/* $OpenBSD: tcp_output.c,v 1.50 2002/05/16 14:10:51 kjc Exp $ */ /* $NetBSD: tcp_output.c,v 1.16 1997/06/03 16:17:09 kml Exp $ */ /* * Copyright (c) 1982, 1986, 1988, 1990, 1993 * 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. * * @(#)COPYRIGHT 1.1 (NRL) 17 January 1995 * * NRL grants permission for redistribution and use in source and binary * forms, with or without modification, of the software and documentation * created at NRL 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 acknowledgements: * This product includes software developed by the University of * California, Berkeley and its contributors. * This product includes software developed at the Information * Technology Division, US Naval Research Laboratory. * 4. Neither the name of the NRL nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL 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 NRL 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. * * The views and conclusions contained in the software and documentation * are those of the authors and should not be interpreted as representing * official policies, either expressed or implied, of the US Naval * Research Laboratory (NRL). */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define TCPOUTFLAGS #include #include #include #include #include #include #ifdef TUBA #include #include #endif #ifdef INET6 #include #endif /* INET6 */ #ifdef TCP_SIGNATURE #include #endif /* TCP_SIGNATURE */ #ifdef notyet extern struct mbuf *m_copypack(); #endif #ifdef TCP_SACK extern int tcprexmtthresh; #endif #ifdef TCP_SACK #ifdef TCP_SACK_DEBUG void tcp_print_holes(struct tcpcb *tp); void tcp_print_holes(struct tcpcb *tp) { struct sackhole *p = tp->snd_holes; if (p == 0) return; printf("Hole report: start--end dups rxmit\n"); while (p) { printf("%x--%x d %d r %x\n", p->start, p->end, p->dups, p->rxmit); p = p->next; } printf("\n"); } #endif /* TCP_SACK_DEBUG */ /* * Returns pointer to a sackhole if there are any pending retransmissions; * NULL otherwise. */ struct sackhole * tcp_sack_output(struct tcpcb *tp) { struct sackhole *p; if (tp->sack_disable) return (NULL); p = tp->snd_holes; while (p) { #ifndef TCP_FACK if (p->dups >= tcprexmtthresh && SEQ_LT(p->rxmit, p->end)) { #else /* In FACK, if p->dups is less than tcprexmtthresh, but * snd_fack advances more than tcprextmtthresh * tp->t_maxseg, * tcp_input() will try fast retransmit. This forces output. */ if ((p->dups >= tcprexmtthresh || tp->t_dupacks == tcprexmtthresh) && SEQ_LT(p->rxmit, p->end)) { #endif /* TCP_FACK */ if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */ p = p->next; continue; } #ifdef TCP_SACK_DEBUG if (p) tcp_print_holes(tp); #endif return (p); } p = p->next; } return (NULL); } /* * After a timeout, the SACK list may be rebuilt. This SACK information * should be used to avoid retransmitting SACKed data. This function * traverses the SACK list to see if snd_nxt should be moved forward. */ void tcp_sack_adjust(struct tcpcb *tp) { struct sackhole *cur = tp->snd_holes; if (cur == NULL) return; /* No holes */ if (SEQ_GEQ(tp->snd_nxt, tp->rcv_lastsack)) return; /* We're already beyond any SACKed blocks */ /* * Two cases for which we want to advance snd_nxt: * i) snd_nxt lies between end of one hole and beginning of another * ii) snd_nxt lies between end of last hole and rcv_lastsack */ while (cur->next) { if (SEQ_LT(tp->snd_nxt, cur->end)) return; if (SEQ_GEQ(tp->snd_nxt, cur->next->start)) cur = cur->next; else { tp->snd_nxt = cur->next->start; return; } } if (SEQ_LT(tp->snd_nxt, cur->end)) return; tp->snd_nxt = tp->rcv_lastsack; return; } #endif /* TCP_SACK */ /* * Tcp output routine: figure out what should be sent and send it. */ int tcp_output(tp) register struct tcpcb *tp; { register struct socket *so = tp->t_inpcb->inp_socket; register long len, win; int off, flags, error; register struct mbuf *m; register struct tcphdr *th; u_char opt[MAX_TCPOPTLEN]; unsigned int optlen, hdrlen; int idle, sendalot = 0; #ifdef TCP_SACK int i, sack_rxmit = 0; struct sackhole *p; #endif #if defined(TCP_SACK) int maxburst = TCP_MAXBURST; #endif #ifdef TCP_SIGNATURE unsigned int sigoff; #endif /* TCP_SIGNATURE */ #ifdef TCP_ECN int needect; #endif #if defined(TCP_SACK) && defined(TCP_SIGNATURE) && defined(DIAGNOSTIC) if (!tp->sack_disable && (tp->t_flags & TF_SIGNATURE)) return (EINVAL); #endif /* defined(TCP_SACK) && defined(TCP_SIGNATURE) && defined(DIAGNOSTIC) */ /* * 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. */ idle = (tp->snd_max == tp->snd_una); if (idle && (tcp_now - tp->t_rcvtime) >= tp->t_rxtcur) /* * We have been idle for "a while" and no acks are * expected to clock out any data we send -- * slow start to get ack "clock" running again. */ tp->snd_cwnd = tp->t_maxseg; again: #ifdef TCP_SACK /* * If we've recently taken a timeout, snd_max will be greater than * snd_nxt. There may be SACK information that allows us to avoid * resending already delivered data. Adjust snd_nxt accordingly. */ if (!tp->sack_disable && SEQ_LT(tp->snd_nxt, tp->snd_max)) tcp_sack_adjust(tp); #endif off = tp->snd_nxt - tp->snd_una; #if defined(TCP_SACK) && defined(TCP_FACK) /* Normally, sendable data is limited by off < tp->snd_cwnd. * But in FACK, sendable data is limited by snd_awnd < snd_cwnd, * regardless of offset. */ if (!tp->sack_disable && (tp->t_dupacks > tcprexmtthresh)) win = tp->snd_wnd; else #endif win = ulmin(tp->snd_wnd, tp->snd_cwnd); flags = tcp_outflags[tp->t_state]; #ifdef TCP_SACK /* * Send any SACK-generated retransmissions. If we're explicitly trying * to send out new data (when sendalot is 1), bypass this function. * If we retransmit in fast recovery mode, decrement snd_cwnd, since * we're replacing a (future) new transmission with a retransmission * now, and we previously incremented snd_cwnd in tcp_input(). */ if (!tp->sack_disable && !sendalot) { if (tp->t_dupacks >= tcprexmtthresh && (p = tcp_sack_output(tp))) { off = p->rxmit - tp->snd_una; sack_rxmit = 1; #if 0 /* Coalesce holes into a single retransmission */ #endif len = min(tp->t_maxseg, p->end - p->rxmit); #ifndef TCP_FACK /* in FACK, hold snd_cwnd constant during recovery */ if (SEQ_LT(tp->snd_una, tp->snd_last)) tp->snd_cwnd -= tp->t_maxseg; #endif } } #endif /* TCP_SACK */ sendalot = 0; /* * 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_force) { if (win == 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 unset 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.sb_cc) flags &= ~TH_FIN; win = 1; } else { TCP_TIMER_DISARM(tp, TCPT_PERSIST); tp->t_rxtshift = 0; } } #ifdef TCP_SACK if (!sack_rxmit) { #endif len = ulmin(so->so_snd.sb_cc, win) - off; #if defined(TCP_SACK) && defined(TCP_FACK) /* * If we're in fast recovery (SEQ_GT(tp->snd_last, tp->snd_una)), and * amount of outstanding data (snd_awnd) is >= snd_cwnd, then * do not send data (like zero window conditions) */ if (!tp->sack_disable && len && SEQ_GT(tp->snd_last, tp->snd_una) && (tp->snd_awnd >= tp->snd_cwnd)) len = 0; #endif /* TCP_FACK */ #ifdef TCP_SACK } #endif if (len < 0) { /* * If FIN has been sent but not acked, * but we haven't been called to retransmit, * len will be -1. 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 (win == 0) { TCP_TIMER_DISARM(tp, TCPT_REXMT); tp->t_rxtshift = 0; tp->snd_nxt = tp->snd_una; if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) tcp_setpersist(tp); } } if (len > tp->t_maxseg) { len = tp->t_maxseg; sendalot = 1; } if (off + len < so->so_snd.sb_cc) flags &= ~TH_FIN; win = sbspace(&so->so_rcv); /* * Sender silly window avoidance. If connection is idle * and can send all data, a maximum segment, * at least a maximum default-size segment do it, * or are forced, do it; otherwise don't bother. * If peer's buffer is tiny, then send * when window is at least half open. * If retransmitting (possibly after persist timer forced us * to send into a small window), then must resend. */ if (len) { if (len == tp->t_maxseg) goto send; if ((idle || tp->t_flags & TF_NODELAY) && len + off >= so->so_snd.sb_cc) goto send; if (tp->t_force) goto send; if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0) goto send; if (SEQ_LT(tp->snd_nxt, tp->snd_max)) goto send; #ifdef TCP_SACK if (sack_rxmit) goto send; #endif } /* * 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 (win > 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 = lmin(win, (long)TCP_MAXWIN << tp->rcv_scale) - (tp->rcv_adv - tp->rcv_nxt); if (adv >= (long) (2 * tp->t_maxseg)) goto send; if (2 * adv >= (long) so->so_rcv.sb_hiwat) goto send; } /* * Send if we owe peer an ACK. */ if (tp->t_flags & TF_ACKNOW) goto send; if (flags & (TH_SYN|TH_RST)) 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, or we're retransmitting the FIN, * then we need to send. */ if (flags & TH_FIN && ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una)) goto send; #ifdef TCP_SACK /* * In SACK, it is possible for tcp_output to fail to send a segment * after the retransmission timer has been turned off. Make sure * that the retransmission timer is set. */ if (SEQ_GT(tp->snd_max, tp->snd_una) && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); return (0); } #endif /* TCP_SACK */ /* * 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 * * tp->t_timer[TCPT_PERSIST] * is set when we are in persist state. * tp->t_force * is set when we are called to send a persist packet. * tp->t_timer[TCPT_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.sb_cc && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 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(network header) + sizeof(struct tcphdr + * optlen <= MHLEN */ optlen = 0; switch (tp->pf) { case 0: /*default to PF_INET*/ #ifdef INET case PF_INET: hdrlen = sizeof(struct ip) + sizeof(struct tcphdr); break; #endif /* INET */ #ifdef INET6 case PF_INET6: hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); break; #endif /* INET6 */ default: return (EPFNOSUPPORT); } if (flags & TH_SYN) { tp->snd_nxt = tp->iss; if ((tp->t_flags & TF_NOOPT) == 0) { u_int16_t mss; opt[0] = TCPOPT_MAXSEG; opt[1] = 4; mss = htons((u_int16_t) tcp_mss(tp, 0)); bcopy((caddr_t)&mss, (caddr_t)(opt + 2), sizeof(mss)); optlen = 4; if (flags & TH_ACK) tcp_mss_update(tp); #ifdef TCP_SACK /* * If this is the first SYN of connection (not a SYN * ACK), include SACK_PERMIT_HDR option. If this is a * SYN ACK, include SACK_PERMIT_HDR option if peer has * already done so. */ if (!tp->sack_disable && ((flags & TH_ACK) == 0 || (tp->t_flags & TF_SACK_PERMIT))) { *((u_int32_t *) (opt + optlen)) = htonl(TCPOPT_SACK_PERMIT_HDR); optlen += 4; } #endif if ((tp->t_flags & TF_REQ_SCALE) && ((flags & TH_ACK) == 0 || (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; } } } /* * 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) == 0 && ((flags & (TH_SYN|TH_ACK)) == TH_SYN || (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(tcp_now); *lp = htonl(tp->ts_recent); optlen += TCPOLEN_TSTAMP_APPA; } #ifdef TCP_SIGNATURE if (tp->t_flags & TF_SIGNATURE) { u_int8_t *bp = (u_int8_t *)(opt + optlen); /* Send signature option */ *(bp++) = TCPOPT_SIGNATURE; *(bp++) = TCPOLEN_SIGNATURE; sigoff = optlen + 2; { unsigned int i; for (i = 0; i < 16; i++) *(bp++) = 0; } optlen += TCPOLEN_SIGNATURE; /* Pad options list to the next 32 bit boundary and * terminate it. */ *bp++ = TCPOPT_NOP; *bp++ = TCPOPT_EOL; optlen += 2; } #endif /* TCP_SIGNATURE */ #ifdef TCP_SACK /* * Send SACKs if necessary. This should be the last option processed. * Only as many SACKs are sent as are permitted by the maximum options * size. No more than three SACKs are sent. */ if (!tp->sack_disable && tp->t_state == TCPS_ESTABLISHED && (tp->t_flags & (TF_SACK_PERMIT|TF_NOOPT)) == TF_SACK_PERMIT && tp->rcv_numsacks) { u_int32_t *lp = (u_int32_t *)(opt + optlen); u_int32_t *olp = lp++; int count = 0; /* actual number of SACKs inserted */ int maxsack = (MAX_TCPOPTLEN - (optlen + 4))/TCPOLEN_SACK; maxsack = min(maxsack, TCP_MAX_SACK); for (i = 0; (i < tp->rcv_numsacks && count < maxsack); i++) { struct sackblk sack = tp->sackblks[i]; if (sack.start == 0 && sack.end == 0) continue; *lp++ = htonl(sack.start); *lp++ = htonl(sack.end); count++; } *olp = htonl(TCPOPT_SACK_HDR|(TCPOLEN_SACK*count+2)); optlen += TCPOLEN_SACK*count + 4; /* including leading NOPs */ } #endif /* TCP_SACK */ #ifdef DIAGNOSTIC if (optlen > MAX_TCPOPTLEN) panic("tcp_output: options too long"); #endif /* DIAGNOSTIC */ hdrlen += optlen; /* * Adjust data length if insertion of options will * bump the packet length beyond the t_maxopd length. */ if (len > tp->t_maxopd - optlen) { len = tp->t_maxopd - optlen; sendalot = 1; flags &= ~TH_FIN; } #ifdef DIAGNOSTIC if (max_linkhdr + hdrlen > MCLBYTES) panic("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_force && len == 1) tcpstat.tcps_sndprobe++; else if (SEQ_LT(tp->snd_nxt, 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.sb_mb, off, (int)len, max_linkhdr + hdrlen)) == 0) { error = ENOBUFS; goto out; } /* * m_copypack left space for our hdr; use it. */ m->m_len += hdrlen; m->m_data -= hdrlen; #else MGETHDR(m, M_DONTWAIT, MT_HEADER); if (m != NULL) { MCLGET(m, M_DONTWAIT); if ((m->m_flags & M_EXT) == 0) { m_freem(m); m = NULL; } } if (m == NULL) { error = ENOBUFS; goto out; } m->m_data += max_linkhdr; m->m_len = hdrlen; if (len <= MCLBYTES - hdrlen - max_linkhdr) { m_copydata(so->so_snd.sb_mb, off, (int) len, mtod(m, caddr_t) + hdrlen); m->m_len += len; } else { m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len); if (m->m_next == 0) { (void) 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.sb_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, M_DONTWAIT, MT_HEADER); if (m != NULL) { MCLGET(m, M_DONTWAIT); if ((m->m_flags & M_EXT) == 0) { m_freem(m); m = NULL; } } if (m == NULL) { error = ENOBUFS; goto out; } m->m_data += max_linkhdr; m->m_len = hdrlen; } m->m_pkthdr.rcvif = (struct ifnet *)0; if (!tp->t_template) panic("tcp_output"); #ifdef DIAGNOSTIC if (tp->t_template->m_len != hdrlen - optlen) panic("tcp_output: template len != hdrlen - optlen"); #endif /* DIAGNOSTIC */ bcopy(mtod(tp->t_template, caddr_t), mtod(m, caddr_t), tp->t_template->m_len); th = (struct tcphdr *)(mtod(m, caddr_t) + tp->t_template->m_len - sizeof(struct tcphdr)); /* * 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)) || TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) th->th_seq = htonl(tp->snd_nxt); else th->th_seq = htonl(tp->snd_max); #ifdef TCP_SACK if (sack_rxmit) { /* * If sendalot was turned on (due to option stuffing), turn it * off. Properly set th_seq field. Advance the ret'x pointer * by len. */ if (sendalot) sendalot = 0; th->th_seq = htonl(p->rxmit); p->rxmit += len; #if defined(TCP_SACK) && defined(TCP_FACK) tp->retran_data += len; #endif /* TCP_FACK */ } #endif /* TCP_SACK */ th->th_ack = htonl(tp->rcv_nxt); if (optlen) { bcopy((caddr_t)opt, (caddr_t)(th + 1), optlen); th->th_off = (sizeof (struct tcphdr) + optlen) >> 2; } #ifdef TCP_ECN if (tcp_do_ecn) { /* * if we have received congestion experienced segs, * set ECE bit. */ if (tp->t_flags & TF_RCVD_CE) { flags |= TH_ECE; tcpstat.tcps_ecn_sndece++; } if (!(tp->t_flags & TF_DISABLE_ECN)) { /* * if this is a SYN seg, set ECE and CWR. * set only ECE for SYN-ACK if peer supports ECN. */ if ((flags & (TH_SYN|TH_ACK)) == TH_SYN) flags |= (TH_ECE|TH_CWR); else if ((tp->t_flags & TF_ECN_PERMIT) && (flags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) flags |= TH_ECE; } /* * if we have reduced the congestion window, notify * the peer by setting CWR bit. */ if ((tp->t_flags & TF_ECN_PERMIT) && (tp->t_flags & TF_SEND_CWR)) { flags |= TH_CWR; tp->t_flags &= ~TF_SEND_CWR; tcpstat.tcps_ecn_sndcwr++; } } #endif th->th_flags = flags; /* * Calculate receive window. Don't shrink window, * but avoid silly window syndrome. */ if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)tp->t_maxseg) win = 0; if (win > (long)TCP_MAXWIN << tp->rcv_scale) win = (long)TCP_MAXWIN << tp->rcv_scale; if (win < (long)(tp->rcv_adv - tp->rcv_nxt)) win = (long)(tp->rcv_adv - tp->rcv_nxt); if (flags & TH_RST) win = 0; th->th_win = htons((u_int16_t) (win>>tp->rcv_scale)); if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { u_int32_t urp = tp->snd_up - tp->snd_nxt; if (urp > IP_MAXPACKET) urp = IP_MAXPACKET; th->th_urp = htons((u_int16_t)urp); 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 */ #ifdef TCP_SIGNATURE if (tp->t_flags & TF_SIGNATURE) { MD5_CTX ctx; union sockaddr_union sa; struct tdb *tdb; bzero(&sa, sizeof(union sockaddr_union)); switch (tp->pf) { case 0: /*default to PF_INET*/ #ifdef INET case AF_INET: sa.sa.sa_len = sizeof(struct sockaddr_in); sa.sa.sa_family = AF_INET; sa.sin.sin_addr = mtod(m, struct ip *)->ip_dst; break; #endif /* INET */ #ifdef INET6 case AF_INET6: sa.sa.sa_len = sizeof(struct sockaddr_in6); sa.sa.sa_family = AF_INET6; sa.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst; break; #endif /* INET6 */ } /* XXX gettdb() should really be called at spltdb(). */ /* XXX this is splsoftnet(), currently they are the same. */ tdb = gettdb(0, &sa, IPPROTO_TCP); if (tdb == NULL) return (EPERM); MD5Init(&ctx); switch (tp->pf) { case 0: /*default to PF_INET*/ #ifdef INET case AF_INET: { struct ippseudo ippseudo; struct ipovly *ipovly; ipovly = mtod(m, struct ipovly *); ippseudo.ippseudo_src = ipovly->ih_src; ippseudo.ippseudo_dst = ipovly->ih_dst; ippseudo.ippseudo_pad = 0; ippseudo.ippseudo_p = IPPROTO_TCP; ippseudo.ippseudo_len = ipovly->ih_len + len + optlen; MD5Update(&ctx, (char *)&ippseudo, sizeof(struct ippseudo)); MD5Update(&ctx, mtod(m, caddr_t) + sizeof(struct ip), sizeof(struct tcphdr)); } break; #endif /* INET */ #ifdef INET6 case AF_INET6: { static int printed = 0; if (!printed) { printf("error: TCP MD5 support for " "IPv6 not yet implemented.\n"); printed = 1; } } break; #endif /* INET6 */ } if (len && m_apply(m, hdrlen, len, tcp_signature_apply, (caddr_t)&ctx)) return (EINVAL); MD5Update(&ctx, tdb->tdb_amxkey, tdb->tdb_amxkeylen); MD5Final(mtod(m, caddr_t) + hdrlen - optlen + sigoff, &ctx); } #endif /* TCP_SIGNATURE */ /* * Put TCP length in extended header, and then * checksum extended header and data. */ switch (tp->pf) { case 0: /*default to PF_INET*/ #ifdef INET case AF_INET: /* Defer checksumming until later (ip_output() or hardware) */ m->m_pkthdr.csum |= M_TCPV4_CSUM_OUT; if (len + optlen) th->th_sum = in_cksum_addword(th->th_sum, htons((u_int16_t)(len + optlen))); break; #endif /* INET */ #ifdef INET6 case AF_INET6: m->m_pkthdr.len = hdrlen + len; th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), hdrlen - sizeof(struct ip6_hdr) + len); break; #endif /* INET6 */ } /* * In transmit state, time the transmission and arrange for * the retransmit. In persist state, just set snd_max. */ if (tp->t_force == 0 || TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { 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; } } #ifdef TCP_SACK if (!tp->sack_disable) { if (sack_rxmit && (p->rxmit != tp->snd_nxt)) { goto timer; } } #endif 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 = tcp_now; tp->t_rtseq = startseq; tcpstat.tcps_segstimed++; } } /* * Set retransmit timer if not currently set, * and not doing an 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. */ #ifdef TCP_SACK timer: if (!tp->sack_disable && sack_rxmit && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && tp->snd_nxt != tp->snd_max) { TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) { TCP_TIMER_DISARM(tp, TCPT_PERSIST); tp->t_rxtshift = 0; } } #endif if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && tp->snd_nxt != tp->snd_una) { TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) { TCP_TIMER_DISARM(tp, TCPT_PERSIST); tp->t_rxtshift = 0; } } } else if (SEQ_GT(tp->snd_nxt + len, tp->snd_max)) tp->snd_max = tp->snd_nxt + len; /* * Trace. */ if (so->so_options & SO_DEBUG) tcp_trace(TA_OUTPUT, tp->t_state, tp, mtod(m, caddr_t), 0, len); /* * 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 = hdrlen + len; #ifdef TCP_ECN /* * if peer is ECN capable, set the ECT bit in the IP header. * but don't set ECT for a pure ack, a retransmit or a window probe. */ needect = 0; if (tcp_do_ecn && (tp->t_flags & TF_ECN_PERMIT)) { if (len == 0 || SEQ_LT(tp->snd_nxt, tp->snd_max) || (tp->t_force && len == 1)) { /* don't set ECT */ } else { needect = 1; tcpstat.tcps_ecn_sndect++; } } #endif switch (tp->pf) { case 0: /*default to PF_INET*/ #ifdef INET case AF_INET: { struct ip *ip; ip = mtod(m, struct ip *); ip->ip_len = m->m_pkthdr.len; ip->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl; ip->ip_tos = tp->t_inpcb->inp_ip.ip_tos; #ifdef TCP_ECN if (needect) ip->ip_tos |= IPTOS_ECN_ECT0; #endif } error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route, (ip_mtudisc ? IP_MTUDISC : 0) | (so->so_options & SO_DONTROUTE), 0, tp->t_inpcb); break; #endif /* INET */ #ifdef INET6 case AF_INET6: { struct ip6_hdr *ipv6; ipv6 = mtod(m, struct ip6_hdr *); ipv6->ip6_plen = m->m_pkthdr.len - sizeof(struct ip6_hdr); ipv6->ip6_nxt = IPPROTO_TCP; ipv6->ip6_hlim = in6_selecthlim(tp->t_inpcb, NULL); #ifdef TCP_ECN if (needect) ipv6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); #endif } error = ip6_output(m, tp->t_inpcb->inp_outputopts6, &tp->t_inpcb->inp_route6, (so->so_options & SO_DONTROUTE), NULL, NULL); break; #endif /* INET6 */ #ifdef TUBA case AF_ISO: if (tp->t_tuba_pcb) error = tuba_output(m, tp); break; #endif /* TUBA */ } #if defined(TCP_SACK) && defined(TCP_FACK) /* Update snd_awnd to reflect the new data that was sent. */ tp->snd_awnd = tcp_seq_subtract(tp->snd_max, tp->snd_fack) + tp->retran_data; #endif /* defined(TCP_SACK) && defined(TCP_FACK) */ if (error) { out: if (error == ENOBUFS) { tcp_quench(tp->t_inpcb, 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(tp->t_inpcb, 0); return (0); } if ((error == EHOSTUNREACH || error == ENETDOWN) && TCPS_HAVERCVDSYN(tp->t_state)) { tp->t_softerror = error; return (0); } /* Restart the delayed ACK timer, if necessary. */ if (tp->t_flags & TF_DELACK) TCP_RESTART_DELACK(tp); return (error); } tcpstat.tcps_sndtotal++; if (tp->t_flags & TF_DELACK) tcpstat.tcps_delack++; /* * 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 (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) tp->rcv_adv = tp->rcv_nxt + win; tp->last_ack_sent = tp->rcv_nxt; tp->t_flags &= ~TF_ACKNOW; TCP_CLEAR_DELACK(tp); #if defined(TCP_SACK) if (sendalot && --maxburst) #else if (sendalot) #endif goto again; return (0); } void tcp_setpersist(struct tcpcb *tp) { int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; int nticks; if (TCP_TIMER_ISARMED(tp, TCPT_REXMT)) panic("tcp_output REXMT"); /* * Start/restart persistance timer. */ if (t < tp->t_rttmin) t = tp->t_rttmin; TCPT_RANGESET(nticks, t * tcp_backoff[tp->t_rxtshift], TCPTV_PERSMIN, TCPTV_PERSMAX); TCP_TIMER_ARM(tp, TCPT_PERSIST, nticks); if (tp->t_rxtshift < TCP_MAXRXTSHIFT) tp->t_rxtshift++; }