIT) && 677 tp->rcv_numsacks > 0) { 678 to.to_flags |= TOF_SACK; 679 to.to_nsacks = tp->rcv_numsacks; 680 to.to_sacks = (u_char *)tp->sackblks; 681 } 682 } 683 #ifdef TCP_SIGNATURE 684 /* TCP-MD5 (RFC2385). */ 685 #ifdef INET6 686 if (!isipv6 && (tp->t_flags & TF_SIGNATURE)) 687 #else 688 if (tp->t_flags & TF_SIGNATURE) 689 #endif /* INET6 */ 690 to.to_flags |= TOF_SIGNATURE; 691 #endif /* TCP_SIGNATURE */ 692 693 /* Processing the options. */ 694 hdrlen += optlen = tcp_addoptions(&to, opt); 695 } 696 697 #ifdef INET6 698 if (isipv6) 699 ipoptlen = ip6_optlen(tp->t_inpcb); 700 else 701 #endif 702 if (tp->t_inpcb->inp_options) 703 ipoptlen = tp->t_inpcb->inp_options->m_len - 704 offsetof(struct ipoption, ipopt_list); 705 else 706 ipoptlen = 0; 707 #ifdef IPSEC 708 ipoptlen += ipsec_optlen; 709 #endif 710 711 /* 712 * Adjust data length if insertion of options will 713 * bump the packet length beyond the t_maxopd length. 714 * Clear the FIN bit because we cut off the tail of 715 * the segment. 716 * 717 * When doing TSO limit a burst to TCP_MAXWIN minus the 718 * IP, TCP and Options length to keep ip->ip_len from 719 * overflowing. Prevent the last segment from being 720 * fractional thus making them all equal sized and set 721 * the flag to continue sending. TSO is disabled when 722 * IP options or IPSEC are present. 723 */ 724 if (len + optlen + ipoptlen > tp->t_maxopd) { 725 flags &= ~TH_FIN; 726 if (tso) { 727 if (len > TCP_MAXWIN - hdrlen - optlen) { 728 len = TCP_MAXWIN - hdrlen - optlen; 729 len = len - (len % (tp->t_maxopd - optlen)); 730 sendalot = 1; 731 } else if (tp->t_flags & TF_NEEDFIN) 732 sendalot = 1; 733 } else { 734 len = tp->t_maxopd - optlen - ipoptlen; 735 sendalot = 1; 736 } 737 } 738 739 /*#ifdef DIAGNOSTIC*/ 740 #ifdef INET6 741 if (max_linkhdr + hdrlen > MCLBYTES) 742 #else 743 if (max_linkhdr + hdrlen > MHLEN) 744 #endif 745 panic("tcphdr too big"); 746 /*#endif*/ 747 748 /* 749 * Grab a header mbuf, attaching a copy of data to 750 * be transmitted, and initialize the header from 751 * the template for sends on this connection. 752 */ 753 if (len) { 754 struct mbuf *mb; 755 u_int moff; 756 757 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 758 V_tcpstat.tcps_sndprobe++; 759 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 760 V_tcpstat.tcps_sndrexmitpack++; 761 V_tcpstat.tcps_sndrexmitbyte += len; 762 } else { 763 V_tcpstat.tcps_sndpack++; 764 V_tcpstat.tcps_sndbyte += len; 765 } 766 #ifdef notyet 767 if ((m = m_copypack(so->so_snd.sb_mb, off, 768 (int)len, max_linkhdr + hdrlen)) == 0) { 769 SOCKBUF_UNLOCK(&so->so_snd); 770 error = ENOBUFS; 771 goto out; 772 } 773 /* 774 * m_copypack left space for our hdr; use it. 775 */ 776 m->m_len += hdrlen; 777 m->m_data -= hdrlen; 778 #else 779 MGETHDR(m, M_DONTWAIT, MT_DATA); 780 if (m == NULL) { 781 SOCKBUF_UNLOCK(&so->so_snd); 782 error = ENOBUFS; 783 goto out; 784 } 785 #ifdef INET6 786 if (MHLEN < hdrlen + max_linkhdr) { 787 MCLGET(m, M_DONTWAIT); 788 if ((m->m_flags & M_EXT) == 0) { 789 SOCKBUF_UNLOCK(&so->so_snd); 790 m_freem(m); 791 error = ENOBUFS; 792 goto out; 793 } 794 } 795 #endif 796 m->m_data += max_linkhdr; 797 m->m_len = hdrlen; 798 799 /* 800 * Start the m_copy functions from the closest mbuf 801 * to the offset in the socket buffer chain. 802 */ 803 mb = sbsndptr(&so->so_snd, off, len, &moff); 804 805 if (len <= MHLEN - hdrlen - max_linkhdr) { 806 m_copydata(mb, moff, (int)len, 807 mtod(m, caddr_t) + hdrlen); 808 m->m_len += len; 809 } else { 810 m->m_next = m_copy(mb, moff, (int)len); 811 if (m->m_next == NULL) { 812 SOCKBUF_UNLOCK(&so->so_snd); 813 (void) m_free(m); 814 error = ENOBUFS; 815 goto out; 816 } 817 } 818 #endif 819 /* 820 * If we're sending everything we've got, set PUSH. 821 * (This will keep happy those implementations which only 822 * give data to the user when a buffer fills or 823 * a PUSH comes in.) 824 */ 825 if (off + len == so->so_snd.sb_cc) 826 flags |= TH_PUSH; 827 SOCKBUF_UNLOCK(&so->so_snd); 828 } else { 829 SOCKBUF_UNLOCK(&so->so_snd); 830 if (tp->t_flags & TF_ACKNOW) 831 V_tcpstat.tcps_sndacks++; 832 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 833 V_tcpstat.tcps_sndctrl++; 834 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 835 V_tcpstat.tcps_sndurg++; 836 else 837 V_tcpstat.tcps_sndwinup++; 838 839 MGETHDR(m, M_DONTWAIT, MT_DATA); 840 if (m == NULL) { 841 error = ENOBUFS; 842 goto out; 843 } 844 #ifdef INET6 845 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 846 MHLEN >= hdrlen) { 847 MH_ALIGN(m, hdrlen); 848 } else 849 #endif 850 m->m_data += max_linkhdr; 851 m->m_len = hdrlen; 852 } 853 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 854 m->m_pkthdr.rcvif = (struct ifnet *)0; 855 #ifdef MAC 856 mac_inpcb_create_mbuf(tp->t_inpcb, m); 857 #endif 858 #ifdef INET6 859 if (isipv6) { 860 ip6 = mtod(m, struct ip6_hdr *); 861 th = (struct tcphdr *)(ip6 + 1); 862 tcpip_fillheaders(tp->t_inpcb, ip6, th); 863 } else 864 #endif /* INET6 */ 865 { 866 ip = mtod(m, struct ip *); 867 ipov = (struct ipovly *)ip; 868 th = (struct tcphdr *)(ip + 1); 869 tcpip_fillheaders(tp->t_inpcb, ip, th); 870 } 871 872 /* 873 * Fill in fields, remembering maximum advertised 874 * window for use in delaying messages about window sizes. 875 * If resending a FIN, be sure not to use a new sequence number. 876 */ 877 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 878 tp->snd_nxt == tp->snd_max) 879 tp->snd_nxt--; 880 /* 881 * If we are starting a connection, send ECN setup 882 * SYN packet. If we are on a retransmit, we may 883 * resend those bits a number of times as per 884 * RFC 3168. 885 */ 886 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 887 if (tp->t_rxtshift >= 1) { 888 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 889 flags |= TH_ECE|TH_CWR; 890 } else 891 flags |= TH_ECE|TH_CWR; 892 } 893 894 if (tp->t_state == TCPS_ESTABLISHED && 895 (tp->t_flags & TF_ECN_PERMIT)) { 896 /* 897 * If the peer has ECN, mark data packets with 898 * ECN capable transmission (ECT). 899 * Ignore pure ack packets, retransmissions and window probes. 900 */ 901 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 902 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 903 #ifdef INET6 904 if (isipv6) 905 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 906 else 907 #endif 908 ip->ip_tos |= IPTOS_ECN_ECT0; 909 V_tcpstat.tcps_ecn_ect0++; 910 } 911 912 /* 913 * Reply with proper ECN notifications. 914 */ 915 if (tp->t_flags & TF_ECN_SND_CWR) { 916 flags |= TH_CWR; 917 tp->t_flags &= ~TF_ECN_SND_CWR; 918 } 919 if (tp->t_flags & TF_ECN_SND_ECE) 920 flags |= TH_ECE; 921 } 922 923 /* 924 * If we are doing retransmissions, then snd_nxt will 925 * not reflect the first unsent octet. For ACK only 926 * packets, we do not want the sequence number of the 927 * retransmitted packet, we want the sequence number 928 * of the next unsent octet. So, if there is no data 929 * (and no SYN or FIN), use snd_max instead of snd_nxt 930 * when filling in ti_seq. But if we are in persist 931 * state, snd_max might reflect one byte beyond the 932 * right edge of the window, so use snd_nxt in that 933 * case, since we know we aren't doing a retransmission. 934 * (retransmit and persist are mutually exclusive...) 935 */ 936 if (sack_rxmit == 0) { 937 if (len || (flags & (TH_SYN|TH_FIN)) || 938 tcp_timer_active(tp, TT_PERSIST)) 939 th->th_seq = htonl(tp->snd_nxt); 940 else 941 th->th_seq = htonl(tp->snd_max); 942 } else { 943 th->th_seq = htonl(p->rxmit); 944 p->rxmit += len; 945 tp->sackhint.sack_bytes_rexmit += len; 946 } 947 th->th_ack = htonl(tp->rcv_nxt); 948 if (optlen) { 949 bcopy(opt, th + 1, optlen); 950 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 951 } 952 th->th_flags = flags; 953 /* 954 * Calculate receive window. Don't shrink window, 955 * but avoid silly window syndrome. 956 */ 957 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 958 recwin < (long)tp->t_maxseg) 959 recwin = 0; 960 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 961 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 962 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 963 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 964 965 /* 966 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 967 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 968 * case is handled in syncache. 969 */ 970 if (flags & TH_SYN) 971 th->th_win = htons((u_short) 972 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 973 else 974 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 975 976 /* 977 * Adjust the RXWIN0SENT flag - indicate that we have advertised 978 * a 0 window. This may cause the remote transmitter to stall. This 979 * flag tells soreceive() to disable delayed acknowledgements when 980 * draining the buffer. This can occur if the receiver is attempting 981 * to read more data than can be buffered prior to transmitting on 982 * the connection. 983 */ 984 if (recwin == 0) 985 tp->t_flags |= TF_RXWIN0SENT; 986 else 987 tp->t_flags &= ~TF_RXWIN0SENT; 988 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 989 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 990 th->th_flags |= TH_URG; 991 } else 992 /* 993 * If no urgent pointer to send, then we pull 994 * the urgent pointer to the left edge of the send window 995 * so that it doesn't drift into the send window on sequence 996 * number wraparound. 997 */ 998 tp->snd_up = tp->snd_una; /* drag it along */ 999 1000 #ifdef TCP_SIGNATURE 1001 #ifdef INET6 1002 if (!isipv6) 1003 #endif 1004 if (tp->t_flags & TF_SIGNATURE) { 1005 int sigoff = to.to_signature - opt; 1006 tcp_signature_compute(m, sizeof(struct ip), len, optlen, 1007 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1008 } 1009 #endif 1010 1011 /* 1012 * Put TCP length in extended header, and then 1013 * checksum extended header and data. 1014 */ 1015 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1016 #ifdef INET6 1017 if (isipv6) 1018 /* 1019 * ip6_plen is not need to be filled now, and will be filled 1020 * in ip6_output. 1021 */ 1022 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 1023 sizeof(struct tcphdr) + optlen + len); 1024 else 1025 #endif /* INET6 */ 1026 { 1027 m->m_pkthdr.csum_flags = CSUM_TCP; 1028 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1029 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1030 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1031 1032 /* IP version must be set here for ipv4/ipv6 checking later */ 1033 KASSERT(ip->ip_v == IPVERSION, 1034 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1035 } 1036 1037 /* 1038 * Enable TSO and specify the size of the segments. 1039 * The TCP pseudo header checksum is always provided. 1040 * XXX: Fixme: This is currently not the case for IPv6. 1041 */ 1042 if (tso) { 1043 m->m_pkthdr.csum_flags = CSUM_TSO; 1044 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1045 } 1046 1047 /* 1048 * In transmit state, time the transmission and arrange for 1049 * the retransmit. In persist state, just set snd_max. 1050 */ 1051 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1052 !tcp_timer_active(tp, TT_PERSIST)) { 1053 tcp_seq startseq = tp->snd_nxt; 1054 1055 /* 1056 * Advance snd_nxt over sequence space of this segment. 1057 */ 1058 if (flags & (TH_SYN|TH_FIN)) { 1059 if (flags & TH_SYN) 1060 tp->snd_nxt++; 1061 if (flags & TH_FIN) { 1062 tp->snd_nxt++; 1063 tp->t_flags |= TF_SENTFIN; 1064 } 1065 } 1066 if (sack_rxmit) 1067 goto timer; 1068 tp->snd_nxt += len; 1069 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1070 tp->snd_max = tp->snd_nxt; 1071 /* 1072 * Time this transmission if not a retransmission and 1073 * not currently timing anything. 1074 */ 1075 if (tp->t_rtttime == 0) { 1076 tp->t_rtttime = ticks; 1077 tp->t_rtseq = startseq; 1078 V_tcpstat.tcps_segstimed++; 1079 } 1080 } 1081 1082 /* 1083 * Set retransmit timer if not currently set, 1084 * and not doing a pure ack or a keep-alive probe. 1085 * Initial value for retransmit timer is smoothed 1086 * round-trip time + 2 * round-trip time variance. 1087 * Initialize shift counter which is used for backoff 1088 * of retransmit time. 1089 */ 1090 timer: 1091 if (!tcp_timer_active(tp, TT_REXMT) && 1092 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1093 (tp->snd_nxt != tp->snd_una))) { 1094 if (tcp_timer_active(tp, TT_PERSIST)) { 1095 tcp_timer_activate(tp, TT_PERSIST, 0); 1096 tp->t_rxtshift = 0; 1097 } 1098 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1099 } 1100 } else { 1101 /* 1102 * Persist case, update snd_max but since we are in 1103 * persist mode (no window) we do not update snd_nxt. 1104 */ 1105 int xlen = len; 1106 if (flags & TH_SYN) 1107 ++xlen; 1108 if (flags & TH_FIN) { 1109 ++xlen; 1110 tp->t_flags |= TF_SENTFIN; 1111 } 1112 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1113 tp->snd_max = tp->snd_nxt + len; 1114 } 1115 1116 #ifdef TCPDEBUG 1117 /* 1118 * Trace. 1119 */ 1120 if (so->so_options & SO_DEBUG) { 1121 u_short save = 0; 1122 #ifdef INET6 1123 if (!isipv6) 1124 #endif 1125 { 1126 save = ipov->ih_len; 1127 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1128 } 1129 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1130 #ifdef INET6 1131 if (!isipv6) 1132 #endif 1133 ipov->ih_len = save; 1134 } 1135 #endif 1136 1137 /* 1138 * Fill in IP length and desired time to live and 1139 * send to IP level. There should be a better way 1140 * to handle ttl and tos; we could keep them in 1141 * the template, but need a way to checksum without them. 1142 */ 1143 /* 1144 * m->m_pkthdr.len should have been set before cksum calcuration, 1145 * because in6_cksum() need it. 1146 */ 1147 #ifdef INET6 1148 if (isipv6) { 1149 /* 1150 * we separately set hoplimit for every segment, since the 1151 * user might want to change the value via setsockopt. 1152 * Also, desired default hop limit might be changed via 1153 * Neighbor Discovery. 1154 */ 1155 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1156 1157 /* TODO: IPv6 IP6TOS_ECT bit on */ 1158 error = ip6_output(m, 1159 tp->t_inpcb->in6p_outputopts, NULL, 1160 ((so->so_options & SO_DONTROUTE) ? 1161 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1162 } else 1163 #endif /* INET6 */ 1164 { 1165 ip->ip_len = m->m_pkthdr.len; 1166 #ifdef INET6 1167 if (INP_CHECK_SOCKAF(so, AF_INET6)) 1168 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1169 #endif /* INET6 */ 1170 /* 1171 * If we do path MTU discovery, then we set DF on every packet. 1172 * This might not be the best thing to do according to RFC3390 1173 * Section 2. However the tcp hostcache migitates the problem 1174 * so it affects only the first tcp connection with a host. 1175 */ 1176 if (V_path_mtu_discovery) 1177 ip->ip_off |= IP_DF; 1178 1179 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1180 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1181 tp->t_inpcb); 1182 } 1183 if (error) { 1184 1185 /* 1186 * We know that the packet was lost, so back out the 1187 * sequence number advance, if any. 1188 * 1189 * If the error is EPERM the packet got blocked by the 1190 * local firewall. Normally we should terminate the 1191 * connection but the blocking may have been spurious 1192 * due to a firewall reconfiguration cycle. So we treat 1193 * it like a packet loss and let the retransmit timer and 1194 * timeouts do their work over time. 1195 * XXX: It is a POLA question whether calling tcp_drop right 1196 * away would be the really correct behavior instead. 1197 */ 1198 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1199 !tcp_timer_active(tp, TT_PERSIST)) && 1200 ((flags & TH_SYN) == 0) && 1201 (error != EPERM)) { 1202 if (sack_rxmit) { 1203 p->rxmit -= len; 1204 tp->sackhint.sack_bytes_rexmit -= len; 1205 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1206 ("sackhint bytes rtx >= 0")); 1207 } else 1208 tp->snd_nxt -= len; 1209 } 1210 out: 1211 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1212 switch (error) { 1213 case EPERM: 1214 tp->t_softerror = error; 1215 return (error); 1216 case ENOBUFS: 1217 if (!tcp_timer_active(tp, TT_REXMT) && 1218 !tcp_timer_active(tp, TT_PERSIST)) 1219 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1220 tp->snd_cwnd = tp->t_maxseg; 1221 return (0); 1222 case EMSGSIZE: 1223 /* 1224 * For some reason the interface we used initially 1225 * to send segments changed to another or lowered 1226 * its MTU. 1227 * 1228 * tcp_mtudisc() will find out the new MTU and as 1229 * its last action, initiate retransmission, so it 1230 * is important to not do so here. 1231 * 1232 * If TSO was active we either got an interface 1233 * without TSO capabilits or TSO was turned off. 1234 * Disable it for this connection as too and 1235 * immediatly retry with MSS sized segments generated 1236 * by this function. 1237 */ 1238 if (tso) 1239 tp->t_flags &= ~TF_TSO; 1240 tcp_mtudisc(tp->t_inpcb, 0); 1241 return (0); 1242 case EHOSTDOWN: 1243 case EHOSTUNREACH: 1244 case ENETDOWN: 1245 case ENETUNREACH: 1246 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1247 tp->t_softerror = error; 1248 return (0); 1249 } 1250 /* FALLTHROUGH */ 1251 default: 1252 return (error); 1253 } 1254 } 1255 V_tcpstat.tcps_sndtotal++; 1256 1257 /* 1258 * Data sent (as far as we can tell). 1259 * If this advertises a larger window than any other segment, 1260 * then remember the size of the advertised window. 1261 * Any pending ACK has now been sent. 1262 */ 1263 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1264 tp->rcv_adv = tp->rcv_nxt + recwin; 1265 tp->last_ack_sent = tp->rcv_nxt; 1266 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1267 if (tcp_timer_active(tp, TT_DELACK)) 1268 tcp_timer_activate(tp, TT_DELACK, 0); 1269 #if 0 1270 /* 1271 * This completely breaks TCP if newreno is turned on. What happens 1272 * is that if delayed-acks are turned on on the receiver, this code 1273 * on the transmitter effectively destroys the TCP window, forcing 1274 * it to four packets (1.5Kx4 = 6K window). 1275 */ 1276 if (sendalot && (!V_tcp_do_newreno || --maxburst)) 1277 goto again; 1278 #endif 1279 if (sendalot) 1280 goto again; 1281 return (0); 1282 } 1283 1284 void 1285 tcp_setpersist(struct tcpcb *tp) 1286 { 1287 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1288 int tt; 1289 1290 if (tcp_timer_active(tp, TT_REXMT)) 1291 panic("tcp_setpersist: retransmit pending"); 1292 /* 1293 * Start/restart persistance timer. 1294 */ 1295 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1296 TCPTV_PERSMIN, TCPTV_PERSMAX); 1297 tcp_timer_activate(tp, TT_PERSIST, tt); 1298 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1299 tp->t_rxtshift++; 1300 } 1301 1302 /* 1303 * Insert TCP options according to the supplied parameters to the place 1304 * optp in a consistent way. Can handle unaligned destinations. 1305 * 1306 * The order of the option processing is crucial for optimal packing and 1307 * alignment for the scarce option space. 1308 * 1309 * The optimal order for a SYN/SYN-ACK segment is: 1310 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1311 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1312 * 1313 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1314 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1315 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1316 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1317 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1318 */ 1319 int 1320 tcp_addoptions(struct tcpopt *to, u_char *optp) 1321 { 1322 u_int mask, optlen = 0; 1323 1324 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1325 if ((to->to_flags & mask) != mask) 1326 continue; 1327 if (optlen == TCP_MAXOLEN) 1328 break; 1329 switch (to->to_flags & mask) { 1330 case TOF_MSS: 1331 while (optlen % 4) { 1332 optlen += TCPOLEN_NOP; 1333 *optp++ = TCPOPT_NOP; 1334 } 1335 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1336 continue; 1337 optlen += TCPOLEN_MAXSEG; 1338 *optp++ = TCPOPT_MAXSEG; 1339 *optp++ = TCPOLEN_MAXSEG; 1340 to->to_mss = htons(to->to_mss); 1341 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1342 optp += sizeof(to->to_mss); 1343 break; 1344 case TOF_SCALE: 1345 while (!optlen || optlen % 2 != 1) { 1346 optlen += TCPOLEN_NOP; 1347 *optp++ = TCPOPT_NOP; 1348 } 1349 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1350 continue; 1351 optlen += TCPOLEN_WINDOW; 1352 *optp++ = TCPOPT_WINDOW; 1353 *optp++ = TCPOLEN_WINDOW; 1354 *optp++ = to->to_wscale; 1355 break; 1356 case TOF_SACKPERM: 1357 while (optlen % 2) { 1358 optlen += TCPOLEN_NOP; 1359 *optp++ = TCPOPT_NOP; 1360 } 1361 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1362 continue; 1363 optlen += TCPOLEN_SACK_PERMITTED; 1364 *optp++ = TCPOPT_SACK_PERMITTED; 1365 *optp++ = TCPOLEN_SACK_PERMITTED; 1366 break; 1367 case TOF_TS: 1368 while (!optlen || optlen % 4 != 2) { 1369 optlen += TCPOLEN_NOP; 1370 *optp++ = TCPOPT_NOP; 1371 } 1372 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1373 continue; 1374 optlen += TCPOLEN_TIMESTAMP; 1375 *optp++ = TCPOPT_TIMESTAMP; 1376 *optp++ = TCPOLEN_TIMESTAMP; 1377 to->to_tsval = htonl(to->to_tsval); 1378 to->to_tsecr = htonl(to->to_tsecr); 1379 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1380 optp += sizeof(to->to_tsval); 1381 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1382 optp += sizeof(to->to_tsecr); 1383 break; 1384 case TOF_SIGNATURE: 1385 { 1386 int siglen = TCPOLEN_SIGNATURE - 2; 1387 1388 while (!optlen || optlen % 4 != 2) { 1389 optlen += TCPOLEN_NOP; 1390 *optp++ = TCPOPT_NOP; 1391 } 1392 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1393 continue; 1394 optlen += TCPOLEN_SIGNATURE; 1395 *optp++ = TCPOPT_SIGNATURE; 1396 *optp++ = TCPOLEN_SIGNATURE; 1397 to->to_signature = optp; 1398 while (siglen--) 1399 *optp++ = 0; 1400 break; 1401 } 1402 case TOF_SACK: 1403 { 1404 int sackblks = 0; 1405 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1406 tcp_seq sack_seq; 1407 1408 while (!optlen || optlen % 4 != 2) { 1409 optlen += TCPOLEN_NOP; 1410 *optp++ = TCPOPT_NOP; 1411 } 1412 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1413 continue; 1414 optlen += TCPOLEN_SACKHDR; 1415 *optp++ = TCPOPT_SACK; 1416 sackblks = min(to->to_nsacks, 1417 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1418 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1419 while (sackblks--) { 1420 sack_seq = htonl(sack->start); 1421 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1422 optp += sizeof(sack_seq); 1423 sack_seq = htonl(sack->end); 1424 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1425 optp += sizeof(sack_seq); 1426 optlen += TCPOLEN_SACK; 1427 sack++; 1428 } 1429 V_tcpstat.tcps_sack_send_blocks++; 1430 break; 1431 } 1432 default: 1433 panic("%s: unknown TCP option type", __func__); 1434 break; 1435 } 1436 } 1437 1438 /* Terminate and pad TCP options to a 4 byte boundary. */ 1439 if (optlen % 4) { 1440 optlen += TCPOLEN_EOL; 1441 *optp++ = TCPOPT_EOL; 1442 } 1443 /* 1444 * According to RFC 793 (STD0007): 1445 * "The content of the header beyond the End-of-Option option 1446 * must be header padding (i.e., zero)." 1447 * and later: "The padding is composed of zeros." 1448 */ 1449 while (optlen % 4) { 1450 optlen += TCPOLEN_PAD; 1451 *optp++ = TCPOPT_PAD; 1452 } 1453 1454 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1455 return (optlen); 1456 } 1457