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sys/netinet/tcp_output.c
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1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD: releng/10.0/sys/netinet/tcp_output.c 254889 2013-08-25 21:54:41Z markj $"); 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_kdtrace.h" 39 #include "opt_tcpdebug.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/domain.h> 44 #include <sys/hhook.h> 45 #include <sys/kernel.h> 46 #include <sys/lock.h> 47 #include <sys/mbuf.h> 48 #include <sys/mutex.h> 49 #include <sys/protosw.h> 50 #include <sys/sdt.h> 51 #include <sys/socket.h> 52 #include <sys/socketvar.h> 53 #include <sys/sysctl.h> 54 55 #include <net/if.h> 56 #include <net/route.h> 57 #include <net/vnet.h> 58 59 #include <netinet/cc.h> 60 #include <netinet/in.h> 61 #include <netinet/in_kdtrace.h> 62 #include <netinet/in_systm.h> 63 #include <netinet/ip.h> 64 #include <netinet/in_pcb.h> 65 #include <netinet/ip_var.h> 66 #include <netinet/ip_options.h> 67 #ifdef INET6 68 #include <netinet6/in6_pcb.h> 69 #include <netinet/ip6.h> 70 #include <netinet6/ip6_var.h> 71 #endif 72 #define TCPOUTFLAGS 73 #include <netinet/tcp_fsm.h> 74 #include <netinet/tcp_seq.h> 75 #include <netinet/tcp_timer.h> 76 #include <netinet/tcp_var.h> 77 #include <netinet/tcpip.h> 78 #ifdef TCPDEBUG 79 #include <netinet/tcp_debug.h> 80 #endif 81 #ifdef TCP_OFFLOAD 82 #include <netinet/tcp_offload.h> 83 #endif 84 85 #ifdef IPSEC 86 #include <netipsec/ipsec.h> 87 #endif /*IPSEC*/ 88 89 #include <machine/in_cksum.h> 90 91 #include <security/mac/mac_framework.h> 92 93 VNET_DEFINE(int, path_mtu_discovery) = 1; 94 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, 95 &VNET_NAME(path_mtu_discovery), 1, 96 "Enable Path MTU Discovery"); 97 98 VNET_DEFINE(int, tcp_do_tso) = 1; 99 #define V_tcp_do_tso VNET(tcp_do_tso) 100 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_RW, 101 &VNET_NAME(tcp_do_tso), 0, 102 "Enable TCP Segmentation Offload"); 103 104 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 105 #define V_tcp_sendspace VNET(tcp_sendspace) 106 SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_RW, 107 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 108 109 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 110 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf) 111 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_RW, 112 &VNET_NAME(tcp_do_autosndbuf), 0, 113 "Enable automatic send buffer sizing"); 114 115 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 116 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc) 117 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_RW, 118 &VNET_NAME(tcp_autosndbuf_inc), 0, 119 "Incrementor step size of automatic send buffer"); 120 121 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 122 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max) 123 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_RW, 124 &VNET_NAME(tcp_autosndbuf_max), 0, 125 "Max size of automatic send buffer"); 126 127 static void inline hhook_run_tcp_est_out(struct tcpcb *tp, 128 struct tcphdr *th, struct tcpopt *to, 129 long len, int tso); 130 static void inline cc_after_idle(struct tcpcb *tp); 131 132 /* 133 * Wrapper for the TCP established output helper hook. 134 */ 135 static void inline 136 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 137 struct tcpopt *to, long len, int tso) 138 { 139 struct tcp_hhook_data hhook_data; 140 141 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 142 hhook_data.tp = tp; 143 hhook_data.th = th; 144 hhook_data.to = to; 145 hhook_data.len = len; 146 hhook_data.tso = tso; 147 148 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 149 tp->osd); 150 } 151 } 152 153 /* 154 * CC wrapper hook functions 155 */ 156 static void inline 157 cc_after_idle(struct tcpcb *tp) 158 { 159 INP_WLOCK_ASSERT(tp->t_inpcb); 160 161 if (CC_ALGO(tp)->after_idle != NULL) 162 CC_ALGO(tp)->after_idle(tp->ccv); 163 } 164 165 /* 166 * Tcp output routine: figure out what should be sent and send it. 167 */ 168 int 169 tcp_output(struct tcpcb *tp) 170 { 171 struct socket *so = tp->t_inpcb->inp_socket; 172 long len, recwin, sendwin; 173 int off, flags, error = 0; /* Keep compiler happy */ 174 struct mbuf *m; 175 struct ip *ip = NULL; 176 struct ipovly *ipov = NULL; 177 struct tcphdr *th; 178 u_char opt[TCP_MAXOLEN]; 179 unsigned ipoptlen, optlen, hdrlen; 180 #ifdef IPSEC 181 unsigned ipsec_optlen = 0; 182 #endif 183 int idle, sendalot; 184 int sack_rxmit, sack_bytes_rxmt; 185 struct sackhole *p; 186 int tso, mtu; 187 struct tcpopt to; 188 #if 0 189 int maxburst = TCP_MAXBURST; 190 #endif 191 #ifdef INET6 192 struct ip6_hdr *ip6 = NULL; 193 int isipv6; 194 195 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 196 #endif 197 198 INP_WLOCK_ASSERT(tp->t_inpcb); 199 200 #ifdef TCP_OFFLOAD 201 if (tp->t_flags & TF_TOE) 202 return (tcp_offload_output(tp)); 203 #endif 204 205 /* 206 * Determine length of data that should be transmitted, 207 * and flags that will be used. 208 * If there is some data or critical controls (SYN, RST) 209 * to send, then transmit; otherwise, investigate further. 210 */ 211 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 212 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 213 cc_after_idle(tp); 214 tp->t_flags &= ~TF_LASTIDLE; 215 if (idle) { 216 if (tp->t_flags & TF_MORETOCOME) { 217 tp->t_flags |= TF_LASTIDLE; 218 idle = 0; 219 } 220 } 221 again: 222 /* 223 * If we've recently taken a timeout, snd_max will be greater than 224 * snd_nxt. There may be SACK information that allows us to avoid 225 * resending already delivered data. Adjust snd_nxt accordingly. 226 */ 227 if ((tp->t_flags & TF_SACK_PERMIT) && 228 SEQ_LT(tp->snd_nxt, tp->snd_max)) 229 tcp_sack_adjust(tp); 230 sendalot = 0; 231 tso = 0; 232 mtu = 0; 233 off = tp->snd_nxt - tp->snd_una; 234 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 235 236 flags = tcp_outflags[tp->t_state]; 237 /* 238 * Send any SACK-generated retransmissions. If we're explicitly trying 239 * to send out new data (when sendalot is 1), bypass this function. 240 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 241 * we're replacing a (future) new transmission with a retransmission 242 * now, and we previously incremented snd_cwnd in tcp_input(). 243 */ 244 /* 245 * Still in sack recovery , reset rxmit flag to zero. 246 */ 247 sack_rxmit = 0; 248 sack_bytes_rxmt = 0; 249 len = 0; 250 p = NULL; 251 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 252 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 253 long cwin; 254 255 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 256 if (cwin < 0) 257 cwin = 0; 258 /* Do not retransmit SACK segments beyond snd_recover */ 259 if (SEQ_GT(p->end, tp->snd_recover)) { 260 /* 261 * (At least) part of sack hole extends beyond 262 * snd_recover. Check to see if we can rexmit data 263 * for this hole. 264 */ 265 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 266 /* 267 * Can't rexmit any more data for this hole. 268 * That data will be rexmitted in the next 269 * sack recovery episode, when snd_recover 270 * moves past p->rxmit. 271 */ 272 p = NULL; 273 goto after_sack_rexmit; 274 } else 275 /* Can rexmit part of the current hole */ 276 len = ((long)ulmin(cwin, 277 tp->snd_recover - p->rxmit)); 278 } else 279 len = ((long)ulmin(cwin, p->end - p->rxmit)); 280 off = p->rxmit - tp->snd_una; 281 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 282 __func__, off)); 283 if (len > 0) { 284 sack_rxmit = 1; 285 sendalot = 1; 286 TCPSTAT_INC(tcps_sack_rexmits); 287 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 288 min(len, tp->t_maxseg)); 289 } 290 } 291 after_sack_rexmit: 292 /* 293 * Get standard flags, and add SYN or FIN if requested by 'hidden' 294 * state flags. 295 */ 296 if (tp->t_flags & TF_NEEDFIN) 297 flags |= TH_FIN; 298 if (tp->t_flags & TF_NEEDSYN) 299 flags |= TH_SYN; 300 301 SOCKBUF_LOCK(&so->so_snd); 302 /* 303 * If in persist timeout with window of 0, send 1 byte. 304 * Otherwise, if window is small but nonzero 305 * and timer expired, we will send what we can 306 * and go to transmit state. 307 */ 308 if (tp->t_flags & TF_FORCEDATA) { 309 if (sendwin == 0) { 310 /* 311 * If we still have some data to send, then 312 * clear the FIN bit. Usually this would 313 * happen below when it realizes that we 314 * aren't sending all the data. However, 315 * if we have exactly 1 byte of unsent data, 316 * then it won't clear the FIN bit below, 317 * and if we are in persist state, we wind 318 * up sending the packet without recording 319 * that we sent the FIN bit. 320 * 321 * We can't just blindly clear the FIN bit, 322 * because if we don't have any more data 323 * to send then the probe will be the FIN 324 * itself. 325 */ 326 if (off < so->so_snd.sb_cc) 327 flags &= ~TH_FIN; 328 sendwin = 1; 329 } else { 330 tcp_timer_activate(tp, TT_PERSIST, 0); 331 tp->t_rxtshift = 0; 332 } 333 } 334 335 /* 336 * If snd_nxt == snd_max and we have transmitted a FIN, the 337 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 338 * a negative length. This can also occur when TCP opens up 339 * its congestion window while receiving additional duplicate 340 * acks after fast-retransmit because TCP will reset snd_nxt 341 * to snd_max after the fast-retransmit. 342 * 343 * In the normal retransmit-FIN-only case, however, snd_nxt will 344 * be set to snd_una, the offset will be 0, and the length may 345 * wind up 0. 346 * 347 * If sack_rxmit is true we are retransmitting from the scoreboard 348 * in which case len is already set. 349 */ 350 if (sack_rxmit == 0) { 351 if (sack_bytes_rxmt == 0) 352 len = ((long)ulmin(so->so_snd.sb_cc, sendwin) - off); 353 else { 354 long cwin; 355 356 /* 357 * We are inside of a SACK recovery episode and are 358 * sending new data, having retransmitted all the 359 * data possible in the scoreboard. 360 */ 361 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 362 - off); 363 /* 364 * Don't remove this (len > 0) check ! 365 * We explicitly check for len > 0 here (although it 366 * isn't really necessary), to work around a gcc 367 * optimization issue - to force gcc to compute 368 * len above. Without this check, the computation 369 * of len is bungled by the optimizer. 370 */ 371 if (len > 0) { 372 cwin = tp->snd_cwnd - 373 (tp->snd_nxt - tp->sack_newdata) - 374 sack_bytes_rxmt; 375 if (cwin < 0) 376 cwin = 0; 377 len = lmin(len, cwin); 378 } 379 } 380 } 381 382 /* 383 * Lop off SYN bit if it has already been sent. However, if this 384 * is SYN-SENT state and if segment contains data and if we don't 385 * know that foreign host supports TAO, suppress sending segment. 386 */ 387 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 388 if (tp->t_state != TCPS_SYN_RECEIVED) 389 flags &= ~TH_SYN; 390 off--, len++; 391 } 392 393 /* 394 * Be careful not to send data and/or FIN on SYN segments. 395 * This measure is needed to prevent interoperability problems 396 * with not fully conformant TCP implementations. 397 */ 398 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 399 len = 0; 400 flags &= ~TH_FIN; 401 } 402 403 if (len < 0) { 404 /* 405 * If FIN has been sent but not acked, 406 * but we haven't been called to retransmit, 407 * len will be < 0. Otherwise, window shrank 408 * after we sent into it. If window shrank to 0, 409 * cancel pending retransmit, pull snd_nxt back 410 * to (closed) window, and set the persist timer 411 * if it isn't already going. If the window didn't 412 * close completely, just wait for an ACK. 413 */ 414 len = 0; 415 if (sendwin == 0) { 416 tcp_timer_activate(tp, TT_REXMT, 0); 417 tp->t_rxtshift = 0; 418 tp->snd_nxt = tp->snd_una; 419 if (!tcp_timer_active(tp, TT_PERSIST)) 420 tcp_setpersist(tp); 421 } 422 } 423 424 /* len will be >= 0 after this point. */ 425 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 426 427 /* 428 * Automatic sizing of send socket buffer. Often the send buffer 429 * size is not optimally adjusted to the actual network conditions 430 * at hand (delay bandwidth product). Setting the buffer size too 431 * small limits throughput on links with high bandwidth and high 432 * delay (eg. trans-continental/oceanic links). Setting the 433 * buffer size too big consumes too much real kernel memory, 434 * especially with many connections on busy servers. 435 * 436 * The criteria to step up the send buffer one notch are: 437 * 1. receive window of remote host is larger than send buffer 438 * (with a fudge factor of 5/4th); 439 * 2. send buffer is filled to 7/8th with data (so we actually 440 * have data to make use of it); 441 * 3. send buffer fill has not hit maximal automatic size; 442 * 4. our send window (slow start and cogestion controlled) is 443 * larger than sent but unacknowledged data in send buffer. 444 * 445 * The remote host receive window scaling factor may limit the 446 * growing of the send buffer before it reaches its allowed 447 * maximum. 448 * 449 * It scales directly with slow start or congestion window 450 * and does at most one step per received ACK. This fast 451 * scaling has the drawback of growing the send buffer beyond 452 * what is strictly necessary to make full use of a given 453 * delay*bandwith product. However testing has shown this not 454 * to be much of an problem. At worst we are trading wasting 455 * of available bandwith (the non-use of it) for wasting some 456 * socket buffer memory. 457 * 458 * TODO: Shrink send buffer during idle periods together 459 * with congestion window. Requires another timer. Has to 460 * wait for upcoming tcp timer rewrite. 461 */ 462 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 463 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 464 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 465 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 466 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 467 if (!sbreserve_locked(&so->so_snd, 468 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 469 V_tcp_autosndbuf_max), so, curthread)) 470 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 471 } 472 } 473 474 /* 475 * Decide if we can use TCP Segmentation Offloading (if supported by 476 * hardware). 477 * 478 * TSO may only be used if we are in a pure bulk sending state. The 479 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 480 * IP options prevent using TSO. With TSO the TCP header is the same 481 * (except for the sequence number) for all generated packets. This 482 * makes it impossible to transmit any options which vary per generated 483 * segment or packet. 484 */ 485 #ifdef IPSEC 486 /* 487 * Pre-calculate here as we save another lookup into the darknesses 488 * of IPsec that way and can actually decide if TSO is ok. 489 */ 490 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 491 #endif 492 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 493 ((tp->t_flags & TF_SIGNATURE) == 0) && 494 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 495 #ifdef IPSEC 496 ipsec_optlen == 0 && 497 #endif 498 tp->t_inpcb->inp_options == NULL && 499 tp->t_inpcb->in6p_options == NULL) 500 tso = 1; 501 502 if (sack_rxmit) { 503 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 504 flags &= ~TH_FIN; 505 } else { 506 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 507 flags &= ~TH_FIN; 508 } 509 510 recwin = sbspace(&so->so_rcv); 511 512 /* 513 * Sender silly window avoidance. We transmit under the following 514 * conditions when len is non-zero: 515 * 516 * - We have a full segment (or more with TSO) 517 * - This is the last buffer in a write()/send() and we are 518 * either idle or running NODELAY 519 * - we've timed out (e.g. persist timer) 520 * - we have more then 1/2 the maximum send window's worth of 521 * data (receiver may be limited the window size) 522 * - we need to retransmit 523 */ 524 if (len) { 525 if (len >= tp->t_maxseg) 526 goto send; 527 /* 528 * NOTE! on localhost connections an 'ack' from the remote 529 * end may occur synchronously with the output and cause 530 * us to flush a buffer queued with moretocome. XXX 531 * 532 * note: the len + off check is almost certainly unnecessary. 533 */ 534 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 535 (idle || (tp->t_flags & TF_NODELAY)) && 536 len + off >= so->so_snd.sb_cc && 537 (tp->t_flags & TF_NOPUSH) == 0) { 538 goto send; 539 } 540 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 541 goto send; 542 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 543 goto send; 544 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 545 goto send; 546 if (sack_rxmit) 547 goto send; 548 } 549 550 /* 551 * Sending of standalone window updates. 552 * 553 * Window updates are important when we close our window due to a 554 * full socket buffer and are opening it again after the application 555 * reads data from it. Once the window has opened again and the 556 * remote end starts to send again the ACK clock takes over and 557 * provides the most current window information. 558 * 559 * We must avoid the silly window syndrome whereas every read 560 * from the receive buffer, no matter how small, causes a window 561 * update to be sent. We also should avoid sending a flurry of 562 * window updates when the socket buffer had queued a lot of data 563 * and the application is doing small reads. 564 * 565 * Prevent a flurry of pointless window updates by only sending 566 * an update when we can increase the advertized window by more 567 * than 1/4th of the socket buffer capacity. When the buffer is 568 * getting full or is very small be more aggressive and send an 569 * update whenever we can increase by two mss sized segments. 570 * In all other situations the ACK's to new incoming data will 571 * carry further window increases. 572 * 573 * Don't send an independent window update if a delayed 574 * ACK is pending (it will get piggy-backed on it) or the 575 * remote side already has done a half-close and won't send 576 * more data. Skip this if the connection is in T/TCP 577 * half-open state. 578 */ 579 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 580 !(tp->t_flags & TF_DELACK) && 581 !TCPS_HAVERCVDFIN(tp->t_state)) { 582 /* 583 * "adv" is the amount we could increase the window, 584 * taking into account that we are limited by 585 * TCP_MAXWIN << tp->rcv_scale. 586 */ 587 long adv; 588 int oldwin; 589 590 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale); 591 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 592 oldwin = (tp->rcv_adv - tp->rcv_nxt); 593 adv -= oldwin; 594 } else 595 oldwin = 0; 596 597 /* 598 * If the new window size ends up being the same as the old 599 * size when it is scaled, then don't force a window update. 600 */ 601 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale) 602 goto dontupdate; 603 604 if (adv >= (long)(2 * tp->t_maxseg) && 605 (adv >= (long)(so->so_rcv.sb_hiwat / 4) || 606 recwin <= (long)(so->so_rcv.sb_hiwat / 8) || 607 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 608 goto send; 609 } 610 dontupdate: 611 612 /* 613 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 614 * is also a catch-all for the retransmit timer timeout case. 615 */ 616 if (tp->t_flags & TF_ACKNOW) 617 goto send; 618 if ((flags & TH_RST) || 619 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 620 goto send; 621 if (SEQ_GT(tp->snd_up, tp->snd_una)) 622 goto send; 623 /* 624 * If our state indicates that FIN should be sent 625 * and we have not yet done so, then we need to send. 626 */ 627 if (flags & TH_FIN && 628 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 629 goto send; 630 /* 631 * In SACK, it is possible for tcp_output to fail to send a segment 632 * after the retransmission timer has been turned off. Make sure 633 * that the retransmission timer is set. 634 */ 635 if ((tp->t_flags & TF_SACK_PERMIT) && 636 SEQ_GT(tp->snd_max, tp->snd_una) && 637 !tcp_timer_active(tp, TT_REXMT) && 638 !tcp_timer_active(tp, TT_PERSIST)) { 639 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 640 goto just_return; 641 } 642 /* 643 * TCP window updates are not reliable, rather a polling protocol 644 * using ``persist'' packets is used to insure receipt of window 645 * updates. The three ``states'' for the output side are: 646 * idle not doing retransmits or persists 647 * persisting to move a small or zero window 648 * (re)transmitting and thereby not persisting 649 * 650 * tcp_timer_active(tp, TT_PERSIST) 651 * is true when we are in persist state. 652 * (tp->t_flags & TF_FORCEDATA) 653 * is set when we are called to send a persist packet. 654 * tcp_timer_active(tp, TT_REXMT) 655 * is set when we are retransmitting 656 * The output side is idle when both timers are zero. 657 * 658 * If send window is too small, there is data to transmit, and no 659 * retransmit or persist is pending, then go to persist state. 660 * If nothing happens soon, send when timer expires: 661 * if window is nonzero, transmit what we can, 662 * otherwise force out a byte. 663 */ 664 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 665 !tcp_timer_active(tp, TT_PERSIST)) { 666 tp->t_rxtshift = 0; 667 tcp_setpersist(tp); 668 } 669 670 /* 671 * No reason to send a segment, just return. 672 */ 673 just_return: 674 SOCKBUF_UNLOCK(&so->so_snd); 675 return (0); 676 677 send: 678 SOCKBUF_LOCK_ASSERT(&so->so_snd); 679 /* 680 * Before ESTABLISHED, force sending of initial options 681 * unless TCP set not to do any options. 682 * NOTE: we assume that the IP/TCP header plus TCP options 683 * always fit in a single mbuf, leaving room for a maximum 684 * link header, i.e. 685 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 686 */ 687 optlen = 0; 688 #ifdef INET6 689 if (isipv6) 690 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 691 else 692 #endif 693 hdrlen = sizeof (struct tcpiphdr); 694 695 /* 696 * Compute options for segment. 697 * We only have to care about SYN and established connection 698 * segments. Options for SYN-ACK segments are handled in TCP 699 * syncache. 700 */ 701 if ((tp->t_flags & TF_NOOPT) == 0) { 702 to.to_flags = 0; 703 /* Maximum segment size. */ 704 if (flags & TH_SYN) { 705 tp->snd_nxt = tp->iss; 706 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 707 to.to_flags |= TOF_MSS; 708 } 709 /* Window scaling. */ 710 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 711 to.to_wscale = tp->request_r_scale; 712 to.to_flags |= TOF_SCALE; 713 } 714 /* Timestamps. */ 715 if ((tp->t_flags & TF_RCVD_TSTMP) || 716 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 717 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 718 to.to_tsecr = tp->ts_recent; 719 to.to_flags |= TOF_TS; 720 /* Set receive buffer autosizing timestamp. */ 721 if (tp->rfbuf_ts == 0 && 722 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 723 tp->rfbuf_ts = tcp_ts_getticks(); 724 } 725 /* Selective ACK's. */ 726 if (tp->t_flags & TF_SACK_PERMIT) { 727 if (flags & TH_SYN) 728 to.to_flags |= TOF_SACKPERM; 729 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 730 (tp->t_flags & TF_SACK_PERMIT) && 731 tp->rcv_numsacks > 0) { 732 to.to_flags |= TOF_SACK; 733 to.to_nsacks = tp->rcv_numsacks; 734 to.to_sacks = (u_char *)tp->sackblks; 735 } 736 } 737 #ifdef TCP_SIGNATURE 738 /* TCP-MD5 (RFC2385). */ 739 if (tp->t_flags & TF_SIGNATURE) 740 to.to_flags |= TOF_SIGNATURE; 741 #endif /* TCP_SIGNATURE */ 742 743 /* Processing the options. */ 744 hdrlen += optlen = tcp_addoptions(&to, opt); 745 } 746 747 #ifdef INET6 748 if (isipv6) 749 ipoptlen = ip6_optlen(tp->t_inpcb); 750 else 751 #endif 752 if (tp->t_inpcb->inp_options) 753 ipoptlen = tp->t_inpcb->inp_options->m_len - 754 offsetof(struct ipoption, ipopt_list); 755 else 756 ipoptlen = 0; 757 #ifdef IPSEC 758 ipoptlen += ipsec_optlen; 759 #endif 760 761 /* 762 * Adjust data length if insertion of options will 763 * bump the packet length beyond the t_maxopd length. 764 * Clear the FIN bit because we cut off the tail of 765 * the segment. 766 */ 767 if (len + optlen + ipoptlen > tp->t_maxopd) { 768 flags &= ~TH_FIN; 769 770 if (tso) { 771 KASSERT(ipoptlen == 0, 772 ("%s: TSO can't do IP options", __func__)); 773 774 /* 775 * Limit a burst to t_tsomax minus IP, 776 * TCP and options length to keep ip->ip_len 777 * from overflowing or exceeding the maximum 778 * length allowed by the network interface. 779 */ 780 if (len > tp->t_tsomax - hdrlen) { 781 len = tp->t_tsomax - hdrlen; 782 sendalot = 1; 783 } 784 785 /* 786 * Prevent the last segment from being 787 * fractional unless the send sockbuf can 788 * be emptied. 789 */ 790 if (sendalot && off + len < so->so_snd.sb_cc) { 791 len -= len % (tp->t_maxopd - optlen); 792 sendalot = 1; 793 } 794 795 /* 796 * Send the FIN in a separate segment 797 * after the bulk sending is done. 798 * We don't trust the TSO implementations 799 * to clear the FIN flag on all but the 800 * last segment. 801 */ 802 if (tp->t_flags & TF_NEEDFIN) 803 sendalot = 1; 804 805 } else { 806 len = tp->t_maxopd - optlen - ipoptlen; 807 sendalot = 1; 808 } 809 } else 810 tso = 0; 811 812 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 813 ("%s: len > IP_MAXPACKET", __func__)); 814 815 /*#ifdef DIAGNOSTIC*/ 816 #ifdef INET6 817 if (max_linkhdr + hdrlen > MCLBYTES) 818 #else 819 if (max_linkhdr + hdrlen > MHLEN) 820 #endif 821 panic("tcphdr too big"); 822 /*#endif*/ 823 824 /* 825 * This KASSERT is here to catch edge cases at a well defined place. 826 * Before, those had triggered (random) panic conditions further down. 827 */ 828 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 829 830 /* 831 * Grab a header mbuf, attaching a copy of data to 832 * be transmitted, and initialize the header from 833 * the template for sends on this connection. 834 */ 835 if (len) { 836 struct mbuf *mb; 837 u_int moff; 838 839 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 840 TCPSTAT_INC(tcps_sndprobe); 841 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 842 tp->t_sndrexmitpack++; 843 TCPSTAT_INC(tcps_sndrexmitpack); 844 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 845 } else { 846 TCPSTAT_INC(tcps_sndpack); 847 TCPSTAT_ADD(tcps_sndbyte, len); 848 } 849 #ifdef INET6 850 if (MHLEN < hdrlen + max_linkhdr) 851 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 852 else 853 #endif 854 m = m_gethdr(M_NOWAIT, MT_DATA); 855 856 if (m == NULL) { 857 SOCKBUF_UNLOCK(&so->so_snd); 858 error = ENOBUFS; 859 sack_rxmit = 0; 860 goto out; 861 } 862 863 m->m_data += max_linkhdr; 864 m->m_len = hdrlen; 865 866 /* 867 * Start the m_copy functions from the closest mbuf 868 * to the offset in the socket buffer chain. 869 */ 870 mb = sbsndptr(&so->so_snd, off, len, &moff); 871 872 if (len <= MHLEN - hdrlen - max_linkhdr) { 873 m_copydata(mb, moff, (int)len, 874 mtod(m, caddr_t) + hdrlen); 875 m->m_len += len; 876 } else { 877 m->m_next = m_copy(mb, moff, (int)len); 878 if (m->m_next == NULL) { 879 SOCKBUF_UNLOCK(&so->so_snd); 880 (void) m_free(m); 881 error = ENOBUFS; 882 sack_rxmit = 0; 883 goto out; 884 } 885 } 886 887 /* 888 * If we're sending everything we've got, set PUSH. 889 * (This will keep happy those implementations which only 890 * give data to the user when a buffer fills or 891 * a PUSH comes in.) 892 */ 893 if (off + len == so->so_snd.sb_cc) 894 flags |= TH_PUSH; 895 SOCKBUF_UNLOCK(&so->so_snd); 896 } else { 897 SOCKBUF_UNLOCK(&so->so_snd); 898 if (tp->t_flags & TF_ACKNOW) 899 TCPSTAT_INC(tcps_sndacks); 900 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 901 TCPSTAT_INC(tcps_sndctrl); 902 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 903 TCPSTAT_INC(tcps_sndurg); 904 else 905 TCPSTAT_INC(tcps_sndwinup); 906 907 m = m_gethdr(M_NOWAIT, MT_DATA); 908 if (m == NULL) { 909 error = ENOBUFS; 910 sack_rxmit = 0; 911 goto out; 912 } 913 #ifdef INET6 914 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 915 MHLEN >= hdrlen) { 916 MH_ALIGN(m, hdrlen); 917 } else 918 #endif 919 m->m_data += max_linkhdr; 920 m->m_len = hdrlen; 921 } 922 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 923 m->m_pkthdr.rcvif = (struct ifnet *)0; 924 #ifdef MAC 925 mac_inpcb_create_mbuf(tp->t_inpcb, m); 926 #endif 927 #ifdef INET6 928 if (isipv6) { 929 ip6 = mtod(m, struct ip6_hdr *); 930 th = (struct tcphdr *)(ip6 + 1); 931 tcpip_fillheaders(tp->t_inpcb, ip6, th); 932 } else 933 #endif /* INET6 */ 934 { 935 ip = mtod(m, struct ip *); 936 ipov = (struct ipovly *)ip; 937 th = (struct tcphdr *)(ip + 1); 938 tcpip_fillheaders(tp->t_inpcb, ip, th); 939 } 940 941 /* 942 * Fill in fields, remembering maximum advertised 943 * window for use in delaying messages about window sizes. 944 * If resending a FIN, be sure not to use a new sequence number. 945 */ 946 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 947 tp->snd_nxt == tp->snd_max) 948 tp->snd_nxt--; 949 /* 950 * If we are starting a connection, send ECN setup 951 * SYN packet. If we are on a retransmit, we may 952 * resend those bits a number of times as per 953 * RFC 3168. 954 */ 955 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 956 if (tp->t_rxtshift >= 1) { 957 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 958 flags |= TH_ECE|TH_CWR; 959 } else 960 flags |= TH_ECE|TH_CWR; 961 } 962 963 if (tp->t_state == TCPS_ESTABLISHED && 964 (tp->t_flags & TF_ECN_PERMIT)) { 965 /* 966 * If the peer has ECN, mark data packets with 967 * ECN capable transmission (ECT). 968 * Ignore pure ack packets, retransmissions and window probes. 969 */ 970 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 971 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 972 #ifdef INET6 973 if (isipv6) 974 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 975 else 976 #endif 977 ip->ip_tos |= IPTOS_ECN_ECT0; 978 TCPSTAT_INC(tcps_ecn_ect0); 979 } 980 981 /* 982 * Reply with proper ECN notifications. 983 */ 984 if (tp->t_flags & TF_ECN_SND_CWR) { 985 flags |= TH_CWR; 986 tp->t_flags &= ~TF_ECN_SND_CWR; 987 } 988 if (tp->t_flags & TF_ECN_SND_ECE) 989 flags |= TH_ECE; 990 } 991 992 /* 993 * If we are doing retransmissions, then snd_nxt will 994 * not reflect the first unsent octet. For ACK only 995 * packets, we do not want the sequence number of the 996 * retransmitted packet, we want the sequence number 997 * of the next unsent octet. So, if there is no data 998 * (and no SYN or FIN), use snd_max instead of snd_nxt 999 * when filling in ti_seq. But if we are in persist 1000 * state, snd_max might reflect one byte beyond the 1001 * right edge of the window, so use snd_nxt in that 1002 * case, since we know we aren't doing a retransmission. 1003 * (retransmit and persist are mutually exclusive...) 1004 */ 1005 if (sack_rxmit == 0) { 1006 if (len || (flags & (TH_SYN|TH_FIN)) || 1007 tcp_timer_active(tp, TT_PERSIST)) 1008 th->th_seq = htonl(tp->snd_nxt); 1009 else 1010 th->th_seq = htonl(tp->snd_max); 1011 } else { 1012 th->th_seq = htonl(p->rxmit); 1013 p->rxmit += len; 1014 tp->sackhint.sack_bytes_rexmit += len; 1015 } 1016 th->th_ack = htonl(tp->rcv_nxt); 1017 if (optlen) { 1018 bcopy(opt, th + 1, optlen); 1019 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1020 } 1021 th->th_flags = flags; 1022 /* 1023 * Calculate receive window. Don't shrink window, 1024 * but avoid silly window syndrome. 1025 */ 1026 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 1027 recwin < (long)tp->t_maxseg) 1028 recwin = 0; 1029 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1030 recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 1031 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 1032 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 1033 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 1034 1035 /* 1036 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1037 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1038 * case is handled in syncache. 1039 */ 1040 if (flags & TH_SYN) 1041 th->th_win = htons((u_short) 1042 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1043 else 1044 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1045 1046 /* 1047 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1048 * a 0 window. This may cause the remote transmitter to stall. This 1049 * flag tells soreceive() to disable delayed acknowledgements when 1050 * draining the buffer. This can occur if the receiver is attempting 1051 * to read more data than can be buffered prior to transmitting on 1052 * the connection. 1053 */ 1054 if (th->th_win == 0) { 1055 tp->t_sndzerowin++; 1056 tp->t_flags |= TF_RXWIN0SENT; 1057 } else 1058 tp->t_flags &= ~TF_RXWIN0SENT; 1059 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1060 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1061 th->th_flags |= TH_URG; 1062 } else 1063 /* 1064 * If no urgent pointer to send, then we pull 1065 * the urgent pointer to the left edge of the send window 1066 * so that it doesn't drift into the send window on sequence 1067 * number wraparound. 1068 */ 1069 tp->snd_up = tp->snd_una; /* drag it along */ 1070 1071 #ifdef TCP_SIGNATURE 1072 if (tp->t_flags & TF_SIGNATURE) { 1073 int sigoff = to.to_signature - opt; 1074 tcp_signature_compute(m, 0, len, optlen, 1075 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1076 } 1077 #endif 1078 1079 /* 1080 * Put TCP length in extended header, and then 1081 * checksum extended header and data. 1082 */ 1083 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1084 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1085 #ifdef INET6 1086 if (isipv6) { 1087 /* 1088 * ip6_plen is not need to be filled now, and will be filled 1089 * in ip6_output. 1090 */ 1091 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1092 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1093 optlen + len, IPPROTO_TCP, 0); 1094 } 1095 #endif 1096 #if defined(INET6) && defined(INET) 1097 else 1098 #endif 1099 #ifdef INET 1100 { 1101 m->m_pkthdr.csum_flags = CSUM_TCP; 1102 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1103 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1104 1105 /* IP version must be set here for ipv4/ipv6 checking later */ 1106 KASSERT(ip->ip_v == IPVERSION, 1107 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1108 } 1109 #endif 1110 1111 /* 1112 * Enable TSO and specify the size of the segments. 1113 * The TCP pseudo header checksum is always provided. 1114 * XXX: Fixme: This is currently not the case for IPv6. 1115 */ 1116 if (tso) { 1117 KASSERT(len > tp->t_maxopd - optlen, 1118 ("%s: len <= tso_segsz", __func__)); 1119 m->m_pkthdr.csum_flags |= CSUM_TSO; 1120 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1121 } 1122 1123 #ifdef IPSEC 1124 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1125 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u", 1126 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1127 #else 1128 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1129 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u", 1130 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1131 #endif 1132 1133 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1134 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1135 1136 #ifdef TCPDEBUG 1137 /* 1138 * Trace. 1139 */ 1140 if (so->so_options & SO_DEBUG) { 1141 u_short save = 0; 1142 #ifdef INET6 1143 if (!isipv6) 1144 #endif 1145 { 1146 save = ipov->ih_len; 1147 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1148 } 1149 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1150 #ifdef INET6 1151 if (!isipv6) 1152 #endif 1153 ipov->ih_len = save; 1154 } 1155 #endif /* TCPDEBUG */ 1156 1157 /* 1158 * Fill in IP length and desired time to live and 1159 * send to IP level. There should be a better way 1160 * to handle ttl and tos; we could keep them in 1161 * the template, but need a way to checksum without them. 1162 */ 1163 /* 1164 * m->m_pkthdr.len should have been set before cksum calcuration, 1165 * because in6_cksum() need it. 1166 */ 1167 #ifdef INET6 1168 if (isipv6) { 1169 struct route_in6 ro; 1170 1171 bzero(&ro, sizeof(ro)); 1172 /* 1173 * we separately set hoplimit for every segment, since the 1174 * user might want to change the value via setsockopt. 1175 * Also, desired default hop limit might be changed via 1176 * Neighbor Discovery. 1177 */ 1178 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1179 1180 /* 1181 * Set the packet size here for the benefit of DTrace probes. 1182 * ip6_output() will set it properly; it's supposed to include 1183 * the option header lengths as well. 1184 */ 1185 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1186 1187 if (tp->t_state == TCPS_SYN_SENT) 1188 TCP_PROBE5(connect_request, NULL, tp, ip6, tp, th); 1189 1190 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1191 1192 /* TODO: IPv6 IP6TOS_ECT bit on */ 1193 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro, 1194 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1195 NULL, NULL, tp->t_inpcb); 1196 1197 if (error == EMSGSIZE && ro.ro_rt != NULL) 1198 mtu = ro.ro_rt->rt_rmx.rmx_mtu; 1199 RO_RTFREE(&ro); 1200 } 1201 #endif /* INET6 */ 1202 #if defined(INET) && defined(INET6) 1203 else 1204 #endif 1205 #ifdef INET 1206 { 1207 struct route ro; 1208 1209 bzero(&ro, sizeof(ro)); 1210 ip->ip_len = htons(m->m_pkthdr.len); 1211 #ifdef INET6 1212 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1213 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1214 #endif /* INET6 */ 1215 /* 1216 * If we do path MTU discovery, then we set DF on every packet. 1217 * This might not be the best thing to do according to RFC3390 1218 * Section 2. However the tcp hostcache migitates the problem 1219 * so it affects only the first tcp connection with a host. 1220 * 1221 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1222 */ 1223 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) 1224 ip->ip_off |= htons(IP_DF); 1225 1226 if (tp->t_state == TCPS_SYN_SENT) 1227 TCP_PROBE5(connect_request, NULL, tp, ip, tp, th); 1228 1229 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1230 1231 error = ip_output(m, tp->t_inpcb->inp_options, &ro, 1232 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1233 tp->t_inpcb); 1234 1235 if (error == EMSGSIZE && ro.ro_rt != NULL) 1236 mtu = ro.ro_rt->rt_rmx.rmx_mtu; 1237 RO_RTFREE(&ro); 1238 } 1239 #endif /* INET */ 1240 1241 out: 1242 /* 1243 * In transmit state, time the transmission and arrange for 1244 * the retransmit. In persist state, just set snd_max. 1245 */ 1246 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1247 !tcp_timer_active(tp, TT_PERSIST)) { 1248 tcp_seq startseq = tp->snd_nxt; 1249 1250 /* 1251 * Advance snd_nxt over sequence space of this segment. 1252 */ 1253 if (flags & (TH_SYN|TH_FIN)) { 1254 if (flags & TH_SYN) 1255 tp->snd_nxt++; 1256 if (flags & TH_FIN) { 1257 tp->snd_nxt++; 1258 tp->t_flags |= TF_SENTFIN; 1259 } 1260 } 1261 if (sack_rxmit) 1262 goto timer; 1263 tp->snd_nxt += len; 1264 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1265 tp->snd_max = tp->snd_nxt; 1266 /* 1267 * Time this transmission if not a retransmission and 1268 * not currently timing anything. 1269 */ 1270 if (tp->t_rtttime == 0) { 1271 tp->t_rtttime = ticks; 1272 tp->t_rtseq = startseq; 1273 TCPSTAT_INC(tcps_segstimed); 1274 } 1275 } 1276 1277 /* 1278 * Set retransmit timer if not currently set, 1279 * and not doing a pure ack or a keep-alive probe. 1280 * Initial value for retransmit timer is smoothed 1281 * round-trip time + 2 * round-trip time variance. 1282 * Initialize shift counter which is used for backoff 1283 * of retransmit time. 1284 */ 1285 timer: 1286 if (!tcp_timer_active(tp, TT_REXMT) && 1287 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1288 (tp->snd_nxt != tp->snd_una))) { 1289 if (tcp_timer_active(tp, TT_PERSIST)) { 1290 tcp_timer_activate(tp, TT_PERSIST, 0); 1291 tp->t_rxtshift = 0; 1292 } 1293 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1294 } 1295 } else { 1296 /* 1297 * Persist case, update snd_max but since we are in 1298 * persist mode (no window) we do not update snd_nxt. 1299 */ 1300 int xlen = len; 1301 if (flags & TH_SYN) 1302 ++xlen; 1303 if (flags & TH_FIN) { 1304 ++xlen; 1305 tp->t_flags |= TF_SENTFIN; 1306 } 1307 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1308 tp->snd_max = tp->snd_nxt + len; 1309 } 1310 1311 if (error) { 1312 1313 /* 1314 * We know that the packet was lost, so back out the 1315 * sequence number advance, if any. 1316 * 1317 * If the error is EPERM the packet got blocked by the 1318 * local firewall. Normally we should terminate the 1319 * connection but the blocking may have been spurious 1320 * due to a firewall reconfiguration cycle. So we treat 1321 * it like a packet loss and let the retransmit timer and 1322 * timeouts do their work over time. 1323 * XXX: It is a POLA question whether calling tcp_drop right 1324 * away would be the really correct behavior instead. 1325 */ 1326 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1327 !tcp_timer_active(tp, TT_PERSIST)) && 1328 ((flags & TH_SYN) == 0) && 1329 (error != EPERM)) { 1330 if (sack_rxmit) { 1331 p->rxmit -= len; 1332 tp->sackhint.sack_bytes_rexmit -= len; 1333 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1334 ("sackhint bytes rtx >= 0")); 1335 } else 1336 tp->snd_nxt -= len; 1337 } 1338 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1339 switch (error) { 1340 case EPERM: 1341 tp->t_softerror = error; 1342 return (error); 1343 case ENOBUFS: 1344 if (!tcp_timer_active(tp, TT_REXMT) && 1345 !tcp_timer_active(tp, TT_PERSIST)) 1346 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1347 tp->snd_cwnd = tp->t_maxseg; 1348 return (0); 1349 case EMSGSIZE: 1350 /* 1351 * For some reason the interface we used initially 1352 * to send segments changed to another or lowered 1353 * its MTU. 1354 * If TSO was active we either got an interface 1355 * without TSO capabilits or TSO was turned off. 1356 * If we obtained mtu from ip_output() then update 1357 * it and try again. 1358 */ 1359 if (tso) 1360 tp->t_flags &= ~TF_TSO; 1361 if (mtu != 0) { 1362 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1363 goto again; 1364 } 1365 return (error); 1366 case EHOSTDOWN: 1367 case EHOSTUNREACH: 1368 case ENETDOWN: 1369 case ENETUNREACH: 1370 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1371 tp->t_softerror = error; 1372 return (0); 1373 } 1374 /* FALLTHROUGH */ 1375 default: 1376 return (error); 1377 } 1378 } 1379 TCPSTAT_INC(tcps_sndtotal); 1380 1381 /* 1382 * Data sent (as far as we can tell). 1383 * If this advertises a larger window than any other segment, 1384 * then remember the size of the advertised window. 1385 * Any pending ACK has now been sent. 1386 */ 1387 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1388 tp->rcv_adv = tp->rcv_nxt + recwin; 1389 tp->last_ack_sent = tp->rcv_nxt; 1390 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1391 if (tcp_timer_active(tp, TT_DELACK)) 1392 tcp_timer_activate(tp, TT_DELACK, 0); 1393 #if 0 1394 /* 1395 * This completely breaks TCP if newreno is turned on. What happens 1396 * is that if delayed-acks are turned on on the receiver, this code 1397 * on the transmitter effectively destroys the TCP window, forcing 1398 * it to four packets (1.5Kx4 = 6K window). 1399 */ 1400 if (sendalot && --maxburst) 1401 goto again; 1402 #endif 1403 if (sendalot) 1404 goto again; 1405 return (0); 1406 } 1407 1408 void 1409 tcp_setpersist(struct tcpcb *tp) 1410 { 1411 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1412 int tt; 1413 1414 tp->t_flags &= ~TF_PREVVALID; 1415 if (tcp_timer_active(tp, TT_REXMT)) 1416 panic("tcp_setpersist: retransmit pending"); 1417 /* 1418 * Start/restart persistance timer. 1419 */ 1420 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1421 TCPTV_PERSMIN, TCPTV_PERSMAX); 1422 tcp_timer_activate(tp, TT_PERSIST, tt); 1423 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1424 tp->t_rxtshift++; 1425 } 1426 1427 /* 1428 * Insert TCP options according to the supplied parameters to the place 1429 * optp in a consistent way. Can handle unaligned destinations. 1430 * 1431 * The order of the option processing is crucial for optimal packing and 1432 * alignment for the scarce option space. 1433 * 1434 * The optimal order for a SYN/SYN-ACK segment is: 1435 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1436 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1437 * 1438 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1439 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1440 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1441 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1442 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1443 */ 1444 int 1445 tcp_addoptions(struct tcpopt *to, u_char *optp) 1446 { 1447 u_int mask, optlen = 0; 1448 1449 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1450 if ((to->to_flags & mask) != mask) 1451 continue; 1452 if (optlen == TCP_MAXOLEN) 1453 break; 1454 switch (to->to_flags & mask) { 1455 case TOF_MSS: 1456 while (optlen % 4) { 1457 optlen += TCPOLEN_NOP; 1458 *optp++ = TCPOPT_NOP; 1459 } 1460 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1461 continue; 1462 optlen += TCPOLEN_MAXSEG; 1463 *optp++ = TCPOPT_MAXSEG; 1464 *optp++ = TCPOLEN_MAXSEG; 1465 to->to_mss = htons(to->to_mss); 1466 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1467 optp += sizeof(to->to_mss); 1468 break; 1469 case TOF_SCALE: 1470 while (!optlen || optlen % 2 != 1) { 1471 optlen += TCPOLEN_NOP; 1472 *optp++ = TCPOPT_NOP; 1473 } 1474 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1475 continue; 1476 optlen += TCPOLEN_WINDOW; 1477 *optp++ = TCPOPT_WINDOW; 1478 *optp++ = TCPOLEN_WINDOW; 1479 *optp++ = to->to_wscale; 1480 break; 1481 case TOF_SACKPERM: 1482 while (optlen % 2) { 1483 optlen += TCPOLEN_NOP; 1484 *optp++ = TCPOPT_NOP; 1485 } 1486 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1487 continue; 1488 optlen += TCPOLEN_SACK_PERMITTED; 1489 *optp++ = TCPOPT_SACK_PERMITTED; 1490 *optp++ = TCPOLEN_SACK_PERMITTED; 1491 break; 1492 case TOF_TS: 1493 while (!optlen || optlen % 4 != 2) { 1494 optlen += TCPOLEN_NOP; 1495 *optp++ = TCPOPT_NOP; 1496 } 1497 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1498 continue; 1499 optlen += TCPOLEN_TIMESTAMP; 1500 *optp++ = TCPOPT_TIMESTAMP; 1501 *optp++ = TCPOLEN_TIMESTAMP; 1502 to->to_tsval = htonl(to->to_tsval); 1503 to->to_tsecr = htonl(to->to_tsecr); 1504 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1505 optp += sizeof(to->to_tsval); 1506 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1507 optp += sizeof(to->to_tsecr); 1508 break; 1509 case TOF_SIGNATURE: 1510 { 1511 int siglen = TCPOLEN_SIGNATURE - 2; 1512 1513 while (!optlen || optlen % 4 != 2) { 1514 optlen += TCPOLEN_NOP; 1515 *optp++ = TCPOPT_NOP; 1516 } 1517 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1518 continue; 1519 optlen += TCPOLEN_SIGNATURE; 1520 *optp++ = TCPOPT_SIGNATURE; 1521 *optp++ = TCPOLEN_SIGNATURE; 1522 to->to_signature = optp; 1523 while (siglen--) 1524 *optp++ = 0; 1525 break; 1526 } 1527 case TOF_SACK: 1528 { 1529 int sackblks = 0; 1530 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1531 tcp_seq sack_seq; 1532 1533 while (!optlen || optlen % 4 != 2) { 1534 optlen += TCPOLEN_NOP; 1535 *optp++ = TCPOPT_NOP; 1536 } 1537 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1538 continue; 1539 optlen += TCPOLEN_SACKHDR; 1540 *optp++ = TCPOPT_SACK; 1541 sackblks = min(to->to_nsacks, 1542 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1543 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1544 while (sackblks--) { 1545 sack_seq = htonl(sack->start); 1546 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1547 optp += sizeof(sack_seq); 1548 sack_seq = htonl(sack->end); 1549 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1550 optp += sizeof(sack_seq); 1551 optlen += TCPOLEN_SACK; 1552 sack++; 1553 } 1554 TCPSTAT_INC(tcps_sack_send_blocks); 1555 break; 1556 } 1557 default: 1558 panic("%s: unknown TCP option type", __func__); 1559 break; 1560 } 1561 } 1562 1563 /* Terminate and pad TCP options to a 4 byte boundary. */ 1564 if (optlen % 4) { 1565 optlen += TCPOLEN_EOL; 1566 *optp++ = TCPOPT_EOL; 1567 } 1568 /* 1569 * According to RFC 793 (STD0007): 1570 * "The content of the header beyond the End-of-Option option 1571 * must be header padding (i.e., zero)." 1572 * and later: "The padding is composed of zeros." 1573 */ 1574 while (optlen % 4) { 1575 optlen += TCPOLEN_PAD; 1576 *optp++ = TCPOPT_PAD; 1577 } 1578 1579 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1580 return (optlen); 1581 }
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