Implement weave dns-lookup

prog/weaveexec/Dockerfile

@@ -9,6 +9,7 @@ RUN apk add --update \
     iproute2 \
     util-linux \
     conntrack-tools \
+    bind-tools \
   && rm -rf /var/cache/apk/*
 
 WORKDIR /home/weave

weave

@@ -47,6 +47,7 @@ weave attach        [<addr> ...] <container_id>
 weave detach        [<addr> ...] <container_id>
 weave dns-add       <ip_address> [<ip_address> ...] <container_id> [-h <fqdn>]
 weave dns-remove    <ip_address> [<ip_address> ...] <container_id> [-h <fqdn>]
+weave dns-lookup    <unqualified_name>
 weave expose        [<addr> ...] [-h <fqdn>]
 weave hide          [<addr> ...]
 weave ps            [<container_id> ...]
@@ -1333,6 +1334,11 @@ case "$COMMAND" in
             delete_dns_fqdn $CONTAINER "$3" $IP_ARGS
         fi
         ;;
+    dns-lookup)
+        [ $# -eq 1 ] || usage
+        docker_bridge_ip
+        dig @$DOCKER_BRIDGE_IP +short $1
+        ;;
     expose)
         collect_cidr_args "$@"
         shift $CIDR_ARG_COUNT