Google Dynamic DNS update script for Tomato firmware

ddns-start.sh

#!/bin/sh

set -u
#set -x

U=username
P=password
H=hostname
IP="$(ip -o addr show ppp0 | awk '/inet / {print $4}')"
DIGIP="$(dig +short $H)"
PROXY=http://127.0.0.1:8118
# args: username password hostname
# Note: you might need to install curl from entware, since curl/libcurl from Tomato firmware might not support https.
google_dns_update() {
  CMD=$(/opt/bin/curl -x $PROXY -s "https://$1:$2@domains.google.com/nic/update?hostname=$3&myip=$4")
  logger "google-ddns-updated: $CMD"
  echo "$CMD"
}
#sleep 30

echo "Interface IP is ${IP}, Query from DNS is ${DIGIP}"

if [ "$DIGIP" != "$IP" ]; then
    google_dns_update $U $P $H $IP
else
    echo "IPs are same, ddns update is not necessary"
fi
	
exit 0