/* $NetBSD: tcp_output.c,v 1.100 2003/08/22 21:53:05 itojun Exp $ */ /* * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. * 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. Neither the name of the 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 PROJECT 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 PROJECT 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). */ /*- * Copyright (c) 1997, 1998, 2001 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation * Facility, NASA Ames Research Center. * * 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 NetBSD * Foundation, Inc. and its contributors. * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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. 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 */ #include __KERNEL_RCSID(0, "$NetBSD: tcp_output.c,v 1.100 2003/08/22 21:53:05 itojun Exp $"); #include "opt_inet.h" #include "opt_ipsec.h" #include "opt_tcp_debug.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef INET6 #ifndef INET #include #endif #include #include #include #include #include #endif #ifdef FAST_IPSEC #include #endif /* FAST_IPSEC*/ #ifdef IPSEC #include #endif #include #define TCPOUTFLAGS #include #include #include #include #include #include #ifdef notyet extern struct mbuf *m_copypack(); #endif #define MAX_TCPOPTLEN 32 /* max # bytes that go in options */ /* * Knob to enable Congestion Window Monitoring, and control the * the burst size it allows. Default burst is 4 packets, per * the Internet draft. */ int tcp_cwm = 0; int tcp_cwm_burstsize = 4; #ifdef TCP_OUTPUT_COUNTERS #include extern struct evcnt tcp_output_bigheader; extern struct evcnt tcp_output_copysmall; extern struct evcnt tcp_output_copybig; extern struct evcnt tcp_output_refbig; #define TCP_OUTPUT_COUNTER_INCR(ev) (ev)->ev_count++ #else #define TCP_OUTPUT_COUNTER_INCR(ev) /* nothing */ #endif /* TCP_OUTPUT_COUNTERS */ static #ifndef GPROF __inline #endif void tcp_segsize(struct tcpcb *tp, int *txsegsizep, int *rxsegsizep) { #ifdef INET struct inpcb *inp = tp->t_inpcb; #endif #ifdef INET6 struct in6pcb *in6p = tp->t_in6pcb; #endif struct socket *so = NULL; struct rtentry *rt; struct ifnet *ifp; int size; int iphlen; int optlen; #ifdef DIAGNOSTIC if (tp->t_inpcb && tp->t_in6pcb) panic("tcp_segsize: both t_inpcb and t_in6pcb are set"); #endif switch (tp->t_family) { #ifdef INET case AF_INET: iphlen = sizeof(struct ip); break; #endif #ifdef INET6 case AF_INET6: iphlen = sizeof(struct ip6_hdr); break; #endif default: size = tcp_mssdflt; goto out; } rt = NULL; #ifdef INET if (inp) { rt = in_pcbrtentry(inp); so = inp->inp_socket; } #endif #ifdef INET6 if (in6p) { rt = in6_pcbrtentry(in6p); so = in6p->in6p_socket; } #endif if (rt == NULL) { size = tcp_mssdflt; goto out; } ifp = rt->rt_ifp; size = tcp_mssdflt; if (tp->t_mtudisc && rt->rt_rmx.rmx_mtu != 0) size = rt->rt_rmx.rmx_mtu - iphlen - sizeof(struct tcphdr); else if (ifp->if_flags & IFF_LOOPBACK) size = ifp->if_mtu - iphlen - sizeof(struct tcphdr); #ifdef INET else if (inp && tp->t_mtudisc) size = ifp->if_mtu - iphlen - sizeof(struct tcphdr); else if (inp && in_localaddr(inp->inp_faddr)) size = ifp->if_mtu - iphlen - sizeof(struct tcphdr); #endif #ifdef INET6 else if (in6p) { #ifdef INET if (IN6_IS_ADDR_V4MAPPED(&in6p->in6p_faddr)) { /* mapped addr case */ struct in_addr d; bcopy(&in6p->in6p_faddr.s6_addr32[3], &d, sizeof(d)); if (tp->t_mtudisc || in_localaddr(d)) size = ifp->if_mtu - iphlen - sizeof(struct tcphdr); } else #endif { /* * for IPv6, path MTU discovery is always turned on, * or the node must use packet size <= 1280. */ size = tp->t_mtudisc ? IN6_LINKMTU(ifp) : IPV6_MMTU; size -= (iphlen + sizeof(struct tcphdr)); } } #endif out: /* * Now we must make room for whatever extra TCP/IP options are in * the packet. */ optlen = tcp_optlen(tp); /* * XXX tp->t_ourmss should have the right size, but without this code * fragmentation will occur... need more investigation */ #ifdef INET if (inp) { #if defined(IPSEC) || defined(FAST_IPSEC) optlen += ipsec4_hdrsiz_tcp(tp); #endif optlen += ip_optlen(inp); } #endif #ifdef INET6 #ifdef INET if (in6p && tp->t_family == AF_INET) { #if defined(IPSEC) || defined(FAST_IPSEC) optlen += ipsec4_hdrsiz_tcp(tp); #endif /* XXX size -= ip_optlen(in6p); */ } else #endif if (in6p && tp->t_family == AF_INET6) { #ifdef IPSEC optlen += ipsec6_hdrsiz_tcp(tp); #endif optlen += ip6_optlen(in6p); } #endif size -= optlen; /* * *rxsegsizep holds *estimated* inbound segment size (estimation * assumes that path MTU is the same for both ways). this is only * for silly window avoidance, do not use the value for other purposes. * * ipseclen is subtracted from both sides, this may not be right. * I'm not quite sure about this (could someone comment). */ *txsegsizep = min(tp->t_peermss - optlen, size); /* * Never send more than half a buffer full. This insures that we can * always keep 2 packets on the wire, no matter what SO_SNDBUF is, and * therefore acks will never be delayed unless we run out of data to * transmit. */ if (so) *txsegsizep = min(so->so_snd.sb_hiwat >> 1, *txsegsizep); *rxsegsizep = min(tp->t_ourmss - optlen, size); if (*txsegsizep != tp->t_segsz) { /* * If the new segment size is larger, we don't want to * mess up the congestion window, but if it is smaller * we'll have to reduce the congestion window to ensure * that we don't get into trouble with initial windows * and the rest. In any case, if the segment size * has changed, chances are the path has, too, and * our congestion window will be different. */ if (*txsegsizep < tp->t_segsz) { tp->snd_cwnd = max((tp->snd_cwnd / tp->t_segsz) * *txsegsizep, *txsegsizep); tp->snd_ssthresh = max((tp->snd_ssthresh / tp->t_segsz) * *txsegsizep, *txsegsizep); } tp->t_segsz = *txsegsizep; } } static #ifndef GPROF __inline #endif int tcp_build_datapkt(struct tcpcb *tp, struct socket *so, int off, long len, int hdrlen, struct mbuf **mp) { struct mbuf *m, *m0; 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) return (ENOBUFS); /* * 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 (__predict_false(m == NULL)) return (ENOBUFS); MCLAIM(m, &tcp_tx_mowner); /* * XXX Because other code assumes headers will fit in * XXX one header mbuf. * * (This code should almost *never* be run.) */ if (__predict_false((max_linkhdr + hdrlen) > MHLEN)) { TCP_OUTPUT_COUNTER_INCR(&tcp_output_bigheader); MCLGET(m, M_DONTWAIT); if ((m->m_flags & M_EXT) == 0) { m_freem(m); return (ENOBUFS); } } m->m_data += max_linkhdr; m->m_len = hdrlen; /* * To avoid traversing the whole sb_mb chain for correct * data to send, remember last sent mbuf, its offset and * the sent size. When called the next time, see if the * data to send is the directly following the previous * transfer. This is important for large TCP windows. */ #ifdef FAST_MBSEARCH if (off == 0 || (tp->t_lastoff + tp->t_lastlen) != off) { #else if (1) { #endif /* * Either a new packet or a retransmit. * Start from the beginning. */ tp->t_lastm = so->so_snd.sb_mb; tp->t_inoff = off; } else tp->t_inoff += tp->t_lastlen; /* Traverse forward to next packet */ while (tp->t_inoff > 0) { if (tp->t_lastm == NULL) panic("tp->t_lastm == NULL"); if (tp->t_inoff < tp->t_lastm->m_len) break; tp->t_inoff -= tp->t_lastm->m_len; tp->t_lastm = tp->t_lastm->m_next; } tp->t_lastoff = off; tp->t_lastlen = len; m0 = tp->t_lastm; off = tp->t_inoff; if (len <= M_TRAILINGSPACE(m)) { m_copydata(m0, off, (int) len, mtod(m, caddr_t) + hdrlen); m->m_len += len; TCP_OUTPUT_COUNTER_INCR(&tcp_output_copysmall); } else { m->m_next = m_copy(m0, off, (int) len); if (m->m_next == NULL) { m_freem(m); return (ENOBUFS); } #ifdef TCP_OUTPUT_COUNTERS if (m->m_next->m_flags & M_EXT) TCP_OUTPUT_COUNTER_INCR(&tcp_output_refbig); else TCP_OUTPUT_COUNTER_INCR(&tcp_output_copybig); #endif /* TCP_OUTPUT_COUNTERS */ } #endif *mp = m; return (0); } /* * Tcp output routine: figure out what should be sent and send it. */ int tcp_output(tp) struct tcpcb *tp; { struct socket *so; struct route *ro; long len, win; int off, flags, error; struct mbuf *m; struct ip *ip; #ifdef INET6 struct ip6_hdr *ip6; #endif struct tcphdr *th; u_char opt[MAX_TCPOPTLEN]; unsigned optlen, hdrlen; int idle, sendalot, txsegsize, rxsegsize; int maxburst = TCP_MAXBURST; int af; /* address family on the wire */ int iphdrlen; #ifdef DIAGNOSTIC if (tp->t_inpcb && tp->t_in6pcb) panic("tcp_output: both t_inpcb and t_in6pcb are set"); #endif so = NULL; ro = NULL; if (tp->t_inpcb) { so = tp->t_inpcb->inp_socket; ro = &tp->t_inpcb->inp_route; } #ifdef INET6 else if (tp->t_in6pcb) { so = tp->t_in6pcb->in6p_socket; ro = (struct route *)&tp->t_in6pcb->in6p_route; } #endif switch (af = tp->t_family) { #ifdef INET case AF_INET: if (tp->t_inpcb) break; #ifdef INET6 /* mapped addr case */ if (tp->t_in6pcb) break; #endif return EINVAL; #endif #ifdef INET6 case AF_INET6: if (tp->t_in6pcb) break; return EINVAL; #endif default: return EAFNOSUPPORT; } tcp_segsize(tp, &txsegsize, &rxsegsize); idle = (tp->snd_max == tp->snd_una); /* * Restart Window computation. From draft-floyd-incr-init-win-03: * * Optionally, a TCP MAY set the restart window to the * minimum of the value used for the initial window and * the current value of cwnd (in other words, using a * larger value for the restart window should never increase * the size of cwnd). */ if (tcp_cwm) { /* * Hughes/Touch/Heidemann Congestion Window Monitoring. * Count the number of packets currently pending * acknowledgement, and limit our congestion window * to a pre-determined allowed burst size plus that count. * This prevents bursting once all pending packets have * been acknowledged (i.e. transmission is idle). * * XXX Link this to Initial Window? */ tp->snd_cwnd = min(tp->snd_cwnd, (tcp_cwm_burstsize * txsegsize) + (tp->snd_nxt - tp->snd_una)); } else { 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. */ int ss = tcp_init_win; #ifdef INET if (tp->t_inpcb && in_localaddr(tp->t_inpcb->inp_faddr)) ss = tcp_init_win_local; #endif #ifdef INET6 if (tp->t_in6pcb && in6_localaddr(&tp->t_in6pcb->in6p_faddr)) ss = tcp_init_win_local; #endif tp->snd_cwnd = min(tp->snd_cwnd, TCP_INITIAL_WINDOW(ss, txsegsize)); } } again: /* * Determine length of data that should be transmitted, and * flags that should be used. If there is some data or critical * controls (SYN, RST) to send, then transmit; otherwise, * investigate further. */ sendalot = 0; off = tp->snd_nxt - tp->snd_una; win = min(tp->snd_wnd, tp->snd_cwnd); flags = tcp_outflags[tp->t_state]; /* * 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; } } if (win < so->so_snd.sb_cc) { len = win - off; flags &= ~TH_FIN; } else len = so->so_snd.sb_cc - off; 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. * * If we have a pending FIN, either it has already been * transmitted or it is outside the window, so drop it. * If the FIN has been transmitted, but this is not a * retransmission, then len must be -1. Therefore we also * prevent here the sending of `gratuitous FINs'. This * eliminates the need to check for that case below (e.g. * to back up snd_nxt before the FIN so that the sequence * number is correct). */ len = 0; flags &= ~TH_FIN; 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 > txsegsize) { len = txsegsize; flags &= ~TH_FIN; sendalot = 1; } 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 == txsegsize) goto send; if ((so->so_state & SS_MORETOCOME) == 0 && ((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) goto send; if (SEQ_LT(tp->snd_nxt, tp->snd_max)) 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 twice the size of the largest segment * we expect to receive (i.e. two 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 = min(win, (long)TCP_MAXWIN << tp->rcv_scale) - (tp->rcv_adv - tp->rcv_nxt); if (adv >= (long) (2 * rxsegsize)) 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_FIN|TH_RST)) goto send; if (SEQ_GT(tp->snd_up, 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 * * 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 (struct tcpiphdr) + optlen <= MCLBYTES */ optlen = 0; switch (af) { #ifdef INET case AF_INET: iphdrlen = sizeof(struct ip) + sizeof(struct tcphdr); break; #endif #ifdef INET6 case AF_INET6: iphdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); break; #endif default: /*pacify gcc*/ iphdrlen = 0; break; } hdrlen = iphdrlen; if (flags & TH_SYN) { struct rtentry *rt; rt = NULL; #ifdef INET if (tp->t_inpcb) rt = in_pcbrtentry(tp->t_inpcb); #endif #ifdef INET6 if (tp->t_in6pcb) rt = in6_pcbrtentry(tp->t_in6pcb); #endif tp->snd_nxt = tp->iss; tp->t_ourmss = tcp_mss_to_advertise(rt != NULL ? rt->rt_ifp : NULL, af); if ((tp->t_flags & TF_NOOPT) == 0) { opt[0] = TCPOPT_MAXSEG; opt[1] = 4; opt[2] = (tp->t_ourmss >> 8) & 0xff; opt[3] = tp->t_ourmss & 0xff; optlen = 4; 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_TIMESTAMP(tp)); *lp = htonl(tp->ts_recent); optlen += TCPOLEN_TSTAMP_APPA; } hdrlen += optlen; #ifdef DIAGNOSTIC if (len > txsegsize) panic("tcp data to be sent is larger than segment"); 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) { error = tcp_build_datapkt(tp, so, off, len, hdrlen, &m); if (error) goto out; /* * 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 && max_linkhdr + hdrlen > MHLEN) { MCLGET(m, M_DONTWAIT); if ((m->m_flags & M_EXT) == 0) { m_freem(m); m = NULL; } } if (m == NULL) { error = ENOBUFS; goto out; } MCLAIM(m, &tcp_tx_mowner); m->m_data += max_linkhdr; m->m_len = hdrlen; } m->m_pkthdr.rcvif = (struct ifnet *)0; switch (af) { #ifdef INET case AF_INET: ip = mtod(m, struct ip *); #ifdef INET6 ip6 = NULL; #endif th = (struct tcphdr *)(ip + 1); break; #endif #ifdef INET6 case AF_INET6: ip = NULL; ip6 = mtod(m, struct ip6_hdr *); th = (struct tcphdr *)(ip6 + 1); break; #endif default: /*pacify gcc*/ ip = NULL; #ifdef INET6 ip6 = NULL; #endif th = NULL; break; } if (tp->t_template == 0) panic("tcp_output"); if (tp->t_template->m_len < iphdrlen) panic("tcp_output"); bcopy(mtod(tp->t_template, caddr_t), mtod(m, caddr_t), iphdrlen); /* * 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); 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; } 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)rxsegsize) 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); 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 */ /* * Set ourselves up to be checksummed just before the packet * hits the wire. */ switch (af) { #ifdef INET case AF_INET: m->m_pkthdr.csum_flags = M_CSUM_TCPv4; m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); if (len + optlen) { /* Fixup the pseudo-header checksum. */ /* XXXJRT Not IP Jumbogram safe. */ th->th_sum = in_cksum_addword(th->th_sum, htons((u_int16_t) (len + optlen))); } break; #endif #ifdef INET6 case AF_INET6: /* * XXX Actually delaying the checksum is Hard * XXX (well, maybe not for Itojun, but it is * XXX for me), but we can still take advantage * XXX of the cached pseudo-header checksum. */ /* equals to hdrlen + len */ m->m_pkthdr.len = sizeof(struct ip6_hdr) + sizeof(struct tcphdr) + optlen + len; #ifdef notyet m->m_pkthdr.csum_flags = M_CSUM_TCPv6; m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); #endif if (len + optlen) { /* Fixup the pseudo-header checksum. */ /* XXXJRT: Not IPv6 Jumbogram safe. */ th->th_sum = in_cksum_addword(th->th_sum, htons((u_int16_t) (len + optlen))); } #ifndef notyet th->th_sum = in6_cksum(m, 0, sizeof(struct ip6_hdr), sizeof(struct tcphdr) + optlen + len); #endif break; #endif } /* * 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. * There are no states in which we send both a SYN and a FIN, * so we collapse the tests for these flags. */ if (flags & (TH_SYN|TH_FIN)) tp->snd_nxt++; 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. */ 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; #ifdef TCP_DEBUG /* * Trace. */ if (so->so_options & SO_DEBUG) tcp_trace(TA_OUTPUT, tp->t_state, tp, m, 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 = hdrlen + len; switch (af) { #ifdef INET case AF_INET: ip->ip_len = htons(m->m_pkthdr.len); if (tp->t_inpcb) { ip->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl; ip->ip_tos = tp->t_inpcb->inp_ip.ip_tos; } #ifdef INET6 else if (tp->t_in6pcb) { ip->ip_ttl = in6_selecthlim(tp->t_in6pcb, NULL); /*XXX*/ ip->ip_tos = 0; /*XXX*/ } #endif break; #endif #ifdef INET6 case AF_INET6: ip6->ip6_nxt = IPPROTO_TCP; if (tp->t_in6pcb) { /* * 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(tp->t_in6pcb, ro->ro_rt ? ro->ro_rt->rt_ifp : NULL); } /* ip6->ip6_flow = ??? */ /* ip6_plen will be filled in ip6_output(). */ break; #endif } #ifdef IPSEC if (ipsec_setsocket(m, so) != 0) { m_freem(m); error = ENOBUFS; goto out; } #endif /*IPSEC*/ switch (af) { #ifdef INET case AF_INET: { struct mbuf *opts; if (tp->t_inpcb) opts = tp->t_inpcb->inp_options; else opts = NULL; error = ip_output(m, opts, ro, (tp->t_mtudisc ? IP_MTUDISC : 0) | (so->so_options & SO_DONTROUTE), (struct ip_moptions *)0, so); break; } #endif #ifdef INET6 case AF_INET6: { struct ip6_pktopts *opts; if (tp->t_in6pcb) opts = tp->t_in6pcb->in6p_outputopts; else opts = NULL; error = ip6_output(m, opts, (struct route_in6 *)ro, so->so_options & SO_DONTROUTE, (struct ip6_moptions *)0, so, NULL); break; } #endif default: error = EAFNOSUPPORT; break; } if (error) { out: if (error == ENOBUFS) { tcpstat.tcps_selfquench++; #ifdef INET if (tp->t_inpcb) tcp_quench(tp->t_inpcb, 0); #endif #ifdef INET6 if (tp->t_in6pcb) tcp6_quench(tp->t_in6pcb, 0); #endif error = 0; } else if ((error == EHOSTUNREACH || error == ENETDOWN) && TCPS_HAVERCVDSYN(tp->t_state)) { tp->t_softerror = error; error = 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); #ifdef DIAGNOSTIC if (maxburst < 0) printf("tcp_output: maxburst exceeded by %d\n", -maxburst); #endif if (sendalot && (!tcp_do_newreno || --maxburst)) goto again; return (0); } void tcp_setpersist(tp) struct tcpcb *tp; { int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> (1 + 2); 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++; }