1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 #include "opt_tcpdebug.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/domain.h> 43 #include <sys/hhook.h> 44 #include <sys/kernel.h> 45 #include <sys/lock.h> 46 #include <sys/mbuf.h> 47 #include <sys/mutex.h> 48 #include <sys/protosw.h> 49 #include <sys/sdt.h> 50 #include <sys/socket.h> 51 #include <sys/socketvar.h> 52 #include <sys/sysctl.h> 53 54 #include <net/if.h> 55 #include <net/route.h> 56 #include <net/vnet.h> 57 58 #include <netinet/cc.h> 59 #include <netinet/in.h> 60 #include <netinet/in_kdtrace.h> 61 #include <netinet/in_systm.h> 62 #include <netinet/ip.h> 63 #include <netinet/in_pcb.h> 64 #include <netinet/ip_var.h> 65 #include <netinet/ip_options.h> 66 #ifdef INET6 67 #include <netinet6/in6_pcb.h> 68 #include <netinet/ip6.h> 69 #include <netinet6/ip6_var.h> 70 #endif 71 #define TCPOUTFLAGS 72 #include <netinet/tcp_fsm.h> 73 #include <netinet/tcp_seq.h> 74 #include <netinet/tcp_timer.h> 75 #include <netinet/tcp_var.h> 76 #include <netinet/tcpip.h> 77 #ifdef TCPDEBUG 78 #include <netinet/tcp_debug.h> 79 #endif 80 #ifdef TCP_OFFLOAD 81 #include <netinet/tcp_offload.h> 82 #endif 83 84 #ifdef IPSEC 85 #include <netipsec/ipsec.h> 86 #endif /*IPSEC*/ 87 88 #include <machine/in_cksum.h> 89 90 #include <security/mac/mac_framework.h> 91 92 VNET_DEFINE(int, path_mtu_discovery) = 1; 93 SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_VNET | CTLFLAG_RW, 94 &VNET_NAME(path_mtu_discovery), 1, 95 "Enable Path MTU Discovery"); 96 97 VNET_DEFINE(int, tcp_do_tso) = 1; 98 #define V_tcp_do_tso VNET(tcp_do_tso) 99 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 100 &VNET_NAME(tcp_do_tso), 0, 101 "Enable TCP Segmentation Offload"); 102 103 VNET_DEFINE(int, tcp_sendspace) = 1024*32; 104 #define V_tcp_sendspace VNET(tcp_sendspace) 105 SYSCTL_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, CTLFLAG_VNET | CTLFLAG_RW, 106 &VNET_NAME(tcp_sendspace), 0, "Initial send socket buffer size"); 107 108 VNET_DEFINE(int, tcp_do_autosndbuf) = 1; 109 #define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf) 110 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 111 &VNET_NAME(tcp_do_autosndbuf), 0, 112 "Enable automatic send buffer sizing"); 113 114 VNET_DEFINE(int, tcp_autosndbuf_inc) = 8*1024; 115 #define V_tcp_autosndbuf_inc VNET(tcp_autosndbuf_inc) 116 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 117 &VNET_NAME(tcp_autosndbuf_inc), 0, 118 "Incrementor step size of automatic send buffer"); 119 120 VNET_DEFINE(int, tcp_autosndbuf_max) = 2*1024*1024; 121 #define V_tcp_autosndbuf_max VNET(tcp_autosndbuf_max) 122 SYSCTL_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 123 &VNET_NAME(tcp_autosndbuf_max), 0, 124 "Max size of automatic send buffer"); 125 126 static void inline hhook_run_tcp_est_out(struct tcpcb *tp, 127 struct tcphdr *th, struct tcpopt *to, 128 long len, int tso); 129 static void inline cc_after_idle(struct tcpcb *tp); 130 131 /* 132 * Wrapper for the TCP established output helper hook. 133 */ 134 static void inline 135 hhook_run_tcp_est_out(struct tcpcb *tp, struct tcphdr *th, 136 struct tcpopt *to, long len, int tso) 137 { 138 struct tcp_hhook_data hhook_data; 139 140 if (V_tcp_hhh[HHOOK_TCP_EST_OUT]->hhh_nhooks > 0) { 141 hhook_data.tp = tp; 142 hhook_data.th = th; 143 hhook_data.to = to; 144 hhook_data.len = len; 145 hhook_data.tso = tso; 146 147 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_OUT], &hhook_data, 148 tp->osd); 149 } 150 } 151 152 /* 153 * CC wrapper hook functions 154 */ 155 static void inline 156 cc_after_idle(struct tcpcb *tp) 157 { 158 INP_WLOCK_ASSERT(tp->t_inpcb); 159 160 if (CC_ALGO(tp)->after_idle != NULL) 161 CC_ALGO(tp)->after_idle(tp->ccv); 162 } 163 164 /* 165 * Tcp output routine: figure out what should be sent and send it. 166 */ 167 int 168 tcp_output(struct tcpcb *tp) 169 { 170 struct socket *so = tp->t_inpcb->inp_socket; 171 long len, recwin, sendwin; 172 int off, flags, error = 0; /* Keep compiler happy */ 173 struct mbuf *m; 174 struct ip *ip = NULL; 175 struct ipovly *ipov = NULL; 176 struct tcphdr *th; 177 u_char opt[TCP_MAXOLEN]; 178 unsigned ipoptlen, optlen, hdrlen; 179 #ifdef IPSEC 180 unsigned ipsec_optlen = 0; 181 #endif 182 int idle, sendalot; 183 int sack_rxmit, sack_bytes_rxmt; 184 struct sackhole *p; 185 int tso, mtu; 186 struct tcpopt to; 187 #if 0 188 int maxburst = TCP_MAXBURST; 189 #endif 190 #ifdef INET6 191 struct ip6_hdr *ip6 = NULL; 192 int isipv6; 193 194 isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; 195 #endif 196 197 INP_WLOCK_ASSERT(tp->t_inpcb); 198 199 #ifdef TCP_OFFLOAD 200 if (tp->t_flags & TF_TOE) 201 return (tcp_offload_output(tp)); 202 #endif 203 204 /* 205 * Determine length of data that should be transmitted, 206 * and flags that will be used. 207 * If there is some data or critical controls (SYN, RST) 208 * to send, then transmit; otherwise, investigate further. 209 */ 210 idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); 211 if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur) 212 cc_after_idle(tp); 213 tp->t_flags &= ~TF_LASTIDLE; 214 if (idle) { 215 if (tp->t_flags & TF_MORETOCOME) { 216 tp->t_flags |= TF_LASTIDLE; 217 idle = 0; 218 } 219 } 220 again: 221 /* 222 * If we've recently taken a timeout, snd_max will be greater than 223 * snd_nxt. There may be SACK information that allows us to avoid 224 * resending already delivered data. Adjust snd_nxt accordingly. 225 */ 226 if ((tp->t_flags & TF_SACK_PERMIT) && 227 SEQ_LT(tp->snd_nxt, tp->snd_max)) 228 tcp_sack_adjust(tp); 229 sendalot = 0; 230 tso = 0; 231 mtu = 0; 232 off = tp->snd_nxt - tp->snd_una; 233 sendwin = min(tp->snd_wnd, tp->snd_cwnd); 234 235 flags = tcp_outflags[tp->t_state]; 236 /* 237 * Send any SACK-generated retransmissions. If we're explicitly trying 238 * to send out new data (when sendalot is 1), bypass this function. 239 * If we retransmit in fast recovery mode, decrement snd_cwnd, since 240 * we're replacing a (future) new transmission with a retransmission 241 * now, and we previously incremented snd_cwnd in tcp_input(). 242 */ 243 /* 244 * Still in sack recovery , reset rxmit flag to zero. 245 */ 246 sack_rxmit = 0; 247 sack_bytes_rxmt = 0; 248 len = 0; 249 p = NULL; 250 if ((tp->t_flags & TF_SACK_PERMIT) && IN_FASTRECOVERY(tp->t_flags) && 251 (p = tcp_sack_output(tp, &sack_bytes_rxmt))) { 252 long cwin; 253 254 cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; 255 if (cwin < 0) 256 cwin = 0; 257 /* Do not retransmit SACK segments beyond snd_recover */ 258 if (SEQ_GT(p->end, tp->snd_recover)) { 259 /* 260 * (At least) part of sack hole extends beyond 261 * snd_recover. Check to see if we can rexmit data 262 * for this hole. 263 */ 264 if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { 265 /* 266 * Can't rexmit any more data for this hole. 267 * That data will be rexmitted in the next 268 * sack recovery episode, when snd_recover 269 * moves past p->rxmit. 270 */ 271 p = NULL; 272 goto after_sack_rexmit; 273 } else 274 /* Can rexmit part of the current hole */ 275 len = ((long)ulmin(cwin, 276 tp->snd_recover - p->rxmit)); 277 } else 278 len = ((long)ulmin(cwin, p->end - p->rxmit)); 279 off = p->rxmit - tp->snd_una; 280 KASSERT(off >= 0,("%s: sack block to the left of una : %d", 281 __func__, off)); 282 if (len > 0) { 283 sack_rxmit = 1; 284 sendalot = 1; 285 TCPSTAT_INC(tcps_sack_rexmits); 286 TCPSTAT_ADD(tcps_sack_rexmit_bytes, 287 min(len, tp->t_maxseg)); 288 } 289 } 290 after_sack_rexmit: 291 /* 292 * Get standard flags, and add SYN or FIN if requested by 'hidden' 293 * state flags. 294 */ 295 if (tp->t_flags & TF_NEEDFIN) 296 flags |= TH_FIN; 297 if (tp->t_flags & TF_NEEDSYN) 298 flags |= TH_SYN; 299 300 SOCKBUF_LOCK(&so->so_snd); 301 /* 302 * If in persist timeout with window of 0, send 1 byte. 303 * Otherwise, if window is small but nonzero 304 * and timer expired, we will send what we can 305 * and go to transmit state. 306 */ 307 if (tp->t_flags & TF_FORCEDATA) { 308 if (sendwin == 0) { 309 /* 310 * If we still have some data to send, then 311 * clear the FIN bit. Usually this would 312 * happen below when it realizes that we 313 * aren't sending all the data. However, 314 * if we have exactly 1 byte of unsent data, 315 * then it won't clear the FIN bit below, 316 * and if we are in persist state, we wind 317 * up sending the packet without recording 318 * that we sent the FIN bit. 319 * 320 * We can't just blindly clear the FIN bit, 321 * because if we don't have any more data 322 * to send then the probe will be the FIN 323 * itself. 324 */ 325 if (off < sbused(&so->so_snd)) 326 flags &= ~TH_FIN; 327 sendwin = 1; 328 } else { 329 tcp_timer_activate(tp, TT_PERSIST, 0); 330 tp->t_rxtshift = 0; 331 } 332 } 333 334 /* 335 * If snd_nxt == snd_max and we have transmitted a FIN, the 336 * offset will be > 0 even if so_snd.sb_cc is 0, resulting in 337 * a negative length. This can also occur when TCP opens up 338 * its congestion window while receiving additional duplicate 339 * acks after fast-retransmit because TCP will reset snd_nxt 340 * to snd_max after the fast-retransmit. 341 * 342 * In the normal retransmit-FIN-only case, however, snd_nxt will 343 * be set to snd_una, the offset will be 0, and the length may 344 * wind up 0. 345 * 346 * If sack_rxmit is true we are retransmitting from the scoreboard 347 * in which case len is already set. 348 */ 349 if (sack_rxmit == 0) { 350 if (sack_bytes_rxmt == 0) 351 len = ((long)ulmin(sbavail(&so->so_snd), sendwin) - 352 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(sbavail(&so->so_snd), 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 * XXXGL: should there be used sbused() or sbavail()? 463 */ 464 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 465 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 466 sbused(&so->so_snd) >= (so->so_snd.sb_hiwat / 8 * 7) && 467 sbused(&so->so_snd) < V_tcp_autosndbuf_max && 468 sendwin >= (sbused(&so->so_snd) - 469 (tp->snd_nxt - tp->snd_una))) { 470 if (!sbreserve_locked(&so->so_snd, 471 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 472 V_tcp_autosndbuf_max), so, curthread)) 473 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 474 } 475 } 476 477 /* 478 * Decide if we can use TCP Segmentation Offloading (if supported by 479 * hardware). 480 * 481 * TSO may only be used if we are in a pure bulk sending state. The 482 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 483 * IP options prevent using TSO. With TSO the TCP header is the same 484 * (except for the sequence number) for all generated packets. This 485 * makes it impossible to transmit any options which vary per generated 486 * segment or packet. 487 */ 488 #ifdef IPSEC 489 /* 490 * Pre-calculate here as we save another lookup into the darknesses 491 * of IPsec that way and can actually decide if TSO is ok. 492 */ 493 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 494 #endif 495 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 496 ((tp->t_flags & TF_SIGNATURE) == 0) && 497 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 498 #ifdef IPSEC 499 ipsec_optlen == 0 && 500 #endif 501 tp->t_inpcb->inp_options == NULL && 502 tp->t_inpcb->in6p_options == NULL) 503 tso = 1; 504 505 if (sack_rxmit) { 506 if (SEQ_LT(p->rxmit + len, tp->snd_una + sbused(&so->so_snd))) 507 flags &= ~TH_FIN; 508 } else { 509 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + 510 sbused(&so->so_snd))) 511 flags &= ~TH_FIN; 512 } 513 514 recwin = sbspace(&so->so_rcv); 515 516 /* 517 * Sender silly window avoidance. We transmit under the following 518 * conditions when len is non-zero: 519 * 520 * - We have a full segment (or more with TSO) 521 * - This is the last buffer in a write()/send() and we are 522 * either idle or running NODELAY 523 * - we've timed out (e.g. persist timer) 524 * - we have more then 1/2 the maximum send window's worth of 525 * data (receiver may be limited the window size) 526 * - we need to retransmit 527 */ 528 if (len) { 529 if (len >= tp->t_maxseg) 530 goto send; 531 /* 532 * NOTE! on localhost connections an 'ack' from the remote 533 * end may occur synchronously with the output and cause 534 * us to flush a buffer queued with moretocome. XXX 535 * 536 * note: the len + off check is almost certainly unnecessary. 537 */ 538 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 539 (idle || (tp->t_flags & TF_NODELAY)) && 540 len + off >= sbavail(&so->so_snd) && 541 (tp->t_flags & TF_NOPUSH) == 0) { 542 goto send; 543 } 544 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 545 goto send; 546 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 547 goto send; 548 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 549 goto send; 550 if (sack_rxmit) 551 goto send; 552 } 553 554 /* 555 * Sending of standalone window updates. 556 * 557 * Window updates are important when we close our window due to a 558 * full socket buffer and are opening it again after the application 559 * reads data from it. Once the window has opened again and the 560 * remote end starts to send again the ACK clock takes over and 561 * provides the most current window information. 562 * 563 * We must avoid the silly window syndrome whereas every read 564 * from the receive buffer, no matter how small, causes a window 565 * update to be sent. We also should avoid sending a flurry of 566 * window updates when the socket buffer had queued a lot of data 567 * and the application is doing small reads. 568 * 569 * Prevent a flurry of pointless window updates by only sending 570 * an update when we can increase the advertized window by more 571 * than 1/4th of the socket buffer capacity. When the buffer is 572 * getting full or is very small be more aggressive and send an 573 * update whenever we can increase by two mss sized segments. 574 * In all other situations the ACK's to new incoming data will 575 * carry further window increases. 576 * 577 * Don't send an independent window update if a delayed 578 * ACK is pending (it will get piggy-backed on it) or the 579 * remote side already has done a half-close and won't send 580 * more data. Skip this if the connection is in T/TCP 581 * half-open state. 582 */ 583 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 584 !(tp->t_flags & TF_DELACK) && 585 !TCPS_HAVERCVDFIN(tp->t_state)) { 586 /* 587 * "adv" is the amount we could increase the window, 588 * taking into account that we are limited by 589 * TCP_MAXWIN << tp->rcv_scale. 590 */ 591 long adv; 592 int oldwin; 593 594 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale); 595 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 596 oldwin = (tp->rcv_adv - tp->rcv_nxt); 597 adv -= oldwin; 598 } else 599 oldwin = 0; 600 601 /* 602 * If the new window size ends up being the same as the old 603 * size when it is scaled, then don't force a window update. 604 */ 605 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale) 606 goto dontupdate; 607 608 if (adv >= (long)(2 * tp->t_maxseg) && 609 (adv >= (long)(so->so_rcv.sb_hiwat / 4) || 610 recwin <= (long)(so->so_rcv.sb_hiwat / 8) || 611 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 612 goto send; 613 } 614 dontupdate: 615 616 /* 617 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 618 * is also a catch-all for the retransmit timer timeout case. 619 */ 620 if (tp->t_flags & TF_ACKNOW) 621 goto send; 622 if ((flags & TH_RST) || 623 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 624 goto send; 625 if (SEQ_GT(tp->snd_up, tp->snd_una)) 626 goto send; 627 /* 628 * If our state indicates that FIN should be sent 629 * and we have not yet done so, then we need to send. 630 */ 631 if (flags & TH_FIN && 632 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 633 goto send; 634 /* 635 * In SACK, it is possible for tcp_output to fail to send a segment 636 * after the retransmission timer has been turned off. Make sure 637 * that the retransmission timer is set. 638 */ 639 if ((tp->t_flags & TF_SACK_PERMIT) && 640 SEQ_GT(tp->snd_max, tp->snd_una) && 641 !tcp_timer_active(tp, TT_REXMT) && 642 !tcp_timer_active(tp, TT_PERSIST)) { 643 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 644 goto just_return; 645 } 646 /* 647 * TCP window updates are not reliable, rather a polling protocol 648 * using ``persist'' packets is used to insure receipt of window 649 * updates. The three ``states'' for the output side are: 650 * idle not doing retransmits or persists 651 * persisting to move a small or zero window 652 * (re)transmitting and thereby not persisting 653 * 654 * tcp_timer_active(tp, TT_PERSIST) 655 * is true when we are in persist state. 656 * (tp->t_flags & TF_FORCEDATA) 657 * is set when we are called to send a persist packet. 658 * tcp_timer_active(tp, TT_REXMT) 659 * is set when we are retransmitting 660 * The output side is idle when both timers are zero. 661 * 662 * If send window is too small, there is data to transmit, and no 663 * retransmit or persist is pending, then go to persist state. 664 * If nothing happens soon, send when timer expires: 665 * if window is nonzero, transmit what we can, 666 * otherwise force out a byte. 667 */ 668 if (sbavail(&so->so_snd) && !tcp_timer_active(tp, TT_REXMT) && 669 !tcp_timer_active(tp, TT_PERSIST)) { 670 tp->t_rxtshift = 0; 671 tcp_setpersist(tp); 672 } 673 674 /* 675 * No reason to send a segment, just return. 676 */ 677 just_return: 678 SOCKBUF_UNLOCK(&so->so_snd); 679 return (0); 680 681 send: 682 SOCKBUF_LOCK_ASSERT(&so->so_snd); 683 if (len > 0) { 684 if (len >= tp->t_maxseg) 685 tp->t_flags2 |= TF2_PLPMTU_MAXSEGSNT; 686 else 687 tp->t_flags2 &= ~TF2_PLPMTU_MAXSEGSNT; 688 } 689 /* 690 * Before ESTABLISHED, force sending of initial options 691 * unless TCP set not to do any options. 692 * NOTE: we assume that the IP/TCP header plus TCP options 693 * always fit in a single mbuf, leaving room for a maximum 694 * link header, i.e. 695 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 696 */ 697 optlen = 0; 698 #ifdef INET6 699 if (isipv6) 700 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 701 else 702 #endif 703 hdrlen = sizeof (struct tcpiphdr); 704 705 /* 706 * Compute options for segment. 707 * We only have to care about SYN and established connection 708 * segments. Options for SYN-ACK segments are handled in TCP 709 * syncache. 710 */ 711 if ((tp->t_flags & TF_NOOPT) == 0) { 712 to.to_flags = 0; 713 /* Maximum segment size. */ 714 if (flags & TH_SYN) { 715 tp->snd_nxt = tp->iss; 716 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 717 to.to_flags |= TOF_MSS; 718 } 719 /* Window scaling. */ 720 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 721 to.to_wscale = tp->request_r_scale; 722 to.to_flags |= TOF_SCALE; 723 } 724 /* Timestamps. */ 725 if ((tp->t_flags & TF_RCVD_TSTMP) || 726 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 727 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 728 to.to_tsecr = tp->ts_recent; 729 to.to_flags |= TOF_TS; 730 /* Set receive buffer autosizing timestamp. */ 731 if (tp->rfbuf_ts == 0 && 732 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 733 tp->rfbuf_ts = tcp_ts_getticks(); 734 } 735 /* Selective ACK's. */ 736 if (tp->t_flags & TF_SACK_PERMIT) { 737 if (flags & TH_SYN) 738 to.to_flags |= TOF_SACKPERM; 739 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 740 (tp->t_flags & TF_SACK_PERMIT) && 741 tp->rcv_numsacks > 0) { 742 to.to_flags |= TOF_SACK; 743 to.to_nsacks = tp->rcv_numsacks; 744 to.to_sacks = (u_char *)tp->sackblks; 745 } 746 } 747 #ifdef TCP_SIGNATURE 748 /* TCP-MD5 (RFC2385). */ 749 if (tp->t_flags & TF_SIGNATURE) 750 to.to_flags |= TOF_SIGNATURE; 751 #endif /* TCP_SIGNATURE */ 752 753 /* Processing the options. */ 754 hdrlen += optlen = tcp_addoptions(&to, opt); 755 } 756 757 #ifdef INET6 758 if (isipv6) 759 ipoptlen = ip6_optlen(tp->t_inpcb); 760 else 761 #endif 762 if (tp->t_inpcb->inp_options) 763 ipoptlen = tp->t_inpcb->inp_options->m_len - 764 offsetof(struct ipoption, ipopt_list); 765 else 766 ipoptlen = 0; 767 #ifdef IPSEC 768 ipoptlen += ipsec_optlen; 769 #endif 770 771 /* 772 * Adjust data length if insertion of options will 773 * bump the packet length beyond the t_maxopd length. 774 * Clear the FIN bit because we cut off the tail of 775 * the segment. 776 */ 777 if (len + optlen + ipoptlen > tp->t_maxopd) { 778 flags &= ~TH_FIN; 779 780 if (tso) { 781 u_int if_hw_tsomax; 782 u_int if_hw_tsomaxsegcount; 783 u_int if_hw_tsomaxsegsize; 784 struct mbuf *mb; 785 u_int moff; 786 int max_len; 787 788 /* extract TSO information */ 789 if_hw_tsomax = tp->t_tsomax; 790 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 791 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 792 793 /* 794 * Limit a TSO burst to prevent it from 795 * overflowing or exceeding the maximum length 796 * allowed by the network interface: 797 */ 798 KASSERT(ipoptlen == 0, 799 ("%s: TSO can't do IP options", __func__)); 800 801 /* 802 * Check if we should limit by maximum payload 803 * length: 804 */ 805 if (if_hw_tsomax != 0) { 806 /* compute maximum TSO length */ 807 max_len = (if_hw_tsomax - hdrlen); 808 if (max_len <= 0) { 809 len = 0; 810 } else if (len > max_len) { 811 sendalot = 1; 812 len = max_len; 813 } 814 } 815 816 /* 817 * Check if we should limit by maximum segment 818 * size and count: 819 */ 820 if (if_hw_tsomaxsegcount != 0 && 821 if_hw_tsomaxsegsize != 0) { 822 max_len = 0; 823 mb = sbsndmbuf(&so->so_snd, off, &moff); 824 825 while (mb != NULL && max_len < len) { 826 u_int mlen; 827 u_int frags; 828 829 /* 830 * Get length of mbuf fragment 831 * and how many hardware frags, 832 * rounded up, it would use: 833 */ 834 mlen = (mb->m_len - moff); 835 frags = howmany(mlen, 836 if_hw_tsomaxsegsize); 837 838 /* Handle special case: Zero Length Mbuf */ 839 if (frags == 0) 840 frags = 1; 841 842 /* 843 * Check if the fragment limit 844 * will be reached or exceeded: 845 */ 846 if (frags >= if_hw_tsomaxsegcount) { 847 max_len += min(mlen, 848 if_hw_tsomaxsegcount * 849 if_hw_tsomaxsegsize); 850 break; 851 } 852 max_len += mlen; 853 if_hw_tsomaxsegcount -= frags; 854 moff = 0; 855 mb = mb->m_next; 856 } 857 if (max_len <= 0) { 858 len = 0; 859 } else if (len > max_len) { 860 sendalot = 1; 861 len = max_len; 862 } 863 } 864 865 /* 866 * Prevent the last segment from being 867 * fractional unless the send sockbuf can be 868 * emptied: 869 */ 870 max_len = (tp->t_maxopd - optlen); 871 if ((off + len) < sbavail(&so->so_snd)) { 872 moff = len % max_len; 873 if (moff != 0) { 874 len -= moff; 875 sendalot = 1; 876 } 877 } 878 879 /* 880 * In case there are too many small fragments 881 * don't use TSO: 882 */ 883 if (len <= max_len) { 884 len = max_len; 885 sendalot = 1; 886 tso = 0; 887 } 888 889 /* 890 * Send the FIN in a separate segment 891 * after the bulk sending is done. 892 * We don't trust the TSO implementations 893 * to clear the FIN flag on all but the 894 * last segment. 895 */ 896 if (tp->t_flags & TF_NEEDFIN) 897 sendalot = 1; 898 899 } else { 900 len = tp->t_maxopd - optlen - ipoptlen; 901 sendalot = 1; 902 } 903 } else 904 tso = 0; 905 906 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 907 ("%s: len > IP_MAXPACKET", __func__)); 908 909 /*#ifdef DIAGNOSTIC*/ 910 #ifdef INET6 911 if (max_linkhdr + hdrlen > MCLBYTES) 912 #else 913 if (max_linkhdr + hdrlen > MHLEN) 914 #endif 915 panic("tcphdr too big"); 916 /*#endif*/ 917 918 /* 919 * This KASSERT is here to catch edge cases at a well defined place. 920 * Before, those had triggered (random) panic conditions further down. 921 */ 922 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 923 924 /* 925 * Grab a header mbuf, attaching a copy of data to 926 * be transmitted, and initialize the header from 927 * the template for sends on this connection. 928 */ 929 if (len) { 930 struct mbuf *mb; 931 u_int moff; 932 933 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 934 TCPSTAT_INC(tcps_sndprobe); 935 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 936 tp->t_sndrexmitpack++; 937 TCPSTAT_INC(tcps_sndrexmitpack); 938 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 939 } else { 940 TCPSTAT_INC(tcps_sndpack); 941 TCPSTAT_ADD(tcps_sndbyte, len); 942 } 943 #ifdef INET6 944 if (MHLEN < hdrlen + max_linkhdr) 945 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 946 else 947 #endif 948 m = m_gethdr(M_NOWAIT, MT_DATA); 949 950 if (m == NULL) { 951 SOCKBUF_UNLOCK(&so->so_snd); 952 error = ENOBUFS; 953 sack_rxmit = 0; 954 goto out; 955 } 956 957 m->m_data += max_linkhdr; 958 m->m_len = hdrlen; 959 960 /* 961 * Start the m_copy functions from the closest mbuf 962 * to the offset in the socket buffer chain. 963 */ 964 mb = sbsndptr(&so->so_snd, off, len, &moff); 965 966 if (len <= MHLEN - hdrlen - max_linkhdr) { 967 m_copydata(mb, moff, (int)len, 968 mtod(m, caddr_t) + hdrlen); 969 m->m_len += len; 970 } else { 971 m->m_next = m_copy(mb, moff, (int)len); 972 if (m->m_next == NULL) { 973 SOCKBUF_UNLOCK(&so->so_snd); 974 (void) m_free(m); 975 error = ENOBUFS; 976 sack_rxmit = 0; 977 goto out; 978 } 979 } 980 981 /* 982 * If we're sending everything we've got, set PUSH. 983 * (This will keep happy those implementations which only 984 * give data to the user when a buffer fills or 985 * a PUSH comes in.) 986 */ 987 if (off + len == sbused(&so->so_snd)) 988 flags |= TH_PUSH; 989 SOCKBUF_UNLOCK(&so->so_snd); 990 } else { 991 SOCKBUF_UNLOCK(&so->so_snd); 992 if (tp->t_flags & TF_ACKNOW) 993 TCPSTAT_INC(tcps_sndacks); 994 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 995 TCPSTAT_INC(tcps_sndctrl); 996 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 997 TCPSTAT_INC(tcps_sndurg); 998 else 999 TCPSTAT_INC(tcps_sndwinup); 1000 1001 m = m_gethdr(M_NOWAIT, MT_DATA); 1002 if (m == NULL) { 1003 error = ENOBUFS; 1004 sack_rxmit = 0; 1005 goto out; 1006 } 1007 #ifdef INET6 1008 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 1009 MHLEN >= hdrlen) { 1010 M_ALIGN(m, hdrlen); 1011 } else 1012 #endif 1013 m->m_data += max_linkhdr; 1014 m->m_len = hdrlen; 1015 } 1016 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1017 m->m_pkthdr.rcvif = (struct ifnet *)0; 1018 #ifdef MAC 1019 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1020 #endif 1021 #ifdef INET6 1022 if (isipv6) { 1023 ip6 = mtod(m, struct ip6_hdr *); 1024 th = (struct tcphdr *)(ip6 + 1); 1025 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1026 } else 1027 #endif /* INET6 */ 1028 { 1029 ip = mtod(m, struct ip *); 1030 ipov = (struct ipovly *)ip; 1031 th = (struct tcphdr *)(ip + 1); 1032 tcpip_fillheaders(tp->t_inpcb, ip, th); 1033 } 1034 1035 /* 1036 * Fill in fields, remembering maximum advertised 1037 * window for use in delaying messages about window sizes. 1038 * If resending a FIN, be sure not to use a new sequence number. 1039 */ 1040 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1041 tp->snd_nxt == tp->snd_max) 1042 tp->snd_nxt--; 1043 /* 1044 * If we are starting a connection, send ECN setup 1045 * SYN packet. If we are on a retransmit, we may 1046 * resend those bits a number of times as per 1047 * RFC 3168. 1048 */ 1049 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 1050 if (tp->t_rxtshift >= 1) { 1051 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1052 flags |= TH_ECE|TH_CWR; 1053 } else 1054 flags |= TH_ECE|TH_CWR; 1055 } 1056 1057 if (tp->t_state == TCPS_ESTABLISHED && 1058 (tp->t_flags & TF_ECN_PERMIT)) { 1059 /* 1060 * If the peer has ECN, mark data packets with 1061 * ECN capable transmission (ECT). 1062 * Ignore pure ack packets, retransmissions and window probes. 1063 */ 1064 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1065 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1066 #ifdef INET6 1067 if (isipv6) 1068 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1069 else 1070 #endif 1071 ip->ip_tos |= IPTOS_ECN_ECT0; 1072 TCPSTAT_INC(tcps_ecn_ect0); 1073 } 1074 1075 /* 1076 * Reply with proper ECN notifications. 1077 */ 1078 if (tp->t_flags & TF_ECN_SND_CWR) { 1079 flags |= TH_CWR; 1080 tp->t_flags &= ~TF_ECN_SND_CWR; 1081 } 1082 if (tp->t_flags & TF_ECN_SND_ECE) 1083 flags |= TH_ECE; 1084 } 1085 1086 /* 1087 * If we are doing retransmissions, then snd_nxt will 1088 * not reflect the first unsent octet. For ACK only 1089 * packets, we do not want the sequence number of the 1090 * retransmitted packet, we want the sequence number 1091 * of the next unsent octet. So, if there is no data 1092 * (and no SYN or FIN), use snd_max instead of snd_nxt 1093 * when filling in ti_seq. But if we are in persist 1094 * state, snd_max might reflect one byte beyond the 1095 * right edge of the window, so use snd_nxt in that 1096 * case, since we know we aren't doing a retransmission. 1097 * (retransmit and persist are mutually exclusive...) 1098 */ 1099 if (sack_rxmit == 0) { 1100 if (len || (flags & (TH_SYN|TH_FIN)) || 1101 tcp_timer_active(tp, TT_PERSIST)) 1102 th->th_seq = htonl(tp->snd_nxt); 1103 else 1104 th->th_seq = htonl(tp->snd_max); 1105 } else { 1106 th->th_seq = htonl(p->rxmit); 1107 p->rxmit += len; 1108 tp->sackhint.sack_bytes_rexmit += len; 1109 } 1110 th->th_ack = htonl(tp->rcv_nxt); 1111 if (optlen) { 1112 bcopy(opt, th + 1, optlen); 1113 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1114 } 1115 th->th_flags = flags; 1116 /* 1117 * Calculate receive window. Don't shrink window, 1118 * but avoid silly window syndrome. 1119 */ 1120 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 1121 recwin < (long)tp->t_maxseg) 1122 recwin = 0; 1123 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1124 recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 1125 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 1126 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 1127 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 1128 1129 /* 1130 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1131 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1132 * case is handled in syncache. 1133 */ 1134 if (flags & TH_SYN) 1135 th->th_win = htons((u_short) 1136 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1137 else 1138 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1139 1140 /* 1141 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1142 * a 0 window. This may cause the remote transmitter to stall. This 1143 * flag tells soreceive() to disable delayed acknowledgements when 1144 * draining the buffer. This can occur if the receiver is attempting 1145 * to read more data than can be buffered prior to transmitting on 1146 * the connection. 1147 */ 1148 if (th->th_win == 0) { 1149 tp->t_sndzerowin++; 1150 tp->t_flags |= TF_RXWIN0SENT; 1151 } else 1152 tp->t_flags &= ~TF_RXWIN0SENT; 1153 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1154 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1155 th->th_flags |= TH_URG; 1156 } else 1157 /* 1158 * If no urgent pointer to send, then we pull 1159 * the urgent pointer to the left edge of the send window 1160 * so that it doesn't drift into the send window on sequence 1161 * number wraparound. 1162 */ 1163 tp->snd_up = tp->snd_una; /* drag it along */ 1164 1165 #ifdef TCP_SIGNATURE 1166 if (tp->t_flags & TF_SIGNATURE) { 1167 int sigoff = to.to_signature - opt; 1168 tcp_signature_compute(m, 0, len, optlen, 1169 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1170 } 1171 #endif 1172 1173 /* 1174 * Put TCP length in extended header, and then 1175 * checksum extended header and data. 1176 */ 1177 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1178 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1179 #ifdef INET6 1180 if (isipv6) { 1181 /* 1182 * ip6_plen is not need to be filled now, and will be filled 1183 * in ip6_output. 1184 */ 1185 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1186 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1187 optlen + len, IPPROTO_TCP, 0); 1188 } 1189 #endif 1190 #if defined(INET6) && defined(INET) 1191 else 1192 #endif 1193 #ifdef INET 1194 { 1195 m->m_pkthdr.csum_flags = CSUM_TCP; 1196 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1197 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1198 1199 /* IP version must be set here for ipv4/ipv6 checking later */ 1200 KASSERT(ip->ip_v == IPVERSION, 1201 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1202 } 1203 #endif 1204 1205 /* 1206 * Enable TSO and specify the size of the segments. 1207 * The TCP pseudo header checksum is always provided. 1208 * XXX: Fixme: This is currently not the case for IPv6. 1209 */ 1210 if (tso) { 1211 KASSERT(len > tp->t_maxopd - optlen, 1212 ("%s: len <= tso_segsz", __func__)); 1213 m->m_pkthdr.csum_flags |= CSUM_TSO; 1214 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1215 } 1216 1217 #ifdef IPSEC 1218 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1219 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u", 1220 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1221 #else 1222 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1223 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u", 1224 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1225 #endif 1226 1227 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1228 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1229 1230 #ifdef TCPDEBUG 1231 /* 1232 * Trace. 1233 */ 1234 if (so->so_options & SO_DEBUG) { 1235 u_short save = 0; 1236 #ifdef INET6 1237 if (!isipv6) 1238 #endif 1239 { 1240 save = ipov->ih_len; 1241 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1242 } 1243 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1244 #ifdef INET6 1245 if (!isipv6) 1246 #endif 1247 ipov->ih_len = save; 1248 } 1249 #endif /* TCPDEBUG */ 1250 1251 /* 1252 * Fill in IP length and desired time to live and 1253 * send to IP level. There should be a better way 1254 * to handle ttl and tos; we could keep them in 1255 * the template, but need a way to checksum without them. 1256 */ 1257 /* 1258 * m->m_pkthdr.len should have been set before checksum calculation, 1259 * because in6_cksum() need it. 1260 */ 1261 #ifdef INET6 1262 if (isipv6) { 1263 struct route_in6 ro; 1264 1265 bzero(&ro, sizeof(ro)); 1266 /* 1267 * we separately set hoplimit for every segment, since the 1268 * user might want to change the value via setsockopt. 1269 * Also, desired default hop limit might be changed via 1270 * Neighbor Discovery. 1271 */ 1272 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1273 1274 /* 1275 * Set the packet size here for the benefit of DTrace probes. 1276 * ip6_output() will set it properly; it's supposed to include 1277 * the option header lengths as well. 1278 */ 1279 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1280 1281 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) 1282 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1283 else 1284 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1285 1286 if (tp->t_state == TCPS_SYN_SENT) 1287 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1288 1289 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1290 1291 /* TODO: IPv6 IP6TOS_ECT bit on */ 1292 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro, 1293 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1294 NULL, NULL, tp->t_inpcb); 1295 1296 if (error == EMSGSIZE && ro.ro_rt != NULL) 1297 mtu = ro.ro_rt->rt_mtu; 1298 RO_RTFREE(&ro); 1299 } 1300 #endif /* INET6 */ 1301 #if defined(INET) && defined(INET6) 1302 else 1303 #endif 1304 #ifdef INET 1305 { 1306 struct route ro; 1307 1308 bzero(&ro, sizeof(ro)); 1309 ip->ip_len = htons(m->m_pkthdr.len); 1310 #ifdef INET6 1311 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1312 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1313 #endif /* INET6 */ 1314 /* 1315 * If we do path MTU discovery, then we set DF on every packet. 1316 * This might not be the best thing to do according to RFC3390 1317 * Section 2. However the tcp hostcache migitates the problem 1318 * so it affects only the first tcp connection with a host. 1319 * 1320 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1321 */ 1322 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) { 1323 ip->ip_off |= htons(IP_DF); 1324 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 1325 } else { 1326 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 1327 } 1328 1329 if (tp->t_state == TCPS_SYN_SENT) 1330 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1331 1332 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1333 1334 error = ip_output(m, tp->t_inpcb->inp_options, &ro, 1335 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1336 tp->t_inpcb); 1337 1338 if (error == EMSGSIZE && ro.ro_rt != NULL) 1339 mtu = ro.ro_rt->rt_mtu; 1340 RO_RTFREE(&ro); 1341 } 1342 #endif /* INET */ 1343 1344 out: 1345 /* 1346 * In transmit state, time the transmission and arrange for 1347 * the retransmit. In persist state, just set snd_max. 1348 */ 1349 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1350 !tcp_timer_active(tp, TT_PERSIST)) { 1351 tcp_seq startseq = tp->snd_nxt; 1352 1353 /* 1354 * Advance snd_nxt over sequence space of this segment. 1355 */ 1356 if (flags & (TH_SYN|TH_FIN)) { 1357 if (flags & TH_SYN) 1358 tp->snd_nxt++; 1359 if (flags & TH_FIN) { 1360 tp->snd_nxt++; 1361 tp->t_flags |= TF_SENTFIN; 1362 } 1363 } 1364 if (sack_rxmit) 1365 goto timer; 1366 tp->snd_nxt += len; 1367 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1368 tp->snd_max = tp->snd_nxt; 1369 /* 1370 * Time this transmission if not a retransmission and 1371 * not currently timing anything. 1372 */ 1373 if (tp->t_rtttime == 0) { 1374 tp->t_rtttime = ticks; 1375 tp->t_rtseq = startseq; 1376 TCPSTAT_INC(tcps_segstimed); 1377 } 1378 } 1379 1380 /* 1381 * Set retransmit timer if not currently set, 1382 * and not doing a pure ack or a keep-alive probe. 1383 * Initial value for retransmit timer is smoothed 1384 * round-trip time + 2 * round-trip time variance. 1385 * Initialize shift counter which is used for backoff 1386 * of retransmit time. 1387 */ 1388 timer: 1389 if (!tcp_timer_active(tp, TT_REXMT) && 1390 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1391 (tp->snd_nxt != tp->snd_una))) { 1392 if (tcp_timer_active(tp, TT_PERSIST)) { 1393 tcp_timer_activate(tp, TT_PERSIST, 0); 1394 tp->t_rxtshift = 0; 1395 } 1396 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1397 } 1398 } else { 1399 /* 1400 * Persist case, update snd_max but since we are in 1401 * persist mode (no window) we do not update snd_nxt. 1402 */ 1403 int xlen = len; 1404 if (flags & TH_SYN) 1405 ++xlen; 1406 if (flags & TH_FIN) { 1407 ++xlen; 1408 tp->t_flags |= TF_SENTFIN; 1409 } 1410 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1411 tp->snd_max = tp->snd_nxt + len; 1412 } 1413 1414 if (error) { 1415 1416 /* 1417 * We know that the packet was lost, so back out the 1418 * sequence number advance, if any. 1419 * 1420 * If the error is EPERM the packet got blocked by the 1421 * local firewall. Normally we should terminate the 1422 * connection but the blocking may have been spurious 1423 * due to a firewall reconfiguration cycle. So we treat 1424 * it like a packet loss and let the retransmit timer and 1425 * timeouts do their work over time. 1426 * XXX: It is a POLA question whether calling tcp_drop right 1427 * away would be the really correct behavior instead. 1428 */ 1429 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1430 !tcp_timer_active(tp, TT_PERSIST)) && 1431 ((flags & TH_SYN) == 0) && 1432 (error != EPERM)) { 1433 if (sack_rxmit) { 1434 p->rxmit -= len; 1435 tp->sackhint.sack_bytes_rexmit -= len; 1436 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1437 ("sackhint bytes rtx >= 0")); 1438 } else 1439 tp->snd_nxt -= len; 1440 } 1441 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1442 switch (error) { 1443 case EPERM: 1444 tp->t_softerror = error; 1445 return (error); 1446 case ENOBUFS: 1447 if (!tcp_timer_active(tp, TT_REXMT) && 1448 !tcp_timer_active(tp, TT_PERSIST)) 1449 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1450 tp->snd_cwnd = tp->t_maxseg; 1451 return (0); 1452 case EMSGSIZE: 1453 /* 1454 * For some reason the interface we used initially 1455 * to send segments changed to another or lowered 1456 * its MTU. 1457 * If TSO was active we either got an interface 1458 * without TSO capabilits or TSO was turned off. 1459 * If we obtained mtu from ip_output() then update 1460 * it and try again. 1461 */ 1462 if (tso) 1463 tp->t_flags &= ~TF_TSO; 1464 if (mtu != 0) { 1465 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1466 goto again; 1467 } 1468 return (error); 1469 case EHOSTDOWN: 1470 case EHOSTUNREACH: 1471 case ENETDOWN: 1472 case ENETUNREACH: 1473 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1474 tp->t_softerror = error; 1475 return (0); 1476 } 1477 /* FALLTHROUGH */ 1478 default: 1479 return (error); 1480 } 1481 } 1482 TCPSTAT_INC(tcps_sndtotal); 1483 1484 /* 1485 * Data sent (as far as we can tell). 1486 * If this advertises a larger window than any other segment, 1487 * then remember the size of the advertised window. 1488 * Any pending ACK has now been sent. 1489 */ 1490 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1491 tp->rcv_adv = tp->rcv_nxt + recwin; 1492 tp->last_ack_sent = tp->rcv_nxt; 1493 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1494 if (tcp_timer_active(tp, TT_DELACK)) 1495 tcp_timer_activate(tp, TT_DELACK, 0); 1496 #if 0 1497 /* 1498 * This completely breaks TCP if newreno is turned on. What happens 1499 * is that if delayed-acks are turned on on the receiver, this code 1500 * on the transmitter effectively destroys the TCP window, forcing 1501 * it to four packets (1.5Kx4 = 6K window). 1502 */ 1503 if (sendalot && --maxburst) 1504 goto again; 1505 #endif 1506 if (sendalot) 1507 goto again; 1508 return (0); 1509 } 1510 1511 void 1512 tcp_setpersist(struct tcpcb *tp) 1513 { 1514 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1515 int tt; 1516 1517 tp->t_flags &= ~TF_PREVVALID; 1518 if (tcp_timer_active(tp, TT_REXMT)) 1519 panic("tcp_setpersist: retransmit pending"); 1520 /* 1521 * Start/restart persistance timer. 1522 */ 1523 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1524 TCPTV_PERSMIN, TCPTV_PERSMAX); 1525 tcp_timer_activate(tp, TT_PERSIST, tt); 1526 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1527 tp->t_rxtshift++; 1528 } 1529 1530 /* 1531 * Insert TCP options according to the supplied parameters to the place 1532 * optp in a consistent way. Can handle unaligned destinations. 1533 * 1534 * The order of the option processing is crucial for optimal packing and 1535 * alignment for the scarce option space. 1536 * 1537 * The optimal order for a SYN/SYN-ACK segment is: 1538 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1539 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1540 * 1541 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1542 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1543 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1544 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1545 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1546 */ 1547 int 1548 tcp_addoptions(struct tcpopt *to, u_char *optp) 1549 { 1550 u_int mask, optlen = 0; 1551 1552 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1553 if ((to->to_flags & mask) != mask) 1554 continue; 1555 if (optlen == TCP_MAXOLEN) 1556 break; 1557 switch (to->to_flags & mask) { 1558 case TOF_MSS: 1559 while (optlen % 4) { 1560 optlen += TCPOLEN_NOP; 1561 *optp++ = TCPOPT_NOP; 1562 } 1563 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1564 continue; 1565 optlen += TCPOLEN_MAXSEG; 1566 *optp++ = TCPOPT_MAXSEG; 1567 *optp++ = TCPOLEN_MAXSEG; 1568 to->to_mss = htons(to->to_mss); 1569 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1570 optp += sizeof(to->to_mss); 1571 break; 1572 case TOF_SCALE: 1573 while (!optlen || optlen % 2 != 1) { 1574 optlen += TCPOLEN_NOP; 1575 *optp++ = TCPOPT_NOP; 1576 } 1577 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1578 continue; 1579 optlen += TCPOLEN_WINDOW; 1580 *optp++ = TCPOPT_WINDOW; 1581 *optp++ = TCPOLEN_WINDOW; 1582 *optp++ = to->to_wscale; 1583 break; 1584 case TOF_SACKPERM: 1585 while (optlen % 2) { 1586 optlen += TCPOLEN_NOP; 1587 *optp++ = TCPOPT_NOP; 1588 } 1589 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1590 continue; 1591 optlen += TCPOLEN_SACK_PERMITTED; 1592 *optp++ = TCPOPT_SACK_PERMITTED; 1593 *optp++ = TCPOLEN_SACK_PERMITTED; 1594 break; 1595 case TOF_TS: 1596 while (!optlen || optlen % 4 != 2) { 1597 optlen += TCPOLEN_NOP; 1598 *optp++ = TCPOPT_NOP; 1599 } 1600 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1601 continue; 1602 optlen += TCPOLEN_TIMESTAMP; 1603 *optp++ = TCPOPT_TIMESTAMP; 1604 *optp++ = TCPOLEN_TIMESTAMP; 1605 to->to_tsval = htonl(to->to_tsval); 1606 to->to_tsecr = htonl(to->to_tsecr); 1607 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1608 optp += sizeof(to->to_tsval); 1609 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1610 optp += sizeof(to->to_tsecr); 1611 break; 1612 case TOF_SIGNATURE: 1613 { 1614 int siglen = TCPOLEN_SIGNATURE - 2; 1615 1616 while (!optlen || optlen % 4 != 2) { 1617 optlen += TCPOLEN_NOP; 1618 *optp++ = TCPOPT_NOP; 1619 } 1620 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1621 continue; 1622 optlen += TCPOLEN_SIGNATURE; 1623 *optp++ = TCPOPT_SIGNATURE; 1624 *optp++ = TCPOLEN_SIGNATURE; 1625 to->to_signature = optp; 1626 while (siglen--) 1627 *optp++ = 0; 1628 break; 1629 } 1630 case TOF_SACK: 1631 { 1632 int sackblks = 0; 1633 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1634 tcp_seq sack_seq; 1635 1636 while (!optlen || optlen % 4 != 2) { 1637 optlen += TCPOLEN_NOP; 1638 *optp++ = TCPOPT_NOP; 1639 } 1640 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1641 continue; 1642 optlen += TCPOLEN_SACKHDR; 1643 *optp++ = TCPOPT_SACK; 1644 sackblks = min(to->to_nsacks, 1645 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1646 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1647 while (sackblks--) { 1648 sack_seq = htonl(sack->start); 1649 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1650 optp += sizeof(sack_seq); 1651 sack_seq = htonl(sack->end); 1652 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1653 optp += sizeof(sack_seq); 1654 optlen += TCPOLEN_SACK; 1655 sack++; 1656 } 1657 TCPSTAT_INC(tcps_sack_send_blocks); 1658 break; 1659 } 1660 default: 1661 panic("%s: unknown TCP option type", __func__); 1662 break; 1663 } 1664 } 1665 1666 /* Terminate and pad TCP options to a 4 byte boundary. */ 1667 if (optlen % 4) { 1668 optlen += TCPOLEN_EOL; 1669 *optp++ = TCPOPT_EOL; 1670 } 1671 /* 1672 * According to RFC 793 (STD0007): 1673 * "The content of the header beyond the End-of-Option option 1674 * must be header padding (i.e., zero)." 1675 * and later: "The padding is composed of zeros." 1676 */ 1677 while (optlen % 4) { 1678 optlen += TCPOLEN_PAD; 1679 *optp++ = TCPOPT_PAD; 1680 } 1681 1682 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1683 return (optlen); 1684 } 1685