Fix to ensure that the correct MSS is advertised for loopback
TCP connections by using the MTU of the interface. Also added a knob, mss_ifmtu, to force all connections to use the MTU of the interface to calculate the advertised MSS.
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kml
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@ -1,4 +1,4 @@
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.\" $NetBSD: sysctl.3,v 1.23 1998/02/05 18:48:01 perry Exp $
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.\" $NetBSD: sysctl.3,v 1.24 1998/04/13 21:24:49 kml Exp $
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.\"
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.\" Copyright (c) 1993
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.\" The Regents of the University of California. All rights reserved.
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@ -499,6 +499,7 @@ The currently defined protocols and names are:
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.It tcp syn_bucket_limit integer yes
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.It tcp syn_cache_interval integer yes
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.It tcp init_win integer yes
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.It tcp mss_ifmtu integer yes
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.It udp checksum integer yes
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.It udp sendspace integer yes
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.It udp recvspace integer yes
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@ -555,6 +556,11 @@ Returns the TCP compressed state engine's timer interval.
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If greater than 0, returns the number of segments used for the inital
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slow start congestion window. A value of 0 indicates that an experimental
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auto-tuning algorithm is being used to compute the initial window.
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.It Li tcp.mss_ifmtu
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If greater than 0, calculate the outgoing MSS based on the MTU of
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the appropriate interface. Otherwise, calculate it based on
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the greater of the MTU of the interface, and the largest (non-loopback)
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interface MTU on the system.
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.It Li udp.checksum
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Returns 1 when UDP checksums are being computed and checked.
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Disabling UDP checksums is strongly discouraged.
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@ -1,4 +1,4 @@
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/* $NetBSD: tcp_input.c,v 1.50 1998/04/07 05:09:19 thorpej Exp $ */
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/* $NetBSD: tcp_input.c,v 1.51 1998/04/13 21:18:19 kml Exp $ */
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/*-
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* Copyright (c) 1997, 1998 The NetBSD Foundation, Inc.
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@ -2160,7 +2160,8 @@ syn_cache_add(so, m, optp, optlen, oi)
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sc->sc_irs = ti->ti_seq;
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sc->sc_iss = tcp_new_iss(sc, sizeof(struct syn_cache), 0);
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sc->sc_peermaxseg = oi->maxseg;
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sc->sc_ourmaxseg = tcp_mss_to_advertise(tp);
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sc->sc_ourmaxseg = tcp_mss_to_advertise(m->m_flags & M_PKTHDR ?
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m->m_pkthdr.rcvif : NULL);
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if (tcp_do_rfc1323 && (tb.t_flags & TF_RCVD_TSTMP))
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sc->sc_flags |= SCF_TIMESTAMP;
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if ((tb.t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
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@ -1,4 +1,4 @@
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/* $NetBSD: tcp_output.c,v 1.33 1998/04/01 22:15:52 thorpej Exp $ */
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/* $NetBSD: tcp_output.c,v 1.34 1998/04/13 21:18:19 kml Exp $ */
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/*-
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* Copyright (c) 1997, 1998 The NetBSD Foundation, Inc.
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@ -394,8 +394,11 @@ send:
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optlen = 0;
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hdrlen = sizeof (struct tcpiphdr);
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if (flags & TH_SYN) {
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struct rtentry *rt = in_pcbrtentry(tp->t_inpcb);
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tp->snd_nxt = tp->iss;
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tp->t_ourmss = tcp_mss_to_advertise(tp);
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tp->t_ourmss = tcp_mss_to_advertise(rt != NULL ?
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rt->rt_ifp : NULL);
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if ((tp->t_flags & TF_NOOPT) == 0) {
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opt[0] = TCPOPT_MAXSEG;
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opt[1] = 4;
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@ -1,4 +1,4 @@
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/* $NetBSD: tcp_subr.c,v 1.46 1998/03/31 22:49:10 thorpej Exp $ */
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/* $NetBSD: tcp_subr.c,v 1.47 1998/04/13 21:18:19 kml Exp $ */
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/*-
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* Copyright (c) 1997, 1998 The NetBSD Foundation, Inc.
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@ -110,6 +110,7 @@ int tcp_mssdflt = TCP_MSS;
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int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ;
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int tcp_do_rfc1323 = 1;
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int tcp_init_win = 1;
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int tcp_mss_ifmtu = 0;
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#ifndef TCBHASHSIZE
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#define TCBHASHSIZE 128
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@ -589,25 +590,38 @@ tcp_mtudisc(inp, errno)
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* socket. If we are the client (we initiated connection), we
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* are called witht he TCPCB for the actual connection.
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*/
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int
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tcp_mss_to_advertise(tp)
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const struct tcpcb *tp;
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u_long
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tcp_mss_to_advertise(ifp)
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const struct ifnet *ifp;
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{
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extern u_long in_maxmtu;
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struct inpcb *inp;
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struct socket *so;
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int mss;
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inp = tp->t_inpcb;
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so = inp->inp_socket;
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u_long mss = 0;
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/*
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* In order to avoid defeating path MTU discovery on the peer,
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* we advertise the max MTU of all attached networks as our MSS,
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* per RFC 1191, section 3.1.
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*
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* We provide the option to advertise just the MTU of
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* the interface on which we hope this connection will
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* be receiving. If we are responding to a SYN, we
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* will have a pretty good idea about this, but when
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* initiating a connection there is a bit more doubt.
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*
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* We also need to ensure that loopback has a large enough
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* MSS, as the loopback MTU is never included in in_maxmtu.
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*/
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mss = in_maxmtu - sizeof(struct tcpiphdr);
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if (ifp != NULL)
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mss = ifp->if_mtu;
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if (tcp_mss_ifmtu == 0)
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mss = max(in_maxmtu, mss);
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if (mss > sizeof(struct tcpiphdr))
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mss -= sizeof(struct tcpiphdr);
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mss = max(tcp_mssdflt, mss);
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return (mss);
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}
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@ -1,4 +1,4 @@
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/* $NetBSD: tcp_usrreq.c,v 1.34 1998/02/19 02:36:44 thorpej Exp $ */
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/* $NetBSD: tcp_usrreq.c,v 1.35 1998/04/13 21:18:20 kml Exp $ */
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/*-
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* Copyright (c) 1997, 1998 The NetBSD Foundation, Inc.
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@ -635,6 +635,9 @@ tcp_sysctl(name, namelen, oldp, oldlenp, newp, newlen)
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case TCPCTL_INIT_WIN:
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return (sysctl_int(oldp, oldlenp, newp, newlen,
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&tcp_init_win));
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case TCPCTL_MSS_IFMTU:
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return (sysctl_int(oldp, oldlenp, newp, newlen,
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&tcp_mss_ifmtu));
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default:
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return (ENOPROTOOPT);
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}
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@ -1,4 +1,4 @@
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/* $NetBSD: tcp_var.h,v 1.40 1998/04/07 05:09:20 thorpej Exp $ */
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/* $NetBSD: tcp_var.h,v 1.41 1998/04/13 21:18:20 kml Exp $ */
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/*-
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* Copyright (c) 1997, 1998 The NetBSD Foundation, Inc.
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@ -373,7 +373,8 @@ struct tcpstat {
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#define TCPCTL_SYN_BUCKET_LIMIT 6 /* max size of hash bucket */
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#define TCPCTL_SYN_CACHE_INTER 7 /* interval of comp. state timer */
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#define TCPCTL_INIT_WIN 8 /* initial window */
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#define TCPCTL_MAXID 9
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#define TCPCTL_MSS_IFMTU 9 /* mss from interface, not in_maxmtu */
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#define TCPCTL_MAXID 10
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#define TCPCTL_NAMES { \
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{ 0, 0 }, \
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@ -385,6 +386,7 @@ struct tcpstat {
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{ "syn_bucket_limit", CTLTYPE_INT }, \
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{ "syn_cache_interval", CTLTYPE_INT },\
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{ "init_win", CTLTYPE_INT }, \
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{ "mss_ifmtu", CTLTYPE_INT }, \
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}
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#ifdef _KERNEL
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@ -394,6 +396,7 @@ u_int32_t tcp_now; /* for RFC 1323 timestamps */
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extern int tcp_do_rfc1323; /* enabled/disabled? */
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extern int tcp_mssdflt; /* default seg size */
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extern int tcp_init_win; /* initial window */
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extern int tcp_mss_ifmtu; /* take MSS from interface, not in_maxmtu */
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extern int tcp_syn_cache_limit; /* max entries for compressed state engine */
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extern int tcp_syn_bucket_limit;/* max entries per hash bucket */
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extern int tcp_syn_cache_interval; /* compressed state timer */
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@ -420,7 +423,7 @@ void tcp_established __P((struct tcpcb *));
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void tcp_fasttimo __P((void));
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void tcp_init __P((void));
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void tcp_input __P((struct mbuf *, ...));
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int tcp_mss_to_advertise __P((const struct tcpcb *));
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u_long tcp_mss_to_advertise __P((const struct ifnet *));
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void tcp_mss_from_peer __P((struct tcpcb *, int));
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void tcp_mtudisc __P((struct inpcb *, int));
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struct tcpcb *
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@ -1,4 +1,4 @@
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.\" $NetBSD: sysctl.8,v 1.19 1998/02/06 06:23:56 perry Exp $
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.\" $NetBSD: sysctl.8,v 1.20 1998/04/13 21:21:13 kml Exp $
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.\"
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.\" Copyright (c) 1993
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.\" The Regents of the University of California. All rights reserved.
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@ -153,6 +153,8 @@ privilege can change the value.
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.It net.inet.tcp.syn_bucket_limit integer yes
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.It net.inet.tcp.syn_cache_interval integer yes
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.It net.inet.tcp.init_win integer yes
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.It net.inet.tcp.init_win integer yes
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.It net.inet.tcp.mss_ifmtu integer yes
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.It net.inet.udp.checksum integer yes
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.It net.inet.udp.sendspace integer yes
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.It net.inet.udp.recvspace integer yes
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