#!/bin/sh

GLOBALROOTS="/etc/dnsroots.global"
GLOBALBK="/etc/dnsroots.global.`date +%Y%m%d`.bk"
TEMPROOTS="`mktemp -p /etc '.dnsroots.XXXXXX'`"
NAMEDROOT="http://www.internic.net/zones/named.root"

# Use curl or wget in path
CURLOPTS="--silent"
CURL="`which curl 2>/dev/null`"
if [ $? -ne 0 ]; then
	CURLOPTS="--quiet -O -"
	CURL="`which wget 2>/dev/null`"
	if [ $? -ne 0 ]; then
		echo "Neither wget nor curl found in path."
		exit 1
	fi
fi

# Download and process update file
"$CURL" $CURLOPTS "$NAMEDROOT" \
	| grep ' A ' | tr -s ' ' | cut -d ' ' -f4 \
	| sort > "$TEMPROOTS"

# Make sure our new file isn't blank
if [ -s "$TEMPROOTS" ]; then
	mv "$GLOBALROOTS" "$GLOBALBK"
	mv "$TEMPROOTS" "$GLOBALROOTS"
	diff -u "$GLOBALBK" "$GLOBALROOTS" > "$GLOBALBK.diff"
	if [ $? -ne 0 ]; then
		echo "Root DNS servers have been updated."
		echo "Changes listed below.  Please update dnscache instances."
		cat "$GLOBALBK.diff"
	else
		# No point keeping empty files
		rm -f "$GLOBALBK.diff"
	fi
else
	echo "We seem to have received a blank root server update."
fi