/* * Copyright (c) 2004 Jeffrey M. Hsu. All rights reserved. * Copyright (c) 2004 The DragonFly Project. All rights reserved. * * This code is derived from software contributed to The DragonFly Project * by Jeffrey M. Hsu. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of The DragonFly Project nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific, prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ /* * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)tcp_output.c 8.4 (Berkeley) 5/24/95 * $FreeBSD: src/sys/netinet/tcp_output.c,v 1.39.2.20 2003/01/29 22:45:36 hsu Exp $ * $DragonFly: src/sys/netinet/tcp_output.c,v 1.34 2007/04/22 01:13:14 dillon Exp $ */ #include "opt_inet6.h" #include "opt_ipsec.h" #include "opt_tcpdebug.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define TCPOUTFLAGS #include #include #include #include #include #ifdef TCPDEBUG #include #endif #ifdef IPSEC #include #endif /*IPSEC*/ #ifdef FAST_IPSEC #include #define IPSEC #endif /*FAST_IPSEC*/ #ifdef notyet extern struct mbuf *m_copypack(); #endif int path_mtu_discovery = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, path_mtu_discovery, CTLFLAG_RW, &path_mtu_discovery, 1, "Enable Path MTU Discovery"); static int avoid_pure_win_update = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, avoid_pure_win_update, CTLFLAG_RW, &avoid_pure_win_update, 1, "Avoid pure window updates when possible"); /* * Tcp output routine: figure out what should be sent and send it. */ int tcp_output(struct tcpcb *tp) { struct inpcb * const inp = tp->t_inpcb; struct socket *so = inp->inp_socket; long len, recvwin, sendwin; int nsacked = 0; int off, flags, error; struct mbuf *m; struct ip *ip = NULL; struct ipovly *ipov = NULL; struct tcphdr *th; u_char opt[TCP_MAXOLEN]; unsigned int ipoptlen, optlen, hdrlen; int idle; boolean_t sendalot; struct ip6_hdr *ip6 = NULL; #ifdef INET6 const boolean_t isipv6 = (inp->inp_vflag & INP_IPV6) != 0; #else const boolean_t isipv6 = FALSE; #endif struct rmxp_tao *taop; /* * Determine length of data that should be transmitted, * and flags that will be used. * If there is some data or critical controls (SYN, RST) * to send, then transmit; otherwise, investigate further. */ /* * If we have been idle for a while, the send congestion window * could be no longer representative of the current state of the link. * So unless we are expecting more acks to come in, slow-start from * scratch to re-determine the send congestion window. */ if (tp->snd_max == tp->snd_una && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) { if (tcp_do_rfc3390) { int initial_cwnd = min(4 * tp->t_maxseg, max(2 * tp->t_maxseg, 4380)); tp->snd_cwnd = min(tp->snd_cwnd, initial_cwnd); } else { tp->snd_cwnd = tp->t_maxseg; } tp->snd_wacked = 0; } /* * Calculate whether the transmit stream was previously idle * and adjust TF_LASTIDLE for the next time. */ idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una); if (idle && (tp->t_flags & TF_MORETOCOME)) tp->t_flags |= TF_LASTIDLE; else tp->t_flags &= ~TF_LASTIDLE; if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && !IN_FASTRECOVERY(tp)) nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt); again: /* Make use of SACK information when slow-starting after a RTO. */ if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max && !IN_FASTRECOVERY(tp)) { tcp_seq old_snd_nxt = tp->snd_nxt; tcp_sack_skip_sacked(&tp->scb, &tp->snd_nxt); nsacked += tp->snd_nxt - old_snd_nxt; } sendalot = FALSE; off = tp->snd_nxt - tp->snd_una; sendwin = min(tp->snd_wnd, tp->snd_cwnd + nsacked); sendwin = min(sendwin, tp->snd_bwnd); flags = tcp_outflags[tp->t_state]; /* * Get standard flags, and add SYN or FIN if requested by 'hidden' * state flags. */ if (tp->t_flags & TF_NEEDFIN) flags |= TH_FIN; if (tp->t_flags & TF_NEEDSYN) flags |= TH_SYN; /* * If in persist timeout with window of 0, send 1 byte. * Otherwise, if window is small but nonzero * and timer expired, we will send what we can * and go to transmit state. */ if (tp->t_flags & TF_FORCE) { if (sendwin == 0) { /* * If we still have some data to send, then * clear the FIN bit. Usually this would * happen below when it realizes that we * aren't sending all the data. However, * if we have exactly 1 byte of unsent data, * then it won't clear the FIN bit below, * and if we are in persist state, we wind * up sending the packet without recording * that we sent the FIN bit. * * We can't just blindly clear the FIN bit, * because if we don't have any more data * to send then the probe will be the FIN * itself. */ if (off < so->so_snd.ssb_cc) flags &= ~TH_FIN; sendwin = 1; } else { callout_stop(tp->tt_persist); tp->t_rxtshift = 0; } } /* * If snd_nxt == snd_max and we have transmitted a FIN, the * offset will be > 0 even if so_snd.ssb_cc is 0, resulting in * a negative length. This can also occur when TCP opens up * its congestion window while receiving additional duplicate * acks after fast-retransmit because TCP will reset snd_nxt * to snd_max after the fast-retransmit. * * In the normal retransmit-FIN-only case, however, snd_nxt will * be set to snd_una, the offset will be 0, and the length may * wind up 0. */ len = (long)ulmin(so->so_snd.ssb_cc, sendwin) - off; /* * Lop off SYN bit if it has already been sent. However, if this * is SYN-SENT state and if segment contains data and if we don't * know that foreign host supports TAO, suppress sending segment. */ if ((flags & TH_SYN) && SEQ_GT(tp->snd_nxt, tp->snd_una)) { flags &= ~TH_SYN; off--, len++; if (len > 0 && tp->t_state == TCPS_SYN_SENT && ((taop = tcp_gettaocache(&inp->inp_inc)) == NULL || taop->tao_ccsent == 0)) return 0; } /* * Be careful not to send data and/or FIN on SYN segments * in cases when no CC option will be sent. * This measure is needed to prevent interoperability problems * with not fully conformant TCP implementations. */ if ((flags & TH_SYN) && ((tp->t_flags & TF_NOOPT) || !(tp->t_flags & TF_REQ_CC) || ((flags & TH_ACK) && !(tp->t_flags & TF_RCVD_CC)))) { len = 0; flags &= ~TH_FIN; } if (len < 0) { /* * If FIN has been sent but not acked, * but we haven't been called to retransmit, * len will be < 0. Otherwise, window shrank * after we sent into it. If window shrank to 0, * cancel pending retransmit, pull snd_nxt back * to (closed) window, and set the persist timer * if it isn't already going. If the window didn't * close completely, just wait for an ACK. */ len = 0; if (sendwin == 0) { callout_stop(tp->tt_rexmt); tp->t_rxtshift = 0; tp->snd_nxt = tp->snd_una; if (!callout_active(tp->tt_persist)) tcp_setpersist(tp); } } /* * len will be >= 0 after this point. Truncate to the maximum * segment length and ensure that FIN is removed if the length * no longer contains the last data byte. */ if (len > tp->t_maxseg) { len = tp->t_maxseg; sendalot = TRUE; } if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.ssb_cc)) flags &= ~TH_FIN; recvwin = ssb_space(&so->so_rcv); /* * Sender silly window avoidance. We transmit under the following * conditions when len is non-zero: * * - We have a full segment * - This is the last buffer in a write()/send() and we are * either idle or running NODELAY * - we've timed out (e.g. persist timer) * - we have more then 1/2 the maximum send window's worth of * data (receiver may be limiting the window size) * - we need to retransmit */ if (len) { if (len == tp->t_maxseg) goto send; /* * NOTE! on localhost connections an 'ack' from the remote * end may occur synchronously with the output and cause * us to flush a buffer queued with moretocome. XXX * * note: the len + off check is almost certainly unnecessary. */ if (!(tp->t_flags & TF_MORETOCOME) && /* normal case */ (idle || (tp->t_flags & TF_NODELAY)) && len + off >= so->so_snd.ssb_cc && !(tp->t_flags & TF_NOPUSH)) { goto send; } if (tp->t_flags & TF_FORCE) /* typ. timeout case */ goto send; if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) goto send; if (SEQ_LT(tp->snd_nxt, tp->snd_max)) /* retransmit case */ goto send; } /* * Compare available window to amount of window * known to peer (as advertised window less * next expected input). If the difference is at least two * max size segments, or at least 50% of the maximum possible * window, then want to send a window update to peer. */ if (recvwin > 0) { /* * "adv" is the amount we can increase the window, * taking into account that we are limited by * TCP_MAXWIN << tp->rcv_scale. */ long adv = min(recvwin, (long)TCP_MAXWIN << tp->rcv_scale) - (tp->rcv_adv - tp->rcv_nxt); /* * This ack case typically occurs when the user has drained * the TCP socket buffer sufficiently to warrent an ack * containing a 'pure window update'... that is, an ack that * ONLY updates the tcp window. * * It is unclear why we would need to do a pure window update * past 2 segments if we are going to do one at 1/2 the high * water mark anyway, especially since under normal conditions * the user program will drain the socket buffer quickly. * The 2-segment pure window update will often add a large * number of extra, unnecessary acks to the stream. * * avoid_pure_win_update now defaults to 1. */ if (avoid_pure_win_update == 0) { if (adv >= (long) (2 * tp->t_maxseg)) goto send; } if (2 * adv >= (long) so->so_rcv.ssb_hiwat) goto send; } /* * Send if we owe the peer an ACK, RST, SYN, or urgent data. ACKNOW * is also a catch-all for the retransmit timer timeout case. */ if (tp->t_flags & TF_ACKNOW) goto send; if ((flags & TH_RST) || ((flags & TH_SYN) && !(tp->t_flags & TF_NEEDSYN))) goto send; if (SEQ_GT(tp->snd_up, tp->snd_una)) goto send; /* * If our state indicates that FIN should be sent * and we have not yet done so, then we need to send. */ if (flags & TH_FIN && (!(tp->t_flags & TF_SENTFIN) || tp->snd_nxt == tp->snd_una)) goto send; /* * TCP window updates are not reliable, rather a polling protocol * using ``persist'' packets is used to insure receipt of window * updates. The three ``states'' for the output side are: * idle not doing retransmits or persists * persisting to move a small or zero window * (re)transmitting and thereby not persisting * * callout_active(tp->tt_persist) * is true when we are in persist state. * The TF_FORCE flag in tp->t_flags * is set when we are called to send a persist packet. * callout_active(tp->tt_rexmt) * is set when we are retransmitting * The output side is idle when both timers are zero. * * If send window is too small, there is data to transmit, and no * retransmit or persist is pending, then go to persist state. * If nothing happens soon, send when timer expires: * if window is nonzero, transmit what we can, * otherwise force out a byte. */ if (so->so_snd.ssb_cc > 0 && !callout_active(tp->tt_rexmt) && !callout_active(tp->tt_persist)) { tp->t_rxtshift = 0; tcp_setpersist(tp); } /* * No reason to send a segment, just return. */ return (0); send: /* * Before ESTABLISHED, force sending of initial options * unless TCP set not to do any options. * NOTE: we assume that the IP/TCP header plus TCP options * always fit in a single mbuf, leaving room for a maximum * link header, i.e. * max_linkhdr + sizeof(struct tcpiphdr) + optlen <= MCLBYTES */ optlen = 0; if (isipv6) hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); else hdrlen = sizeof(struct tcpiphdr); if (flags & TH_SYN) { tp->snd_nxt = tp->iss; if (!(tp->t_flags & TF_NOOPT)) { u_short mss; opt[0] = TCPOPT_MAXSEG; opt[1] = TCPOLEN_MAXSEG; mss = htons((u_short) tcp_mssopt(tp)); memcpy(opt + 2, &mss, sizeof mss); optlen = TCPOLEN_MAXSEG; if ((tp->t_flags & TF_REQ_SCALE) && (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_SCALE))) { *((u_int32_t *)(opt + optlen)) = htonl( TCPOPT_NOP << 24 | TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | tp->request_r_scale); optlen += 4; } if ((tcp_do_sack && !(flags & TH_ACK)) || tp->t_flags & TF_SACK_PERMITTED) { uint32_t *lp = (uint32_t *)(opt + optlen); *lp = htonl(TCPOPT_SACK_PERMITTED_ALIGNED); optlen += TCPOLEN_SACK_PERMITTED_ALIGNED; } } } /* * Send a timestamp and echo-reply if this is a SYN and our side * wants to use timestamps (TF_REQ_TSTMP is set) or both our side * and our peer have sent timestamps in our SYN's. */ if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && !(flags & TH_RST) && (!(flags & TH_ACK) || (tp->t_flags & TF_RCVD_TSTMP))) { u_int32_t *lp = (u_int32_t *)(opt + optlen); /* Form timestamp option as shown in appendix A of RFC 1323. */ *lp++ = htonl(TCPOPT_TSTAMP_HDR); *lp++ = htonl(ticks); *lp = htonl(tp->ts_recent); optlen += TCPOLEN_TSTAMP_APPA; } /* * Send `CC-family' options if our side wants to use them (TF_REQ_CC), * options are allowed (!TF_NOOPT) and it's not a RST. */ if ((tp->t_flags & (TF_REQ_CC | TF_NOOPT)) == TF_REQ_CC && !(flags & TH_RST)) { switch (flags & (TH_SYN | TH_ACK)) { /* * This is a normal ACK, send CC if we received CC before * from our peer. */ case TH_ACK: if (!(tp->t_flags & TF_RCVD_CC)) break; /*FALLTHROUGH*/ /* * We can only get here in T/TCP's SYN_SENT* state, when * we're a sending a non-SYN segment without waiting for * the ACK of our SYN. A check above assures that we only * do this if our peer understands T/TCP. */ case 0: opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_CC; opt[optlen++] = TCPOLEN_CC; *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); optlen += 4; break; /* * This is our initial SYN, check whether we have to use * CC or CC.new. */ case TH_SYN: opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_NOP; opt[optlen++] = tp->t_flags & TF_SENDCCNEW ? TCPOPT_CCNEW : TCPOPT_CC; opt[optlen++] = TCPOLEN_CC; *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); optlen += 4; break; /* * This is a SYN,ACK; send CC and CC.echo if we received * CC from our peer. */ case (TH_SYN | TH_ACK): if (tp->t_flags & TF_RCVD_CC) { opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_CC; opt[optlen++] = TCPOLEN_CC; *(u_int32_t *)&opt[optlen] = htonl(tp->cc_send); optlen += 4; opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_NOP; opt[optlen++] = TCPOPT_CCECHO; opt[optlen++] = TCPOLEN_CC; *(u_int32_t *)&opt[optlen] = htonl(tp->cc_recv); optlen += 4; } break; } } /* * If this is a SACK connection and we have a block to report, * fill in the SACK blocks in the TCP options. */ if ((tp->t_flags & (TF_SACK_PERMITTED | TF_NOOPT)) == TF_SACK_PERMITTED && (!LIST_EMPTY(&tp->t_segq) || tp->reportblk.rblk_start != tp->reportblk.rblk_end)) tcp_sack_fill_report(tp, opt, &optlen); KASSERT(optlen <= TCP_MAXOLEN, ("too many TCP options")); hdrlen += optlen; if (isipv6) { ipoptlen = ip6_optlen(inp); } else { if (inp->inp_options) { ipoptlen = inp->inp_options->m_len - offsetof(struct ipoption, ipopt_list); } else { ipoptlen = 0; } } #ifdef IPSEC ipoptlen += ipsec_hdrsiz_tcp(tp); #endif /* * Adjust data length if insertion of options will bump the packet * length beyond the t_maxopd length. Clear FIN to prevent premature * closure since there is still more data to send after this (now * truncated) packet. * * If just the options do not fit we are in a no-win situation and * we treat it as an unreachable host. */ if (len + optlen + ipoptlen > tp->t_maxopd) { if (tp->t_maxopd <= optlen + ipoptlen) { static time_t last_optlen_report; if (last_optlen_report != time_second) { last_optlen_report = time_second; kprintf("tcpcb %p: MSS (%d) too small to hold options!\n", tp, tp->t_maxopd); } error = EHOSTUNREACH; goto out; } else { flags &= ~TH_FIN; len = tp->t_maxopd - optlen - ipoptlen; sendalot = TRUE; } } #ifdef INET6 KASSERT(max_linkhdr + hdrlen <= MCLBYTES, ("tcphdr too big")); #else KASSERT(max_linkhdr + hdrlen <= MHLEN, ("tcphdr too big")); #endif /* * Grab a header mbuf, attaching a copy of data to * be transmitted, and initialize the header from * the template for sends on this connection. */ if (len) { if ((tp->t_flags & TF_FORCE) && len == 1) tcpstat.tcps_sndprobe++; else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { if (tp->snd_nxt == tp->snd_una) tp->snd_max_rexmt = tp->snd_max; tcpstat.tcps_sndrexmitpack++; tcpstat.tcps_sndrexmitbyte += len; } else { tcpstat.tcps_sndpack++; tcpstat.tcps_sndbyte += len; } #ifdef notyet if ((m = m_copypack(so->so_snd.ssb_mb, off, (int)len, max_linkhdr + hdrlen)) == NULL) { error = ENOBUFS; goto out; } /* * m_copypack left space for our hdr; use it. */ m->m_len += hdrlen; m->m_data -= hdrlen; #else #ifndef INET6 m = m_gethdr(MB_DONTWAIT, MT_HEADER); #else m = m_getl(hdrlen + max_linkhdr, MB_DONTWAIT, MT_HEADER, M_PKTHDR, NULL); #endif if (m == NULL) { error = ENOBUFS; goto out; } m->m_data += max_linkhdr; m->m_len = hdrlen; if (len <= MHLEN - hdrlen - max_linkhdr) { m_copydata(so->so_snd.ssb_mb, off, (int) len, mtod(m, caddr_t) + hdrlen); m->m_len += len; } else { m->m_next = m_copy(so->so_snd.ssb_mb, off, (int) len); if (m->m_next == NULL) { m_free(m); error = ENOBUFS; goto out; } } #endif /* * If we're sending everything we've got, set PUSH. * (This will keep happy those implementations which only * give data to the user when a buffer fills or * a PUSH comes in.) */ if (off + len == so->so_snd.ssb_cc) flags |= TH_PUSH; } else { if (tp->t_flags & TF_ACKNOW) tcpstat.tcps_sndacks++; else if (flags & (TH_SYN | TH_FIN | TH_RST)) tcpstat.tcps_sndctrl++; else if (SEQ_GT(tp->snd_up, tp->snd_una)) tcpstat.tcps_sndurg++; else tcpstat.tcps_sndwinup++; MGETHDR(m, MB_DONTWAIT, MT_HEADER); if (m == NULL) { error = ENOBUFS; goto out; } if (isipv6 && (hdrlen + max_linkhdr > MHLEN) && hdrlen <= MHLEN) MH_ALIGN(m, hdrlen); else m->m_data += max_linkhdr; m->m_len = hdrlen; } m->m_pkthdr.rcvif = (struct ifnet *)0; if (isipv6) { ip6 = mtod(m, struct ip6_hdr *); th = (struct tcphdr *)(ip6 + 1); tcp_fillheaders(tp, ip6, th); } else { ip = mtod(m, struct ip *); ipov = (struct ipovly *)ip; th = (struct tcphdr *)(ip + 1); /* this picks up the pseudo header (w/o the length) */ tcp_fillheaders(tp, ip, th); } /* * Fill in fields, remembering maximum advertised * window for use in delaying messages about window sizes. * If resending a FIN, be sure not to use a new sequence number. */ if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && tp->snd_nxt == tp->snd_max) tp->snd_nxt--; /* * If we are doing retransmissions, then snd_nxt will * not reflect the first unsent octet. For ACK only * packets, we do not want the sequence number of the * retransmitted packet, we want the sequence number * of the next unsent octet. So, if there is no data * (and no SYN or FIN), use snd_max instead of snd_nxt * when filling in ti_seq. But if we are in persist * state, snd_max might reflect one byte beyond the * right edge of the window, so use snd_nxt in that * case, since we know we aren't doing a retransmission. * (retransmit and persist are mutually exclusive...) */ if (len || (flags & (TH_SYN|TH_FIN)) || callout_active(tp->tt_persist)) th->th_seq = htonl(tp->snd_nxt); else th->th_seq = htonl(tp->snd_max); th->th_ack = htonl(tp->rcv_nxt); if (optlen) { bcopy(opt, th + 1, optlen); th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; } th->th_flags = flags; /* * Calculate receive window. Don't shrink window, * but avoid silly window syndrome. */ if (recvwin < (long)(so->so_rcv.ssb_hiwat / 4) && recvwin < (long)tp->t_maxseg) recvwin = 0; if (recvwin < (long)(tp->rcv_adv - tp->rcv_nxt)) recvwin = (long)(tp->rcv_adv - tp->rcv_nxt); if (recvwin > (long)TCP_MAXWIN << tp->rcv_scale) recvwin = (long)TCP_MAXWIN << tp->rcv_scale; th->th_win = htons((u_short) (recvwin>>tp->rcv_scale)); /* * Adjust the RXWIN0SENT flag - indicate that we have advertised * a 0 window. This may cause the remote transmitter to stall. This * flag tells soreceive() to disable delayed acknowledgements when * draining the buffer. This can occur if the receiver is attempting * to read more data then can be buffered prior to transmitting on * the connection. */ if (recvwin == 0) tp->t_flags |= TF_RXWIN0SENT; else tp->t_flags &= ~TF_RXWIN0SENT; if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { th->th_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); th->th_flags |= TH_URG; } else { /* * If no urgent pointer to send, then we pull * the urgent pointer to the left edge of the send window * so that it doesn't drift into the send window on sequence * number wraparound. */ tp->snd_up = tp->snd_una; /* drag it along */ } /* * Put TCP length in extended header, and then * checksum extended header and data. */ m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */ if (isipv6) { /* * ip6_plen is not need to be filled now, and will be filled * in ip6_output(). */ th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), sizeof(struct tcphdr) + optlen + len); } else { m->m_pkthdr.csum_flags = CSUM_TCP; m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); if (len + optlen) th->th_sum = in_addword(th->th_sum, htons((u_short)(optlen + len))); /* IP version must be set here for ipv4/ipv6 checking later */ KASSERT(ip->ip_v == IPVERSION, ("%s: IP version incorrect: %d", __func__, ip->ip_v)); } /* * In transmit state, time the transmission and arrange for * the retransmit. In persist state, just set snd_max. */ if (!(tp->t_flags & TF_FORCE) || !callout_active(tp->tt_persist)) { tcp_seq startseq = tp->snd_nxt; /* * Advance snd_nxt over sequence space of this segment. */ if (flags & (TH_SYN | TH_FIN)) { if (flags & TH_SYN) tp->snd_nxt++; if (flags & TH_FIN) { tp->snd_nxt++; tp->t_flags |= TF_SENTFIN; } } tp->snd_nxt += len; if (SEQ_GT(tp->snd_nxt, tp->snd_max)) { tp->snd_max = tp->snd_nxt; /* * Time this transmission if not a retransmission and * not currently timing anything. */ if (tp->t_rtttime == 0) { tp->t_rtttime = ticks; tp->t_rtseq = startseq; tcpstat.tcps_segstimed++; } } /* * Set retransmit timer if not currently set, * and not doing a pure ack or a keep-alive probe. * Initial value for retransmit timer is smoothed * round-trip time + 2 * round-trip time variance. * Initialize shift counter which is used for backoff * of retransmit time. */ if (!callout_active(tp->tt_rexmt) && tp->snd_nxt != tp->snd_una) { if (callout_active(tp->tt_persist)) { callout_stop(tp->tt_persist); tp->t_rxtshift = 0; } callout_reset(tp->tt_rexmt, tp->t_rxtcur, tcp_timer_rexmt, tp); } } else { /* * Persist case, update snd_max but since we are in * persist mode (no window) we do not update snd_nxt. */ int xlen = len; if (flags & TH_SYN) ++xlen; if (flags & TH_FIN) { ++xlen; tp->t_flags |= TF_SENTFIN; } if (SEQ_GT(tp->snd_nxt + xlen, tp->snd_max)) tp->snd_max = tp->snd_nxt + xlen; } #ifdef TCPDEBUG /* * Trace. */ if (so->so_options & SO_DEBUG) tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, void *), th, 0); #endif /* * Fill in IP length and desired time to live and * send to IP level. There should be a better way * to handle ttl and tos; we could keep them in * the template, but need a way to checksum without them. */ /* * m->m_pkthdr.len should have been set before cksum calcuration, * because in6_cksum() need it. */ if (isipv6) { /* * we separately set hoplimit for every segment, since the * user might want to change the value via setsockopt. * Also, desired default hop limit might be changed via * Neighbor Discovery. */ ip6->ip6_hlim = in6_selecthlim(inp, (inp->in6p_route.ro_rt ? inp->in6p_route.ro_rt->rt_ifp : NULL)); /* TODO: IPv6 IP6TOS_ECT bit on */ error = ip6_output(m, inp->in6p_outputopts, &inp->in6p_route, (so->so_options & SO_DONTROUTE), NULL, NULL, inp); } else { struct rtentry *rt; ip->ip_len = m->m_pkthdr.len; #ifdef INET6 if (INP_CHECK_SOCKAF(so, AF_INET6)) ip->ip_ttl = in6_selecthlim(inp, (inp->in6p_route.ro_rt ? inp->in6p_route.ro_rt->rt_ifp : NULL)); else #endif ip->ip_ttl = inp->inp_ip_ttl; /* XXX */ ip->ip_tos = inp->inp_ip_tos; /* XXX */ /* * See if we should do MTU discovery. * We do it only if the following are true: * 1) we have a valid route to the destination * 2) the MTU is not locked (if it is, * then discovery has been disabled) */ if (path_mtu_discovery && (rt = inp->inp_route.ro_rt) && (rt->rt_flags & RTF_UP) && !(rt->rt_rmx.rmx_locks & RTV_MTU)) ip->ip_off |= IP_DF; error = ip_output(m, inp->inp_options, &inp->inp_route, (so->so_options & SO_DONTROUTE), NULL, inp); } if (error) { /* * We know that the packet was lost, so back out the * sequence number advance, if any. */ if (!(tp->t_flags & TF_FORCE) || !callout_active(tp->tt_persist)) { /* * No need to check for TH_FIN here because * the TF_SENTFIN flag handles that case. */ if (!(flags & TH_SYN)) tp->snd_nxt -= len; } out: if (error == ENOBUFS) { /* * If we can't send, make sure there is something * to get us going again later. Persist state * is not necessarily right, but it is close enough. */ if (!callout_active(tp->tt_rexmt) && !callout_active(tp->tt_persist)) { tp->t_rxtshift = 0; tcp_setpersist(tp); } tcp_quench(inp, 0); return (0); } if (error == EMSGSIZE) { /* * ip_output() will have already fixed the route * for us. tcp_mtudisc() will, as its last action, * initiate retransmission, so it is important to * not do so here. */ tcp_mtudisc(inp, 0); return 0; } if ((error == EHOSTUNREACH || error == ENETDOWN) && TCPS_HAVERCVDSYN(tp->t_state)) { tp->t_softerror = error; return (0); } return (error); } tcpstat.tcps_sndtotal++; /* * Data sent (as far as we can tell). * If this advertises a larger window than any other segment, * then remember the size of the advertised window. * Any pending ACK has now been sent. */ if (recvwin > 0 && SEQ_GT(tp->rcv_nxt + recvwin, tp->rcv_adv)) tp->rcv_adv = tp->rcv_nxt + recvwin; tp->last_ack_sent = tp->rcv_nxt; tp->t_flags &= ~TF_ACKNOW; if (tcp_delack_enabled) callout_stop(tp->tt_delack); if (sendalot) goto again; return (0); } void tcp_setpersist(struct tcpcb *tp) { int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; int tt; if (callout_active(tp->tt_rexmt)) panic("tcp_setpersist: retransmit pending"); /* * Start/restart persistance timer. */ TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, TCPTV_PERSMAX); callout_reset(tp->tt_persist, tt, tcp_timer_persist, tp); if (tp->t_rxtshift < TCP_MAXRXTSHIFT) tp->t_rxtshift++; }