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; 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 * We have been idle for "a while" and no acks are 180 * expected to clock out any data we send -- 181 * slow start to get ack "clock" running again. 182 * 183 * Set the slow-start flight size depending on whether 184 * this is a local network or not. 185 */ 186 int ss = V_ss_fltsz; 187 #ifdef INET6 188 if (isipv6) { 189 if (in6_localaddr(&tp->t_inpcb->in6p_faddr)) 190 ss = V_ss_fltsz_local; 191 } else 192 #endif /* INET6 */ 193 if (in_localaddr(tp->t_inpcb->inp_faddr)) 194 ss = V_ss_fltsz_local; 195 tp->snd_cwnd = tp->t_maxseg * ss; 196 } 197 tp->t_flags &= ~TF_LASTIDLE; 198 if (idle) { 199 if (tp->t_flags & TF_MORETOCOME) { 200 tp->t_flags |= TF_LASTIDLE; 201 idle = 0; 202 } 203 } 204 again: 205 /* 206 * If we've recently taken a timeout, snd_max will be greater than 207 * snd_nxt. There may be SACK information that allows us to avoid 208 * resending already delivered data. Adjust snd_nxt accordingly. 209 */ 210 if ((tp->t_flags & TF_SACK_PERMIT) && 211 SEQ_LT(tp->snd_nxt, tp->snd_max)) 212 tcp_sack_adjust(tp); 213 sendalot = 0; 214 tso = 0; 215 off = tp->snd_nxt - tp->snd_una; 216 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 217 sendwin = min(sendwin, tp->snd_bwnd); 218 219 flags = tcp_outflags[tp->t_state]; 220 /* 221 * Send any SACK-generated retransmissions. If we're explicitly trying 222 * to send out new data (when sendalot is 1), bypass this function. 223 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 224 * we're replacing a (future) new transmission with a retransmission 225 * now, and we previously incremented snd_cwnd in tcp_input(). 226 */ 227 /* 228 * Still in sack recovery , reset rxmit flag to zero. 229 */ 230 sack_rxmit = 0; 231 sack_bytes_rxmt = 0; 232 len = 0; 233 p = NULL; 234 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp) && 235 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 236 long cwin; 237 238 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 239 if (cwin < 0) 240 cwin = 0; 241 /* Do not retransmit SACK segments beyond snd_recover */ 242 if (SEQ_GT(p->end, tp->snd_recover)) { 243 /* 244 * (At least) part of sack hole extends beyond 245 * snd_recover. Check to see if we can rexmit data 246 * for this hole. 247 */ 248 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 249 /* 250 * Can't rexmit any more data for this hole. 251 * That data will be rexmitted in the next 252 * sack recovery episode, when snd_recover 253 * moves past p->rxmit. 254 */ 255 p = NULL; 256 goto after_sack_rexmit; 257 } else 258 /* Can rexmit part of the current hole */ 259 len = ((long)ulmin(cwin, 260 tp->snd_recover - p->rxmit)); 261 } else 262 len = ((long)ulmin(cwin, p->end - p->rxmit)); 263 off = p->rxmit - tp->snd_una; 264 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 265 __func__, off)); 266 if (len > 0) { 267 sack_rxmit = 1; 268 sendalot = 1; 269 TCPSTAT_INC(tcps_sack_rexmits); 270 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 271 min(len, tp->t_maxseg)); 272 } 273 } 274 after_sack_rexmit: 275 /* 276 * Get standard flags, and add SYN or FIN if requested by 'hidden' 277 * state flags. 278 */ 279 if (tp->t_flags & TF_NEEDFIN) 280 flags |= TH_FIN; 281 if (tp->t_flags & TF_NEEDSYN) 282 flags |= TH_SYN; 283 284 SOCKBUF_LOCK(&so->so_snd); 285 /* 286 * If in persist timeout with window of 0, send 1 byte. 287 * Otherwise, if window is small but nonzero 288 * and timer expired, we will send what we can 289 * and go to transmit state. 290 */ 291 if (tp->t_flags & TF_FORCEDATA) { 292 if (sendwin == 0) { 293 /* 294 * If we still have some data to send, then 295 * clear the FIN bit. Usually this would 296 * happen below when it realizes that we 297 * aren't sending all the data. However, 298 * if we have exactly 1 byte of unsent data, 299 * then it won't clear the FIN bit below, 300 * and if we are in persist state, we wind 301 * up sending the packet without recording 302 * that we sent the FIN bit. 303 * 304 * We can't just blindly clear the FIN bit, 305 * because if we don't have any more data 306 * to send then the probe will be the FIN 307 * itself. 308 */ 309 if (off < so->so_snd.sb_cc) 310 flags &= ~TH_FIN; 311 sendwin = 1; 312 } else { 313 tcp_timer_activate(tp, TT_PERSIST, 0); 314 tp->t_rxtshift = 0; 315 } 316 } 317 318 /* 319 * If snd_nxt == snd_max and we have transmitted a FIN, the 320 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 321 * a negative length. This can also occur when TCP opens up 322 * its congestion window while receiving additional duplicate 323 * acks after fast-retransmit because TCP will reset snd_nxt 324 * to snd_max after the fast-retransmit. 325 * 326 * In the normal retransmit-FIN-only case, however, snd_nxt will 327 * be set to snd_una, the offset will be 0, and the length may 328 * wind up 0. 329 * 330 * If sack_rxmit is true we are retransmitting from the scoreboard 331 * in which case len is already set. 332 */ 333 if (sack_rxmit == 0) { 334 if (sack_bytes_rxmt == 0) 335 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 336 else { 337 long cwin; 338 339 /* 340 * We are inside of a SACK recovery episode and are 341 * sending new data, having retransmitted all the 342 * data possible in the scoreboard. 343 */ 344 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 345 - off); 346 /* 347 * Don't remove this (len > 0) check ! 348 * We explicitly check for len > 0 here (although it 349 * isn't really necessary), to work around a gcc 350 * optimization issue - to force gcc to compute 351 * len above. Without this check, the computation 352 * of len is bungled by the optimizer. 353 */ 354 if (len > 0) { 355 cwin = tp->snd_cwnd - 356 (tp->snd_nxt - tp->sack_newdata) - 357 sack_bytes_rxmt; 358 if (cwin < 0) 359 cwin = 0; 360 len = lmin(len, cwin); 361 } 362 } 363 } 364 365 /* 366 * Lop off SYN bit if it has already been sent. However, if this 367 * is SYN-SENT state and if segment contains data and if we don't 368 * know that foreign host supports TAO, suppress sending segment. 369 */ 370 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 371 if (tp->t_state != TCPS_SYN_RECEIVED) 372 flags &= ~TH_SYN; 373 off--, len++; 374 } 375 376 /* 377 * Be careful not to send data and/or FIN on SYN segments. 378 * This measure is needed to prevent interoperability problems 379 * with not fully conformant TCP implementations. 380 */ 381 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 382 len = 0; 383 flags &= ~TH_FIN; 384 } 385 386 if (len < 0) { 387 /* 388 * If FIN has been sent but not acked, 389 * but we haven't been called to retransmit, 390 * len will be < 0. Otherwise, window shrank 391 * after we sent into it. If window shrank to 0, 392 * cancel pending retransmit, pull snd_nxt back 393 * to (closed) window, and set the persist timer 394 * if it isn't already going. If the window didn't 395 * close completely, just wait for an ACK. 396 */ 397 len = 0; 398 if (sendwin == 0) { 399 tcp_timer_activate(tp, TT_REXMT, 0); 400 tp->t_rxtshift = 0; 401 tp->snd_nxt = tp->snd_una; 402 if (!tcp_timer_active(tp, TT_PERSIST)) 403 tcp_setpersist(tp); 404 } 405 } 406 407 /* len will be >= 0 after this point. */ 408 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 409 410 /* 411 * Automatic sizing of send socket buffer. Often the send buffer 412 * size is not optimally adjusted to the actual network conditions 413 * at hand (delay bandwidth product). Setting the buffer size too 414 * small limits throughput on links with high bandwidth and high 415 * delay (eg. trans-continental/oceanic links). Setting the 416 * buffer size too big consumes too much real kernel memory, 417 * especially with many connections on busy servers. 418 * 419 * The criteria to step up the send buffer one notch are: 420 * 1. receive window of remote host is larger than send buffer 421 * (with a fudge factor of 5/4th); 422 * 2. send buffer is filled to 7/8th with data (so we actually 423 * have data to make use of it); 424 * 3. send buffer fill has not hit maximal automatic size; 425 * 4. our send window (slow start and cogestion controlled) is 426 * larger than sent but unacknowledged data in send buffer. 427 * 428 * The remote host receive window scaling factor may limit the 429 * growing of the send buffer before it reaches its allowed 430 * maximum. 431 * 432 * It scales directly with slow start or congestion window 433 * and does at most one step per received ACK. This fast 434 * scaling has the drawback of growing the send buffer beyond 435 * what is strictly necessary to make full use of a given 436 * delay*bandwith product. However testing has shown this not 437 * to be much of an problem. At worst we are trading wasting 438 * of available bandwith (the non-use of it) for wasting some 439 * socket buffer memory. 440 * 441 * TODO: Shrink send buffer during idle periods together 442 * with congestion window. Requires another timer. Has to 443 * wait for upcoming tcp timer rewrite. 444 */ 445 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 446 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 447 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 448 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 449 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 450 if (!sbreserve_locked(&so->so_snd, 451 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 452 V_tcp_autosndbuf_max), so, curthread)) 453 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 454 } 455 } 456 457 /* 458 * Truncate to the maximum segment length or enable TCP Segmentation 459 * Offloading (if supported by hardware) and ensure that FIN is removed 460 * if the length no longer contains the last data byte. 461 * 462 * TSO may only be used if we are in a pure bulk sending state. The 463 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 464 * IP options prevent using TSO. With TSO the TCP header is the same 465 * (except for the sequence number) for all generated packets. This 466 * makes it impossible to transmit any options which vary per generated 467 * segment or packet. 468 * 469 * The length of TSO bursts is limited to TCP_MAXWIN. That limit and 470 * removal of FIN (if not already catched here) are handled later after 471 * the exact length of the TCP options are known. 472 */ 473 #ifdef IPSEC 474 /* 475 * Pre-calculate here as we save another lookup into the darknesses 476 * of IPsec that way and can actually decide if TSO is ok. 477 */ 478 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 479 #endif 480 if (len > tp->t_maxseg) { 481 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && 482 ((tp->t_flags & TF_SIGNATURE) == 0) && 483 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 484 tp->t_inpcb->inp_options == NULL && 485 tp->t_inpcb->in6p_options == NULL 486 #ifdef IPSEC 487 && ipsec_optlen == 0 488 #endif 489 ) { 490 tso = 1; 491 } else { 492 len = tp->t_maxseg; 493 sendalot = 1; 494 } 495 } 496 497 if (sack_rxmit) { 498 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 499 flags &= ~TH_FIN; 500 } else { 501 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 502 flags &= ~TH_FIN; 503 } 504 505 recwin = sbspace(&so->so_rcv); 506 507 /* 508 * Sender silly window avoidance. We transmit under the following 509 * conditions when len is non-zero: 510 * 511 * - We have a full segment (or more with TSO) 512 * - This is the last buffer in a write()/send() and we are 513 * either idle or running NODELAY 514 * - we've timed out (e.g. persist timer) 515 * - we have more then 1/2 the maximum send window's worth of 516 * data (receiver may be limited the window size) 517 * - we need to retransmit 518 */ 519 if (len) { 520 if (len >= tp->t_maxseg) 521 goto send; 522 /* 523 * NOTE! on localhost connections an 'ack' from the remote 524 * end may occur synchronously with the output and cause 525 * us to flush a buffer queued with moretocome. XXX 526 * 527 * note: the len + off check is almost certainly unnecessary. 528 */ 529 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 530 (idle || (tp->t_flags & TF_NODELAY)) && 531 len + off >= so->so_snd.sb_cc && 532 (tp->t_flags & TF_NOPUSH) == 0) { 533 goto send; 534 } 535 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 536 goto send; 537 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 538 goto send; 539 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 540 goto send; 541 if (sack_rxmit) 542 goto send; 543 } 544 545 /* 546 * Compare available window to amount of window 547 * known to peer (as advertised window less 548 * next expected input). If the difference is at least two 549 * max size segments, or at least 50% of the maximum possible 550 * window, then want to send a window update to peer. 551 * Skip this if the connection is in T/TCP half-open state. 552 * Don't send pure window updates when the peer has closed 553 * the connection and won't ever send more data. 554 */ 555 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 556 !TCPS_HAVERCVDFIN(tp->t_state)) { 557 /* 558 * "adv" is the amount we can increase the window, 559 * taking into account that we are limited by 560 * TCP_MAXWIN << tp->rcv_scale. 561 */ 562 long adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale) - 563 (tp->rcv_adv - tp->rcv_nxt); 564 565 if (adv >= (long) (2 * tp->t_maxseg)) 566 goto send; 567 if (2 * adv >= (long) so->so_rcv.sb_hiwat) 568 goto send; 569 } 570 571 /* 572 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 573 * is also a catch-all for the retransmit timer timeout case. 574 */ 575 if (tp->t_flags & TF_ACKNOW) 576 goto send; 577 if ((flags & TH_RST) || 578 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 579 goto send; 580 if (SEQ_GT(tp->snd_up, tp->snd_una)) 581 goto send; 582 /* 583 * If our state indicates that FIN should be sent 584 * and we have not yet done so, then we need to send. 585 */ 586 if (flags & TH_FIN && 587 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 588 goto send; 589 /* 590 * In SACK, it is possible for tcp_output to fail to send a segment 591 * after the retransmission timer has been turned off. Make sure 592 * that the retransmission timer is set. 593 */ 594 if ((tp->t_flags & TF_SACK_PERMIT) && 595 SEQ_GT(tp->snd_max, tp->snd_una) && 596 !tcp_timer_active(tp, TT_REXMT) && 597 !tcp_timer_active(tp, TT_PERSIST)) { 598 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 599 goto just_return; 600 } 601 /* 602 * TCP window updates are not reliable, rather a polling protocol 603 * using ``persist'' packets is used to insure receipt of window 604 * updates. The three ``states'' for the output side are: 605 * idle not doing retransmits or persists 606 * persisting to move a small or zero window 607 * (re)transmitting and thereby not persisting 608 * 609 * tcp_timer_active(tp, TT_PERSIST) 610 * is true when we are in persist state. 611 * (tp->t_flags & TF_FORCEDATA) 612 * is set when we are called to send a persist packet. 613 * tcp_timer_active(tp, TT_REXMT) 614 * is set when we are retransmitting 615 * The output side is idle when both timers are zero. 616 * 617 * If send window is too small, there is data to transmit, and no 618 * retransmit or persist is pending, then go to persist state. 619 * If nothing happens soon, send when timer expires: 620 * if window is nonzero, transmit what we can, 621 * otherwise force out a byte. 622 */ 623 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 624 !tcp_timer_active(tp, TT_PERSIST)) { 625 tp->t_rxtshift = 0; 626 tcp_setpersist(tp); 627 } 628 629 /* 630 * No reason to send a segment, just return. 631 */ 632 just_return: 633 SOCKBUF_UNLOCK(&so->so_snd); 634 return (0); 635 636 send: 637 SOCKBUF_LOCK_ASSERT(&so->so_snd); 638 /* 639 * Before ESTABLISHED, force sending of initial options 640 * unless TCP set not to do any options. 641 * NOTE: we assume that the IP/TCP header plus TCP options 642 * always fit in a single mbuf, leaving room for a maximum 643 * link header, i.e. 644 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 645 */ 646 optlen = 0; 647 #ifdef INET6 648 if (isipv6) 649 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 650 else 651 #endif 652 hdrlen = sizeof (struct tcpiphdr); 653 654 /* 655 * Compute options for segment. 656 * We only have to care about SYN and established connection 657 * segments. Options for SYN-ACK segments are handled in TCP 658 * syncache. 659 */ 660 if ((tp->t_flags & TF_NOOPT) == 0) { 661 to.to_flags = 0; 662 /* Maximum segment size. */ 663 if (flags & TH_SYN) { 664 tp->snd_nxt = tp->iss; 665 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 666 to.to_flags |= TOF_MSS; 667 } 668 /* Window scaling. */ 669 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 670 to.to_wscale = tp->request_r_scale; 671 to.to_flags |= TOF_SCALE; 672 } 673 /* Timestamps. */ 674 if ((tp->t_flags & TF_RCVD_TSTMP) || 675 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 676 to.to_tsval = ticks + tp->ts_offset; 677 to.to_tsecr = tp->ts_recent; 678 to.to_flags |= TOF_TS; 679 /* Set receive buffer autosizing timestamp. */ 680 if (tp->rfbuf_ts == 0 && 681 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 682 tp->rfbuf_ts = ticks; 683 } 684 /* Selective ACK's. */ 685 if (tp->t_flags & TF_SACK_PERMIT) { 686 if (flags & TH_SYN) 687 to.to_flags |= TOF_SACKPERM; 688 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 689 (tp->t_flags & TF_SACK_PERMIT) && 690 tp->rcv_numsacks > 0) { 691 to.to_flags |= TOF_SACK; 692 to.to_nsacks = tp->rcv_numsacks; 693 to.to_sacks = (u_char *)tp->sackblks; 694 } 695 } 696 #ifdef TCP_SIGNATURE 697 /* TCP-MD5 (RFC2385). */ 698 if (tp->t_flags & TF_SIGNATURE) 699 to.to_flags |= TOF_SIGNATURE; 700 #endif /* TCP_SIGNATURE */ 701 702 /* Processing the options. */ 703 hdrlen += optlen = tcp_addoptions(&to, opt); 704 } 705 706 #ifdef INET6 707 if (isipv6) 708 ipoptlen = ip6_optlen(tp->t_inpcb); 709 else 710 #endif 711 if (tp->t_inpcb->inp_options) 712 ipoptlen = tp->t_inpcb->inp_options->m_len - 713 offsetof(struct ipoption, ipopt_list); 714 else 715 ipoptlen = 0; 716 #ifdef IPSEC 717 ipoptlen += ipsec_optlen; 718 #endif 719 720 /* 721 * Adjust data length if insertion of options will 722 * bump the packet length beyond the t_maxopd length. 723 * Clear the FIN bit because we cut off the tail of 724 * the segment. 725 * 726 * When doing TSO limit a burst to TCP_MAXWIN minus the 727 * IP, TCP and Options length to keep ip->ip_len from 728 * overflowing. Prevent the last segment from being 729 * fractional thus making them all equal sized and set 730 * the flag to continue sending. TSO is disabled when 731 * IP options or IPSEC are present. 732 */ 733 if (len + optlen + ipoptlen > tp->t_maxopd) { 734 flags &= ~TH_FIN; 735 if (tso) { 736 if (len > TCP_MAXWIN - hdrlen - optlen) { 737 len = TCP_MAXWIN - hdrlen - optlen; 738 len = len - (len % (tp->t_maxopd - optlen)); 739 sendalot = 1; 740 } else if (tp->t_flags & TF_NEEDFIN) 741 sendalot = 1; 742 } else { 743 len = tp->t_maxopd - optlen - ipoptlen; 744 sendalot = 1; 745 } 746 } 747 748 /*#ifdef DIAGNOSTIC*/ 749 #ifdef INET6 750 if (max_linkhdr + hdrlen > MCLBYTES) 751 #else 752 if (max_linkhdr + hdrlen > MHLEN) 753 #endif 754 panic("tcphdr too big"); 755 /*#endif*/ 756 757 /* 758 * This KASSERT is here to catch edge cases at a well defined place. 759 * Before, those had triggered (random) panic conditions further down. 760 */ 761 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 762 763 /* 764 * Grab a header mbuf, attaching a copy of data to 765 * be transmitted, and initialize the header from 766 * the template for sends on this connection. 767 */ 768 if (len) { 769 struct mbuf *mb; 770 u_int moff; 771 772 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 773 TCPSTAT_INC(tcps_sndprobe); 774 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 775 TCPSTAT_INC(tcps_sndrexmitpack); 776 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 777 } else { 778 TCPSTAT_INC(tcps_sndpack); 779 TCPSTAT_ADD(tcps_sndbyte, len); 780 } 781 #ifdef notyet 782 if ((m = m_copypack(so->so_snd.sb_mb, off, 783 (int)len, max_linkhdr + hdrlen)) == 0) { 784 SOCKBUF_UNLOCK(&so->so_snd); 785 error = ENOBUFS; 786 goto out; 787 } 788 /* 789 * m_copypack left space for our hdr; use it. 790 */ 791 m->m_len += hdrlen; 792 m->m_data -= hdrlen; 793 #else 794 MGETHDR(m, M_DONTWAIT, MT_DATA); 795 if (m == NULL) { 796 SOCKBUF_UNLOCK(&so->so_snd); 797 error = ENOBUFS; 798 goto out; 799 } 800 #ifdef INET6 801 if (MHLEN < hdrlen + max_linkhdr) { 802 MCLGET(m, M_DONTWAIT); 803 if ((m->m_flags & M_EXT) == 0) { 804 SOCKBUF_UNLOCK(&so->so_snd); 805 m_freem(m); 806 error = ENOBUFS; 807 goto out; 808 } 809 } 810 #endif 811 m->m_data += max_linkhdr; 812 m->m_len = hdrlen; 813 814 /* 815 * Start the m_copy functions from the closest mbuf 816 * to the offset in the socket buffer chain. 817 */ 818 mb = sbsndptr(&so->so_snd, off, len, &moff); 819 820 if (len <= MHLEN - hdrlen - max_linkhdr) { 821 m_copydata(mb, moff, (int)len, 822 mtod(m, caddr_t) + hdrlen); 823 m->m_len += len; 824 } else { 825 m->m_next = m_copy(mb, moff, (int)len); 826 if (m->m_next == NULL) { 827 SOCKBUF_UNLOCK(&so->so_snd); 828 (void) m_free(m); 829 error = ENOBUFS; 830 goto out; 831 } 832 } 833 #endif 834 /* 835 * If we're sending everything we've got, set PUSH. 836 * (This will keep happy those implementations which only 837 * give data to the user when a buffer fills or 838 * a PUSH comes in.) 839 */ 840 if (off + len == so->so_snd.sb_cc) 841 flags |= TH_PUSH; 842 SOCKBUF_UNLOCK(&so->so_snd); 843 } else { 844 SOCKBUF_UNLOCK(&so->so_snd); 845 if (tp->t_flags & TF_ACKNOW) 846 TCPSTAT_INC(tcps_sndacks); 847 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 848 TCPSTAT_INC(tcps_sndctrl); 849 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 850 TCPSTAT_INC(tcps_sndurg); 851 else 852 TCPSTAT_INC(tcps_sndwinup); 853 854 MGETHDR(m, M_DONTWAIT, MT_DATA); 855 if (m == NULL) { 856 error = ENOBUFS; 857 goto out; 858 } 859 #ifdef INET6 860 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 861 MHLEN >= hdrlen) { 862 MH_ALIGN(m, hdrlen); 863 } else 864 #endif 865 m->m_data += max_linkhdr; 866 m->m_len = hdrlen; 867 } 868 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 869 m->m_pkthdr.rcvif = (struct ifnet *)0; 870 #ifdef MAC 871 mac_inpcb_create_mbuf(tp->t_inpcb, m); 872 #endif 873 #ifdef INET6 874 if (isipv6) { 875 ip6 = mtod(m, struct ip6_hdr *); 876 th = (struct tcphdr *)(ip6 + 1); 877 tcpip_fillheaders(tp->t_inpcb, ip6, th); 878 } else 879 #endif /* INET6 */ 880 { 881 ip = mtod(m, struct ip *); 882 ipov = (struct ipovly *)ip; 883 th = (struct tcphdr *)(ip + 1); 884 tcpip_fillheaders(tp->t_inpcb, ip, th); 885 } 886 887 /* 888 * Fill in fields, remembering maximum advertised 889 * window for use in delaying messages about window sizes. 890 * If resending a FIN, be sure not to use a new sequence number. 891 */ 892 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 893 tp->snd_nxt == tp->snd_max) 894 tp->snd_nxt--; 895 /* 896 * If we are starting a connection, send ECN setup 897 * SYN packet. If we are on a retransmit, we may 898 * resend those bits a number of times as per 899 * RFC 3168. 900 */ 901 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 902 if (tp->t_rxtshift >= 1) { 903 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 904 flags |= TH_ECE|TH_CWR; 905 } else 906 flags |= TH_ECE|TH_CWR; 907 } 908 909 if (tp->t_state == TCPS_ESTABLISHED && 910 (tp->t_flags & TF_ECN_PERMIT)) { 911 /* 912 * If the peer has ECN, mark data packets with 913 * ECN capable transmission (ECT). 914 * Ignore pure ack packets, retransmissions and window probes. 915 */ 916 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 917 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 918 #ifdef INET6 919 if (isipv6) 920 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 921 else 922 #endif 923 ip->ip_tos |= IPTOS_ECN_ECT0; 924 TCPSTAT_INC(tcps_ecn_ect0); 925 } 926 927 /* 928 * Reply with proper ECN notifications. 929 */ 930 if (tp->t_flags & TF_ECN_SND_CWR) { 931 flags |= TH_CWR; 932 tp->t_flags &= ~TF_ECN_SND_CWR; 933 } 934 if (tp->t_flags & TF_ECN_SND_ECE) 935 flags |= TH_ECE; 936 } 937 938 /* 939 * If we are doing retransmissions, then snd_nxt will 940 * not reflect the first unsent octet. For ACK only 941 * packets, we do not want the sequence number of the 942 * retransmitted packet, we want the sequence number 943 * of the next unsent octet. So, if there is no data 944 * (and no SYN or FIN), use snd_max instead of snd_nxt 945 * when filling in ti_seq. But if we are in persist 946 * state, snd_max might reflect one byte beyond the 947 * right edge of the window, so use snd_nxt in that 948 * case, since we know we aren't doing a retransmission. 949 * (retransmit and persist are mutually exclusive...) 950 */ 951 if (sack_rxmit == 0) { 952 if (len || (flags & (TH_SYN|TH_FIN)) || 953 tcp_timer_active(tp, TT_PERSIST)) 954 th->th_seq = htonl(tp->snd_nxt); 955 else 956 th->th_seq = htonl(tp->snd_max); 957 } else { 958 th->th_seq = htonl(p->rxmit); 959 p->rxmit += len; 960 tp->sackhint.sack_bytes_rexmit += len; 961 } 962 th->th_ack = htonl(tp->rcv_nxt); 963 if (optlen) { 964 bcopy(opt, th + 1, optlen); 965 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 966 } 967 th->th_flags = flags; 968 /* 969 * Calculate receive window. Don't shrink window, 970 * but avoid silly window syndrome. 971 */ 972 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 973 recwin < (long)tp->t_maxseg) 974 recwin = 0; 975 if (recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 976 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 977 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 978 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 979 980 /* 981 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 982 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 983 * case is handled in syncache. 984 */ 985 if (flags & TH_SYN) 986 th->th_win = htons((u_short) 987 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 988 else 989 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 990 991 /* 992 * Adjust the RXWIN0SENT flag - indicate that we have advertised 993 * a 0 window. This may cause the remote transmitter to stall. This 994 * flag tells soreceive() to disable delayed acknowledgements when 995 * draining the buffer. This can occur if the receiver is attempting 996 * to read more data than can be buffered prior to transmitting on 997 * the connection. 998 */ 999 if (th->th_win == 0) 1000 tp->t_flags |= TF_RXWIN0SENT; 1001 else 1002 tp->t_flags &= ~TF_RXWIN0SENT; 1003 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1004 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1005 th->th_flags |= TH_URG; 1006 } else 1007 /* 1008 * If no urgent pointer to send, then we pull 1009 * the urgent pointer to the left edge of the send window 1010 * so that it doesn't drift into the send window on sequence 1011 * number wraparound. 1012 */ 1013 tp->snd_up = tp->snd_una; /* drag it along */ 1014 1015 #ifdef TCP_SIGNATURE 1016 if (tp->t_flags & TF_SIGNATURE) { 1017 int sigoff = to.to_signature - opt; 1018 tcp_signature_compute(m, 0, len, optlen, 1019 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1020 } 1021 #endif 1022 1023 /* 1024 * Put TCP length in extended header, and then 1025 * checksum extended header and data. 1026 */ 1027 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1028 #ifdef INET6 1029 if (isipv6) 1030 /* 1031 * ip6_plen is not need to be filled now, and will be filled 1032 * in ip6_output. 1033 */ 1034 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), 1035 sizeof(struct tcphdr) + optlen + len); 1036 else 1037 #endif /* INET6 */ 1038 { 1039 m->m_pkthdr.csum_flags = CSUM_TCP; 1040 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1041 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1042 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1043 1044 /* IP version must be set here for ipv4/ipv6 checking later */ 1045 KASSERT(ip->ip_v == IPVERSION, 1046 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1047 } 1048 1049 /* 1050 * Enable TSO and specify the size of the segments. 1051 * The TCP pseudo header checksum is always provided. 1052 * XXX: Fixme: This is currently not the case for IPv6. 1053 */ 1054 if (tso) { 1055 KASSERT(len > tp->t_maxopd - optlen, 1056 ("%s: len <= tso_segsz", __func__)); 1057 m->m_pkthdr.csum_flags |= CSUM_TSO; 1058 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1059 } 1060 1061 /* 1062 * In transmit state, time the transmission and arrange for 1063 * the retransmit. In persist state, just set snd_max. 1064 */ 1065 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1066 !tcp_timer_active(tp, TT_PERSIST)) { 1067 tcp_seq startseq = tp->snd_nxt; 1068 1069 /* 1070 * Advance snd_nxt over sequence space of this segment. 1071 */ 1072 if (flags & (TH_SYN|TH_FIN)) { 1073 if (flags & TH_SYN) 1074 tp->snd_nxt++; 1075 if (flags & TH_FIN) { 1076 tp->snd_nxt++; 1077 tp->t_flags |= TF_SENTFIN; 1078 } 1079 } 1080 if (sack_rxmit) 1081 goto timer; 1082 tp->snd_nxt += len; 1083 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1084 tp->snd_max = tp->snd_nxt; 1085 /* 1086 * Time this transmission if not a retransmission and 1087 * not currently timing anything. 1088 */ 1089 if (tp->t_rtttime == 0) { 1090 tp->t_rtttime = ticks; 1091 tp->t_rtseq = startseq; 1092 TCPSTAT_INC(tcps_segstimed); 1093 } 1094 } 1095 1096 /* 1097 * Set retransmit timer if not currently set, 1098 * and not doing a pure ack or a keep-alive probe. 1099 * Initial value for retransmit timer is smoothed 1100 * round-trip time + 2 * round-trip time variance. 1101 * Initialize shift counter which is used for backoff 1102 * of retransmit time. 1103 */ 1104 timer: 1105 if (!tcp_timer_active(tp, TT_REXMT) && 1106 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1107 (tp->snd_nxt != tp->snd_una))) { 1108 if (tcp_timer_active(tp, TT_PERSIST)) { 1109 tcp_timer_activate(tp, TT_PERSIST, 0); 1110 tp->t_rxtshift = 0; 1111 } 1112 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1113 } 1114 } else { 1115 /* 1116 * Persist case, update snd_max but since we are in 1117 * persist mode (no window) we do not update snd_nxt. 1118 */ 1119 int xlen = len; 1120 if (flags & TH_SYN) 1121 ++xlen; 1122 if (flags & TH_FIN) { 1123 ++xlen; 1124 tp->t_flags |= TF_SENTFIN; 1125 } 1126 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1127 tp->snd_max = tp->snd_nxt + len; 1128 } 1129 1130 #ifdef TCPDEBUG 1131 /* 1132 * Trace. 1133 */ 1134 if (so->so_options & SO_DEBUG) { 1135 u_short save = 0; 1136 #ifdef INET6 1137 if (!isipv6) 1138 #endif 1139 { 1140 save = ipov->ih_len; 1141 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1142 } 1143 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1144 #ifdef INET6 1145 if (!isipv6) 1146 #endif 1147 ipov->ih_len = save; 1148 } 1149 #endif 1150 1151 /* 1152 * Fill in IP length and desired time to live and 1153 * send to IP level. There should be a better way 1154 * to handle ttl and tos; we could keep them in 1155 * the template, but need a way to checksum without them. 1156 */ 1157 /* 1158 * m->m_pkthdr.len should have been set before cksum calcuration, 1159 * because in6_cksum() need it. 1160 */ 1161 #ifdef INET6 1162 if (isipv6) { 1163 /* 1164 * we separately set hoplimit for every segment, since the 1165 * user might want to change the value via setsockopt. 1166 * Also, desired default hop limit might be changed via 1167 * Neighbor Discovery. 1168 */ 1169 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1170 1171 /* TODO: IPv6 IP6TOS_ECT bit on */ 1172 error = ip6_output(m, 1173 tp->t_inpcb->in6p_outputopts, NULL, 1174 ((so->so_options & SO_DONTROUTE) ? 1175 IP_ROUTETOIF : 0), NULL, NULL, tp->t_inpcb); 1176 } else 1177 #endif /* INET6 */ 1178 { 1179 ip->ip_len = m->m_pkthdr.len; 1180 #ifdef INET6 1181 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1182 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1183 #endif /* INET6 */ 1184 /* 1185 * If we do path MTU discovery, then we set DF on every packet. 1186 * This might not be the best thing to do according to RFC3390 1187 * Section 2. However the tcp hostcache migitates the problem 1188 * so it affects only the first tcp connection with a host. 1189 * 1190 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1191 */ 1192 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) 1193 ip->ip_off |= IP_DF; 1194 1195 error = ip_output(m, tp->t_inpcb->inp_options, NULL, 1196 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1197 tp->t_inpcb); 1198 } 1199 if (error) { 1200 1201 /* 1202 * We know that the packet was lost, so back out the 1203 * sequence number advance, if any. 1204 * 1205 * If the error is EPERM the packet got blocked by the 1206 * local firewall. Normally we should terminate the 1207 * connection but the blocking may have been spurious 1208 * due to a firewall reconfiguration cycle. So we treat 1209 * it like a packet loss and let the retransmit timer and 1210 * timeouts do their work over time. 1211 * XXX: It is a POLA question whether calling tcp_drop right 1212 * away would be the really correct behavior instead. 1213 */ 1214 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1215 !tcp_timer_active(tp, TT_PERSIST)) && 1216 ((flags & TH_SYN) == 0) && 1217 (error != EPERM)) { 1218 if (sack_rxmit) { 1219 p->rxmit -= len; 1220 tp->sackhint.sack_bytes_rexmit -= len; 1221 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1222 ("sackhint bytes rtx >= 0")); 1223 } else 1224 tp->snd_nxt -= len; 1225 } 1226 out: 1227 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1228 switch (error) { 1229 case EPERM: 1230 tp->t_softerror = error; 1231 return (error); 1232 case ENOBUFS: 1233 if (!tcp_timer_active(tp, TT_REXMT) && 1234 !tcp_timer_active(tp, TT_PERSIST)) 1235 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1236 tp->snd_cwnd = tp->t_maxseg; 1237 return (0); 1238 case EMSGSIZE: 1239 /* 1240 * For some reason the interface we used initially 1241 * to send segments changed to another or lowered 1242 * its MTU. 1243 * 1244 * tcp_mtudisc() will find out the new MTU and as 1245 * its last action, initiate retransmission, so it 1246 * is important to not do so here. 1247 * 1248 * If TSO was active we either got an interface 1249 * without TSO capabilits or TSO was turned off. 1250 * Disable it for this connection as too and 1251 * immediatly retry with MSS sized segments generated 1252 * by this function. 1253 */ 1254 if (tso) 1255 tp->t_flags &= ~TF_TSO; 1256 tcp_mtudisc(tp->t_inpcb, 0); 1257 return (0); 1258 case EHOSTDOWN: 1259 case EHOSTUNREACH: 1260 case ENETDOWN: 1261 case ENETUNREACH: 1262 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1263 tp->t_softerror = error; 1264 return (0); 1265 } 1266 /* FALLTHROUGH */ 1267 default: 1268 return (error); 1269 } 1270 } 1271 TCPSTAT_INC(tcps_sndtotal); 1272 1273 /* 1274 * Data sent (as far as we can tell). 1275 * If this advertises a larger window than any other segment, 1276 * then remember the size of the advertised window. 1277 * Any pending ACK has now been sent. 1278 */ 1279 if (recwin > 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1280 tp->rcv_adv = tp->rcv_nxt + recwin; 1281 tp->last_ack_sent = tp->rcv_nxt; 1282 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1283 if (tcp_timer_active(tp, TT_DELACK)) 1284 tcp_timer_activate(tp, TT_DELACK, 0); 1285 #if 0 1286 /* 1287 * This completely breaks TCP if newreno is turned on. What happens 1288 * is that if delayed-acks are turned on on the receiver, this code 1289 * on the transmitter effectively destroys the TCP window, forcing 1290 * it to four packets (1.5Kx4 = 6K window). 1291 */ 1292 if (sendalot && (!V_tcp_do_newreno || --maxburst)) 1293 goto again; 1294 #endif 1295 if (sendalot) 1296 goto again; 1297 return (0); 1298 } 1299 1300 void 1301 tcp_setpersist(struct tcpcb *tp) 1302 { 1303 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1304 int tt; 1305 1306 if (tcp_timer_active(tp, TT_REXMT)) 1307 panic("tcp_setpersist: retransmit pending"); 1308 /* 1309 * Start/restart persistance timer. 1310 */ 1311 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1312 TCPTV_PERSMIN, TCPTV_PERSMAX); 1313 tcp_timer_activate(tp, TT_PERSIST, tt); 1314 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1315 tp->t_rxtshift++; 1316 } 1317 1318 /* 1319 * Insert TCP options according to the supplied parameters to the place 1320 * optp in a consistent way. Can handle unaligned destinations. 1321 * 1322 * The order of the option processing is crucial for optimal packing and 1323 * alignment for the scarce option space. 1324 * 1325 * The optimal order for a SYN/SYN-ACK segment is: 1326 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1327 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1328 * 1329 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1330 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1331 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1332 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1333 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1334 */ 1335 int 1336 tcp_addoptions(struct tcpopt *to, u_char *optp) 1337 { 1338 u_int mask, optlen = 0; 1339 1340 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1341 if ((to->to_flags & mask) != mask) 1342 continue; 1343 if (optlen == TCP_MAXOLEN) 1344 break; 1345 switch (to->to_flags & mask) { 1346 case TOF_MSS: 1347 while (optlen % 4) { 1348 optlen += TCPOLEN_NOP; 1349 *optp++ = TCPOPT_NOP; 1350 } 1351 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1352 continue; 1353 optlen += TCPOLEN_MAXSEG; 1354 *optp++ = TCPOPT_MAXSEG; 1355 *optp++ = TCPOLEN_MAXSEG; 1356 to->to_mss = htons(to->to_mss); 1357 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1358 optp += sizeof(to->to_mss); 1359 break; 1360 case TOF_SCALE: 1361 while (!optlen || optlen % 2 != 1) { 1362 optlen += TCPOLEN_NOP; 1363 *optp++ = TCPOPT_NOP; 1364 } 1365 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1366 continue; 1367 optlen += TCPOLEN_WINDOW; 1368 *optp++ = TCPOPT_WINDOW; 1369 *optp++ = TCPOLEN_WINDOW; 1370 *optp++ = to->to_wscale; 1371 break; 1372 case TOF_SACKPERM: 1373 while (optlen % 2) { 1374 optlen += TCPOLEN_NOP; 1375 *optp++ = TCPOPT_NOP; 1376 } 1377 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1378 continue; 1379 optlen += TCPOLEN_SACK_PERMITTED; 1380 *optp++ = TCPOPT_SACK_PERMITTED; 1381 *optp++ = TCPOLEN_SACK_PERMITTED; 1382 break; 1383 case TOF_TS: 1384 while (!optlen || optlen % 4 != 2) { 1385 optlen += TCPOLEN_NOP; 1386 *optp++ = TCPOPT_NOP; 1387 } 1388 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1389 continue; 1390 optlen += TCPOLEN_TIMESTAMP; 1391 *optp++ = TCPOPT_TIMESTAMP; 1392 *optp++ = TCPOLEN_TIMESTAMP; 1393 to->to_tsval = htonl(to->to_tsval); 1394 to->to_tsecr = htonl(to->to_tsecr); 1395 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1396 optp += sizeof(to->to_tsval); 1397 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1398 optp += sizeof(to->to_tsecr); 1399 break; 1400 case TOF_SIGNATURE: 1401 { 1402 int siglen = TCPOLEN_SIGNATURE - 2; 1403 1404 while (!optlen || optlen % 4 != 2) { 1405 optlen += TCPOLEN_NOP; 1406 *optp++ = TCPOPT_NOP; 1407 } 1408 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1409 continue; 1410 optlen += TCPOLEN_SIGNATURE; 1411 *optp++ = TCPOPT_SIGNATURE; 1412 *optp++ = TCPOLEN_SIGNATURE; 1413 to->to_signature = optp; 1414 while (siglen--) 1415 *optp++ = 0; 1416 break; 1417 } 1418 case TOF_SACK: 1419 { 1420 int sackblks = 0; 1421 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1422 tcp_seq sack_seq; 1423 1424 while (!optlen || optlen % 4 != 2) { 1425 optlen += TCPOLEN_NOP; 1426 *optp++ = TCPOPT_NOP; 1427 } 1428 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1429 continue; 1430 optlen += TCPOLEN_SACKHDR; 1431 *optp++ = TCPOPT_SACK; 1432 sackblks = min(to->to_nsacks, 1433 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1434 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1435 while (sackblks--) { 1436 sack_seq = htonl(sack->start); 1437 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1438 optp += sizeof(sack_seq); 1439 sack_seq = htonl(sack->end); 1440 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1441 optp += sizeof(sack_seq); 1442 optlen += TCPOLEN_SACK; 1443 sack++; 1444 } 1445 TCPSTAT_INC(tcps_sack_send_blocks); 1446 break; 1447 } 1448 default: 1449 panic("%s: unknown TCP option type", __func__); 1450 break; 1451 } 1452 } 1453 1454 /* Terminate and pad TCP options to a 4 byte boundary. */ 1455 if (optlen % 4) { 1456 optlen += TCPOLEN_EOL; 1457 *optp++ = TCPOPT_EOL; 1458 } 1459 /* 1460 * According to RFC 793 (STD0007): 1461 * "The content of the header beyond the End-of-Option option 1462 * must be header padding (i.e., zero)." 1463 * and later: "The padding is composed of zeros." 1464 */ 1465 while (optlen % 4) { 1466 optlen += TCPOLEN_PAD; 1467 *optp++ = TCPOPT_PAD; 1468 } 1469 1470 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1471 return (optlen); 1472 } 1473