Control network settings with sysctl.conf

Jul 22, '02 08:43:39AM

Contributed by: timrob

I recall a hint called Broadband Optimizer a while ago. I have since figured out a way to use the Freebsd style sysctl.conf to control your network settings. Read the rest of the article for the how-to...

The first thing is to create a sysctl.conf file...

 % sudo emacs /etc/sysctl.conf
...and put your settings in it. For example, I'll use the Broadband Optimizers settings:
net.inet.tcp.sendspace: 65536
net.inet.tcp.recvspace: 65536
net.inet.tcp.delayed_ack: 0
net.inet.udp.recvspace: 73728
The next thing is to create an rc.sysctl file:
 % sudo emacs /etc/rc.sysctl
Put the following in it:
#!/bin/sh
#
# Copyright (c) 1999 Warner Losh
# 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.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
#
# $FreeBSD: src/etc/rc.sysctl,v 1.4.4.6 2002/04/15 00:44:13 dougb Exp $
#

#
# Read in /etc/sysctl.conf and set things accordingly
#

if [ -f /etc/sysctl.conf ]; then
while read var comments
do
case ${var} in
#*|'')
;;
*)
mib=${var%=*}
val=${var#*=}

if current_value=`sysctl -n ${mib} 2>/dev/null`; then
case ${current_value} in
${val}) ;;
*)
sysctl -w ${var}
;;
esac
else
case ${1} in
last)
echo "Warning: sysctl ${mib} does not exist"
;;
esac
fi
;;
esac
done
The final step is to edit the Startup Item:
 % sudo emacs /System/Library/StartupItems/SystemTuning/SystemTuning
At the end of the file where it says...
sysctl -w kern.maxvnodes=${newvnodes}
...add the following:
if [ -r /etc/rc.sysctl ]; then
sh /etc/rc.sysctl first
fi
Now all you have to do is add parameters to /etc/sysctl.conf and they will be read at boot.

[Editor's note: I have not tested this script myself!]

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