ddhcpd-gateway-update

#!/bin/sh

CACHE_TTL=600
CACHE_FILE=/tmp/ddhcp_gw_cache

GW_UPDATE_TRIES=5


verbose() {
	[ -n "$VERBOSE" ] && ( >&2 echo $@ )
}

mac_to_ipv6_ll() {
	IFS=':'; set $1; unset IFS
	echo "fe80::$(printf %02x $((0x$1 ^ 2)))$2:${3}ff:fe$4:$5$6"
}

get_gw_ipv4_address() {
	local gwmac="$1"
	local gwid="`echo "$gwmac" | tr -d ':'`"
	gluon-neighbour-info -p 1001 -d "`mac_to_ipv6_ll "$gwmac"`" -i br-client -r gateway | \
		while read resp; do
			local node_id="`echo "$resp" | jsonfilter -e '$.node_id'`"
			if [ "$node_id" = "$gwid" ]; then
				echo "$resp" | jsonfilter -e '$.address.ipv4'
			fi
		done
}

gateway_lost() {
	verbose Gateway lost, removing dhcp options
	rm -f "$CACHE_FILE"
	/usr/sbin/ddhcpdctl -r 3
	/usr/sbin/ddhcpdctl -r 6
}

update_gateway() {
	verbose Updating dhcp options
	/usr/sbin/ddhcpdctl -o "3:4:$1"
	/usr/sbin/ddhcpdctl -o "6:4:$1"
}

gwmac="`batctl gwl | grep '=>' | cut -d' ' -f2`"
[ -z "$gwmac" ] && {
	verbose Failed to determine mac address of current gateway
	gateway_lost
	exit 1
}

verbose Got gateway mac address: "$gwmac"

[ -f "$CACHE_FILE" ] && {
	verbose Retrieving cache
	source "$CACHE_FILE"
	now="`date +'%s'`"
	if echo "$last_update_time" | egrep -q '^[0-9]+$' && \
	    echo "$last_gwaddr" | egrep -q '^(([0-9]){1,3}\.){3}[0-9]{1,3}$'; then
		verbose Gateway mac address cache found, age $(($now - $last_update_time))
		if [ "$gwmac" = "$last_gwmac" ] && \
		    [ $(($now - $last_update_time)) -lt "$CACHE_TTL" ]; then
			verbose Cache is up to date
			update_gateway "$last_gwaddr"
			exit 0
		fi
	fi
	verbose Updating cache
}

for _ in seq "$GW_UPDATE_TRIES"; do
	gwaddr="`get_gw_ipv4_address "$gwmac"`"
	[ -n "$gwaddr" ] && break
done
[ -z "$gwaddr" ] && {
	verbose Failed to retrieve gateway IPv4 address
	gateway_lost
	exit 2
}

verbose Got gateway IPv4 address: "$gwaddr"

echo "last_gwmac=\"$gwmac\"" > "$CACHE_FILE"
echo "last_gwaddr=\"$gwaddr\"" >> "$CACHE_FILE"
echo "last_update_time=`date +'%s'`" >> "$CACHE_FILE"

update_gateway "$gwaddr"