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_VNET_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, 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_VNET_INT(_net_inet_tcp, OID_AUTO, tso, 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_VNET_INT(_net_inet_tcp, TCPCTL_SENDSPACE, sendspace, 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_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_auto, 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_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_inc, 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_VNET_INT(_net_inet_tcp, OID_AUTO, sendbuf_max, 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 < so->so_snd.sb_cc) 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(so->so_snd.sb_cc, sendwin) - off); 352 else { 353 long cwin; 354 355 /* 356 * We are inside of a SACK recovery episode and are 357 * sending new data, having retransmitted all the 358 * data possible in the scoreboard. 359 */ 360 len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd) 361 - off); 362 /* 363 * Don't remove this (len > 0) check ! 364 * We explicitly check for len > 0 here (although it 365 * isn't really necessary), to work around a gcc 366 * optimization issue - to force gcc to compute 367 * len above. Without this check, the computation 368 * of len is bungled by the optimizer. 369 */ 370 if (len > 0) { 371 cwin = tp->snd_cwnd - 372 (tp->snd_nxt - tp->sack_newdata) - 373 sack_bytes_rxmt; 374 if (cwin < 0) 375 cwin = 0; 376 len = lmin(len, cwin); 377 } 378 } 379 } 380 381 /* 382 * Lop off SYN bit if it has already been sent. However, if this 383 * is SYN-SENT state and if segment contains data and if we don't 384 * know that foreign host supports TAO, suppress sending segment. 385 */ 386 if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { 387 if (tp->t_state != TCPS_SYN_RECEIVED) 388 flags &= ~TH_SYN; 389 off--, len++; 390 } 391 392 /* 393 * Be careful not to send data and/or FIN on SYN segments. 394 * This measure is needed to prevent interoperability problems 395 * with not fully conformant TCP implementations. 396 */ 397 if ((flags & TH_SYN) && (tp->t_flags & TF_NOOPT)) { 398 len = 0; 399 flags &= ~TH_FIN; 400 } 401 402 if (len < 0) { 403 /* 404 * If FIN has been sent but not acked, 405 * but we haven't been called to retransmit, 406 * len will be < 0. Otherwise, window shrank 407 * after we sent into it. If window shrank to 0, 408 * cancel pending retransmit, pull snd_nxt back 409 * to (closed) window, and set the persist timer 410 * if it isn't already going. If the window didn't 411 * close completely, just wait for an ACK. 412 */ 413 len = 0; 414 if (sendwin == 0) { 415 tcp_timer_activate(tp, TT_REXMT, 0); 416 tp->t_rxtshift = 0; 417 tp->snd_nxt = tp->snd_una; 418 if (!tcp_timer_active(tp, TT_PERSIST)) 419 tcp_setpersist(tp); 420 } 421 } 422 423 /* len will be >= 0 after this point. */ 424 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 425 426 /* 427 * Automatic sizing of send socket buffer. Often the send buffer 428 * size is not optimally adjusted to the actual network conditions 429 * at hand (delay bandwidth product). Setting the buffer size too 430 * small limits throughput on links with high bandwidth and high 431 * delay (eg. trans-continental/oceanic links). Setting the 432 * buffer size too big consumes too much real kernel memory, 433 * especially with many connections on busy servers. 434 * 435 * The criteria to step up the send buffer one notch are: 436 * 1. receive window of remote host is larger than send buffer 437 * (with a fudge factor of 5/4th); 438 * 2. send buffer is filled to 7/8th with data (so we actually 439 * have data to make use of it); 440 * 3. send buffer fill has not hit maximal automatic size; 441 * 4. our send window (slow start and cogestion controlled) is 442 * larger than sent but unacknowledged data in send buffer. 443 * 444 * The remote host receive window scaling factor may limit the 445 * growing of the send buffer before it reaches its allowed 446 * maximum. 447 * 448 * It scales directly with slow start or congestion window 449 * and does at most one step per received ACK. This fast 450 * scaling has the drawback of growing the send buffer beyond 451 * what is strictly necessary to make full use of a given 452 * delay*bandwith product. However testing has shown this not 453 * to be much of an problem. At worst we are trading wasting 454 * of available bandwith (the non-use of it) for wasting some 455 * socket buffer memory. 456 * 457 * TODO: Shrink send buffer during idle periods together 458 * with congestion window. Requires another timer. Has to 459 * wait for upcoming tcp timer rewrite. 460 */ 461 if (V_tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { 462 if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && 463 so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && 464 so->so_snd.sb_cc < V_tcp_autosndbuf_max && 465 sendwin >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { 466 if (!sbreserve_locked(&so->so_snd, 467 min(so->so_snd.sb_hiwat + V_tcp_autosndbuf_inc, 468 V_tcp_autosndbuf_max), so, curthread)) 469 so->so_snd.sb_flags &= ~SB_AUTOSIZE; 470 } 471 } 472 473 /* 474 * Decide if we can use TCP Segmentation Offloading (if supported by 475 * hardware). 476 * 477 * TSO may only be used if we are in a pure bulk sending state. The 478 * presence of TCP-MD5, SACK retransmits, SACK advertizements and 479 * IP options prevent using TSO. With TSO the TCP header is the same 480 * (except for the sequence number) for all generated packets. This 481 * makes it impossible to transmit any options which vary per generated 482 * segment or packet. 483 */ 484 #ifdef IPSEC 485 /* 486 * Pre-calculate here as we save another lookup into the darknesses 487 * of IPsec that way and can actually decide if TSO is ok. 488 */ 489 ipsec_optlen = ipsec_hdrsiz_tcp(tp); 490 #endif 491 if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg && 492 ((tp->t_flags & TF_SIGNATURE) == 0) && 493 tp->rcv_numsacks == 0 && sack_rxmit == 0 && 494 #ifdef IPSEC 495 ipsec_optlen == 0 && 496 #endif 497 tp->t_inpcb->inp_options == NULL && 498 tp->t_inpcb->in6p_options == NULL) 499 tso = 1; 500 501 if (sack_rxmit) { 502 if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc)) 503 flags &= ~TH_FIN; 504 } else { 505 if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc)) 506 flags &= ~TH_FIN; 507 } 508 509 recwin = sbspace(&so->so_rcv); 510 511 /* 512 * Sender silly window avoidance. We transmit under the following 513 * conditions when len is non-zero: 514 * 515 * - We have a full segment (or more with TSO) 516 * - This is the last buffer in a write()/send() and we are 517 * either idle or running NODELAY 518 * - we've timed out (e.g. persist timer) 519 * - we have more then 1/2 the maximum send window's worth of 520 * data (receiver may be limited the window size) 521 * - we need to retransmit 522 */ 523 if (len) { 524 if (len >= tp->t_maxseg) 525 goto send; 526 /* 527 * NOTE! on localhost connections an 'ack' from the remote 528 * end may occur synchronously with the output and cause 529 * us to flush a buffer queued with moretocome. XXX 530 * 531 * note: the len + off check is almost certainly unnecessary. 532 */ 533 if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ 534 (idle || (tp->t_flags & TF_NODELAY)) && 535 len + off >= so->so_snd.sb_cc && 536 (tp->t_flags & TF_NOPUSH) == 0) { 537 goto send; 538 } 539 if (tp->t_flags & TF_FORCEDATA) /* typ. timeout case */ 540 goto send; 541 if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) 542 goto send; 543 if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ 544 goto send; 545 if (sack_rxmit) 546 goto send; 547 } 548 549 /* 550 * Sending of standalone window updates. 551 * 552 * Window updates are important when we close our window due to a 553 * full socket buffer and are opening it again after the application 554 * reads data from it. Once the window has opened again and the 555 * remote end starts to send again the ACK clock takes over and 556 * provides the most current window information. 557 * 558 * We must avoid the silly window syndrome whereas every read 559 * from the receive buffer, no matter how small, causes a window 560 * update to be sent. We also should avoid sending a flurry of 561 * window updates when the socket buffer had queued a lot of data 562 * and the application is doing small reads. 563 * 564 * Prevent a flurry of pointless window updates by only sending 565 * an update when we can increase the advertized window by more 566 * than 1/4th of the socket buffer capacity. When the buffer is 567 * getting full or is very small be more aggressive and send an 568 * update whenever we can increase by two mss sized segments. 569 * In all other situations the ACK's to new incoming data will 570 * carry further window increases. 571 * 572 * Don't send an independent window update if a delayed 573 * ACK is pending (it will get piggy-backed on it) or the 574 * remote side already has done a half-close and won't send 575 * more data. Skip this if the connection is in T/TCP 576 * half-open state. 577 */ 578 if (recwin > 0 && !(tp->t_flags & TF_NEEDSYN) && 579 !(tp->t_flags & TF_DELACK) && 580 !TCPS_HAVERCVDFIN(tp->t_state)) { 581 /* 582 * "adv" is the amount we could increase the window, 583 * taking into account that we are limited by 584 * TCP_MAXWIN << tp->rcv_scale. 585 */ 586 long adv; 587 int oldwin; 588 589 adv = min(recwin, (long)TCP_MAXWIN << tp->rcv_scale); 590 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) { 591 oldwin = (tp->rcv_adv - tp->rcv_nxt); 592 adv -= oldwin; 593 } else 594 oldwin = 0; 595 596 /* 597 * If the new window size ends up being the same as the old 598 * size when it is scaled, then don't force a window update. 599 */ 600 if (oldwin >> tp->rcv_scale == (adv + oldwin) >> tp->rcv_scale) 601 goto dontupdate; 602 603 if (adv >= (long)(2 * tp->t_maxseg) && 604 (adv >= (long)(so->so_rcv.sb_hiwat / 4) || 605 recwin <= (long)(so->so_rcv.sb_hiwat / 8) || 606 so->so_rcv.sb_hiwat <= 8 * tp->t_maxseg)) 607 goto send; 608 } 609 dontupdate: 610 611 /* 612 * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW 613 * is also a catch-all for the retransmit timer timeout case. 614 */ 615 if (tp->t_flags & TF_ACKNOW) 616 goto send; 617 if ((flags & TH_RST) || 618 ((flags & TH_SYN) && (tp->t_flags & TF_NEEDSYN) == 0)) 619 goto send; 620 if (SEQ_GT(tp->snd_up, tp->snd_una)) 621 goto send; 622 /* 623 * If our state indicates that FIN should be sent 624 * and we have not yet done so, then we need to send. 625 */ 626 if (flags & TH_FIN && 627 ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) 628 goto send; 629 /* 630 * In SACK, it is possible for tcp_output to fail to send a segment 631 * after the retransmission timer has been turned off. Make sure 632 * that the retransmission timer is set. 633 */ 634 if ((tp->t_flags & TF_SACK_PERMIT) && 635 SEQ_GT(tp->snd_max, tp->snd_una) && 636 !tcp_timer_active(tp, TT_REXMT) && 637 !tcp_timer_active(tp, TT_PERSIST)) { 638 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 639 goto just_return; 640 } 641 /* 642 * TCP window updates are not reliable, rather a polling protocol 643 * using ``persist'' packets is used to insure receipt of window 644 * updates. The three ``states'' for the output side are: 645 * idle not doing retransmits or persists 646 * persisting to move a small or zero window 647 * (re)transmitting and thereby not persisting 648 * 649 * tcp_timer_active(tp, TT_PERSIST) 650 * is true when we are in persist state. 651 * (tp->t_flags & TF_FORCEDATA) 652 * is set when we are called to send a persist packet. 653 * tcp_timer_active(tp, TT_REXMT) 654 * is set when we are retransmitting 655 * The output side is idle when both timers are zero. 656 * 657 * If send window is too small, there is data to transmit, and no 658 * retransmit or persist is pending, then go to persist state. 659 * If nothing happens soon, send when timer expires: 660 * if window is nonzero, transmit what we can, 661 * otherwise force out a byte. 662 */ 663 if (so->so_snd.sb_cc && !tcp_timer_active(tp, TT_REXMT) && 664 !tcp_timer_active(tp, TT_PERSIST)) { 665 tp->t_rxtshift = 0; 666 tcp_setpersist(tp); 667 } 668 669 /* 670 * No reason to send a segment, just return. 671 */ 672 just_return: 673 SOCKBUF_UNLOCK(&so->so_snd); 674 return (0); 675 676 send: 677 SOCKBUF_LOCK_ASSERT(&so->so_snd); 678 /* 679 * Before ESTABLISHED, force sending of initial options 680 * unless TCP set not to do any options. 681 * NOTE: we assume that the IP/TCP header plus TCP options 682 * always fit in a single mbuf, leaving room for a maximum 683 * link header, i.e. 684 * max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES 685 */ 686 optlen = 0; 687 #ifdef INET6 688 if (isipv6) 689 hdrlen = sizeof (struct ip6_hdr) + sizeof (struct tcphdr); 690 else 691 #endif 692 hdrlen = sizeof (struct tcpiphdr); 693 694 /* 695 * Compute options for segment. 696 * We only have to care about SYN and established connection 697 * segments. Options for SYN-ACK segments are handled in TCP 698 * syncache. 699 */ 700 if ((tp->t_flags & TF_NOOPT) == 0) { 701 to.to_flags = 0; 702 /* Maximum segment size. */ 703 if (flags & TH_SYN) { 704 tp->snd_nxt = tp->iss; 705 to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc); 706 to.to_flags |= TOF_MSS; 707 } 708 /* Window scaling. */ 709 if ((flags & TH_SYN) && (tp->t_flags & TF_REQ_SCALE)) { 710 to.to_wscale = tp->request_r_scale; 711 to.to_flags |= TOF_SCALE; 712 } 713 /* Timestamps. */ 714 if ((tp->t_flags & TF_RCVD_TSTMP) || 715 ((flags & TH_SYN) && (tp->t_flags & TF_REQ_TSTMP))) { 716 to.to_tsval = tcp_ts_getticks() + tp->ts_offset; 717 to.to_tsecr = tp->ts_recent; 718 to.to_flags |= TOF_TS; 719 /* Set receive buffer autosizing timestamp. */ 720 if (tp->rfbuf_ts == 0 && 721 (so->so_rcv.sb_flags & SB_AUTOSIZE)) 722 tp->rfbuf_ts = tcp_ts_getticks(); 723 } 724 /* Selective ACK's. */ 725 if (tp->t_flags & TF_SACK_PERMIT) { 726 if (flags & TH_SYN) 727 to.to_flags |= TOF_SACKPERM; 728 else if (TCPS_HAVEESTABLISHED(tp->t_state) && 729 (tp->t_flags & TF_SACK_PERMIT) && 730 tp->rcv_numsacks > 0) { 731 to.to_flags |= TOF_SACK; 732 to.to_nsacks = tp->rcv_numsacks; 733 to.to_sacks = (u_char *)tp->sackblks; 734 } 735 } 736 #ifdef TCP_SIGNATURE 737 /* TCP-MD5 (RFC2385). */ 738 if (tp->t_flags & TF_SIGNATURE) 739 to.to_flags |= TOF_SIGNATURE; 740 #endif /* TCP_SIGNATURE */ 741 742 /* Processing the options. */ 743 hdrlen += optlen = tcp_addoptions(&to, opt); 744 } 745 746 #ifdef INET6 747 if (isipv6) 748 ipoptlen = ip6_optlen(tp->t_inpcb); 749 else 750 #endif 751 if (tp->t_inpcb->inp_options) 752 ipoptlen = tp->t_inpcb->inp_options->m_len - 753 offsetof(struct ipoption, ipopt_list); 754 else 755 ipoptlen = 0; 756 #ifdef IPSEC 757 ipoptlen += ipsec_optlen; 758 #endif 759 760 /* 761 * Adjust data length if insertion of options will 762 * bump the packet length beyond the t_maxopd length. 763 * Clear the FIN bit because we cut off the tail of 764 * the segment. 765 */ 766 if (len + optlen + ipoptlen > tp->t_maxopd) { 767 flags &= ~TH_FIN; 768 769 if (tso) { 770 u_int if_hw_tsomax; 771 u_int if_hw_tsomaxsegcount; 772 u_int if_hw_tsomaxsegsize; 773 struct mbuf *mb; 774 u_int moff; 775 int max_len; 776 777 /* extract TSO information */ 778 if_hw_tsomax = tp->t_tsomax; 779 if_hw_tsomaxsegcount = tp->t_tsomaxsegcount; 780 if_hw_tsomaxsegsize = tp->t_tsomaxsegsize; 781 782 /* 783 * Limit a TSO burst to prevent it from 784 * overflowing or exceeding the maximum length 785 * allowed by the network interface: 786 */ 787 KASSERT(ipoptlen == 0, 788 ("%s: TSO can't do IP options", __func__)); 789 790 /* 791 * Check if we should limit by maximum payload 792 * length: 793 */ 794 if (if_hw_tsomax != 0) { 795 /* compute maximum TSO length */ 796 max_len = (if_hw_tsomax - hdrlen); 797 if (max_len <= 0) { 798 len = 0; 799 } else if (len > (u_int)max_len) { 800 sendalot = 1; 801 len = (u_int)max_len; 802 } 803 } 804 805 /* 806 * Check if we should limit by maximum segment 807 * size and count: 808 */ 809 if (if_hw_tsomaxsegcount != 0 && if_hw_tsomaxsegsize != 0) { 810 max_len = 0; 811 mb = sbsndmbuf(&so->so_snd, off, &moff); 812 813 while (mb != NULL && (u_int)max_len < len) { 814 u_int cur_length; 815 u_int cur_frags; 816 817 /* 818 * Get length of mbuf fragment 819 * and how many hardware 820 * frags, rounded up, it would 821 * use: 822 */ 823 cur_length = (mb->m_len - moff); 824 cur_frags = (cur_length + if_hw_tsomaxsegsize - 825 1) / if_hw_tsomaxsegsize; 826 827 /* Handle special case: Zero Length Mbuf */ 828 if (cur_frags == 0) 829 cur_frags = 1; 830 831 /* 832 * Check if the fragment limit 833 * will be reached or 834 * exceeded: 835 */ 836 if (cur_frags >= if_hw_tsomaxsegcount) { 837 max_len += min(cur_length, 838 if_hw_tsomaxsegcount * 839 if_hw_tsomaxsegsize); 840 break; 841 } 842 max_len += cur_length; 843 if_hw_tsomaxsegcount -= cur_frags; 844 moff = 0; 845 mb = mb->m_next; 846 } 847 if (max_len <= 0) { 848 len = 0; 849 } else if (len > (u_int)max_len) { 850 sendalot = 1; 851 len = (u_int)max_len; 852 } 853 } 854 855 /* 856 * Prevent the last segment from being 857 * fractional unless the send sockbuf can be 858 * emptied: 859 */ 860 max_len = (tp->t_maxopd - optlen); 861 if ((off + len) < so->so_snd.sb_cc) { 862 moff = len % (u_int)max_len; 863 if (moff != 0) { 864 len -= moff; 865 sendalot = 1; 866 } 867 } 868 869 /* 870 * In case there are too many small fragments 871 * don't use TSO: 872 */ 873 if (len <= (u_int)max_len) { 874 len = (u_int)max_len; 875 sendalot = 1; 876 tso = 0; 877 } 878 879 /* 880 * Send the FIN in a separate segment 881 * after the bulk sending is done. 882 * We don't trust the TSO implementations 883 * to clear the FIN flag on all but the 884 * last segment. 885 */ 886 if (tp->t_flags & TF_NEEDFIN) 887 sendalot = 1; 888 889 } else { 890 len = tp->t_maxopd - optlen - ipoptlen; 891 sendalot = 1; 892 } 893 } else 894 tso = 0; 895 896 KASSERT(len + hdrlen + ipoptlen <= IP_MAXPACKET, 897 ("%s: len > IP_MAXPACKET", __func__)); 898 899 /*#ifdef DIAGNOSTIC*/ 900 #ifdef INET6 901 if (max_linkhdr + hdrlen > MCLBYTES) 902 #else 903 if (max_linkhdr + hdrlen > MHLEN) 904 #endif 905 panic("tcphdr too big"); 906 /*#endif*/ 907 908 /* 909 * This KASSERT is here to catch edge cases at a well defined place. 910 * Before, those had triggered (random) panic conditions further down. 911 */ 912 KASSERT(len >= 0, ("[%s:%d]: len < 0", __func__, __LINE__)); 913 914 /* 915 * Grab a header mbuf, attaching a copy of data to 916 * be transmitted, and initialize the header from 917 * the template for sends on this connection. 918 */ 919 if (len) { 920 struct mbuf *mb; 921 u_int moff; 922 923 if ((tp->t_flags & TF_FORCEDATA) && len == 1) 924 TCPSTAT_INC(tcps_sndprobe); 925 else if (SEQ_LT(tp->snd_nxt, tp->snd_max) || sack_rxmit) { 926 tp->t_sndrexmitpack++; 927 TCPSTAT_INC(tcps_sndrexmitpack); 928 TCPSTAT_ADD(tcps_sndrexmitbyte, len); 929 } else { 930 TCPSTAT_INC(tcps_sndpack); 931 TCPSTAT_ADD(tcps_sndbyte, len); 932 } 933 #ifdef INET6 934 if (MHLEN < hdrlen + max_linkhdr) 935 m = m_getcl(M_NOWAIT, MT_DATA, M_PKTHDR); 936 else 937 #endif 938 m = m_gethdr(M_NOWAIT, MT_DATA); 939 940 if (m == NULL) { 941 SOCKBUF_UNLOCK(&so->so_snd); 942 error = ENOBUFS; 943 sack_rxmit = 0; 944 goto out; 945 } 946 947 m->m_data += max_linkhdr; 948 m->m_len = hdrlen; 949 950 /* 951 * Start the m_copy functions from the closest mbuf 952 * to the offset in the socket buffer chain. 953 */ 954 mb = sbsndptr(&so->so_snd, off, len, &moff); 955 956 if (len <= MHLEN - hdrlen - max_linkhdr) { 957 m_copydata(mb, moff, (int)len, 958 mtod(m, caddr_t) + hdrlen); 959 m->m_len += len; 960 } else { 961 m->m_next = m_copy(mb, moff, (int)len); 962 if (m->m_next == NULL) { 963 SOCKBUF_UNLOCK(&so->so_snd); 964 (void) m_free(m); 965 error = ENOBUFS; 966 sack_rxmit = 0; 967 goto out; 968 } 969 } 970 971 /* 972 * If we're sending everything we've got, set PUSH. 973 * (This will keep happy those implementations which only 974 * give data to the user when a buffer fills or 975 * a PUSH comes in.) 976 */ 977 if (off + len == so->so_snd.sb_cc) 978 flags |= TH_PUSH; 979 SOCKBUF_UNLOCK(&so->so_snd); 980 } else { 981 SOCKBUF_UNLOCK(&so->so_snd); 982 if (tp->t_flags & TF_ACKNOW) 983 TCPSTAT_INC(tcps_sndacks); 984 else if (flags & (TH_SYN|TH_FIN|TH_RST)) 985 TCPSTAT_INC(tcps_sndctrl); 986 else if (SEQ_GT(tp->snd_up, tp->snd_una)) 987 TCPSTAT_INC(tcps_sndurg); 988 else 989 TCPSTAT_INC(tcps_sndwinup); 990 991 m = m_gethdr(M_NOWAIT, MT_DATA); 992 if (m == NULL) { 993 error = ENOBUFS; 994 sack_rxmit = 0; 995 goto out; 996 } 997 #ifdef INET6 998 if (isipv6 && (MHLEN < hdrlen + max_linkhdr) && 999 MHLEN >= hdrlen) { 1000 MH_ALIGN(m, hdrlen); 1001 } else 1002 #endif 1003 m->m_data += max_linkhdr; 1004 m->m_len = hdrlen; 1005 } 1006 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); 1007 m->m_pkthdr.rcvif = (struct ifnet *)0; 1008 #ifdef MAC 1009 mac_inpcb_create_mbuf(tp->t_inpcb, m); 1010 #endif 1011 #ifdef INET6 1012 if (isipv6) { 1013 ip6 = mtod(m, struct ip6_hdr *); 1014 th = (struct tcphdr *)(ip6 + 1); 1015 tcpip_fillheaders(tp->t_inpcb, ip6, th); 1016 } else 1017 #endif /* INET6 */ 1018 { 1019 ip = mtod(m, struct ip *); 1020 ipov = (struct ipovly *)ip; 1021 th = (struct tcphdr *)(ip + 1); 1022 tcpip_fillheaders(tp->t_inpcb, ip, th); 1023 } 1024 1025 /* 1026 * Fill in fields, remembering maximum advertised 1027 * window for use in delaying messages about window sizes. 1028 * If resending a FIN, be sure not to use a new sequence number. 1029 */ 1030 if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 1031 tp->snd_nxt == tp->snd_max) 1032 tp->snd_nxt--; 1033 /* 1034 * If we are starting a connection, send ECN setup 1035 * SYN packet. If we are on a retransmit, we may 1036 * resend those bits a number of times as per 1037 * RFC 3168. 1038 */ 1039 if (tp->t_state == TCPS_SYN_SENT && V_tcp_do_ecn) { 1040 if (tp->t_rxtshift >= 1) { 1041 if (tp->t_rxtshift <= V_tcp_ecn_maxretries) 1042 flags |= TH_ECE|TH_CWR; 1043 } else 1044 flags |= TH_ECE|TH_CWR; 1045 } 1046 1047 if (tp->t_state == TCPS_ESTABLISHED && 1048 (tp->t_flags & TF_ECN_PERMIT)) { 1049 /* 1050 * If the peer has ECN, mark data packets with 1051 * ECN capable transmission (ECT). 1052 * Ignore pure ack packets, retransmissions and window probes. 1053 */ 1054 if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && 1055 !((tp->t_flags & TF_FORCEDATA) && len == 1)) { 1056 #ifdef INET6 1057 if (isipv6) 1058 ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); 1059 else 1060 #endif 1061 ip->ip_tos |= IPTOS_ECN_ECT0; 1062 TCPSTAT_INC(tcps_ecn_ect0); 1063 } 1064 1065 /* 1066 * Reply with proper ECN notifications. 1067 */ 1068 if (tp->t_flags & TF_ECN_SND_CWR) { 1069 flags |= TH_CWR; 1070 tp->t_flags &= ~TF_ECN_SND_CWR; 1071 } 1072 if (tp->t_flags & TF_ECN_SND_ECE) 1073 flags |= TH_ECE; 1074 } 1075 1076 /* 1077 * If we are doing retransmissions, then snd_nxt will 1078 * not reflect the first unsent octet. For ACK only 1079 * packets, we do not want the sequence number of the 1080 * retransmitted packet, we want the sequence number 1081 * of the next unsent octet. So, if there is no data 1082 * (and no SYN or FIN), use snd_max instead of snd_nxt 1083 * when filling in ti_seq. But if we are in persist 1084 * state, snd_max might reflect one byte beyond the 1085 * right edge of the window, so use snd_nxt in that 1086 * case, since we know we aren't doing a retransmission. 1087 * (retransmit and persist are mutually exclusive...) 1088 */ 1089 if (sack_rxmit == 0) { 1090 if (len || (flags & (TH_SYN|TH_FIN)) || 1091 tcp_timer_active(tp, TT_PERSIST)) 1092 th->th_seq = htonl(tp->snd_nxt); 1093 else 1094 th->th_seq = htonl(tp->snd_max); 1095 } else { 1096 th->th_seq = htonl(p->rxmit); 1097 p->rxmit += len; 1098 tp->sackhint.sack_bytes_rexmit += len; 1099 } 1100 th->th_ack = htonl(tp->rcv_nxt); 1101 if (optlen) { 1102 bcopy(opt, th + 1, optlen); 1103 th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; 1104 } 1105 th->th_flags = flags; 1106 /* 1107 * Calculate receive window. Don't shrink window, 1108 * but avoid silly window syndrome. 1109 */ 1110 if (recwin < (long)(so->so_rcv.sb_hiwat / 4) && 1111 recwin < (long)tp->t_maxseg) 1112 recwin = 0; 1113 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) && 1114 recwin < (long)(tp->rcv_adv - tp->rcv_nxt)) 1115 recwin = (long)(tp->rcv_adv - tp->rcv_nxt); 1116 if (recwin > (long)TCP_MAXWIN << tp->rcv_scale) 1117 recwin = (long)TCP_MAXWIN << tp->rcv_scale; 1118 1119 /* 1120 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1121 * or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK> 1122 * case is handled in syncache. 1123 */ 1124 if (flags & TH_SYN) 1125 th->th_win = htons((u_short) 1126 (min(sbspace(&so->so_rcv), TCP_MAXWIN))); 1127 else 1128 th->th_win = htons((u_short)(recwin >> tp->rcv_scale)); 1129 1130 /* 1131 * Adjust the RXWIN0SENT flag - indicate that we have advertised 1132 * a 0 window. This may cause the remote transmitter to stall. This 1133 * flag tells soreceive() to disable delayed acknowledgements when 1134 * draining the buffer. This can occur if the receiver is attempting 1135 * to read more data than can be buffered prior to transmitting on 1136 * the connection. 1137 */ 1138 if (th->th_win == 0) { 1139 tp->t_sndzerowin++; 1140 tp->t_flags |= TF_RXWIN0SENT; 1141 } else 1142 tp->t_flags &= ~TF_RXWIN0SENT; 1143 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 1144 th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); 1145 th->th_flags |= TH_URG; 1146 } else 1147 /* 1148 * If no urgent pointer to send, then we pull 1149 * the urgent pointer to the left edge of the send window 1150 * so that it doesn't drift into the send window on sequence 1151 * number wraparound. 1152 */ 1153 tp->snd_up = tp->snd_una; /* drag it along */ 1154 1155 #ifdef TCP_SIGNATURE 1156 if (tp->t_flags & TF_SIGNATURE) { 1157 int sigoff = to.to_signature - opt; 1158 tcp_signature_compute(m, 0, len, optlen, 1159 (u_char *)(th + 1) + sigoff, IPSEC_DIR_OUTBOUND); 1160 } 1161 #endif 1162 1163 /* 1164 * Put TCP length in extended header, and then 1165 * checksum extended header and data. 1166 */ 1167 m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ 1168 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); 1169 #ifdef INET6 1170 if (isipv6) { 1171 /* 1172 * ip6_plen is not need to be filled now, and will be filled 1173 * in ip6_output. 1174 */ 1175 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6; 1176 th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) + 1177 optlen + len, IPPROTO_TCP, 0); 1178 } 1179 #endif 1180 #if defined(INET6) && defined(INET) 1181 else 1182 #endif 1183 #ifdef INET 1184 { 1185 m->m_pkthdr.csum_flags = CSUM_TCP; 1186 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, 1187 htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen)); 1188 1189 /* IP version must be set here for ipv4/ipv6 checking later */ 1190 KASSERT(ip->ip_v == IPVERSION, 1191 ("%s: IP version incorrect: %d", __func__, ip->ip_v)); 1192 } 1193 #endif 1194 1195 /* 1196 * Enable TSO and specify the size of the segments. 1197 * The TCP pseudo header checksum is always provided. 1198 * XXX: Fixme: This is currently not the case for IPv6. 1199 */ 1200 if (tso) { 1201 KASSERT(len > tp->t_maxopd - optlen, 1202 ("%s: len <= tso_segsz", __func__)); 1203 m->m_pkthdr.csum_flags |= CSUM_TSO; 1204 m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; 1205 } 1206 1207 #ifdef IPSEC 1208 KASSERT(len + hdrlen + ipoptlen - ipsec_optlen == m_length(m, NULL), 1209 ("%s: mbuf chain shorter than expected: %ld + %u + %u - %u != %u", 1210 __func__, len, hdrlen, ipoptlen, ipsec_optlen, m_length(m, NULL))); 1211 #else 1212 KASSERT(len + hdrlen + ipoptlen == m_length(m, NULL), 1213 ("%s: mbuf chain shorter than expected: %ld + %u + %u != %u", 1214 __func__, len, hdrlen, ipoptlen, m_length(m, NULL))); 1215 #endif 1216 1217 /* Run HHOOK_TCP_ESTABLISHED_OUT helper hooks. */ 1218 hhook_run_tcp_est_out(tp, th, &to, len, tso); 1219 1220 #ifdef TCPDEBUG 1221 /* 1222 * Trace. 1223 */ 1224 if (so->so_options & SO_DEBUG) { 1225 u_short save = 0; 1226 #ifdef INET6 1227 if (!isipv6) 1228 #endif 1229 { 1230 save = ipov->ih_len; 1231 ipov->ih_len = htons(m->m_pkthdr.len /* - hdrlen + (th->th_off << 2) */); 1232 } 1233 tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); 1234 #ifdef INET6 1235 if (!isipv6) 1236 #endif 1237 ipov->ih_len = save; 1238 } 1239 #endif /* TCPDEBUG */ 1240 1241 /* 1242 * Fill in IP length and desired time to live and 1243 * send to IP level. There should be a better way 1244 * to handle ttl and tos; we could keep them in 1245 * the template, but need a way to checksum without them. 1246 */ 1247 /* 1248 * m->m_pkthdr.len should have been set before checksum calculation, 1249 * because in6_cksum() need it. 1250 */ 1251 #ifdef INET6 1252 if (isipv6) { 1253 struct route_in6 ro; 1254 1255 bzero(&ro, sizeof(ro)); 1256 /* 1257 * we separately set hoplimit for every segment, since the 1258 * user might want to change the value via setsockopt. 1259 * Also, desired default hop limit might be changed via 1260 * Neighbor Discovery. 1261 */ 1262 ip6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); 1263 1264 /* 1265 * Set the packet size here for the benefit of DTrace probes. 1266 * ip6_output() will set it properly; it's supposed to include 1267 * the option header lengths as well. 1268 */ 1269 ip6->ip6_plen = htons(m->m_pkthdr.len - sizeof(*ip6)); 1270 1271 if (tp->t_state == TCPS_SYN_SENT) 1272 TCP_PROBE5(connect__request, NULL, tp, ip6, tp, th); 1273 1274 TCP_PROBE5(send, NULL, tp, ip6, tp, th); 1275 1276 /* TODO: IPv6 IP6TOS_ECT bit on */ 1277 error = ip6_output(m, tp->t_inpcb->in6p_outputopts, &ro, 1278 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 1279 NULL, NULL, tp->t_inpcb); 1280 1281 if (error == EMSGSIZE && ro.ro_rt != NULL) 1282 mtu = ro.ro_rt->rt_mtu; 1283 RO_RTFREE(&ro); 1284 } 1285 #endif /* INET6 */ 1286 #if defined(INET) && defined(INET6) 1287 else 1288 #endif 1289 #ifdef INET 1290 { 1291 struct route ro; 1292 1293 bzero(&ro, sizeof(ro)); 1294 ip->ip_len = htons(m->m_pkthdr.len); 1295 #ifdef INET6 1296 if (tp->t_inpcb->inp_vflag & INP_IPV6PROTO) 1297 ip->ip_ttl = in6_selecthlim(tp->t_inpcb, NULL); 1298 #endif /* INET6 */ 1299 /* 1300 * If we do path MTU discovery, then we set DF on every packet. 1301 * This might not be the best thing to do according to RFC3390 1302 * Section 2. However the tcp hostcache migitates the problem 1303 * so it affects only the first tcp connection with a host. 1304 * 1305 * NB: Don't set DF on small MTU/MSS to have a safe fallback. 1306 */ 1307 if (V_path_mtu_discovery && tp->t_maxopd > V_tcp_minmss) 1308 ip->ip_off |= htons(IP_DF); 1309 1310 if (tp->t_state == TCPS_SYN_SENT) 1311 TCP_PROBE5(connect__request, NULL, tp, ip, tp, th); 1312 1313 TCP_PROBE5(send, NULL, tp, ip, tp, th); 1314 1315 error = ip_output(m, tp->t_inpcb->inp_options, &ro, 1316 ((so->so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0), 0, 1317 tp->t_inpcb); 1318 1319 if (error == EMSGSIZE && ro.ro_rt != NULL) 1320 mtu = ro.ro_rt->rt_mtu; 1321 RO_RTFREE(&ro); 1322 } 1323 #endif /* INET */ 1324 1325 out: 1326 /* 1327 * In transmit state, time the transmission and arrange for 1328 * the retransmit. In persist state, just set snd_max. 1329 */ 1330 if ((tp->t_flags & TF_FORCEDATA) == 0 || 1331 !tcp_timer_active(tp, TT_PERSIST)) { 1332 tcp_seq startseq = tp->snd_nxt; 1333 1334 /* 1335 * Advance snd_nxt over sequence space of this segment. 1336 */ 1337 if (flags & (TH_SYN|TH_FIN)) { 1338 if (flags & TH_SYN) 1339 tp->snd_nxt++; 1340 if (flags & TH_FIN) { 1341 tp->snd_nxt++; 1342 tp->t_flags |= TF_SENTFIN; 1343 } 1344 } 1345 if (sack_rxmit) 1346 goto timer; 1347 tp->snd_nxt += len; 1348 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { 1349 tp->snd_max = tp->snd_nxt; 1350 /* 1351 * Time this transmission if not a retransmission and 1352 * not currently timing anything. 1353 */ 1354 if (tp->t_rtttime == 0) { 1355 tp->t_rtttime = ticks; 1356 tp->t_rtseq = startseq; 1357 TCPSTAT_INC(tcps_segstimed); 1358 } 1359 } 1360 1361 /* 1362 * Set retransmit timer if not currently set, 1363 * and not doing a pure ack or a keep-alive probe. 1364 * Initial value for retransmit timer is smoothed 1365 * round-trip time + 2 * round-trip time variance. 1366 * Initialize shift counter which is used for backoff 1367 * of retransmit time. 1368 */ 1369 timer: 1370 if (!tcp_timer_active(tp, TT_REXMT) && 1371 ((sack_rxmit && tp->snd_nxt != tp->snd_max) || 1372 (tp->snd_nxt != tp->snd_una))) { 1373 if (tcp_timer_active(tp, TT_PERSIST)) { 1374 tcp_timer_activate(tp, TT_PERSIST, 0); 1375 tp->t_rxtshift = 0; 1376 } 1377 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1378 } 1379 } else { 1380 /* 1381 * Persist case, update snd_max but since we are in 1382 * persist mode (no window) we do not update snd_nxt. 1383 */ 1384 int xlen = len; 1385 if (flags & TH_SYN) 1386 ++xlen; 1387 if (flags & TH_FIN) { 1388 ++xlen; 1389 tp->t_flags |= TF_SENTFIN; 1390 } 1391 if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) 1392 tp->snd_max = tp->snd_nxt + len; 1393 } 1394 1395 if (error) { 1396 1397 /* 1398 * We know that the packet was lost, so back out the 1399 * sequence number advance, if any. 1400 * 1401 * If the error is EPERM the packet got blocked by the 1402 * local firewall. Normally we should terminate the 1403 * connection but the blocking may have been spurious 1404 * due to a firewall reconfiguration cycle. So we treat 1405 * it like a packet loss and let the retransmit timer and 1406 * timeouts do their work over time. 1407 * XXX: It is a POLA question whether calling tcp_drop right 1408 * away would be the really correct behavior instead. 1409 */ 1410 if (((tp->t_flags & TF_FORCEDATA) == 0 || 1411 !tcp_timer_active(tp, TT_PERSIST)) && 1412 ((flags & TH_SYN) == 0) && 1413 (error != EPERM)) { 1414 if (sack_rxmit) { 1415 p->rxmit -= len; 1416 tp->sackhint.sack_bytes_rexmit -= len; 1417 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 1418 ("sackhint bytes rtx >= 0")); 1419 } else 1420 tp->snd_nxt -= len; 1421 } 1422 SOCKBUF_UNLOCK_ASSERT(&so->so_snd); /* Check gotos. */ 1423 switch (error) { 1424 case EPERM: 1425 tp->t_softerror = error; 1426 return (error); 1427 case ENOBUFS: 1428 if (!tcp_timer_active(tp, TT_REXMT) && 1429 !tcp_timer_active(tp, TT_PERSIST)) 1430 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 1431 tp->snd_cwnd = tp->t_maxseg; 1432 return (0); 1433 case EMSGSIZE: 1434 /* 1435 * For some reason the interface we used initially 1436 * to send segments changed to another or lowered 1437 * its MTU. 1438 * If TSO was active we either got an interface 1439 * without TSO capabilits or TSO was turned off. 1440 * If we obtained mtu from ip_output() then update 1441 * it and try again. 1442 */ 1443 if (tso) 1444 tp->t_flags &= ~TF_TSO; 1445 if (mtu != 0) { 1446 tcp_mss_update(tp, -1, mtu, NULL, NULL); 1447 goto again; 1448 } 1449 return (error); 1450 case EHOSTDOWN: 1451 case EHOSTUNREACH: 1452 case ENETDOWN: 1453 case ENETUNREACH: 1454 if (TCPS_HAVERCVDSYN(tp->t_state)) { 1455 tp->t_softerror = error; 1456 return (0); 1457 } 1458 /* FALLTHROUGH */ 1459 default: 1460 return (error); 1461 } 1462 } 1463 TCPSTAT_INC(tcps_sndtotal); 1464 1465 /* 1466 * Data sent (as far as we can tell). 1467 * If this advertises a larger window than any other segment, 1468 * then remember the size of the advertised window. 1469 * Any pending ACK has now been sent. 1470 */ 1471 if (recwin >= 0 && SEQ_GT(tp->rcv_nxt + recwin, tp->rcv_adv)) 1472 tp->rcv_adv = tp->rcv_nxt + recwin; 1473 tp->last_ack_sent = tp->rcv_nxt; 1474 tp->t_flags &= ~(TF_ACKNOW | TF_DELACK); 1475 if (tcp_timer_active(tp, TT_DELACK)) 1476 tcp_timer_activate(tp, TT_DELACK, 0); 1477 #if 0 1478 /* 1479 * This completely breaks TCP if newreno is turned on. What happens 1480 * is that if delayed-acks are turned on on the receiver, this code 1481 * on the transmitter effectively destroys the TCP window, forcing 1482 * it to four packets (1.5Kx4 = 6K window). 1483 */ 1484 if (sendalot && --maxburst) 1485 goto again; 1486 #endif 1487 if (sendalot) 1488 goto again; 1489 return (0); 1490 } 1491 1492 void 1493 tcp_setpersist(struct tcpcb *tp) 1494 { 1495 int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 1496 int tt; 1497 1498 tp->t_flags &= ~TF_PREVVALID; 1499 if (tcp_timer_active(tp, TT_REXMT)) 1500 panic("tcp_setpersist: retransmit pending"); 1501 /* 1502 * Start/restart persistance timer. 1503 */ 1504 TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], 1505 TCPTV_PERSMIN, TCPTV_PERSMAX); 1506 tcp_timer_activate(tp, TT_PERSIST, tt); 1507 if (tp->t_rxtshift < TCP_MAXRXTSHIFT) 1508 tp->t_rxtshift++; 1509 } 1510 1511 /* 1512 * Insert TCP options according to the supplied parameters to the place 1513 * optp in a consistent way. Can handle unaligned destinations. 1514 * 1515 * The order of the option processing is crucial for optimal packing and 1516 * alignment for the scarce option space. 1517 * 1518 * The optimal order for a SYN/SYN-ACK segment is: 1519 * MSS (4) + NOP (1) + Window scale (3) + SACK permitted (2) + 1520 * Timestamp (10) + Signature (18) = 38 bytes out of a maximum of 40. 1521 * 1522 * The SACK options should be last. SACK blocks consume 8*n+2 bytes. 1523 * So a full size SACK blocks option is 34 bytes (with 4 SACK blocks). 1524 * At minimum we need 10 bytes (to generate 1 SACK block). If both 1525 * TCP Timestamps (12 bytes) and TCP Signatures (18 bytes) are present, 1526 * we only have 10 bytes for SACK options (40 - (12 + 18)). 1527 */ 1528 int 1529 tcp_addoptions(struct tcpopt *to, u_char *optp) 1530 { 1531 u_int mask, optlen = 0; 1532 1533 for (mask = 1; mask < TOF_MAXOPT; mask <<= 1) { 1534 if ((to->to_flags & mask) != mask) 1535 continue; 1536 if (optlen == TCP_MAXOLEN) 1537 break; 1538 switch (to->to_flags & mask) { 1539 case TOF_MSS: 1540 while (optlen % 4) { 1541 optlen += TCPOLEN_NOP; 1542 *optp++ = TCPOPT_NOP; 1543 } 1544 if (TCP_MAXOLEN - optlen < TCPOLEN_MAXSEG) 1545 continue; 1546 optlen += TCPOLEN_MAXSEG; 1547 *optp++ = TCPOPT_MAXSEG; 1548 *optp++ = TCPOLEN_MAXSEG; 1549 to->to_mss = htons(to->to_mss); 1550 bcopy((u_char *)&to->to_mss, optp, sizeof(to->to_mss)); 1551 optp += sizeof(to->to_mss); 1552 break; 1553 case TOF_SCALE: 1554 while (!optlen || optlen % 2 != 1) { 1555 optlen += TCPOLEN_NOP; 1556 *optp++ = TCPOPT_NOP; 1557 } 1558 if (TCP_MAXOLEN - optlen < TCPOLEN_WINDOW) 1559 continue; 1560 optlen += TCPOLEN_WINDOW; 1561 *optp++ = TCPOPT_WINDOW; 1562 *optp++ = TCPOLEN_WINDOW; 1563 *optp++ = to->to_wscale; 1564 break; 1565 case TOF_SACKPERM: 1566 while (optlen % 2) { 1567 optlen += TCPOLEN_NOP; 1568 *optp++ = TCPOPT_NOP; 1569 } 1570 if (TCP_MAXOLEN - optlen < TCPOLEN_SACK_PERMITTED) 1571 continue; 1572 optlen += TCPOLEN_SACK_PERMITTED; 1573 *optp++ = TCPOPT_SACK_PERMITTED; 1574 *optp++ = TCPOLEN_SACK_PERMITTED; 1575 break; 1576 case TOF_TS: 1577 while (!optlen || optlen % 4 != 2) { 1578 optlen += TCPOLEN_NOP; 1579 *optp++ = TCPOPT_NOP; 1580 } 1581 if (TCP_MAXOLEN - optlen < TCPOLEN_TIMESTAMP) 1582 continue; 1583 optlen += TCPOLEN_TIMESTAMP; 1584 *optp++ = TCPOPT_TIMESTAMP; 1585 *optp++ = TCPOLEN_TIMESTAMP; 1586 to->to_tsval = htonl(to->to_tsval); 1587 to->to_tsecr = htonl(to->to_tsecr); 1588 bcopy((u_char *)&to->to_tsval, optp, sizeof(to->to_tsval)); 1589 optp += sizeof(to->to_tsval); 1590 bcopy((u_char *)&to->to_tsecr, optp, sizeof(to->to_tsecr)); 1591 optp += sizeof(to->to_tsecr); 1592 break; 1593 case TOF_SIGNATURE: 1594 { 1595 int siglen = TCPOLEN_SIGNATURE - 2; 1596 1597 while (!optlen || optlen % 4 != 2) { 1598 optlen += TCPOLEN_NOP; 1599 *optp++ = TCPOPT_NOP; 1600 } 1601 if (TCP_MAXOLEN - optlen < TCPOLEN_SIGNATURE) 1602 continue; 1603 optlen += TCPOLEN_SIGNATURE; 1604 *optp++ = TCPOPT_SIGNATURE; 1605 *optp++ = TCPOLEN_SIGNATURE; 1606 to->to_signature = optp; 1607 while (siglen--) 1608 *optp++ = 0; 1609 break; 1610 } 1611 case TOF_SACK: 1612 { 1613 int sackblks = 0; 1614 struct sackblk *sack = (struct sackblk *)to->to_sacks; 1615 tcp_seq sack_seq; 1616 1617 while (!optlen || optlen % 4 != 2) { 1618 optlen += TCPOLEN_NOP; 1619 *optp++ = TCPOPT_NOP; 1620 } 1621 if (TCP_MAXOLEN - optlen < TCPOLEN_SACKHDR + TCPOLEN_SACK) 1622 continue; 1623 optlen += TCPOLEN_SACKHDR; 1624 *optp++ = TCPOPT_SACK; 1625 sackblks = min(to->to_nsacks, 1626 (TCP_MAXOLEN - optlen) / TCPOLEN_SACK); 1627 *optp++ = TCPOLEN_SACKHDR + sackblks * TCPOLEN_SACK; 1628 while (sackblks--) { 1629 sack_seq = htonl(sack->start); 1630 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1631 optp += sizeof(sack_seq); 1632 sack_seq = htonl(sack->end); 1633 bcopy((u_char *)&sack_seq, optp, sizeof(sack_seq)); 1634 optp += sizeof(sack_seq); 1635 optlen += TCPOLEN_SACK; 1636 sack++; 1637 } 1638 TCPSTAT_INC(tcps_sack_send_blocks); 1639 break; 1640 } 1641 default: 1642 panic("%s: unknown TCP option type", __func__); 1643 break; 1644 } 1645 } 1646 1647 /* Terminate and pad TCP options to a 4 byte boundary. */ 1648 if (optlen % 4) { 1649 optlen += TCPOLEN_EOL; 1650 *optp++ = TCPOPT_EOL; 1651 } 1652 /* 1653 * According to RFC 793 (STD0007): 1654 * "The content of the header beyond the End-of-Option option 1655 * must be header padding (i.e., zero)." 1656 * and later: "The padding is composed of zeros." 1657 */ 1658 while (optlen % 4) { 1659 optlen += TCPOLEN_PAD; 1660 *optp++ = TCPOPT_PAD; 1661 } 1662 1663 KASSERT(optlen <= TCP_MAXOLEN, ("%s: TCP options too long", __func__)); 1664 return (optlen); 1665 } 1666