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/hhook.h> 44 #include <sys/kernel.h> 45 #include <sys/lock.h> 46 #include <sys/mbuf.h> 47 #include <sys/mutex.h> 48 #include <sys/protosw.h> 49 #include <sys/socket.h> 50 #include <sys/socketvar.h> 51 #include <sys/sysctl.h> 52 53 #include <net/if.h> 54 #include <net/route.h> 55 #include <net/vnet.h> 56 57 #include <netinet/cc.h> 58 #include <netinet/in.h> 59 #include <netinet/in_systm.h> 60 #include <netinet/ip.h> 61 #include <netinet/in_pcb.h> 62 #include <netinet/ip_var.h> 63 #include <netinet/ip_options.h> 64 #ifdef INET6 65 #include <netinet6/in6_pcb.h> 66 #include <netinet/ip6.h> 67 #include <netinet6/ip6_var.h> 68 #endif 69 #define TCPOUTFLAGS 70 #include <netinet/tcp_fsm.h> 71 #include <netinet/tcp_seq.h> 72 #include <netinet/tcp_timer.h> 73 #include <netinet/tcp_var.h> 74 #include <netinet/tcpip.h> 75 #ifdef TCPDEBUG 76 #include <netinet/tcp_debug.h> 77 #endif 78 79 #ifdef IPSEC 80 #include <netipsec/ipsec.h> 81 #endif /*IPSEC*/ 82 83 #include <machine/in_cksum.h> 84 85 #include <security/mac/mac_framework.h> 86 87 #ifdef notyet 88 extern struct mbuf *m_copypack(); 89 #endif 90 91 VNET_DEFINE(int, path_mtu_discovery) = 1; 92 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 93 &VNET_NAME(path_mtu_discovery), 1, 94 "Enable Path MTU Discovery"); 95 96 VNET_DEFINE(int, ss_fltsz) = 1; 97 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, slowstart_flightsize, CTLFLAG_RW, 98 &VNET_NAME(ss_fltsz), 1, 99 "Slow start flight size"); 100 101 VNET_DEFINE(int, ss_fltsz_local) = 4; 102 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, local_slowstart_flightsize, 103 CTLFLAG_RW, &VNET_NAME(ss_fltsz_local), 1, 104 "Slow start flight size for local networks"); 105 106 VNET_DEFINE(int, tcp_do_tso) = 1; 107 #define V_tcp_do_tso VNET(tcp_do_tso) 108 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 109 &VNET_NAME(tcp_do_tso), 0, 110 "Enable TCP Segmentation Offload"); 111 112 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 113 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf) 114 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 115 &VNET_NAME(tcp_do_autosndbuf), 0, 116 "Enable automatic send buffer sizing"); 117 118 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 119 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc) 120 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 121 &VNET_NAME(tcp_autosndbuf_inc), 0, 122 "Incrementor step size of automatic send buffer"); 123 124 VNET_DEFINE(int, tcp_autosndbuf_max) = 256*1024; 125 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max) 126 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 127 &VNET_NAME(tcp_autosndbuf_max), 0, 128 "Max size of automatic send buffer"); 129 130 static void inline hhook_run_tcp_est_out(struct tcpcb *tp, 131 struct tcphdr *th, struct tcpopt *to, 132 long len, int tso); 133 static void inline cc_after_idle(struct tcpcb *tp); 134 135 /* 136 * Wrapper for the TCP established ouput helper hook. 137 */ 138 static void inline 139 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 140 struct tcpopt *to, long len, int tso) 141 { 142 struct tcp_hhook_data hhook_data; 143 144 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 145 hhook_data.tp = tp; 146 hhook_data.th = th; 147 hhook_data.to = to; 148 hhook_data.len = len; 149 hhook_data.tso = tso; 150 151 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 152 tp->osd); 153 } 154 } 155 156 /* 157 * CC wrapper hook functions 158 */ 159 static void inline 160 cc_after_idle(struct tcpcb *tp) 161 { 162 INP_WLOCK_ASSERT(tp->t_inpcb); 163 164 if (CC_ALGO(tp)->after_idle != NULL) 165 CC_ALGO(tp)->after_idle(tp->ccv); 166 } 167 168 /* 169 * Tcp output routine: figure out what should be sent and send it. 170 */ 171 int 172 tcp_output(struct tcpcb *tp) 173 { 174 struct socket *so = tp->t_inpcb->inp_socket; 175 long len, recwin, sendwin; 176 int off, flags, error; 177 struct mbuf *m; 178 struct ip *ip = NULL; 179 struct ipovly *ipov = NULL; 180 struct tcphdr *th; 181 u_char opt[TCP_MAXOLEN]; 182 unsigned ipoptlen, optlen, hdrlen; 183 #ifdef IPSEC 184 unsigned ipsec_optlen = 0; 185 #endif 186 int idle, sendalot; 187 int sack_rxmit, sack_bytes_rxmt; 188 struct sackhole *p; 189 int tso; 190 struct tcpopt to; 191 #if 0 192 int maxburst = TCP_MAXBURST; 193 #endif 194 #ifdef INET6 195 struct ip6_hdr *ip6 = NULL; 196 int isipv6; 197 198 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 199 #endif 200 201 INP_WLOCK_ASSERT(tp->t_inpcb); 202 203 /* 204 * Determine length of data that should be transmitted, 205 * and flags that will be used. 206 * If there is some data or critical controls (SYN, RST) 207 * to send, then transmit; otherwise, investigate further. 208 */ 209 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 210 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 211 cc_after_idle(tp); 212 tp->t_flags &= ~TF_LASTIDLE; 213 if (idle) { 214 if (tp->t_flags & TF_MORETOCOME) { 215 tp->t_flags |= TF_LASTIDLE; 216 idle = 0; 217 } 218 } 219 again: 220 /* 221 * If we've recently taken a timeout, snd_max will be greater than 222 * snd_nxt. There may be SACK information that allows us to avoid 223 * resending already delivered data. Adjust snd_nxt accordingly. 224 */ 225 if ((tp->t_flags & TF_SACK_PERMIT) && 226 SEQ_LT(tp->snd_nxt, tp->snd_max)) 227 tcp_sack_adjust(tp); 228 sendalot = 0; 229 tso = 0; 230 off = tp->snd_nxt - tp->snd_una; 231 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 232 233 flags = tcp_outflags[tp->t_state]; 234 /* 235 * Send any SACK-generated retransmissions. If we're explicitly trying 236 * to send out new data (when sendalot is 1), bypass this function. 237 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 238 * we're replacing a (future) new transmission with a retransmission 239 * now, and we previously incremented snd_cwnd in tcp_input(). 240 */ 241 /* 242 * Still in sack recovery , reset rxmit flag to zero. 243 */ 244 sack_rxmit = 0; 245 sack_bytes_rxmt = 0; 246 len = 0; 247 p = NULL; 248 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 249 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 250 long cwin; 251 252 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 253 if (cwin < 0) 254 cwin = 0; 255 /* Do not retransmit SACK segments beyond snd_recover */ 256 if (SEQ_GT(p->end, tp->snd_recover)) { 257 /* 258 * (At least) part of sack hole extends beyond 259 * snd_recover. Check to see if we can rexmit data 260 * for this hole. 261 */ 262 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 263 /* 264 * Can't rexmit any more data for this hole. 265 * That data will be rexmitted in the next 266 * sack recovery episode, when snd_recover 267 * moves past p->rxmit. 268 */ 269 p = NULL; 270 goto after_sack_rexmit; 271 } else 272 /* Can rexmit part of the current hole */ 273 len = ((long)ulmin(cwin, 274 tp->snd_recover - p->rxmit)); 275 } else 276 len = ((long)ulmin(cwin, p->end - p->rxmit)); 277 off = p->rxmit - tp->snd_una; 278 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 279 __func__, off)); 280 if (len > 0) { 281 sack_rxmit = 1; 282 sendalot = 1; 283 TCPSTAT_INC(tcps_sack_rexmits); 284 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 285 min(len, tp->t_maxseg)); 286 } 287 } 288 after_sack_rexmit: 289 /* 290 * Get standard flags, and add SYN or FIN if requested by 'hidden' 291 * state flags. 292 */ 293 if (tp->t_flags & TF_NEEDFIN) 294 flags |= TH_FIN; 295 if (tp->t_flags & TF_NEEDSYN) 296 flags |= TH_SYN; 297 298 SOCKBUF_LOCK(&so->so_snd); 299 /* 300 * If in persist timeout with window of 0, send 1 byte. 301 * Otherwise, if window is small but nonzero 302 * and timer expired, we will send what we can 303 * and go to transmit state. 304 */ 305 if (tp->t_flags & TF_FORCEDATA) { 306 if (sendwin == 0) { 307 /* 308 * If we still have some data to send, then 309 * clear the FIN bit. Usually this would 310 * happen below when it realizes that we 311 * aren't sending all the data. However, 312 * if we have exactly 1 byte of unsent data, 313 * then it won't clear the FIN bit below, 314 * and if we are in persist state, we wind 315 * up sending the packet without recording 316 * that we sent the FIN bit. 317 * 318 * We can't just blindly clear the FIN bit, 319 * because if we don't have any more data 320 * to send then the probe will be the FIN 321 * itself. 322 */ 323 if (off < so->so_snd.sb_cc) 324 flags &= ~TH_FIN; 325 sendwin = 1; 326 } else { 327 tcp_timer_activate(tp, TT_PERSIST, 0); 328 tp->t_rxtshift = 0; 329 } 330 } 331 332 /* 333 * If snd_nxt == snd_max and we have transmitted a FIN, the 334 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 335 * a negative length. This can also occur when TCP opens up 336 * its congestion window while receiving additional duplicate 337 * acks after fast-retransmit because TCP will reset snd_nxt 338 * to snd_max after the fast-retransmit. 339 * 340 * In the normal retransmit-FIN-only case, however, snd_nxt will 341 * be set to snd_una, the offset will be 0, and the length may 342 * wind up 0. 343 * 344 * If sack_rxmit is true we are retransmitting from the scoreboard 345 * in which case len is already set. 346 */ 347 if (sack_rxmit == 0) { 348 if (sack_bytes_rxmt == 0) 349 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 350 else { 351 long cwin; 352 353 /* 354 * We are inside of a SACK recovery episode and are 355 * sending new data, having retransmitted all the 356 * data possible in the scoreboard. 357 */ 358 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 359 - off); 360 /* 361 * Don't remove this (len > 0) check ! 362 * We explicitly check for len > 0 here (although it 363 * isn't really necessary), to work around a gcc 364 * optimization issue - to force gcc to compute 365 * len above. Without this check, the computation 366 * of len is bungled by the optimizer. 367 */ 368 if (len > 0) { 369 cwin = tp->snd_cwnd - 370 (tp->snd_nxt - tp->sack_newdata) - 371 sack_bytes_rxmt; 372 if (cwin < 0) 373 cwin = 0; 374 len = lmin(len, cwin); 375 } 376 } 377 } 378 379 /* 380 * Lop off SYN bit if it has already been sent. However, if this 381 * is SYN-SENT state and if segment contains data and if we don't 382 * know that foreign host supports TAO, suppress sending segment. 383 */ 384 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 385 if (tp->t_state != TCPS_SYN_RECEIVED) 386 flags &= ~TH_SYN; 387 off--, len++; 388 } 389 390 /* 391 * Be careful not to send data and/or FIN on SYN segments. 392 * This measure is needed to prevent interoperability problems 393 * with not fully conformant TCP implementations. 394 */ 395 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 396 len = 0; 397 flags &= ~TH_FIN; 398 } 399 400 if (len < 0) { 401 /* 402 * If FIN has been sent but not acked, 403 * but we haven't been called to retransmit, 404 * len will be < 0. Otherwise, window shrank 405 * after we sent into it. If window shrank to 0, 406 * cancel pending retransmit, pull snd_nxt back 407 * to (closed) window, and set the persist timer 408 * if it isn't already going. If the window didn't 409 * close completely, just wait for an ACK. 410 */ 411 len = 0; 412 if (sendwin == 0) { 413 tcp_timer_activate(tp, TT_REXMT, 0); 414 tp->t_rxtshift = 0; 415 tp->snd_nxt = tp->snd_una; 416 if (!tcp_timer_active(tp, TT_PERSIST)) 417 tcp_setpersist(tp); 418 } 419 } 420 421 /* len will be >= 0 after this point. */ 422 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 423 424 /* 425 * Automatic sizing of send socket buffer. Often the send buffer 426 * size is not optimally adjusted to the actual network conditions 427 * at hand (delay bandwidth product). Setting the buffer size too 428 * small limits throughput on links with high bandwidth and high 429 * delay (eg. trans-continental/oceanic links). Setting the 430 * buffer size too big consumes too much real kernel memory, 431 * especially with many connections on busy servers. 432 * 433 * The criteria to step up the send buffer one notch are: 434 * 1. receive window of remote host is larger than send buffer 435 * (with a fudge factor of 5/4th); 436 * 2. send buffer is filled to 7/8th with data (so we actually 437 * have data to make use of it); 438 * 3. send buffer fill has not hit maximal automatic size; 439 * 4. our send window (slow start and cogestion controlled) is 440 * larger than sent but unacknowledged data in send buffer. 441 * 442 * The remote host receive window scaling factor may limit the 443 * growing of the send buffer before it reaches its allowed 444 * maximum. 445 * 446 * It scales directly with slow start or congestion window 447 * and does at most one step per received ACK. This fast 448 * scaling has the drawback of growing the send buffer beyond 449 * what is strictly necessary to make full use of a given 450 * delay*bandwith product. However testing has shown this not 451 * to be much of an problem. At worst we are trading wasting 452 * of available bandwith (the non-use of it) for wasting some 453 * socket buffer memory. 454 * 455 * TODO: Shrink send buffer during idle periods together 456 * with congestion window. Requires another timer. Has to 457 * wait for upcoming tcp timer rewrite. 458 */ 459 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 460 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 461 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 462 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 463 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 464 if (!sbreserve_locked(&so->so_snd, 465 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 466 V_tcp_autosndbuf_max), so, curthread)) 467 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 468 } 469 } 470 471 /* 472 * Decide if we can use TCP Segmentation Offloading (if supported by 473 * hardware). 474 * 475 * TSO may only be used if we are in a pure bulk sending state. The 476 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 477 * IP options prevent using TSO. With TSO the TCP header is the same 478 * (except for the sequence number) for all generated packets. This 479 * makes it impossible to transmit any options which vary per generated 480 * segment or packet. 481 */ 482 #ifdef IPSEC 483 /* 484 * Pre-calculate here as we save another lookup into the darknesses 485 * of IPsec that way and can actually decide if TSO is ok. 486 */ 487 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 488 #endif 489 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 490 ((tp->t_flags & TF_SIGNATURE) == 0) && 491 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 492 #ifdef IPSEC 493 ipsec_optlen == 0 && 494 #endif 495 tp->t_inpcb->inp_options == NULL && 496 tp->t_inpcb->in6p_options == NULL) 497 tso = 1; 498 499 if (sack_rxmit) { 500 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 501 flags &= ~TH_FIN; 502 } else { 503 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 504 flags &= ~TH_FIN; 505 } 506 507 recwin = sbspace(&so->so_rcv); 508 509 /* 510 * Sender silly window avoidance. We transmit under the following 511 * conditions when len is non-zero: 512 * 513 * - We have a full segment (or more with TSO) 514 * - This is the last buffer in a write()/send() and we are 515 * either idle or running NODELAY 516 * - we've timed out (e.g. persist timer) 517 * - we have more then 1/2 the maximum send window's worth of 518 * data (receiver may be limited the window size) 519 * - we need to retransmit 520 */ 521 if (len) { 522 if (len >= tp->t_maxseg) 523 goto send; 524 /* 525 * NOTE! on localhost connections an 'ack' from the remote 526 * end may occur synchronously with the output and cause 527 * us to flush a buffer queued with moretocome. XXX 528 * 529 * note: the len + off check is almost certainly unnecessary. 530 */ 531 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 532 (idle || (tp->t_flags & TF_NODELAY)) && 533 len + off >= so->so_snd.sb_cc && 534 (tp->t_flags & TF_NOPUSH) == 0) { 535 goto send; 536 } 537 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 538 goto send; 539 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 540 goto send; 541 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 542 goto send; 543 if (sack_rxmit) 544 goto send; 545 } 546 547 /* 548 * Compare available window to amount of window 549 * known to peer (as advertised window less 550 * next expected input). If the difference is at least two 551 * max size segments, or at least 50% of the maximum possible 552 * window, then want to send a window update to peer. 553 * Skip this if the connection is in T/TCP half-open state. 554 * Don't send pure window updates when the peer has closed 555 * the connection and won't ever send more data. 556 */ 557 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 558 !TCPS_HAVERCVDFIN(tp->t_state)) { 559 /* 560 * "adv" is the amount we can increase the window, 561 * taking into account that we are limited by 562 * TCP_MAXWIN << tp->rcv_scale. 563 */ 564 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 565 (tp->rcv_adv - tp->rcv_nxt); 566 567 if (adv >= (long) (2 * tp->t_maxseg)) 568 goto send; 569 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 570 goto send; 571 } 572 573 /* 574 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 575 * is also a catch-all for the retransmit timer timeout case. 576 */ 577 if (tp->t_flags & TF_ACKNOW) 578 goto send; 579 if ((flags & TH_RST) || 580 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 581 goto send; 582 if (SEQ_GT(tp->snd_up, tp->snd_una)) 583 goto send; 584 /* 585 * If our state indicates that FIN should be sent 586 * and we have not yet done so, then we need to send. 587 */ 588 if (flags & TH_FIN && 589 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 590 goto send; 591 /* 592 * In SACK, it is possible for tcp_output to fail to send a segment 593 * after the retransmission timer has been turned off. Make sure 594 * that the retransmission timer is set. 595 */ 596 if ((tp->t_flags & TF_SACK_PERMIT) && 597 SEQ_GT(tp->snd_max, tp->snd_una) && 598 !tcp_timer_active(tp, TT_REXMT) && 599 !tcp_timer_active(tp, TT_PERSIST)) { 600 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 601 goto just_return; 602 } 603 /* 604 * TCP window updates are not reliable, rather a polling protocol 605 * using ``persist'' packets is used to insure receipt of window 606 * updates. The three ``states'' for the output side are: 607 * idle not doing retransmits or persists 608 * persisting to move a small or zero window 609 * (re)transmitting and thereby not persisting 610 * 611 * tcp_timer_active(tp, TT_PERSIST) 612 * is true when we are in persist state. 613 * (tp->t_flags & TF_FORCEDATA) 614 * is set when we are called to send a persist packet. 615 * tcp_timer_active(tp, TT_REXMT) 616 * is set when we are retransmitting 617 * The output side is idle when both timers are zero. 618 * 619 * If send window is too small, there is data to transmit, and no 620 * retransmit or persist is pending, then go to persist state. 621 * If nothing happens soon, send when timer expires: 622 * if window is nonzero, transmit what we can, 623 * otherwise force out a byte. 624 */ 625 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 626 !tcp_timer_active(tp, TT_PERSIST)) { 627 tp->t_rxtshift = 0; 628 tcp_setpersist(tp); 629 } 630 631 /* 632 * No reason to send a segment, just return. 633 */ 634 just_return: 635 SOCKBUF_UNLOCK(&so->so_snd); 636 return (0); 637 638 send: 639 SOCKBUF_LOCK_ASSERT(&so->so_snd); 640 /* 641 * Before ESTABLISHED, force sending of initial options 642 * unless TCP set not to do any options. 643 * NOTE: we assume that the IP/TCP header plus TCP options 644 * always fit in a single mbuf, leaving room for a maximum 645 * link header, i.e. 646 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 647 */ 648 optlen = 0; 649 #ifdef INET6 650 if (isipv6) 651 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 652 else 653 #endif 654 hdrlen = sizeof (struct tcpiphdr); 655 656 /* 657 * Compute options for segment. 658 * We only have to care about SYN and established connection 659 * segments. Options for SYN-ACK segments are handled in TCP 660 * syncache. 661 */ 662 if ((tp->t_flags & TF_NOOPT) == 0) { 663 to.to_flags = 0; 664 /* Maximum segment size. */ 665 if (flags & TH_SYN) { 666 tp->snd_nxt = tp->iss; 667 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 668 to.to_flags |= TOF_MSS; 669 } 670 /* Window scaling. */ 671 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 672 to.to_wscale = tp->request_r_scale; 673 to.to_flags |= TOF_SCALE; 674 } 675 /* Timestamps. */ 676 if ((tp->t_flags & TF_RCVD_TSTMP) || 677 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 678 to.to_tsval = ticks + tp->ts_offset; 679 to.to_tsecr = tp->ts_recent; 680 to.to_flags |= TOF_TS; 681 /* Set receive buffer autosizing timestamp. */ 682 if (tp->rfbuf_ts == 0 && 683 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 684 tp->rfbuf_ts = ticks; 685 } 686 /* Selective ACK's. */ 687 if (tp->t_flags & TF_SACK_PERMIT) { 688 if (flags & TH_SYN) 689 to.to_flags |= TOF_SACKPERM; 690 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 691 (tp->t_flags & TF_SACK_PERMIT) && 692 tp->rcv_numsacks > 0) { 693 to.to_flags |= TOF_SACK; 694 to.to_nsacks = tp->rcv_numsacks; 695 to.to_sacks = (u_char *)tp->sackblks; 696 } 697 } 698 #ifdef TCP_SIGNATURE 699 /* TCP-MD5 (RFC2385). */ 700 if (tp->t_flags & TF_SIGNATURE) 701 to.to_flags |= TOF_SIGNATURE; 702 #endif /* TCP_SIGNATURE */ 703 704 /* Processing the options. */ 705 hdrlen += optlen = tcp_addoptions(&to, opt); 706 } 707 708 #ifdef INET6 709 if (isipv6) 710 ipoptlen = ip6_optlen(tp->t_inpcb); 711 else 712 #endif 713 if (tp->t_inpcb->inp_options) 714 ipoptlen = tp->t_inpcb->inp_options->m_len - 715 offsetof(struct ipoption, ipopt_list); 716 else 717 ipoptlen = 0; 718 #ifdef IPSEC 719 ipoptlen += ipsec_optlen; 720 #endif 721 722 /* 723 * Adjust data length if insertion of options will 724 * bump the packet length beyond the t_maxopd length. 725 * Clear the FIN bit because we cut off the tail of 726 * the segment. 727 */ 728 if (len + optlen + ipoptlen > tp->t_maxopd) { 729 flags &= ~TH_FIN; 730 731 if (tso) { 732 KASSERT(ipoptlen == 0, 733 ("%s: TSO can't do IP options", __func__)); 734 735 /* 736 * Limit a burst to IP_MAXPACKET minus IP, 737 * TCP and options length to keep ip->ip_len 738 * from overflowing. 739 */ 740 if (len > IP_MAXPACKET - hdrlen) { 741 len = IP_MAXPACKET - hdrlen; 742 sendalot = 1; 743 } 744 745 /* 746 * Prevent the last segment from being 747 * fractional unless the send sockbuf can 748 * be emptied. 749 */ 750 if (sendalot && off + len < so->so_snd.sb_cc) { 751 len -= len % (tp->t_maxopd - optlen); 752 sendalot = 1; 753 } 754 755 /* 756 * Send the FIN in a separate segment 757 * after the bulk sending is done. 758 * We don't trust the TSO implementations 759 * to clear the FIN flag on all but the 760 * last segment. 761 */ 762 if (tp->t_flags & TF_NEEDFIN) 763 sendalot = 1; 764 765 } else { 766 len = tp->t_maxopd - optlen - ipoptlen; 767 sendalot = 1; 768 } 769 } else 770 tso = 0; 771 772 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 773 ("%s: len > IP_MAXPACKET", __func__)); 774 775 /*#ifdef DIAGNOSTIC*/ 776 #ifdef INET6 777 if (max_linkhdr + hdrlen > MCLBYTES) 778 #else 779 if (max_linkhdr + hdrlen > MHLEN) 780 #endif 781 panic("tcphdr too big"); 782 /*#endif*/ 783 784 /* 785 * This KASSERT is here to catch edge cases at a well defined place. 786 * Before, those had triggered (random) panic conditions further down. 787 */ 788 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 789 790 /* 791 * Grab a header mbuf, attaching a copy of data to 792 * be transmitted, and initialize the header from 793 * the template for sends on this connection. 794 */ 795 if (len) { 796 struct mbuf *mb; 797 u_int moff; 798 799 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 800 TCPSTAT_INC(tcps_sndprobe); 801 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 802 tp->t_sndrexmitpack++; 803 TCPSTAT_INC(tcps_sndrexmitpack); 804 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 805 } else { 806 TCPSTAT_INC(tcps_sndpack); 807 TCPSTAT_ADD(tcps_sndbyte, len); 808 } 809 #ifdef notyet 810 if ((m = m_copypack(so->so_snd.sb_mb, off, 811 (int)len, max_linkhdr + hdrlen)) == 0) { 812 SOCKBUF_UNLOCK(&so->so_snd); 813 error = ENOBUFS; 814 goto out; 815 } 816 /* 817 * m_copypack left space for our hdr; use it. 818 */ 819 m->m_len += hdrlen; 820 m->m_data -= hdrlen; 821 #else 822 MGETHDR(m, M_DONTWAIT, MT_DATA); 823 if (m == NULL) { 824 SOCKBUF_UNLOCK(&so->so_snd); 825 error = ENOBUFS; 826 goto out; 827 } 828 #ifdef INET6 829 if (MHLEN < hdrlen + max_linkhdr) { 830 MCLGET(m, M_DONTWAIT); 831 if ((m->m_flags & M_EXT) == 0) { 832 SOCKBUF_UNLOCK(&so->so_snd); 833 m_freem(m); 834 error = ENOBUFS; 835 goto out; 836 } 837 } 838 #endif 839 m->m_data += max_linkhdr; 840 m->m_len = hdrlen; 841 842 /* 843 * Start the m_copy functions from the closest mbuf 844 * to the offset in the socket buffer chain. 845 */ 846 mb = sbsndptr(&so->so_snd, off, len, &moff); 847 848 if (len <= MHLEN - hdrlen - max_linkhdr) { 849 m_copydata(mb, moff, (int)len, 850 mtod(m, caddr_t) + hdrlen); 851 m->m_len += len; 852 } else { 853 m->m_next = m_copy(mb, moff, (int)len); 854 if (m->m_next == NULL) { 855 SOCKBUF_UNLOCK(&so->so_snd); 856 (void) m_free(m); 857 error = ENOBUFS; 858 goto out; 859 } 860 } 861 #endif 862 /* 863 * If we're sending everything we've got, set PUSH. 864 * (This will keep happy those implementations which only 865 * give data to the user when a buffer fills or 866 * a PUSH comes in.) 867 */ 868 if (off + len == so->so_snd.sb_cc) 869 flags |= TH_PUSH; 870 SOCKBUF_UNLOCK(&so->so_snd); 871 } else { 872 SOCKBUF_UNLOCK(&so->so_snd); 873 if (tp->t_flags & TF_ACKNOW) 874 TCPSTAT_INC(tcps_sndacks); 875 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 876 TCPSTAT_INC(tcps_sndctrl); 877 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 878 TCPSTAT_INC(tcps_sndurg); 879 else 880 TCPSTAT_INC(tcps_sndwinup); 881 882 MGETHDR(m, M_DONTWAIT, MT_DATA); 883 if (m == NULL) { 884 error = ENOBUFS; 885 goto out; 886 } 887 #ifdef INET6 888 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 889 MHLEN >= hdrlen) { 890 MH_ALIGN(m, hdrlen); 891 } else 892 #endif 893 m->m_data += max_linkhdr; 894 m->m_len = hdrlen; 895 } 896 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 897 m->m_pkthdr.rcvif = (struct ifnet *)0; 898 #ifdef MAC 899 mac_inpcb_create_mbuf(tp->t_inpcb, m); 900 #endif 901 #ifdef INET6 902 if (isipv6) { 903 ip6 = mtod(m, struct ip6_hdr *); 904 th = (struct tcphdr *)(ip6 + 1); 905 tcpip_fillheaders(tp->t_inpcb, ip6, th); 906 } else 907 #endif /* INET6 */ 908 { 909 ip = mtod(m, struct ip *); 910 ipov = (struct ipovly *)ip; 911 th = (struct tcphdr *)(ip + 1); 912 tcpip_fillheaders(tp->t_inpcb, ip, th); 913 } 914 915 /* 916 * Fill in fields, remembering maximum advertised 917 * window for use in delaying messages about window sizes. 918 * If resending a FIN, be sure not to use a new sequence number. 919 */ 920 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 921 tp->snd_nxt == tp->snd_max) 922 tp->snd_nxt--; 923 /* 924 * If we are starting a connection, send ECN setup 925 * SYN packet. If we are on a retransmit, we may 926 * resend those bits a number of times as per 927 * RFC 3168. 928 */ 929 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 930 if (tp->t_rxtshift >= 1) { 931 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 932 flags |= TH_ECE|TH_CWR; 933 } else 934 flags |= TH_ECE|TH_CWR; 935 } 936 937 if (tp->t_state == TCPS_ESTABLISHED && 938 (tp->t_flags & TF_ECN_PERMIT)) { 939 /* 940 * If the peer has ECN, mark data packets with 941 * ECN capable transmission (ECT). 942 * Ignore pure ack packets, retransmissions and window probes. 943 */ 944 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 945 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 946 #ifdef INET6 947 if (isipv6) 948 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 949 else 950 #endif 951 ip->ip_tos |= IPTOS_ECN_ECT0; 952 TCPSTAT_INC(tcps_ecn_ect0); 953 } 954 955 /* 956 * Reply with proper ECN notifications. 957 */ 958 if (tp->t_flags & TF_ECN_SND_CWR) { 959 flags |= TH_CWR; 960 tp->t_flags &= ~TF_ECN_SND_CWR; 961 } 962 if (tp->t_flags & TF_ECN_SND_ECE) 963 flags |= TH_ECE; 964 } 965 966 /* 967 * If we are doing retransmissions, then snd_nxt will 968 * not reflect the first unsent octet. For ACK only 969 * packets, we do not want the sequence number of the 970 * retransmitted packet, we want the sequence number 971 * of the next unsent octet. So, if there is no data 972 * (and no SYN or FIN), use snd_max instead of snd_nxt 973 * when filling in ti_seq. But if we are in persist 974 * state, snd_max might reflect one byte beyond the 975 * right edge of the window, so use snd_nxt in that 976 * case, since we know we aren't doing a retransmission. 977 * (retransmit and persist are mutually exclusive...) 978 */ 979 if (sack_rxmit == 0) { 980 if (len || (flags & (TH_SYN|TH_FIN)) || 981 tcp_timer_active(tp, TT_PERSIST)) 982 th->th_seq = htonl(tp->snd_nxt); 983 else 984 th->th_seq = htonl(tp->snd_max); 985 } else { 986 th->th_seq = htonl(p->rxmit); 987 p->rxmit += len; 988 tp->sackhint.sack_bytes_rexmit += len; 989 } 990 th->th_ack = htonl(tp->rcv_nxt); 991 if (optlen) { 992 bcopy(opt, th + 1, optlen); 993 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 994 } 995 th->th_flags = flags; 996 /* 997 * Calculate receive window. Don't shrink window, 998 * but avoid silly window syndrome. 999 */ 1000 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 1001 recwin < (long)tp->t_maxseg) 1002 recwin = 0; 1003 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 1004 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 1005 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 1006 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 1007 1008 /* 1009 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1010 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1011 * case is handled in syncache. 1012 */ 1013 if (flags & TH_SYN) 1014 th->th_win = htons((u_short) 1015 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1016 else 1017 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1018 1019 /* 1020 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1021 * a 0 window. This may cause the remote transmitter to stall. This 1022 * flag tells soreceive() to disable delayed acknowledgements when 1023 * draining the buffer. This can occur if the receiver is attempting 1024 * to read more data than can be buffered prior to transmitting on 1025 * the connection. 1026 */ 1027 if (th->th_win == 0) { 1028 tp->t_sndzerowin++; 1029 tp->t_flags |= TF_RXWIN0SENT; 1030 } else 1031 tp->t_flags &= ~TF_RXWIN0SENT; 1032 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1033 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1034 th->th_flags |= TH_URG; 1035 } else 1036 /* 1037 * If no urgent pointer to send, then we pull 1038 * the urgent pointer to the left edge of the send window 1039 * so that it doesn't drift into the send window on sequence 1040 * number wraparound. 1041 */ 1042 tp->snd_up = tp->snd_una; /* drag it along */ 1043 1044 #ifdef TCP_SIGNATURE 1045 if (tp->t_flags & TF_SIGNATURE) { 1046 int sigoff = to.to_signature - opt; 1047 tcp_signature_compute(m, 0, len, optlen, 1048 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1049 } 1050 #endif 1051 1052 /* 1053 * Put TCP length in extended header, and then 1054 * checksum extended header and data. 1055 */ 1056 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1057 #ifdef INET6 1058 if (isipv6) 1059 /* 1060 * ip6_plen is not need to be filled now, and will be filled 1061 * in ip6_output. 1062 */ 1063 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 1064 sizeof(struct tcphdr) + optlen + len); 1065 else 1066 #endif /* INET6 */ 1067 { 1068 m->m_pkthdr.csum_flags = CSUM_TCP; 1069 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1070 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1071 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1072 1073 /* IP version must be set here for ipv4/ipv6 checking later */ 1074 KASSERT(ip->ip_v == IPVERSION, 1075 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1076 } 1077 1078 /* 1079 * Enable TSO and specify the size of the segments. 1080 * The TCP pseudo header checksum is always provided. 1081 * XXX: Fixme: This is currently not the case for IPv6. 1082 */ 1083 if (tso) { 1084 KASSERT(len > tp->t_maxopd - optlen, 1085 ("%s: len <= tso_segsz", __func__)); 1086 m->m_pkthdr.csum_flags |= CSUM_TSO; 1087 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1088 } 1089 1090 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1091 ("%s: mbuf chain shorter than expected", __func__)); 1092 1093 /* 1094 * In transmit state, time the transmission and arrange for 1095 * the retransmit. In persist state, just set snd_max. 1096 */ 1097 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1098 !tcp_timer_active(tp, TT_PERSIST)) { 1099 tcp_seq startseq = tp->snd_nxt; 1100 1101 /* 1102 * Advance snd_nxt over sequence space of this segment. 1103 */ 1104 if (flags & (TH_SYN|TH_FIN)) { 1105 if (flags & TH_SYN) 1106 tp->snd_nxt++; 1107 if (flags & TH_FIN) { 1108 tp->snd_nxt++; 1109 tp->t_flags |= TF_SENTFIN; 1110 } 1111 } 1112 if (sack_rxmit) 1113 goto timer; 1114 tp->snd_nxt += len; 1115 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1116 tp->snd_max = tp->snd_nxt; 1117 /* 1118 * Time this transmission if not a retransmission and 1119 * not currently timing anything. 1120 */ 1121 if (tp->t_rtttime == 0) { 1122 tp->t_rtttime = ticks; 1123 tp->t_rtseq = startseq; 1124 TCPSTAT_INC(tcps_segstimed); 1125 } 1126 } 1127 1128 /* 1129 * Set retransmit timer if not currently set, 1130 * and not doing a pure ack or a keep-alive probe. 1131 * Initial value for retransmit timer is smoothed 1132 * round-trip time + 2 * round-trip time variance. 1133 * Initialize shift counter which is used for backoff 1134 * of retransmit time. 1135 */ 1136 timer: 1137 if (!tcp_timer_active(tp, TT_REXMT) && 1138 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1139 (tp->snd_nxt != tp->snd_una))) { 1140 if (tcp_timer_active(tp, TT_PERSIST)) { 1141 tcp_timer_activate(tp, TT_PERSIST, 0); 1142 tp->t_rxtshift = 0; 1143 } 1144 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1145 } 1146 } else { 1147 /* 1148 * Persist case, update snd_max but since we are in 1149 * persist mode (no window) we do not update snd_nxt. 1150 */ 1151 int xlen = len; 1152 if (flags & TH_SYN) 1153 ++xlen; 1154 if (flags & TH_FIN) { 1155 ++xlen; 1156 tp->t_flags |= TF_SENTFIN; 1157 } 1158 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1159 tp->snd_max = tp->snd_nxt + len; 1160 } 1161 1162 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1163 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1164 1165 #ifdef TCPDEBUG 1166 /* 1167 * Trace. 1168 */ 1169 if (so->so_options & SO_DEBUG) { 1170 u_short save = 0; 1171 #ifdef INET6 1172 if (!isipv6) 1173 #endif 1174 { 1175 save = ipov->ih_len; 1176 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1177 } 1178 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1179 #ifdef INET6 1180 if (!isipv6) 1181 #endif 1182 ipov->ih_len = save; 1183 } 1184 #endif 1185 1186 /* 1187 * Fill in IP length and desired time to live and 1188 * send to IP level. There should be a better way 1189 * to handle ttl and tos; we could keep them in 1190 * the template, but need a way to checksum without them. 1191 */ 1192 /* 1193 * m->m_pkthdr.len should have been set before cksum calcuration, 1194 * because in6_cksum() need it. 1195 */ 1196 #ifdef INET6 1197 if (isipv6) { 1198 /* 1199 * we separately set hoplimit for every segment, since the 1200 * user might want to change the value via setsockopt. 1201 * Also, desired default hop limit might be changed via 1202 * Neighbor Discovery. 1203 */ 1204 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1205 1206 /* TODO: IPv6 IP6TOS_ECT bit on */ 1207 error = ip6_output(m, 1208 tp->t_inpcb->in6p_outputopts, NULL, 1209 ((so->so_options & SO_DONTROUTE) ? 1210 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1211 } else 1212 #endif /* INET6 */ 1213 { 1214 ip->ip_len = m->m_pkthdr.len; 1215 #ifdef INET6 1216 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1217 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1218 #endif /* INET6 */ 1219 /* 1220 * If we do path MTU discovery, then we set DF on every packet. 1221 * This might not be the best thing to do according to RFC3390 1222 * Section 2. However the tcp hostcache migitates the problem 1223 * so it affects only the first tcp connection with a host. 1224 * 1225 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1226 */ 1227 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) 1228 ip->ip_off |= IP_DF; 1229 1230 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1231 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1232 tp->t_inpcb); 1233 } 1234 if (error) { 1235 1236 /* 1237 * We know that the packet was lost, so back out the 1238 * sequence number advance, if any. 1239 * 1240 * If the error is EPERM the packet got blocked by the 1241 * local firewall. Normally we should terminate the 1242 * connection but the blocking may have been spurious 1243 * due to a firewall reconfiguration cycle. So we treat 1244 * it like a packet loss and let the retransmit timer and 1245 * timeouts do their work over time. 1246 * XXX: It is a POLA question whether calling tcp_drop right 1247 * away would be the really correct behavior instead. 1248 */ 1249 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1250 !tcp_timer_active(tp, TT_PERSIST)) && 1251 ((flags & TH_SYN) == 0) && 1252 (error != EPERM)) { 1253 if (sack_rxmit) { 1254 p->rxmit -= len; 1255 tp->sackhint.sack_bytes_rexmit -= len; 1256 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1257 ("sackhint bytes rtx >= 0")); 1258 } else 1259 tp->snd_nxt -= len; 1260 } 1261 out: 1262 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1263 switch (error) { 1264 case EPERM: 1265 tp->t_softerror = error; 1266 return (error); 1267 case ENOBUFS: 1268 if (!tcp_timer_active(tp, TT_REXMT) && 1269 !tcp_timer_active(tp, TT_PERSIST)) 1270 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1271 tp->snd_cwnd = tp->t_maxseg; 1272 return (0); 1273 case EMSGSIZE: 1274 /* 1275 * For some reason the interface we used initially 1276 * to send segments changed to another or lowered 1277 * its MTU. 1278 * 1279 * tcp_mtudisc() will find out the new MTU and as 1280 * its last action, initiate retransmission, so it 1281 * is important to not do so here. 1282 * 1283 * If TSO was active we either got an interface 1284 * without TSO capabilits or TSO was turned off. 1285 * Disable it for this connection as too and 1286 * immediatly retry with MSS sized segments generated 1287 * by this function. 1288 */ 1289 if (tso) 1290 tp->t_flags &= ~TF_TSO; 1291 tcp_mtudisc(tp->t_inpcb, 0); 1292 return (0); 1293 case EHOSTDOWN: 1294 case EHOSTUNREACH: 1295 case ENETDOWN: 1296 case ENETUNREACH: 1297 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1298 tp->t_softerror = error; 1299 return (0); 1300 } 1301 /* FALLTHROUGH */ 1302 default: 1303 return (error); 1304 } 1305 } 1306 TCPSTAT_INC(tcps_sndtotal); 1307 1308 /* 1309 * Data sent (as far as we can tell). 1310 * If this advertises a larger window than any other segment, 1311 * then remember the size of the advertised window. 1312 * Any pending ACK has now been sent. 1313 */ 1314 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1315 tp->rcv_adv = tp->rcv_nxt + recwin; 1316 tp->last_ack_sent = tp->rcv_nxt; 1317 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1318 if (tcp_timer_active(tp, TT_DELACK)) 1319 tcp_timer_activate(tp, TT_DELACK, 0); 1320 #if 0 1321 /* 1322 * This completely breaks TCP if newreno is turned on. What happens 1323 * is that if delayed-acks are turned on on the receiver, this code 1324 * on the transmitter effectively destroys the TCP window, forcing 1325 * it to four packets (1.5Kx4 = 6K window). 1326 */ 1327 if (sendalot && --maxburst) 1328 goto again; 1329 #endif 1330 if (sendalot) 1331 goto again; 1332 return (0); 1333 } 1334 1335 void 1336 tcp_setpersist(struct tcpcb *tp) 1337 { 1338 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1339 int tt; 1340 1341 if (tcp_timer_active(tp, TT_REXMT)) 1342 panic("tcp_setpersist: retransmit pending"); 1343 /* 1344 * Start/restart persistance timer. 1345 */ 1346 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1347 TCPTV_PERSMIN, TCPTV_PERSMAX); 1348 tcp_timer_activate(tp, TT_PERSIST, tt); 1349 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1350 tp->t_rxtshift++; 1351 } 1352 1353 /* 1354 * Insert TCP options according to the supplied parameters to the place 1355 * optp in a consistent way. Can handle unaligned destinations. 1356 * 1357 * The order of the option processing is crucial for optimal packing and 1358 * alignment for the scarce option space. 1359 * 1360 * The optimal order for a SYN/SYN-ACK segment is: 1361 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1362 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1363 * 1364 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1365 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1366 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1367 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1368 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1369 */ 1370 int 1371 tcp_addoptions(struct tcpopt *to, u_char *optp) 1372 { 1373 u_int mask, optlen = 0; 1374 1375 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1376 if ((to->to_flags & mask) != mask) 1377 continue; 1378 if (optlen == TCP_MAXOLEN) 1379 break; 1380 switch (to->to_flags & mask) { 1381 case TOF_MSS: 1382 while (optlen % 4) { 1383 optlen += TCPOLEN_NOP; 1384 *optp++ = TCPOPT_NOP; 1385 } 1386 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1387 continue; 1388 optlen += TCPOLEN_MAXSEG; 1389 *optp++ = TCPOPT_MAXSEG; 1390 *optp++ = TCPOLEN_MAXSEG; 1391 to->to_mss = htons(to->to_mss); 1392 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1393 optp += sizeof(to->to_mss); 1394 break; 1395 case TOF_SCALE: 1396 while (!optlen || optlen % 2 != 1) { 1397 optlen += TCPOLEN_NOP; 1398 *optp++ = TCPOPT_NOP; 1399 } 1400 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1401 continue; 1402 optlen += TCPOLEN_WINDOW; 1403 *optp++ = TCPOPT_WINDOW; 1404 *optp++ = TCPOLEN_WINDOW; 1405 *optp++ = to->to_wscale; 1406 break; 1407 case TOF_SACKPERM: 1408 while (optlen % 2) { 1409 optlen += TCPOLEN_NOP; 1410 *optp++ = TCPOPT_NOP; 1411 } 1412 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1413 continue; 1414 optlen += TCPOLEN_SACK_PERMITTED; 1415 *optp++ = TCPOPT_SACK_PERMITTED; 1416 *optp++ = TCPOLEN_SACK_PERMITTED; 1417 break; 1418 case TOF_TS: 1419 while (!optlen || optlen % 4 != 2) { 1420 optlen += TCPOLEN_NOP; 1421 *optp++ = TCPOPT_NOP; 1422 } 1423 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1424 continue; 1425 optlen += TCPOLEN_TIMESTAMP; 1426 *optp++ = TCPOPT_TIMESTAMP; 1427 *optp++ = TCPOLEN_TIMESTAMP; 1428 to->to_tsval = htonl(to->to_tsval); 1429 to->to_tsecr = htonl(to->to_tsecr); 1430 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1431 optp += sizeof(to->to_tsval); 1432 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1433 optp += sizeof(to->to_tsecr); 1434 break; 1435 case TOF_SIGNATURE: 1436 { 1437 int siglen = TCPOLEN_SIGNATURE - 2; 1438 1439 while (!optlen || optlen % 4 != 2) { 1440 optlen += TCPOLEN_NOP; 1441 *optp++ = TCPOPT_NOP; 1442 } 1443 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1444 continue; 1445 optlen += TCPOLEN_SIGNATURE; 1446 *optp++ = TCPOPT_SIGNATURE; 1447 *optp++ = TCPOLEN_SIGNATURE; 1448 to->to_signature = optp; 1449 while (siglen--) 1450 *optp++ = 0; 1451 break; 1452 } 1453 case TOF_SACK: 1454 { 1455 int sackblks = 0; 1456 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1457 tcp_seq sack_seq; 1458 1459 while (!optlen || optlen % 4 != 2) { 1460 optlen += TCPOLEN_NOP; 1461 *optp++ = TCPOPT_NOP; 1462 } 1463 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1464 continue; 1465 optlen += TCPOLEN_SACKHDR; 1466 *optp++ = TCPOPT_SACK; 1467 sackblks = min(to->to_nsacks, 1468 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1469 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1470 while (sackblks--) { 1471 sack_seq = htonl(sack->start); 1472 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1473 optp += sizeof(sack_seq); 1474 sack_seq = htonl(sack->end); 1475 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1476 optp += sizeof(sack_seq); 1477 optlen += TCPOLEN_SACK; 1478 sack++; 1479 } 1480 TCPSTAT_INC(tcps_sack_send_blocks); 1481 break; 1482 } 1483 default: 1484 panic("%s: unknown TCP option type", __func__); 1485 break; 1486 } 1487 } 1488 1489 /* Terminate and pad TCP options to a 4 byte boundary. */ 1490 if (optlen % 4) { 1491 optlen += TCPOLEN_EOL; 1492 *optp++ = TCPOPT_EOL; 1493 } 1494 /* 1495 * According to RFC 793 (STD0007): 1496 * "The content of the header beyond the End-of-Option option 1497 * must be header padding (i.e., zero)." 1498 * and later: "The padding is composed of zeros." 1499 */ 1500 while (optlen % 4) { 1501 optlen += TCPOLEN_PAD; 1502 *optp++ = TCPOPT_PAD; 1503 } 1504 1505 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1506 return (optlen); 1507 } 1508