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_tcpdebug.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/domain.h> 43 #include <sys/kernel.h> 44 #include <sys/lock.h> 45 #include <sys/mbuf.h> 46 #include <sys/mutex.h> 47 #include <sys/protosw.h> 48 #include <sys/socket.h> 49 #include <sys/socketvar.h> 50 #include <sys/sysctl.h> 51 52 #include <net/if.h> 53 #include <net/route.h> 54 #include <net/vnet.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 VNET_DEFINE(int, path_mtu_discovery) = 1; 91 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 92 &VNET_NAME(path_mtu_discovery), 1, 93 "Enable Path MTU Discovery"); 94 95 VNET_DEFINE(int, ss_fltsz) = 1; 96 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 97 &VNET_NAME(ss_fltsz), 1, 98 "Slow start flight size"); 99 100 VNET_DEFINE(int, ss_fltsz_local) = 4; 101 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, 102 CTLFLAG_RW, &VNET_NAME(ss_fltsz_local), 1, 103 "Slow start flight size for local networks"); 104 105 VNET_DEFINE(int, tcp_do_newreno) = 1; 106 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, 107 &VNET_NAME(tcp_do_newreno), 0, 108 "Enable NewReno Algorithms"); 109 110 VNET_DEFINE(int, tcp_do_tso) = 1; 111 #define V_tcp_do_tso VNET(tcp_do_tso) 112 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 113 &VNET_NAME(tcp_do_tso), 0, 114 "Enable TCP Segmentation Offload"); 115 116 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 117 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf) 118 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 119 &VNET_NAME(tcp_do_autosndbuf), 0, 120 "Enable automatic send buffer sizing"); 121 122 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 123 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc) 124 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 125 &VNET_NAME(tcp_autosndbuf_inc), 0, 126 "Incrementor step size of automatic send buffer"); 127 128 VNET_DEFINE(int, tcp_autosndbuf_max) = 256*1024; 129 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max) 130 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 131 &VNET_NAME(tcp_autosndbuf_max), 0, 132 "Max size of automatic send buffer"); 133 134 135 /* 136 * Tcp output routine: figure out what should be sent and send it. 137 */ 138 int 139 tcp_output(struct tcpcb *tp) 140 { 141 struct socket *so = tp->t_inpcb->inp_socket; 142 long len, recwin, sendwin; 143 int off, flags, error, rw; 144 struct mbuf *m; 145 struct ip *ip = NULL; 146 struct ipovly *ipov = NULL; 147 struct tcphdr *th; 148 u_char opt[TCP_MAXOLEN]; 149 unsigned ipoptlen, optlen, hdrlen; 150 #ifdef IPSEC 151 unsigned ipsec_optlen = 0; 152 #endif 153 int idle, sendalot; 154 int sack_rxmit, sack_bytes_rxmt; 155 struct sackhole *p; 156 int tso; 157 struct tcpopt to; 158 #if 0 159 int maxburst = TCP_MAXBURST; 160 #endif 161 #ifdef INET6 162 struct ip6_hdr *ip6 = NULL; 163 int isipv6; 164 165 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 166 #endif 167 168 INP_WLOCK_ASSERT(tp->t_inpcb); 169 170 /* 171 * Determine length of data that should be transmitted, 172 * and flags that will be used. 173 * If there is some data or critical controls (SYN, RST) 174 * to send, then transmit; otherwise, investigate further. 175 */ 176 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 177 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) { 178 /* 179 * If we've been idle for more than one retransmit 180 * timeout the old congestion window is no longer 181 * current and we have to reduce it to the restart 182 * window before we can transmit again. 183 * 184 * The restart window is the initial window or the last 185 * CWND, whichever is smaller. 186 * 187 * This is done to prevent us from flooding the path with 188 * a full CWND at wirespeed, overloading router and switch 189 * buffers along the way. 190 * 191 * See RFC5681 Section 4.1. "Restarting Idle Connections". 192 */ 193 if (V_tcp_do_rfc3390) 194 rw = min(4 * tp->t_maxseg, 195 max(2 * tp->t_maxseg, 4380)); 196 #ifdef INET6 197 else if ((isipv6 ? in6_localaddr(&tp->t_inpcb->in6p_faddr) : 198 in_localaddr(tp->t_inpcb->inp_faddr))) 199 #else 200 else if (in_localaddr(tp->t_inpcb->inp_faddr)) 201 #endif 202 rw = V_ss_fltsz_local * tp->t_maxseg; 203 else 204 rw = V_ss_fltsz * tp->t_maxseg; 205 206 tp->snd_cwnd = min(rw, tp->snd_cwnd); 207 } 208 tp->t_flags &= ~TF_LASTIDLE; 209 if (idle) { 210 if (tp->t_flags & TF_MORETOCOME) { 211 tp->t_flags |= TF_LASTIDLE; 212 idle = 0; 213 } 214 } 215 again: 216 /* 217 * If we've recently taken a timeout, snd_max will be greater than 218 * snd_nxt. There may be SACK information that allows us to avoid 219 * resending already delivered data. Adjust snd_nxt accordingly. 220 */ 221 if ((tp->t_flags & TF_SACK_PERMIT) && 222 SEQ_LT(tp->snd_nxt, tp->snd_max)) 223 tcp_sack_adjust(tp); 224 sendalot = 0; 225 tso = 0; 226 off = tp->snd_nxt - tp->snd_una; 227 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 228 229 flags = tcp_outflags[tp->t_state]; 230 /* 231 * Send any SACK-generated retransmissions. If we're explicitly trying 232 * to send out new data (when sendalot is 1), bypass this function. 233 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 234 * we're replacing a (future) new transmission with a retransmission 235 * now, and we previously incremented snd_cwnd in tcp_input(). 236 */ 237 /* 238 * Still in sack recovery , reset rxmit flag to zero. 239 */ 240 sack_rxmit = 0; 241 sack_bytes_rxmt = 0; 242 len = 0; 243 p = NULL; 244 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp) && 245 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 246 long cwin; 247 248 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 249 if (cwin < 0) 250 cwin = 0; 251 /* Do not retransmit SACK segments beyond snd_recover */ 252 if (SEQ_GT(p->end, tp->snd_recover)) { 253 /* 254 * (At least) part of sack hole extends beyond 255 * snd_recover. Check to see if we can rexmit data 256 * for this hole. 257 */ 258 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 259 /* 260 * Can't rexmit any more data for this hole. 261 * That data will be rexmitted in the next 262 * sack recovery episode, when snd_recover 263 * moves past p->rxmit. 264 */ 265 p = NULL; 266 goto after_sack_rexmit; 267 } else 268 /* Can rexmit part of the current hole */ 269 len = ((long)ulmin(cwin, 270 tp->snd_recover - p->rxmit)); 271 } else 272 len = ((long)ulmin(cwin, p->end - p->rxmit)); 273 off = p->rxmit - tp->snd_una; 274 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 275 __func__, off)); 276 if (len > 0) { 277 sack_rxmit = 1; 278 sendalot = 1; 279 TCPSTAT_INC(tcps_sack_rexmits); 280 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 281 min(len, tp->t_maxseg)); 282 } 283 } 284 after_sack_rexmit: 285 /* 286 * Get standard flags, and add SYN or FIN if requested by 'hidden' 287 * state flags. 288 */ 289 if (tp->t_flags & TF_NEEDFIN) 290 flags |= TH_FIN; 291 if (tp->t_flags & TF_NEEDSYN) 292 flags |= TH_SYN; 293 294 SOCKBUF_LOCK(&so->so_snd); 295 /* 296 * If in persist timeout with window of 0, send 1 byte. 297 * Otherwise, if window is small but nonzero 298 * and timer expired, we will send what we can 299 * and go to transmit state. 300 */ 301 if (tp->t_flags & TF_FORCEDATA) { 302 if (sendwin == 0) { 303 /* 304 * If we still have some data to send, then 305 * clear the FIN bit. Usually this would 306 * happen below when it realizes that we 307 * aren't sending all the data. However, 308 * if we have exactly 1 byte of unsent data, 309 * then it won't clear the FIN bit below, 310 * and if we are in persist state, we wind 311 * up sending the packet without recording 312 * that we sent the FIN bit. 313 * 314 * We can't just blindly clear the FIN bit, 315 * because if we don't have any more data 316 * to send then the probe will be the FIN 317 * itself. 318 */ 319 if (off < so->so_snd.sb_cc) 320 flags &= ~TH_FIN; 321 sendwin = 1; 322 } else { 323 tcp_timer_activate(tp, TT_PERSIST, 0); 324 tp->t_rxtshift = 0; 325 } 326 } 327 328 /* 329 * If snd_nxt == snd_max and we have transmitted a FIN, the 330 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 331 * a negative length. This can also occur when TCP opens up 332 * its congestion window while receiving additional duplicate 333 * acks after fast-retransmit because TCP will reset snd_nxt 334 * to snd_max after the fast-retransmit. 335 * 336 * In the normal retransmit-FIN-only case, however, snd_nxt will 337 * be set to snd_una, the offset will be 0, and the length may 338 * wind up 0. 339 * 340 * If sack_rxmit is true we are retransmitting from the scoreboard 341 * in which case len is already set. 342 */ 343 if (sack_rxmit == 0) { 344 if (sack_bytes_rxmt == 0) 345 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 346 else { 347 long cwin; 348 349 /* 350 * We are inside of a SACK recovery episode and are 351 * sending new data, having retransmitted all the 352 * data possible in the scoreboard. 353 */ 354 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 355 - off); 356 /* 357 * Don't remove this (len > 0) check ! 358 * We explicitly check for len > 0 here (although it 359 * isn't really necessary), to work around a gcc 360 * optimization issue - to force gcc to compute 361 * len above. Without this check, the computation 362 * of len is bungled by the optimizer. 363 */ 364 if (len > 0) { 365 cwin = tp->snd_cwnd - 366 (tp->snd_nxt - tp->sack_newdata) - 367 sack_bytes_rxmt; 368 if (cwin < 0) 369 cwin = 0; 370 len = lmin(len, cwin); 371 } 372 } 373 } 374 375 /* 376 * Lop off SYN bit if it has already been sent. However, if this 377 * is SYN-SENT state and if segment contains data and if we don't 378 * know that foreign host supports TAO, suppress sending segment. 379 */ 380 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 381 if (tp->t_state != TCPS_SYN_RECEIVED) 382 flags &= ~TH_SYN; 383 off--, len++; 384 } 385 386 /* 387 * Be careful not to send data and/or FIN on SYN segments. 388 * This measure is needed to prevent interoperability problems 389 * with not fully conformant TCP implementations. 390 */ 391 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 392 len = 0; 393 flags &= ~TH_FIN; 394 } 395 396 if (len < 0) { 397 /* 398 * If FIN has been sent but not acked, 399 * but we haven't been called to retransmit, 400 * len will be < 0. Otherwise, window shrank 401 * after we sent into it. If window shrank to 0, 402 * cancel pending retransmit, pull snd_nxt back 403 * to (closed) window, and set the persist timer 404 * if it isn't already going. If the window didn't 405 * close completely, just wait for an ACK. 406 */ 407 len = 0; 408 if (sendwin == 0) { 409 tcp_timer_activate(tp, TT_REXMT, 0); 410 tp->t_rxtshift = 0; 411 tp->snd_nxt = tp->snd_una; 412 if (!tcp_timer_active(tp, TT_PERSIST)) 413 tcp_setpersist(tp); 414 } 415 } 416 417 /* len will be >= 0 after this point. */ 418 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 419 420 /* 421 * Automatic sizing of send socket buffer. Often the send buffer 422 * size is not optimally adjusted to the actual network conditions 423 * at hand (delay bandwidth product). Setting the buffer size too 424 * small limits throughput on links with high bandwidth and high 425 * delay (eg. trans-continental/oceanic links). Setting the 426 * buffer size too big consumes too much real kernel memory, 427 * especially with many connections on busy servers. 428 * 429 * The criteria to step up the send buffer one notch are: 430 * 1. receive window of remote host is larger than send buffer 431 * (with a fudge factor of 5/4th); 432 * 2. send buffer is filled to 7/8th with data (so we actually 433 * have data to make use of it); 434 * 3. send buffer fill has not hit maximal automatic size; 435 * 4. our send window (slow start and cogestion controlled) is 436 * larger than sent but unacknowledged data in send buffer. 437 * 438 * The remote host receive window scaling factor may limit the 439 * growing of the send buffer before it reaches its allowed 440 * maximum. 441 * 442 * It scales directly with slow start or congestion window 443 * and does at most one step per received ACK. This fast 444 * scaling has the drawback of growing the send buffer beyond 445 * what is strictly necessary to make full use of a given 446 * delay*bandwith product. However testing has shown this not 447 * to be much of an problem. At worst we are trading wasting 448 * of available bandwith (the non-use of it) for wasting some 449 * socket buffer memory. 450 * 451 * TODO: Shrink send buffer during idle periods together 452 * with congestion window. Requires another timer. Has to 453 * wait for upcoming tcp timer rewrite. 454 */ 455 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 456 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 457 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 458 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 459 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 460 if (!sbreserve_locked(&so->so_snd, 461 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 462 V_tcp_autosndbuf_max), so, curthread)) 463 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 464 } 465 } 466 467 /* 468 * Decide if we can use TCP Segmentation Offloading (if supported by 469 * hardware). 470 * 471 * TSO may only be used if we are in a pure bulk sending state. The 472 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 473 * IP options prevent using TSO. With TSO the TCP header is the same 474 * (except for the sequence number) for all generated packets. This 475 * makes it impossible to transmit any options which vary per generated 476 * segment or packet. 477 */ 478 #ifdef IPSEC 479 /* 480 * Pre-calculate here as we save another lookup into the darknesses 481 * of IPsec that way and can actually decide if TSO is ok. 482 */ 483 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 484 #endif 485 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 486 ((tp->t_flags & TF_SIGNATURE) == 0) && 487 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 488 #ifdef IPSEC 489 ipsec_optlen == 0 && 490 #endif 491 tp->t_inpcb->inp_options == NULL && 492 tp->t_inpcb->in6p_options == NULL) 493 tso = 1; 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 = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 561 (tp->rcv_adv - tp->rcv_nxt); 562 563 if (adv >= (long) (2 * tp->t_maxseg)) 564 goto send; 565 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 566 goto send; 567 } 568 569 /* 570 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 571 * is also a catch-all for the retransmit timer timeout case. 572 */ 573 if (tp->t_flags & TF_ACKNOW) 574 goto send; 575 if ((flags & TH_RST) || 576 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 577 goto send; 578 if (SEQ_GT(tp->snd_up, tp->snd_una)) 579 goto send; 580 /* 581 * If our state indicates that FIN should be sent 582 * and we have not yet done so, then we need to send. 583 */ 584 if (flags & TH_FIN && 585 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 586 goto send; 587 /* 588 * In SACK, it is possible for tcp_output to fail to send a segment 589 * after the retransmission timer has been turned off. Make sure 590 * that the retransmission timer is set. 591 */ 592 if ((tp->t_flags & TF_SACK_PERMIT) && 593 SEQ_GT(tp->snd_max, tp->snd_una) && 594 !tcp_timer_active(tp, TT_REXMT) && 595 !tcp_timer_active(tp, TT_PERSIST)) { 596 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 597 goto just_return; 598 } 599 /* 600 * TCP window updates are not reliable, rather a polling protocol 601 * using ``persist'' packets is used to insure receipt of window 602 * updates. The three ``states'' for the output side are: 603 * idle not doing retransmits or persists 604 * persisting to move a small or zero window 605 * (re)transmitting and thereby not persisting 606 * 607 * tcp_timer_active(tp, TT_PERSIST) 608 * is true when we are in persist state. 609 * (tp->t_flags & TF_FORCEDATA) 610 * is set when we are called to send a persist packet. 611 * tcp_timer_active(tp, TT_REXMT) 612 * is set when we are retransmitting 613 * The output side is idle when both timers are zero. 614 * 615 * If send window is too small, there is data to transmit, and no 616 * retransmit or persist is pending, then go to persist state. 617 * If nothing happens soon, send when timer expires: 618 * if window is nonzero, transmit what we can, 619 * otherwise force out a byte. 620 */ 621 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 622 !tcp_timer_active(tp, TT_PERSIST)) { 623 tp->t_rxtshift = 0; 624 tcp_setpersist(tp); 625 } 626 627 /* 628 * No reason to send a segment, just return. 629 */ 630 just_return: 631 SOCKBUF_UNLOCK(&so->so_snd); 632 return (0); 633 634 send: 635 SOCKBUF_LOCK_ASSERT(&so->so_snd); 636 /* 637 * Before ESTABLISHED, force sending of initial options 638 * unless TCP set not to do any options. 639 * NOTE: we assume that the IP/TCP header plus TCP options 640 * always fit in a single mbuf, leaving room for a maximum 641 * link header, i.e. 642 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 643 */ 644 optlen = 0; 645 #ifdef INET6 646 if (isipv6) 647 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 648 else 649 #endif 650 hdrlen = sizeof (struct tcpiphdr); 651 652 /* 653 * Compute options for segment. 654 * We only have to care about SYN and established connection 655 * segments. Options for SYN-ACK segments are handled in TCP 656 * syncache. 657 */ 658 if ((tp->t_flags & TF_NOOPT) == 0) { 659 to.to_flags = 0; 660 /* Maximum segment size. */ 661 if (flags & TH_SYN) { 662 tp->snd_nxt = tp->iss; 663 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 664 to.to_flags |= TOF_MSS; 665 } 666 /* Window scaling. */ 667 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 668 to.to_wscale = tp->request_r_scale; 669 to.to_flags |= TOF_SCALE; 670 } 671 /* Timestamps. */ 672 if ((tp->t_flags & TF_RCVD_TSTMP) || 673 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 674 to.to_tsval = ticks + tp->ts_offset; 675 to.to_tsecr = tp->ts_recent; 676 to.to_flags |= TOF_TS; 677 /* Set receive buffer autosizing timestamp. */ 678 if (tp->rfbuf_ts == 0 && 679 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 680 tp->rfbuf_ts = ticks; 681 } 682 /* Selective ACK's. */ 683 if (tp->t_flags & TF_SACK_PERMIT) { 684 if (flags & TH_SYN) 685 to.to_flags |= TOF_SACKPERM; 686 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 687 (tp->t_flags & TF_SACK_PERMIT) && 688 tp->rcv_numsacks > 0) { 689 to.to_flags |= TOF_SACK; 690 to.to_nsacks = tp->rcv_numsacks; 691 to.to_sacks = (u_char *)tp->sackblks; 692 } 693 } 694 #ifdef TCP_SIGNATURE 695 /* TCP-MD5 (RFC2385). */ 696 if (tp->t_flags & TF_SIGNATURE) 697 to.to_flags |= TOF_SIGNATURE; 698 #endif /* TCP_SIGNATURE */ 699 700 /* Processing the options. */ 701 hdrlen += optlen = tcp_addoptions(&to, opt); 702 } 703 704 #ifdef INET6 705 if (isipv6) 706 ipoptlen = ip6_optlen(tp->t_inpcb); 707 else 708 #endif 709 if (tp->t_inpcb->inp_options) 710 ipoptlen = tp->t_inpcb->inp_options->m_len - 711 offsetof(struct ipoption, ipopt_list); 712 else 713 ipoptlen = 0; 714 #ifdef IPSEC 715 ipoptlen += ipsec_optlen; 716 #endif 717 718 /* 719 * Adjust data length if insertion of options will 720 * bump the packet length beyond the t_maxopd length. 721 * Clear the FIN bit because we cut off the tail of 722 * the segment. 723 */ 724 if (len + optlen + ipoptlen > tp->t_maxopd) { 725 flags &= ~TH_FIN; 726 727 if (tso) { 728 KASSERT(ipoptlen == 0, 729 ("%s: TSO can't do IP options", __func__)); 730 731 /* 732 * Limit a burst to IP_MAXPACKET minus IP, 733 * TCP and options length to keep ip->ip_len 734 * from overflowing. 735 */ 736 if (len > IP_MAXPACKET - hdrlen) { 737 len = IP_MAXPACKET - hdrlen; 738 sendalot = 1; 739 } 740 741 /* 742 * Prevent the last segment from being 743 * fractional unless the send sockbuf can 744 * be emptied. 745 */ 746 if (sendalot && off + len < so->so_snd.sb_cc) { 747 len -= len % (tp->t_maxopd - optlen); 748 sendalot = 1; 749 } 750 751 /* 752 * Send the FIN in a separate segment 753 * after the bulk sending is done. 754 * We don't trust the TSO implementations 755 * to clear the FIN flag on all but the 756 * last segment. 757 */ 758 if (tp->t_flags & TF_NEEDFIN) 759 sendalot = 1; 760 761 } else { 762 len = tp->t_maxopd - optlen - ipoptlen; 763 sendalot = 1; 764 } 765 } else 766 tso = 0; 767 768 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 769 ("%s: len > IP_MAXPACKET", __func__)); 770 771 /*#ifdef DIAGNOSTIC*/ 772 #ifdef INET6 773 if (max_linkhdr + hdrlen > MCLBYTES) 774 #else 775 if (max_linkhdr + hdrlen > MHLEN) 776 #endif 777 panic("tcphdr too big"); 778 /*#endif*/ 779 780 /* 781 * This KASSERT is here to catch edge cases at a well defined place. 782 * Before, those had triggered (random) panic conditions further down. 783 */ 784 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 785 786 /* 787 * Grab a header mbuf, attaching a copy of data to 788 * be transmitted, and initialize the header from 789 * the template for sends on this connection. 790 */ 791 if (len) { 792 struct mbuf *mb; 793 u_int moff; 794 795 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 796 TCPSTAT_INC(tcps_sndprobe); 797 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 798 TCPSTAT_INC(tcps_sndrexmitpack); 799 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 800 } else { 801 TCPSTAT_INC(tcps_sndpack); 802 TCPSTAT_ADD(tcps_sndbyte, len); 803 } 804 #ifdef notyet 805 if ((m = m_copypack(so->so_snd.sb_mb, off, 806 (int)len, max_linkhdr + hdrlen)) == 0) { 807 SOCKBUF_UNLOCK(&so->so_snd); 808 error = ENOBUFS; 809 goto out; 810 } 811 /* 812 * m_copypack left space for our hdr; use it. 813 */ 814 m->m_len += hdrlen; 815 m->m_data -= hdrlen; 816 #else 817 MGETHDR(m, M_DONTWAIT, MT_DATA); 818 if (m == NULL) { 819 SOCKBUF_UNLOCK(&so->so_snd); 820 error = ENOBUFS; 821 goto out; 822 } 823 #ifdef INET6 824 if (MHLEN < hdrlen + max_linkhdr) { 825 MCLGET(m, M_DONTWAIT); 826 if ((m->m_flags & M_EXT) == 0) { 827 SOCKBUF_UNLOCK(&so->so_snd); 828 m_freem(m); 829 error = ENOBUFS; 830 goto out; 831 } 832 } 833 #endif 834 m->m_data += max_linkhdr; 835 m->m_len = hdrlen; 836 837 /* 838 * Start the m_copy functions from the closest mbuf 839 * to the offset in the socket buffer chain. 840 */ 841 mb = sbsndptr(&so->so_snd, off, len, &moff); 842 843 if (len <= MHLEN - hdrlen - max_linkhdr) { 844 m_copydata(mb, moff, (int)len, 845 mtod(m, caddr_t) + hdrlen); 846 m->m_len += len; 847 } else { 848 m->m_next = m_copy(mb, moff, (int)len); 849 if (m->m_next == NULL) { 850 SOCKBUF_UNLOCK(&so->so_snd); 851 (void) m_free(m); 852 error = ENOBUFS; 853 goto out; 854 } 855 } 856 #endif 857 /* 858 * If we're sending everything we've got, set PUSH. 859 * (This will keep happy those implementations which only 860 * give data to the user when a buffer fills or 861 * a PUSH comes in.) 862 */ 863 if (off + len == so->so_snd.sb_cc) 864 flags |= TH_PUSH; 865 SOCKBUF_UNLOCK(&so->so_snd); 866 } else { 867 SOCKBUF_UNLOCK(&so->so_snd); 868 if (tp->t_flags & TF_ACKNOW) 869 TCPSTAT_INC(tcps_sndacks); 870 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 871 TCPSTAT_INC(tcps_sndctrl); 872 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 873 TCPSTAT_INC(tcps_sndurg); 874 else 875 TCPSTAT_INC(tcps_sndwinup); 876 877 MGETHDR(m, M_DONTWAIT, MT_DATA); 878 if (m == NULL) { 879 error = ENOBUFS; 880 goto out; 881 } 882 #ifdef INET6 883 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 884 MHLEN >= hdrlen) { 885 MH_ALIGN(m, hdrlen); 886 } else 887 #endif 888 m->m_data += max_linkhdr; 889 m->m_len = hdrlen; 890 } 891 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 892 m->m_pkthdr.rcvif = (struct ifnet *)0; 893 #ifdef MAC 894 mac_inpcb_create_mbuf(tp->t_inpcb, m); 895 #endif 896 #ifdef INET6 897 if (isipv6) { 898 ip6 = mtod(m, struct ip6_hdr *); 899 th = (struct tcphdr *)(ip6 + 1); 900 tcpip_fillheaders(tp->t_inpcb, ip6, th); 901 } else 902 #endif /* INET6 */ 903 { 904 ip = mtod(m, struct ip *); 905 ipov = (struct ipovly *)ip; 906 th = (struct tcphdr *)(ip + 1); 907 tcpip_fillheaders(tp->t_inpcb, ip, th); 908 } 909 910 /* 911 * Fill in fields, remembering maximum advertised 912 * window for use in delaying messages about window sizes. 913 * If resending a FIN, be sure not to use a new sequence number. 914 */ 915 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 916 tp->snd_nxt == tp->snd_max) 917 tp->snd_nxt--; 918 /* 919 * If we are starting a connection, send ECN setup 920 * SYN packet. If we are on a retransmit, we may 921 * resend those bits a number of times as per 922 * RFC 3168. 923 */ 924 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 925 if (tp->t_rxtshift >= 1) { 926 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 927 flags |= TH_ECE|TH_CWR; 928 } else 929 flags |= TH_ECE|TH_CWR; 930 } 931 932 if (tp->t_state == TCPS_ESTABLISHED && 933 (tp->t_flags & TF_ECN_PERMIT)) { 934 /* 935 * If the peer has ECN, mark data packets with 936 * ECN capable transmission (ECT). 937 * Ignore pure ack packets, retransmissions and window probes. 938 */ 939 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 940 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 941 #ifdef INET6 942 if (isipv6) 943 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 944 else 945 #endif 946 ip->ip_tos |= IPTOS_ECN_ECT0; 947 TCPSTAT_INC(tcps_ecn_ect0); 948 } 949 950 /* 951 * Reply with proper ECN notifications. 952 */ 953 if (tp->t_flags & TF_ECN_SND_CWR) { 954 flags |= TH_CWR; 955 tp->t_flags &= ~TF_ECN_SND_CWR; 956 } 957 if (tp->t_flags & TF_ECN_SND_ECE) 958 flags |= TH_ECE; 959 } 960 961 /* 962 * If we are doing retransmissions, then snd_nxt will 963 * not reflect the first unsent octet. For ACK only 964 * packets, we do not want the sequence number of the 965 * retransmitted packet, we want the sequence number 966 * of the next unsent octet. So, if there is no data 967 * (and no SYN or FIN), use snd_max instead of snd_nxt 968 * when filling in ti_seq. But if we are in persist 969 * state, snd_max might reflect one byte beyond the 970 * right edge of the window, so use snd_nxt in that 971 * case, since we know we aren't doing a retransmission. 972 * (retransmit and persist are mutually exclusive...) 973 */ 974 if (sack_rxmit == 0) { 975 if (len || (flags & (TH_SYN|TH_FIN)) || 976 tcp_timer_active(tp, TT_PERSIST)) 977 th->th_seq = htonl(tp->snd_nxt); 978 else 979 th->th_seq = htonl(tp->snd_max); 980 } else { 981 th->th_seq = htonl(p->rxmit); 982 p->rxmit += len; 983 tp->sackhint.sack_bytes_rexmit += len; 984 } 985 th->th_ack = htonl(tp->rcv_nxt); 986 if (optlen) { 987 bcopy(opt, th + 1, optlen); 988 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 989 } 990 th->th_flags = flags; 991 /* 992 * Calculate receive window. Don't shrink window, 993 * but avoid silly window syndrome. 994 */ 995 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 996 recwin < (long)tp->t_maxseg) 997 recwin = 0; 998 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 999 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 1000 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 1001 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 1002 1003 /* 1004 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1005 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1006 * case is handled in syncache. 1007 */ 1008 if (flags & TH_SYN) 1009 th->th_win = htons((u_short) 1010 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1011 else 1012 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1013 1014 /* 1015 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1016 * a 0 window. This may cause the remote transmitter to stall. This 1017 * flag tells soreceive() to disable delayed acknowledgements when 1018 * draining the buffer. This can occur if the receiver is attempting 1019 * to read more data than can be buffered prior to transmitting on 1020 * the connection. 1021 */ 1022 if (th->th_win == 0) 1023 tp->t_flags |= TF_RXWIN0SENT; 1024 else 1025 tp->t_flags &= ~TF_RXWIN0SENT; 1026 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1027 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1028 th->th_flags |= TH_URG; 1029 } else 1030 /* 1031 * If no urgent pointer to send, then we pull 1032 * the urgent pointer to the left edge of the send window 1033 * so that it doesn't drift into the send window on sequence 1034 * number wraparound. 1035 */ 1036 tp->snd_up = tp->snd_una; /* drag it along */ 1037 1038 #ifdef TCP_SIGNATURE 1039 if (tp->t_flags & TF_SIGNATURE) { 1040 int sigoff = to.to_signature - opt; 1041 tcp_signature_compute(m, 0, len, optlen, 1042 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1043 } 1044 #endif 1045 1046 /* 1047 * Put TCP length in extended header, and then 1048 * checksum extended header and data. 1049 */ 1050 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1051 #ifdef INET6 1052 if (isipv6) 1053 /* 1054 * ip6_plen is not need to be filled now, and will be filled 1055 * in ip6_output. 1056 */ 1057 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 1058 sizeof(struct tcphdr) + optlen + len); 1059 else 1060 #endif /* INET6 */ 1061 { 1062 m->m_pkthdr.csum_flags = CSUM_TCP; 1063 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1064 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1065 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1066 1067 /* IP version must be set here for ipv4/ipv6 checking later */ 1068 KASSERT(ip->ip_v == IPVERSION, 1069 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1070 } 1071 1072 /* 1073 * Enable TSO and specify the size of the segments. 1074 * The TCP pseudo header checksum is always provided. 1075 * XXX: Fixme: This is currently not the case for IPv6. 1076 */ 1077 if (tso) { 1078 KASSERT(len > tp->t_maxopd - optlen, 1079 ("%s: len <= tso_segsz", __func__)); 1080 m->m_pkthdr.csum_flags |= CSUM_TSO; 1081 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1082 } 1083 1084 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1085 ("%s: mbuf chain shorter than expected", __func__)); 1086 1087 /* 1088 * In transmit state, time the transmission and arrange for 1089 * the retransmit. In persist state, just set snd_max. 1090 */ 1091 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1092 !tcp_timer_active(tp, TT_PERSIST)) { 1093 tcp_seq startseq = tp->snd_nxt; 1094 1095 /* 1096 * Advance snd_nxt over sequence space of this segment. 1097 */ 1098 if (flags & (TH_SYN|TH_FIN)) { 1099 if (flags & TH_SYN) 1100 tp->snd_nxt++; 1101 if (flags & TH_FIN) { 1102 tp->snd_nxt++; 1103 tp->t_flags |= TF_SENTFIN; 1104 } 1105 } 1106 if (sack_rxmit) 1107 goto timer; 1108 tp->snd_nxt += len; 1109 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1110 tp->snd_max = tp->snd_nxt; 1111 /* 1112 * Time this transmission if not a retransmission and 1113 * not currently timing anything. 1114 */ 1115 if (tp->t_rtttime == 0) { 1116 tp->t_rtttime = ticks; 1117 tp->t_rtseq = startseq; 1118 TCPSTAT_INC(tcps_segstimed); 1119 } 1120 } 1121 1122 /* 1123 * Set retransmit timer if not currently set, 1124 * and not doing a pure ack or a keep-alive probe. 1125 * Initial value for retransmit timer is smoothed 1126 * round-trip time + 2 * round-trip time variance. 1127 * Initialize shift counter which is used for backoff 1128 * of retransmit time. 1129 */ 1130 timer: 1131 if (!tcp_timer_active(tp, TT_REXMT) && 1132 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1133 (tp->snd_nxt != tp->snd_una))) { 1134 if (tcp_timer_active(tp, TT_PERSIST)) { 1135 tcp_timer_activate(tp, TT_PERSIST, 0); 1136 tp->t_rxtshift = 0; 1137 } 1138 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1139 } 1140 } else { 1141 /* 1142 * Persist case, update snd_max but since we are in 1143 * persist mode (no window) we do not update snd_nxt. 1144 */ 1145 int xlen = len; 1146 if (flags & TH_SYN) 1147 ++xlen; 1148 if (flags & TH_FIN) { 1149 ++xlen; 1150 tp->t_flags |= TF_SENTFIN; 1151 } 1152 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1153 tp->snd_max = tp->snd_nxt + len; 1154 } 1155 1156 #ifdef TCPDEBUG 1157 /* 1158 * Trace. 1159 */ 1160 if (so->so_options & SO_DEBUG) { 1161 u_short save = 0; 1162 #ifdef INET6 1163 if (!isipv6) 1164 #endif 1165 { 1166 save = ipov->ih_len; 1167 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1168 } 1169 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1170 #ifdef INET6 1171 if (!isipv6) 1172 #endif 1173 ipov->ih_len = save; 1174 } 1175 #endif 1176 1177 /* 1178 * Fill in IP length and desired time to live and 1179 * send to IP level. There should be a better way 1180 * to handle ttl and tos; we could keep them in 1181 * the template, but need a way to checksum without them. 1182 */ 1183 /* 1184 * m->m_pkthdr.len should have been set before cksum calcuration, 1185 * because in6_cksum() need it. 1186 */ 1187 #ifdef INET6 1188 if (isipv6) { 1189 /* 1190 * we separately set hoplimit for every segment, since the 1191 * user might want to change the value via setsockopt. 1192 * Also, desired default hop limit might be changed via 1193 * Neighbor Discovery. 1194 */ 1195 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1196 1197 /* TODO: IPv6 IP6TOS_ECT bit on */ 1198 error = ip6_output(m, 1199 tp->t_inpcb->in6p_outputopts, NULL, 1200 ((so->so_options & SO_DONTROUTE) ? 1201 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1202 } else 1203 #endif /* INET6 */ 1204 { 1205 ip->ip_len = m->m_pkthdr.len; 1206 #ifdef INET6 1207 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1208 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1209 #endif /* INET6 */ 1210 /* 1211 * If we do path MTU discovery, then we set DF on every packet. 1212 * This might not be the best thing to do according to RFC3390 1213 * Section 2. However the tcp hostcache migitates the problem 1214 * so it affects only the first tcp connection with a host. 1215 * 1216 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1217 */ 1218 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) 1219 ip->ip_off |= IP_DF; 1220 1221 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1222 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1223 tp->t_inpcb); 1224 } 1225 if (error) { 1226 1227 /* 1228 * We know that the packet was lost, so back out the 1229 * sequence number advance, if any. 1230 * 1231 * If the error is EPERM the packet got blocked by the 1232 * local firewall. Normally we should terminate the 1233 * connection but the blocking may have been spurious 1234 * due to a firewall reconfiguration cycle. So we treat 1235 * it like a packet loss and let the retransmit timer and 1236 * timeouts do their work over time. 1237 * XXX: It is a POLA question whether calling tcp_drop right 1238 * away would be the really correct behavior instead. 1239 */ 1240 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1241 !tcp_timer_active(tp, TT_PERSIST)) && 1242 ((flags & TH_SYN) == 0) && 1243 (error != EPERM)) { 1244 if (sack_rxmit) { 1245 p->rxmit -= len; 1246 tp->sackhint.sack_bytes_rexmit -= len; 1247 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1248 ("sackhint bytes rtx >= 0")); 1249 } else 1250 tp->snd_nxt -= len; 1251 } 1252 out: 1253 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1254 switch (error) { 1255 case EPERM: 1256 tp->t_softerror = error; 1257 return (error); 1258 case ENOBUFS: 1259 if (!tcp_timer_active(tp, TT_REXMT) && 1260 !tcp_timer_active(tp, TT_PERSIST)) 1261 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1262 tp->snd_cwnd = tp->t_maxseg; 1263 return (0); 1264 case EMSGSIZE: 1265 /* 1266 * For some reason the interface we used initially 1267 * to send segments changed to another or lowered 1268 * its MTU. 1269 * 1270 * tcp_mtudisc() will find out the new MTU and as 1271 * its last action, initiate retransmission, so it 1272 * is important to not do so here. 1273 * 1274 * If TSO was active we either got an interface 1275 * without TSO capabilits or TSO was turned off. 1276 * Disable it for this connection as too and 1277 * immediatly retry with MSS sized segments generated 1278 * by this function. 1279 */ 1280 if (tso) 1281 tp->t_flags &= ~TF_TSO; 1282 tcp_mtudisc(tp->t_inpcb, 0); 1283 return (0); 1284 case EHOSTDOWN: 1285 case EHOSTUNREACH: 1286 case ENETDOWN: 1287 case ENETUNREACH: 1288 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1289 tp->t_softerror = error; 1290 return (0); 1291 } 1292 /* FALLTHROUGH */ 1293 default: 1294 return (error); 1295 } 1296 } 1297 TCPSTAT_INC(tcps_sndtotal); 1298 1299 /* 1300 * Data sent (as far as we can tell). 1301 * If this advertises a larger window than any other segment, 1302 * then remember the size of the advertised window. 1303 * Any pending ACK has now been sent. 1304 */ 1305 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1306 tp->rcv_adv = tp->rcv_nxt + recwin; 1307 tp->last_ack_sent = tp->rcv_nxt; 1308 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1309 if (tcp_timer_active(tp, TT_DELACK)) 1310 tcp_timer_activate(tp, TT_DELACK, 0); 1311 #if 0 1312 /* 1313 * This completely breaks TCP if newreno is turned on. What happens 1314 * is that if delayed-acks are turned on on the receiver, this code 1315 * on the transmitter effectively destroys the TCP window, forcing 1316 * it to four packets (1.5Kx4 = 6K window). 1317 */ 1318 if (sendalot && (!V_tcp_do_newreno || --maxburst)) 1319 goto again; 1320 #endif 1321 if (sendalot) 1322 goto again; 1323 return (0); 1324 } 1325 1326 void 1327 tcp_setpersist(struct tcpcb *tp) 1328 { 1329 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1330 int tt; 1331 1332 if (tcp_timer_active(tp, TT_REXMT)) 1333 panic("tcp_setpersist: retransmit pending"); 1334 /* 1335 * Start/restart persistance timer. 1336 */ 1337 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1338 TCPTV_PERSMIN, TCPTV_PERSMAX); 1339 tcp_timer_activate(tp, TT_PERSIST, tt); 1340 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1341 tp->t_rxtshift++; 1342 } 1343 1344 /* 1345 * Insert TCP options according to the supplied parameters to the place 1346 * optp in a consistent way. Can handle unaligned destinations. 1347 * 1348 * The order of the option processing is crucial for optimal packing and 1349 * alignment for the scarce option space. 1350 * 1351 * The optimal order for a SYN/SYN-ACK segment is: 1352 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1353 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1354 * 1355 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1356 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1357 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1358 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1359 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1360 */ 1361 int 1362 tcp_addoptions(struct tcpopt *to, u_char *optp) 1363 { 1364 u_int mask, optlen = 0; 1365 1366 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1367 if ((to->to_flags & mask) != mask) 1368 continue; 1369 if (optlen == TCP_MAXOLEN) 1370 break; 1371 switch (to->to_flags & mask) { 1372 case TOF_MSS: 1373 while (optlen % 4) { 1374 optlen += TCPOLEN_NOP; 1375 *optp++ = TCPOPT_NOP; 1376 } 1377 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1378 continue; 1379 optlen += TCPOLEN_MAXSEG; 1380 *optp++ = TCPOPT_MAXSEG; 1381 *optp++ = TCPOLEN_MAXSEG; 1382 to->to_mss = htons(to->to_mss); 1383 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1384 optp += sizeof(to->to_mss); 1385 break; 1386 case TOF_SCALE: 1387 while (!optlen || optlen % 2 != 1) { 1388 optlen += TCPOLEN_NOP; 1389 *optp++ = TCPOPT_NOP; 1390 } 1391 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1392 continue; 1393 optlen += TCPOLEN_WINDOW; 1394 *optp++ = TCPOPT_WINDOW; 1395 *optp++ = TCPOLEN_WINDOW; 1396 *optp++ = to->to_wscale; 1397 break; 1398 case TOF_SACKPERM: 1399 while (optlen % 2) { 1400 optlen += TCPOLEN_NOP; 1401 *optp++ = TCPOPT_NOP; 1402 } 1403 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1404 continue; 1405 optlen += TCPOLEN_SACK_PERMITTED; 1406 *optp++ = TCPOPT_SACK_PERMITTED; 1407 *optp++ = TCPOLEN_SACK_PERMITTED; 1408 break; 1409 case TOF_TS: 1410 while (!optlen || optlen % 4 != 2) { 1411 optlen += TCPOLEN_NOP; 1412 *optp++ = TCPOPT_NOP; 1413 } 1414 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1415 continue; 1416 optlen += TCPOLEN_TIMESTAMP; 1417 *optp++ = TCPOPT_TIMESTAMP; 1418 *optp++ = TCPOLEN_TIMESTAMP; 1419 to->to_tsval = htonl(to->to_tsval); 1420 to->to_tsecr = htonl(to->to_tsecr); 1421 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1422 optp += sizeof(to->to_tsval); 1423 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1424 optp += sizeof(to->to_tsecr); 1425 break; 1426 case TOF_SIGNATURE: 1427 { 1428 int siglen = TCPOLEN_SIGNATURE - 2; 1429 1430 while (!optlen || optlen % 4 != 2) { 1431 optlen += TCPOLEN_NOP; 1432 *optp++ = TCPOPT_NOP; 1433 } 1434 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1435 continue; 1436 optlen += TCPOLEN_SIGNATURE; 1437 *optp++ = TCPOPT_SIGNATURE; 1438 *optp++ = TCPOLEN_SIGNATURE; 1439 to->to_signature = optp; 1440 while (siglen--) 1441 *optp++ = 0; 1442 break; 1443 } 1444 case TOF_SACK: 1445 { 1446 int sackblks = 0; 1447 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1448 tcp_seq sack_seq; 1449 1450 while (!optlen || optlen % 4 != 2) { 1451 optlen += TCPOLEN_NOP; 1452 *optp++ = TCPOPT_NOP; 1453 } 1454 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1455 continue; 1456 optlen += TCPOLEN_SACKHDR; 1457 *optp++ = TCPOPT_SACK; 1458 sackblks = min(to->to_nsacks, 1459 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1460 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1461 while (sackblks--) { 1462 sack_seq = htonl(sack->start); 1463 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1464 optp += sizeof(sack_seq); 1465 sack_seq = htonl(sack->end); 1466 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1467 optp += sizeof(sack_seq); 1468 optlen += TCPOLEN_SACK; 1469 sack++; 1470 } 1471 TCPSTAT_INC(tcps_sack_send_blocks); 1472 break; 1473 } 1474 default: 1475 panic("%s: unknown TCP option type", __func__); 1476 break; 1477 } 1478 } 1479 1480 /* Terminate and pad TCP options to a 4 byte boundary. */ 1481 if (optlen % 4) { 1482 optlen += TCPOLEN_EOL; 1483 *optp++ = TCPOPT_EOL; 1484 } 1485 /* 1486 * According to RFC 793 (STD0007): 1487 * "The content of the header beyond the End-of-Option option 1488 * must be header padding (i.e., zero)." 1489 * and later: "The padding is composed of zeros." 1490 */ 1491 while (optlen % 4) { 1492 optlen += TCPOLEN_PAD; 1493 *optp++ = TCPOPT_PAD; 1494 } 1495 1496 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1497 return (optlen); 1498 } 1499