#!/bin/bash
#
# This script registers/removes docker containers IP addresses
# from the local unbound resolver in the post-start / pre-stop actions.
#
# For action pre-start, it checks if there is a CID file that needs to be
# cleaned away to not prevent the new container from starting.
#

# sunet_docker_pre-post: CID d05a0842ce1700ee3328d42ccf5c2f29cc3d71fa6dcc6a72f994f8d032453be7
# sunet_docker_pre-post: ACTION pre-stop
# sunet_docker_pre-post: IMAGE docker.sunet.se/eduid/eduid-mm-service
# sunet_docker_pre-post: NAME eduid-mm-service
#for e in "CID" "ACTION" "IMAGE" "NAME"; do
#    logger -t sunet_docker_pre-post "$e `printenv $e`"
#done

logtag="sunet_docker_pre-post[$ACTION]"
logger -t "${logtag}" "$NAME ($IMAGE), CID: '$CID'"

if [ "x$ACTION" = "xpre-start" ]; then
    if [ -f "${CIDFILE}" ]; then
        # Clean away the CID file in pre-start if the container is in fact not running
	docker inspect "${CID}" 2>/dev/null || (
	    logger -t "${logtag}" "Removing left-over CID file '${CIDFILE}' (CID ${CID})";
	    rm -f "${CIDFILE}"
	  )
    fi

    # Remove any stopped container with this name to prevent the docker start script
    # from just restarting that one (instead of starting the currently tagged image,
    # which might be newer than the one used by the old container)
    docker inspect "${NAME}" && docker rm "${NAME}"
    exit 0
fi

if [ "x${CID}" = "x" ]; then
    CID=$(docker inspect --format '{{ .Id }}' "${NAME}" 2>/dev/null)

    if [ "x${CID}" = "x" ]; then
	# sometimes containers start slow...
	for retry in 1 2 3 4 5; do
	    sleep 1
	    logger -t "${logtag}" "Retrying CID lookup for ${NAME}"
	    CID=$(docker inspect --format '{{ .Id }}' "${NAME}" 2>/dev/null)
	    if [ "x${CID}" != "x" ]; then
		break
	    fi
	done
    fi

    if [ "x${CID}" = "x" ]; then
	logger -t "${logtag}" "No CID provided or found! Aborting."
	exit 0
    fi

    logger -t "${logtag}" "Found CID ${CID} using docker inspect on '${NAME}'"
fi

# Remove registered name.
# XXX this does NOT handle multiple instances of the same image running on
# a single Docker host!
logger -t "${logtag}" "Un-registering ${NAME}.docker"
unbound-control local_data_remove "${NAME}.docker." > /dev/null

# If it is a container starting up, register it's IP address
if [ "x$ACTION" = "xpost-start" ]; then
    ip=$(docker inspect --format '{{ .NetworkSettings.IPAddress }}' "${CID}" 2>/dev/null)
    if [ "x${ip}" = "x" ]; then
	logger -t "${logtag}" "Failed to get IP from CID ${CID}. Aborting."
	exit 0
    fi
    unbound-control local_data "${NAME}.docker. 60 IN A ${ip}" > /dev/null
    # Register reverse pointer - there is no local_data_ptr command unfortunately
    ptr=$(echo "${ip}" | awk -F . '{print $4"."$3"."$2"."$1".in-addr.arpa."}')
    unbound-control local_data "${ptr} 60 IN PTR ${NAME}.docker."
    logger -t "${logtag}" "Registered ${NAME}.docker at ${ip}"
fi