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dnsmasq

    1: #!/bin/bash
    2: # 
    3: # /usr/sbin/dnsmasq-portforward
    4: #
    5: # A script which gets run when the dnsmasq DHCP lease database changes.
    6: # It logs to $LOGFILE, if it exists, and maintains port-forwards using
    7: # IP-tables so that they always point to the correct host. See
    8: # $PORTSFILE for details on configuring this. dnsmasq must be version 2.34 
    9: # or later.
   10: #
   11: # To enable this script, add 
   12: #    dhcp-script=/usr/sbin/dnsmasq-portforward
   13: # to /etc/dnsmasq.conf
   14: #
   15: # To enable logging, touch $LOGFILE
   16: #
   17: 
   18: PORTSFILE=/etc/portforward
   19: LOGFILE=/var/log/dhcp.log
   20: IPTABLES=/sbin/iptables
   21: 
   22: action=${1:-0}
   23: hostname=${4}
   24: 
   25: # log what's going on.
   26: if [ -f ${LOGFILE} ] ; then
   27:     date +"%D %T $*" >>${LOGFILE}
   28: fi
   29: 
   30: # If a lease gets stripped of a name, we see that as an "old" action
   31: # with DNSMASQ_OLD_HOSTNAME set, convert it into a "del" 
   32: if [ ${DNSMASQ_OLD_HOSTNAME} ] && [ ${action} = old ] ; then
   33:     action=del
   34:     hostname=${DNSMASQ_OLD_HOSTNAME}
   35: fi
   36: 
   37: # IPv6 leases are not our concern. no NAT there!
   38: if [ ${DNSMASQ_IAID} ] ; then
   39:    exit 0
   40: fi
   41: 
   42: # action init is not relevant, and will only be seen when leasefile-ro is set.
   43: if [ ${action} = init ] ; then
   44:     exit 0
   45: fi
   46: 
   47: # action tftp is not relevant.
   48: if [ ${action} = tftp ] ; then
   49:     exit 0
   50: fi
   51: 
   52: if [ ${hostname} ]; then
   53:     ports=$(sed -n -e "/^${hostname}\ .*/ s/^.* //p" ${PORTSFILE})
   54: 
   55:     for port in $ports; do
   56: 	verb=removed
   57: 	protocol=tcp
   58: 	if [ ${port:0:1} = u ] ; then
   59: 	    protocol=udp 
   60: 	    port=${port/u/}
   61: 	fi
   62: 	src=${port/:*/}
   63: 	dst=${port/*:/}
   64: # delete first, to avoid multiple copies of rules.
   65: 	${IPTABLES} -t nat -D PREROUTING -p $protocol --destination-port $src -j DNAT --to-destination ${3}:$dst
   66:         if [ ${action} != del ] ; then
   67: 	    ${IPTABLES} -t nat -A PREROUTING -p $protocol --destination-port $src -j DNAT --to-destination ${3}:$dst
   68: 	    verb=added
   69: 	fi
   70: 	if [ -f ${LOGFILE} ] ; then
   71: 	    echo "     DNAT $protocol $src to ${3}:$dst ${verb}." >>${LOGFILE}
   72: 	fi
   73:     done
   74: fi
   75:     
   76: exit 0
   77: 
   78: