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#!/bin/sh
# /etc/rc.d/rc.ip_forward: start/stop IP packet forwarding
#
# If you intend to run your Linux box as a router, i.e. as a
# computer that forwards and redistributes network packets, you
# will need to enable IP packet forwarding in your kernel.
#
# To activate IP packet forwarding at boot time, make this
# script executable: chmod 755 /etc/rc.d/rc.ip_forward
#
# To disable IP packet forwarding at boot time, make this
# script non-executable: chmod 644 /etc/rc.d/rc.ip_forward
# Start IP packet forwarding:
ip_forward_start() {
if [ -f /proc/sys/net/ipv4/ip_forward ]; then
echo "Activating IPv4 packet forwarding."
echo 1 > /proc/sys/net/ipv4/ip_forward
# Changing /proc/sys/net/ipv4/ip_forward results in resetting all
# non-default ipv4 parameters for the interface as mentioned in
# /usr/src/linux/Documentation/networking/ip-sysctl.txt. So, we
# will reapply any ipv4 sysctl parameters now:
if [ -r /etc/sysctl.conf ]; then
/bin/grep ipv4 /etc/sysctl.conf | sysctl -p - 1> /dev/null 2> /dev/null
fi
fi
# When using IPv4 packet forwarding, you will also get the
# rp_filter, which automatically rejects incoming packets if the
# routing table entry for their source address doesn't match the
# network interface they're arriving on. This has security
# advantages because it prevents the so-called IP spoofing,
# however it can pose problems if you use asymmetric routing
# (packets from you to a host take a different path than packets
# from that host to you) or if you operate a non-routing host
# which has several IP addresses on different interfaces. To
# turn rp_filter off, uncomment the lines below:
#if [ -r /proc/sys/net/ipv4/conf/all/rp_filter ]; then
# echo "Disabling rp_filter."
# echo 0 > /proc/sys/net/ipv4/conf/all/rp_filter
#fi
}
# Stop IP packet forwarding:
ip_forward_stop() {
if [ -f /proc/sys/net/ipv4/ip_forward ]; then
echo "Disabling IPv4 packet forwarding."
echo 0 > /proc/sys/net/ipv4/ip_forward
# Changing /proc/sys/net/ipv4/ip_forward results in resetting all
# non-default ipv4 parameters for the interface as mentioned in
# /usr/src/linux/Documentation/networking/ip-sysctl.txt. So, we
# will reapply any ipv4 sysctl parameters now:
if [ -r /etc/sysctl.conf ]; then
/bin/grep ipv4 /etc/sysctl.conf | sysctl -p - 1> /dev/null 2> /dev/null
fi
fi
}
# Restart IP packet forwarding:
ip_forward_restart() {
ip_forward_stop
sleep 1
ip_forward_start
}
case "$1" in
'start')
ip_forward_start
;;
'stop')
ip_forward_stop
;;
'restart')
ip_forward_restart
;;
*)
echo "usage $0 start|stop|restart"
esac
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