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