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on-dhcp-event.sh
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on-dhcp-event.sh
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#!/bin/bash
# This script came from ubnt.com forum user "bradd" in the following post
# http://community.ubnt.com/t5/EdgeMAX/Automatic-DNS-resolution-of-DHCP-client-names/td-p/651311
# It has been modified by Ubiquiti to update the /etc/host file
# instead of adding to the CLI.
# Thanks to forum user "itsmarcos" for bug fix & improvements
# Thanks to forum user "ruudboon" for multiple domain fix
# Thanks to forum user "chibby85" for expire patch and static-mapping
if [ $# -lt 5 ]; then
echo Invalid args
logger -s -t on-dhcp-event "Invalid args \"$@\""
exit 1
fi
action=$1
client_name=$2
client_ip=$3
client_mac=$4
domain=$5
file=/etc/hosts
changes=0
if [ "$domain" == "..YYZ!" ]; then
client_fqdn_name=$client_name
client_search_expr=$client_name
else
client_fqdn_name=$client_name.$domain
client_search_expr="$client_name\\.$domain"
fi
case "$action" in
commit) # add mapping for new lease
echo "- new lease event, setting static mapping for host "\
"$client_fqdn_name (MAC=$client_mac, IP=$client_ip)"
#
# grep fails miserably with \t in the search expression.
# In the following line one <Ctrl-V> <TAB> is used after $client_search_expr
# followed by a single space
grep -q " $client_search_expr #on-dhcp-event " $file
if [ $? == 0 ]; then
echo pattern found, removing
wc1=`cat $file | wc -l`
sudo sed -i "/ $client_search_expr\t #on-dhcp-event /d" $file
wc2=`cat $file | wc -l`
if [ "$wc1" -eq "$wc2" ]; then
echo No change
fi
else
echo pattern NOT found
fi
# check if hostname already exists (e.g. a static host mapping)
# if so don't overwrite
grep -q " $client_search_expr " $file
if [ $? == 0 ]; then
echo host $client_fqdn_name already exists, exiting
exit 1
fi
line="$client_ip\t $client_fqdn_name\t #on-dhcp-event $client_mac"
sudo sh -c "echo -e '$line' >> $file"
((changes++))
echo Entry was added
;;
release) # delete mapping for released address
echo "- lease release event, deleting static mapping for host $client_fqdn_name"
wc1=`cat $file | wc -l`
sudo sed -i "/ $client_search_expr\t #on-dhcp-event /d" $file
wc2=`cat $file | wc -l`
if [ "$wc1" -eq "$wc2" ]; then
echo No change
else
echo Entry was removed
((changes++))
fi
;;
*)
logger -s -t on-dhcp-event "Invalid command \"$1\""
exit 1;
;;
esac
if [ $changes -gt 0 ]; then
echo Success
pid=`pgrep pdns_recursor`
if [ -n "$pid" ]; then
sudo rec_control reload-zones
fi
else
echo No changes made
fi
exit 0

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