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|
#!/bin/bash
#
# /usr/sbin/dnsmasq-portforward
#
# A script which gets run when the dnsmasq DHCP lease database changes.
# It logs to $LOGFILE, if it exists, and maintains port-forwards using
# IP-tables so that they always point to the correct host. See
# $PORTSFILE for details on configuring this. dnsmasq must be version 2.34
# or later.
#
# To enable this script, add
# dhcp-script=/usr/sbin/dnsmasq-portforward
# to /etc/dnsmasq.conf
#
# To enable logging, touch $LOGFILE
#
PORTSFILE=/etc/portforward
LOGFILE=/var/log/dhcp.log
IPTABLES=/sbin/iptables
action=${1:-0}
hostname=${4}
# log what's going on.
if [ -f ${LOGFILE} ] ; then
date +"%D %T $*" >>${LOGFILE}
fi
# If a lease gets stripped of a name, we see that as an "old" action
# with DNSMASQ_OLD_HOSTNAME set, convert it into a "del"
if [ ${DNSMASQ_OLD_HOSTNAME} ] && [ ${action} = old ] ; then
action=del
hostname=${DNSMASQ_OLD_HOSTNAME}
fi
# action init is not relevant, and will only be seen when leasefile-ro is set.
if [ ${action} = init ] ; then
exit 0
fi
if [ ${hostname} ]; then
ports=$(sed -n -e "/^${hostname}\ .*/ s/^.* //p" ${PORTSFILE})
for port in $ports; do
verb=removed
protocol=tcp
if [ ${port:0:1} = u ] ; then
protocol=udp
port=${port/u/}
fi
src=${port/:*/}
dst=${port/*:/}
# delete first, to avoid multiple copies of rules.
${IPTABLES} -t nat -D PREROUTING -p $protocol --destination-port $src -j DNAT --to-destination ${3}:$dst
if [ ${action} != del ] ; then
${IPTABLES} -t nat -A PREROUTING -p $protocol --destination-port $src -j DNAT --to-destination ${3}:$dst
verb=added
fi
if [ -f ${LOGFILE} ] ; then
echo " DNAT $protocol $src to ${3}:$dst ${verb}." >>${LOGFILE}
fi
done
fi
exit 0
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