/* $NetBSD: tcp_output.c,v 1.218.2.1 2023/09/21 13:22:46 martin 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, 2005, 2006 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. * This code is derived from software contributed to The NetBSD Foundation * by Charles M. Hannum. * This code is derived from software contributed to The NetBSD Foundation * by Rui Paulo. * * 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. * * 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 1.218.2.1 2023/09/21 13:22:46 martin Exp $"); #ifdef _KERNEL_OPT #include "opt_inet.h" #include "opt_ipsec.h" #include "opt_tcp_debug.h" #endif #include #include #include #include #include #include #include #include #include #ifdef TCP_SIGNATURE #include #endif #include #include #include #include #include #include #include #ifdef INET6 #include #include #include #include #include #endif #ifdef IPSEC #include #include #ifdef INET6 #include #endif #endif #include #define TCPOUTFLAGS #include #include #include #include #include #include #include #include #include /* * Knob to enable Congestion Window Monitoring, and control * the burst size it allows. Default burst is 4 packets, per * the Internet draft. */ int tcp_cwm = 0; int tcp_cwm_burstsize = 4; int tcp_do_autosndbuf = 1; int tcp_autosndbuf_inc = 8 * 1024; int tcp_autosndbuf_max = 256 * 1024; #ifdef TCP_OUTPUT_COUNTERS #include extern struct evcnt tcp_output_bigheader; extern struct evcnt tcp_output_predict_hit; extern struct evcnt tcp_output_predict_miss; 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 int tcp_segsize(struct tcpcb *tp, int *txsegsizep, int *rxsegsizep, bool *alwaysfragp) { struct inpcb *inp = tp->t_inpcb; struct socket *so = NULL; struct rtentry *rt; struct ifnet *ifp; int size; int hdrlen; int optlen; *alwaysfragp = false; size = tcp_mssdflt; switch (tp->t_family) { case AF_INET: hdrlen = sizeof(struct ip) + sizeof(struct tcphdr); break; #ifdef INET6 case AF_INET6: hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); break; #endif default: hdrlen = 1; /* prevent zero sized segments */ goto out; } rt = inpcb_rtentry(inp); so = inp->inp_socket; if (rt == NULL) { goto out; } ifp = rt->rt_ifp; if (tp->t_mtudisc && rt->rt_rmx.rmx_mtu != 0) { #ifdef INET6 if (inp->inp_af == AF_INET6 && rt->rt_rmx.rmx_mtu < IPV6_MMTU) { /* * RFC2460 section 5, last paragraph: if path MTU is * smaller than 1280, use 1280 as packet size and * attach fragment header. */ size = IPV6_MMTU - hdrlen - sizeof(struct ip6_frag); *alwaysfragp = true; } else size = rt->rt_rmx.rmx_mtu - hdrlen; #else size = rt->rt_rmx.rmx_mtu - hdrlen; #endif } else if (ifp->if_flags & IFF_LOOPBACK) size = ifp->if_mtu - hdrlen; else if (inp->inp_af == AF_INET && tp->t_mtudisc) size = ifp->if_mtu - hdrlen; else if (inp->inp_af == AF_INET && in_localaddr(in4p_faddr(inp))) size = ifp->if_mtu - hdrlen; #ifdef INET6 else if (inp->inp_af == AF_INET6) { if (IN6_IS_ADDR_V4MAPPED(&in6p_faddr(inp))) { /* mapped addr case */ struct in_addr d; memcpy(&d, &in6p_faddr(inp).s6_addr32[3], sizeof(d)); if (tp->t_mtudisc || in_localaddr(d)) size = ifp->if_mtu - hdrlen; } else { /* * for IPv6, path MTU discovery is always turned on, * or the node must use packet size <= 1280. */ size = tp->t_mtudisc ? ifp->if_mtu : IPV6_MMTU; size -= hdrlen; } } #endif inpcb_rtentry_unref(rt, inp); 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 */ if (inp->inp_af == AF_INET) { #if defined(IPSEC) if (ipsec_used && !ipsec_pcb_skip_ipsec(inp->inp_sp, IPSEC_DIR_OUTBOUND)) optlen += ipsec4_hdrsiz_tcp(tp); #endif optlen += ip_optlen(inp); } #ifdef INET6 if (inp->inp_af == AF_INET6 && tp->t_family == AF_INET) { #if defined(IPSEC) if (ipsec_used && !ipsec_pcb_skip_ipsec(inp->inp_sp, IPSEC_DIR_OUTBOUND)) optlen += ipsec4_hdrsiz_tcp(tp); #endif /* XXX size -= ip_optlen(in6p); */ } else if (inp->inp_af == AF_INET6) { #if defined(IPSEC) if (ipsec_used && !ipsec_pcb_skip_ipsec(inp->inp_sp, IPSEC_DIR_OUTBOUND)) optlen += ipsec6_hdrsiz_tcp(tp); #endif optlen += ip6_optlen(inp); } #endif size -= optlen; /* * There may not be any room for data if mtu is too small. This * includes zero-sized. */ if (size <= 0) { return EMSGSIZE; } /* * *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 = uimin(tp->t_peermss - optlen, size); *rxsegsizep = uimin(tp->t_ourmss - 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 = uimin(so->so_snd.sb_hiwat >> 1, *txsegsizep); } /* * A segment must at least store header + options */ if (*txsegsizep < hdrlen + optlen) { return EMSGSIZE; } 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 = uimax((tp->snd_cwnd / tp->t_segsz) * *txsegsizep, *txsegsizep); tp->snd_ssthresh = uimax((tp->snd_ssthresh / tp->t_segsz) * *txsegsizep, *txsegsizep); } tp->t_segsz = *txsegsizep; } return 0; } static int tcp_build_datapkt(struct tcpcb *tp, struct socket *so, int off, long len, int hdrlen, struct mbuf **mp) { struct mbuf *m, *m0; uint64_t *tcps; tcps = TCP_STAT_GETREF(); if (tp->t_force && len == 1) tcps[TCP_STAT_SNDPROBE]++; else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) { tp->t_sndrexmitpack++; tcps[TCP_STAT_SNDREXMITPACK]++; tcps[TCP_STAT_SNDREXMITBYTE] += len; } else { tcps[TCP_STAT_SNDPACK]++; tcps[TCP_STAT_SNDBYTE] += len; } TCP_STAT_PUTREF(); 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 directly following the previous transfer. * This is important for large TCP windows. */ if (off == 0 || tp->t_lastm == NULL || (tp->t_lastoff + tp->t_lastlen) != off) { TCP_OUTPUT_COUNTER_INCR(&tcp_output_predict_miss); /* * Either a new packet or a retransmit. * Start from the beginning. */ tp->t_lastm = so->so_snd.sb_mb; tp->t_inoff = off; } else { TCP_OUTPUT_COUNTER_INCR(&tcp_output_predict_hit); 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, char *) + hdrlen); m->m_len += len; TCP_OUTPUT_COUNTER_INCR(&tcp_output_copysmall); } else { m->m_next = m_copym(m0, off, (int)len, M_DONTWAIT); 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 } *mp = m; return 0; } /* * Tcp output routine: figure out what should be sent and send it. */ int tcp_output(struct tcpcb *tp) { struct rtentry *rt = NULL; 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], *optp; #define OPT_FITS(more) ((optlen + (more)) <= sizeof(opt)) unsigned optlen, hdrlen, packetlen; unsigned int sack_numblks; int idle, sendalot, txsegsize, rxsegsize; int txsegsize_nosack; int maxburst = TCP_MAXBURST; int af; /* address family on the wire */ int iphdrlen; int has_tso4, has_tso6; int has_tso, use_tso; bool alwaysfrag; int sack_rxmit; int sack_bytes_rxmt; int ecn_tos; struct sackhole *p; #ifdef TCP_SIGNATURE int sigoff = 0; #endif uint64_t *tcps; so = tp->t_inpcb->inp_socket; ro = &tp->t_inpcb->inp_route; switch (af = tp->t_family) { case AF_INET: case AF_INET6: if (tp->t_inpcb) break; return EINVAL; default: return EAFNOSUPPORT; } if (tcp_segsize(tp, &txsegsize, &rxsegsize, &alwaysfrag)) return EMSGSIZE; idle = (tp->snd_max == tp->snd_una); /* * Determine if we can use TCP segmentation offload: * - If we're using IPv4 * - If there is not an IPsec policy that prevents it * - If the interface can do it */ has_tso4 = has_tso6 = false; has_tso4 = tp->t_inpcb->inp_af == AF_INET && #if defined(IPSEC) (!ipsec_used || ipsec_pcb_skip_ipsec(tp->t_inpcb->inp_sp, IPSEC_DIR_OUTBOUND)) && #endif (rt = rtcache_validate(&tp->t_inpcb->inp_route)) != NULL && (rt->rt_ifp->if_capenable & IFCAP_TSOv4) != 0; if (rt != NULL) { rtcache_unref(rt, &tp->t_inpcb->inp_route); rt = NULL; } #if defined(INET6) has_tso6 = tp->t_inpcb->inp_af == AF_INET6 && #if defined(IPSEC) (!ipsec_used || ipsec_pcb_skip_ipsec(tp->t_inpcb->inp_sp, IPSEC_DIR_OUTBOUND)) && #endif (rt = rtcache_validate(&tp->t_inpcb->inp_route)) != NULL && (rt->rt_ifp->if_capenable & IFCAP_TSOv6) != 0; if (rt != NULL) rtcache_unref(rt, &tp->t_inpcb->inp_route); #endif /* defined(INET6) */ has_tso = (has_tso4 || has_tso6) && !alwaysfrag; /* * 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 = uimin(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; if (tp->t_inpcb->inp_af == AF_INET && in_localaddr(in4p_faddr(tp->t_inpcb))) ss = tcp_init_win_local; #ifdef INET6 else if (tp->t_inpcb->inp_af == AF_INET6 && in6_localaddr(&in6p_faddr(tp->t_inpcb))) ss = tcp_init_win_local; #endif tp->snd_cwnd = uimin(tp->snd_cwnd, TCP_INITIAL_WINDOW(ss, txsegsize)); } } txsegsize_nosack = txsegsize; again: ecn_tos = 0; use_tso = has_tso; if ((tp->t_flags & (TF_ECN_SND_CWR|TF_ECN_SND_ECE)) != 0) { /* don't duplicate CWR/ECE. */ use_tso = 0; } TCP_REASS_LOCK(tp); sack_numblks = tcp_sack_numblks(tp); if (sack_numblks) { int sackoptlen; sackoptlen = TCP_SACK_OPTLEN(sack_numblks); if (sackoptlen > txsegsize_nosack) { sack_numblks = 0; /* give up SACK */ txsegsize = txsegsize_nosack; } else { if ((tp->rcv_sack_flags & TCPSACK_HAVED) != 0) { /* don't duplicate D-SACK. */ use_tso = 0; } txsegsize = txsegsize_nosack - sackoptlen; } } else { txsegsize = txsegsize_nosack; } /* * 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. * * Readjust SACK information to avoid resending duplicate data. */ if (TCP_SACK_ENABLED(tp) && SEQ_LT(tp->snd_nxt, tp->snd_max)) tcp_sack_adjust(tp); sendalot = 0; off = tp->snd_nxt - tp->snd_una; win = uimin(tp->snd_wnd, tp->snd_cwnd); flags = tcp_outflags[tp->t_state]; /* * 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(). */ /* * Still in sack recovery, reset rxmit flag to zero. */ sack_rxmit = 0; sack_bytes_rxmt = 0; len = 0; p = NULL; do { long cwin; if (!TCP_SACK_ENABLED(tp)) break; if (tp->t_partialacks < 0) break; p = tcp_sack_output(tp, &sack_bytes_rxmt); if (p == NULL) break; cwin = uimin(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt; if (cwin < 0) cwin = 0; /* Do not retransmit SACK segments beyond snd_recover */ if (SEQ_GT(p->end, tp->snd_recover)) { /* * (At least) part of sack hole extends beyond * snd_recover. Check to see if we can rexmit data * for this hole. */ if (SEQ_GEQ(p->rxmit, tp->snd_recover)) { /* * Can't rexmit any more data for this hole. * That data will be rexmitted in the next * sack recovery episode, when snd_recover * moves past p->rxmit. */ p = NULL; break; } /* Can rexmit part of the current hole */ len = ((long)ulmin(cwin, tp->snd_recover - p->rxmit)); } else len = ((long)ulmin(cwin, p->end - p->rxmit)); off = p->rxmit - tp->snd_una; if (off + len > so->so_snd.sb_cc) { /* 1 for TH_FIN */ KASSERT(off + len == so->so_snd.sb_cc + 1); KASSERT(p->rxmit + len == tp->snd_max); len = so->so_snd.sb_cc - off; } if (len > 0) { sack_rxmit = 1; sendalot = 1; } } while (/*CONSTCOND*/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; } } if (sack_rxmit == 0) { if (TCP_SACK_ENABLED(tp) && tp->t_partialacks >= 0) { long cwin; /* * We are inside of a SACK recovery episode and are * sending new data, having retransmitted all the * data possible in the scoreboard. */ if (tp->snd_wnd < so->so_snd.sb_cc) { len = tp->snd_wnd - off; flags &= ~TH_FIN; } else { len = so->so_snd.sb_cc - off; } /* * From FreeBSD: * Don't remove this (len > 0) check ! * We explicitly check for len > 0 here (although it * isn't really necessary), to work around a gcc * optimization issue - to force gcc to compute * len above. Without this check, the computation * of len is bungled by the optimizer. */ if (len > 0) { cwin = tp->snd_cwnd - (tp->snd_nxt - tp->sack_newdata) - sack_bytes_rxmt; if (cwin < 0) cwin = 0; if (cwin < len) { len = cwin; flags &= ~TH_FIN; } } } else 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); } } /* * Automatic sizing enables the performance of large buffers * and most of the efficiency of small ones by only allocating * space when it is needed. * * The criteria to step up the send buffer one notch are: * 1. receive window of remote host is larger than send buffer * (with a fudge factor of 5/4th); * 2. send buffer is filled to 7/8th with data (so we actually * have data to make use of it); * 3. send buffer fill has not hit maximal automatic size; * 4. our send window (slow start and cogestion controlled) is * larger than sent but unacknowledged data in send buffer. * * The remote host receive window scaling factor may limit the * growing of the send buffer before it reaches its allowed * maximum. * * It scales directly with slow start or congestion window * and does at most one step per received ACK. This fast * scaling has the drawback of growing the send buffer beyond * what is strictly necessary to make full use of a given * delay*bandwidth product. However testing has shown this not * to be much of an problem. At worst we are trading wasting * of available bandwidth (the non-use of it) for wasting some * socket buffer memory. * * TODO: Shrink send buffer during idle periods together * with congestion window. Requires another timer. */ if (tcp_do_autosndbuf && so->so_snd.sb_flags & SB_AUTOSIZE) { if ((tp->snd_wnd / 4 * 5) >= so->so_snd.sb_hiwat && so->so_snd.sb_cc >= (so->so_snd.sb_hiwat / 8 * 7) && so->so_snd.sb_cc < tcp_autosndbuf_max && win >= (so->so_snd.sb_cc - (tp->snd_nxt - tp->snd_una))) { if (!sbreserve(&so->so_snd, uimin(so->so_snd.sb_hiwat + tcp_autosndbuf_inc, tcp_autosndbuf_max), so)) so->so_snd.sb_flags &= ~SB_AUTOSIZE; } } if (len > txsegsize) { if (use_tso) { /* * Truncate TSO transfers to IP_MAXPACKET, and make * sure that we send equal size transfers down the * stack (rather than big-small-big-small-...). */ #ifdef INET6 CTASSERT(IPV6_MAXPACKET == IP_MAXPACKET); #endif len = (uimin(len, IP_MAXPACKET) / txsegsize) * txsegsize; if (len <= txsegsize) { use_tso = 0; } } else len = txsegsize; flags &= ~TH_FIN; sendalot = 1; } else use_tso = 0; if (sack_rxmit) { if (SEQ_LT(p->rxmit + len, tp->snd_una + 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 >= 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; if (sack_rxmit) 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 recwin = uimin(win, (long)TCP_MAXWIN << tp->rcv_scale); long oldwin, adv; /* * rcv_nxt may overtake rcv_adv when we accept a * zero-window probe. */ if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) oldwin = tp->rcv_adv - tp->rcv_nxt; else oldwin = 0; /* * If the new window size ends up being the same as or * less than the old size when it is scaled, then * don't force a window update. */ if (recwin >> tp->rcv_scale <= oldwin >> tp->rcv_scale) goto dontupdate; adv = recwin - oldwin; if (adv >= (long) (2 * rxsegsize)) goto send; if (2 * adv >= (long) so->so_rcv.sb_hiwat) goto send; } dontupdate: /* * 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; /* * 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 (TCP_SACK_ENABLED(tp) && SEQ_GT(tp->snd_max, tp->snd_una) && !TCP_TIMER_ISARMED(tp, TCPT_REXMT) && !TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) { TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); goto just_return; } /* * 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. */ just_return: TCP_REASS_UNLOCK(tp); 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 + IP_header + TCP_header + optlen <= MCLBYTES */ optlen = 0; optp = opt; switch (af) { case AF_INET: iphdrlen = sizeof(struct ip) + sizeof(struct tcphdr); break; #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 *synrt; synrt = inpcb_rtentry(tp->t_inpcb); tp->snd_nxt = tp->iss; tp->t_ourmss = tcp_mss_to_advertise(synrt != NULL ? synrt->rt_ifp : NULL, af); inpcb_rtentry_unref(synrt, tp->t_inpcb); if ((tp->t_flags & TF_NOOPT) == 0 && OPT_FITS(TCPOLEN_MAXSEG)) { *optp++ = TCPOPT_MAXSEG; *optp++ = TCPOLEN_MAXSEG; *optp++ = (tp->t_ourmss >> 8) & 0xff; *optp++ = tp->t_ourmss & 0xff; optlen += TCPOLEN_MAXSEG; if ((tp->t_flags & TF_REQ_SCALE) && ((flags & TH_ACK) == 0 || (tp->t_flags & TF_RCVD_SCALE)) && OPT_FITS(TCPOLEN_WINDOW + TCPOLEN_NOP)) { *((uint32_t *)optp) = htonl( TCPOPT_NOP << 24 | TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | tp->request_r_scale); optp += TCPOLEN_WINDOW + TCPOLEN_NOP; optlen += TCPOLEN_WINDOW + TCPOLEN_NOP; } if (tcp_do_sack && OPT_FITS(TCPOLEN_SACK_PERMITTED)) { *optp++ = TCPOPT_SACK_PERMITTED; *optp++ = TCPOLEN_SACK_PERMITTED; optlen += TCPOLEN_SACK_PERMITTED; } } } /* * 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))) { int alen = 0; while (optlen % 4 != 2) { optlen += TCPOLEN_NOP; *optp++ = TCPOPT_NOP; alen++; } if (OPT_FITS(TCPOLEN_TIMESTAMP)) { *optp++ = TCPOPT_TIMESTAMP; *optp++ = TCPOLEN_TIMESTAMP; uint32_t *lp = (uint32_t *)optp; /* Form timestamp option (appendix A of RFC 1323) */ *lp++ = htonl(TCP_TIMESTAMP(tp)); *lp = htonl(tp->ts_recent); optp += TCPOLEN_TIMESTAMP - 2; optlen += TCPOLEN_TIMESTAMP; /* Set receive buffer autosizing timestamp. */ if (tp->rfbuf_ts == 0 && (so->so_rcv.sb_flags & SB_AUTOSIZE)) tp->rfbuf_ts = TCP_TIMESTAMP(tp); } else { optp -= alen; optlen -= alen; } } #ifdef TCP_SIGNATURE if (tp->t_flags & TF_SIGNATURE) { /* * Initialize TCP-MD5 option (RFC2385) */ if (!OPT_FITS(TCPOLEN_SIGNATURE)) goto reset; *optp++ = TCPOPT_SIGNATURE; *optp++ = TCPOLEN_SIGNATURE; sigoff = optlen + 2; memset(optp, 0, TCP_SIGLEN); optlen += TCPOLEN_SIGNATURE; optp += TCP_SIGLEN; } #endif /* * Tack on the SACK block if it is necessary. */ if (sack_numblks) { int alen = 0; int sack_len = sack_numblks * 8; while (optlen % 4 != 2) { optlen += TCPOLEN_NOP; *optp++ = TCPOPT_NOP; alen++; } if (OPT_FITS(sack_len + 2)) { struct ipqent *tiqe; *optp++ = TCPOPT_SACK; *optp++ = sack_len + 2; uint32_t *lp = (uint32_t *)optp; if ((tp->rcv_sack_flags & TCPSACK_HAVED) != 0) { sack_numblks--; *lp++ = htonl(tp->rcv_dsack_block.left); *lp++ = htonl(tp->rcv_dsack_block.right); tp->rcv_sack_flags &= ~TCPSACK_HAVED; } for (tiqe = TAILQ_FIRST(&tp->timeq); sack_numblks > 0; tiqe = TAILQ_NEXT(tiqe, ipqe_timeq)) { KASSERT(tiqe != NULL); sack_numblks--; *lp++ = htonl(tiqe->ipqe_seq); *lp++ = htonl(tiqe->ipqe_seq + tiqe->ipqe_len + ((tiqe->ipqe_flags & TH_FIN) != 0 ? 1 : 0)); } optlen += sack_len + 2; optp += sack_len; } else { optp -= alen; optlen -= alen; } } /* Terminate and pad TCP options to a 4 byte boundary. */ if (optlen % 4) { if (!OPT_FITS(TCPOLEN_EOL)) { reset: TCP_REASS_UNLOCK(tp); error = ECONNABORTED; goto out; } optlen += TCPOLEN_EOL; *optp++ = TCPOPT_EOL; } /* * According to RFC 793 (STD0007): * "The content of the header beyond the End-of-Option option * must be header padding (i.e., zero)." * and later: "The padding is composed of zeros." */ while (optlen % 4) { if (!OPT_FITS(TCPOLEN_PAD)) goto reset; optlen += TCPOLEN_PAD; *optp++ = TCPOPT_PAD; } TCP_REASS_UNLOCK(tp); hdrlen += optlen; #ifdef DIAGNOSTIC if (!use_tso && len > txsegsize) panic("tcp data to be sent is larger than segment"); else if (use_tso && len > IP_MAXPACKET) panic("tcp data to be sent is larger than max TSO size"); 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 { tcps = TCP_STAT_GETREF(); if (tp->t_flags & TF_ACKNOW) tcps[TCP_STAT_SNDACKS]++; else if (flags & (TH_SYN|TH_FIN|TH_RST)) tcps[TCP_STAT_SNDCTRL]++; else if (SEQ_GT(tp->snd_up, tp->snd_una)) tcps[TCP_STAT_SNDURG]++; else tcps[TCP_STAT_SNDWINUP]++; TCP_STAT_PUTREF(); 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_reset_rcvif(m); switch (af) { case AF_INET: ip = mtod(m, struct ip *); #ifdef INET6 ip6 = NULL; #endif th = (struct tcphdr *)(ip + 1); break; #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 == NULL) panic("%s: no template", __func__); if (tp->t_template->m_len < iphdrlen) panic("%s: %d < %d", __func__, tp->t_template->m_len, iphdrlen); bcopy(mtod(tp->t_template, void *), mtod(m, void *), iphdrlen); /* * If we are starting a connection, send ECN setup * SYN packet. If we are on a retransmit, we may * resend those bits a number of times as per * RFC 3168. */ if (tp->t_state == TCPS_SYN_SENT && tcp_do_ecn) { if (tp->t_flags & TF_SYN_REXMT) { if (tp->t_ecn_retries--) flags |= TH_ECE|TH_CWR; } else { flags |= TH_ECE|TH_CWR; tp->t_ecn_retries = tcp_ecn_maxretries; } } if (TCP_ECN_ALLOWED(tp)) { /* * If the peer has ECN, mark data packets * ECN capable. Ignore pure ack packets, retransmissions * and window probes. */ if (len > 0 && SEQ_GEQ(tp->snd_nxt, tp->snd_max) && !(tp->t_force && len == 1)) { ecn_tos = IPTOS_ECN_ECT0; TCP_STATINC(TCP_STAT_ECN_ECT); } /* * Reply with proper ECN notifications. */ if (tp->t_flags & TF_ECN_SND_CWR) { flags |= TH_CWR; tp->t_flags &= ~TF_ECN_SND_CWR; } if (tp->t_flags & TF_ECN_SND_ECE) { flags |= TH_ECE; } } /* * 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 (TCP_SACK_ENABLED(tp) && sack_rxmit) { th->th_seq = htonl(p->rxmit); p->rxmit += len; } else { 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) { memcpy(th + 1, opt, 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)(int32_t)(tp->rcv_adv - tp->rcv_nxt)) win = (long)(int32_t)(tp->rcv_adv - tp->rcv_nxt); th->th_win = htons((u_int16_t) (win>>tp->rcv_scale)); if (th->th_win == 0) { tp->t_sndzerowin++; } 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 (sigoff && (tp->t_flags & TF_SIGNATURE)) { struct secasvar *sav; u_int8_t *sigp; sav = tcp_signature_getsav(m); if (sav == NULL) { if (m) m_freem(m); return EPERM; } m->m_pkthdr.len = hdrlen + len; sigp = (char *)th + sizeof(*th) + sigoff; tcp_signature(m, th, (char *)th - mtod(m, char *), sav, sigp); key_sa_recordxfer(sav, m); KEY_SA_UNREF(&sav); } #endif /* * Set ourselves up to be checksummed just before the packet * hits the wire. */ switch (af) { case AF_INET: m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); if (use_tso) { m->m_pkthdr.segsz = txsegsize; m->m_pkthdr.csum_flags = M_CSUM_TSOv4; } else { m->m_pkthdr.csum_flags = M_CSUM_TCPv4; 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; #ifdef INET6 case AF_INET6: m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); if (use_tso) { m->m_pkthdr.segsz = txsegsize; m->m_pkthdr.csum_flags = M_CSUM_TSOv6; } else { m->m_pkthdr.csum_flags = M_CSUM_TCPv6; 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))); } } 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++; if (sack_rxmit) goto timer; 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; TCP_STATINC(TCP_STAT_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. */ timer: if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0) { if ((sack_rxmit && tp->snd_nxt != tp->snd_max) || tp->snd_nxt != tp->snd_una) { if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) { TCP_TIMER_DISARM(tp, TCPT_PERSIST); tp->t_rxtshift = 0; } TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); } else if (len == 0 && so->so_snd.sb_cc > 0 && TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { /* * If we are sending a window probe and there's * unacked data in the socket, make sure at * least the persist timer is running. */ tp->t_rxtshift = 0; tcp_setpersist(tp); } } } 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) { case AF_INET: ip->ip_len = htons(m->m_pkthdr.len); packetlen = m->m_pkthdr.len; if (tp->t_inpcb->inp_af == AF_INET) { ip->ip_ttl = in4p_ip(tp->t_inpcb).ip_ttl; ip->ip_tos = in4p_ip(tp->t_inpcb).ip_tos | ecn_tos; } #ifdef INET6 else if (tp->t_inpcb->inp_af == AF_INET6) { ip->ip_ttl = in6pcb_selecthlim(tp->t_inpcb, NULL); /*XXX*/ ip->ip_tos = ecn_tos; /*XXX*/ } #endif break; #ifdef INET6 case AF_INET6: packetlen = m->m_pkthdr.len; ip6->ip6_nxt = IPPROTO_TCP; if (tp->t_family == AF_INET6) { /* * 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 = in6pcb_selecthlim_rt(tp->t_inpcb); } ip6->ip6_flow |= htonl(ecn_tos << 20); /* ip6->ip6_flow = ??? (from template) */ /* ip6_plen will be filled in ip6_output(). */ break; #endif default: /*pacify gcc*/ packetlen = 0; break; } switch (af) { case AF_INET: { struct mbuf *opts; if (tp->t_inpcb->inp_af == AF_INET) 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), NULL, tp->t_inpcb); break; } #ifdef INET6 case AF_INET6: { struct ip6_pktopts *opts; if (tp->t_inpcb->inp_af == AF_INET6) opts = in6p_outputopts(tp->t_inpcb); else opts = NULL; error = ip6_output(m, opts, ro, so->so_options & SO_DONTROUTE, NULL, tp->t_inpcb, NULL); break; } #endif default: error = EAFNOSUPPORT; break; } if (error) { out: if (error == ENOBUFS) { TCP_STATINC(TCP_STAT_SELFQUENCH); tcp_quench(tp->t_inpcb); error = 0; } else if ((error == EHOSTUNREACH || error == ENETDOWN || error == EHOSTDOWN) && TCPS_HAVERCVDSYN(tp->t_state)) { tp->t_softerror = error; error = 0; } /* Back out the sequence number advance. */ if (sack_rxmit) p->rxmit -= len; /* Restart the delayed ACK timer, if necessary. */ if (tp->t_flags & TF_DELACK) TCP_RESTART_DELACK(tp); return error; } if (packetlen > tp->t_pmtud_mtu_sent) tp->t_pmtud_mtu_sent = packetlen; tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_SNDTOTAL]++; if (tp->t_flags & TF_DELACK) tcps[TCP_STAT_DELACK]++; TCP_STAT_PUTREF(); /* * 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 && (tp->t_congctl == &tcp_reno_ctl || --maxburst)) goto again; return 0; } void tcp_setpersist(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++; }