Do all weave operations from within the container

Fixes #523

docker/Dockerfile

@@ -3,7 +3,7 @@ MAINTAINER Weaveworks Inc <help@weave.works>
 LABEL works.weave.role=system
 WORKDIR /home/weave
 RUN echo "http://dl-4.alpinelinux.org/alpine/edge/testing" >>/etc/apk/repositories && \
-	apk add --update runit conntrack-tools iproute2 util-linux && \
+	apk add --update runit conntrack-tools iproute2 util-linux curl && \
 	rm -rf /var/cache/apk/*
 ADD ./docker.tgz /
 ADD ./weave /usr/bin/

docker/entrypoint.sh

@@ -1,29 +1,63 @@
 #!/bin/sh
 
 usage() {
-	echo "$0 --dns <IP> --hostname <NAME> --searchpath <SEARCHPATH> --app.foo bar --probe.foo bar"
+	echo "$0 --app.foo bar --probe.foo bar"
 	exit 1
 }
 
 # This script exists to modify the network settings in the scope containers
 # as docker doesn't allow it when started with --net=host
 
+WEAVE_CONTAINER_NAME=weave
+DOCKER_BRIDGE=docker0
+HOSTNAME=scope
+DOMAIN=weave.local
+IP_REGEXP="[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}"
+
+container_ip() {
+    if ! status=$(docker inspect --format='{{.State.Running}} {{.NetworkSettings.IPAddress}}' $1 2>/dev/null); then
+        echo "$2" >&2
+        return 1
+    fi
+    case "$status" in
+        "true ")
+            echo "$1 container has no IP address; is Docker networking enabled?" >&2
+            return 1
+            ;;
+        true*)
+            CONTAINER_IP="${status#true }"
+            ;;
+        *)
+            echo "$3" >&2
+            return 1
+            ;;
+    esac
+}
+
+is_running() {
+    status=$(docker inspect --format='{{.State.Running}}' $1 2>/dev/null) && [ "$status" = "true" ]
+    return $?
+}
+
+docker_bridge_ip() {
+    local DOCKER_BRIDGE_IP=$(ip -f inet address show dev $DOCKER_BRIDGE | grep -m1 -o 'inet \([.0-9]\)*')
+    echo ${DOCKER_BRIDGE_IP#inet }
+}
+
+# Run `weave expose` if it's not already exposed.
+weave_expose() {
+    status=$(weave --local ps weave:expose | awk '{print $3}' 2>/dev/null)
+    if [ "$status" = "" ]; then
+        weave --local expose
+    fi
+}
+
 mkdir -p /etc/weave
 APP_ARGS=""
 PROBE_ARGS=""
 
 while true; do
     case "$1" in
-        --dns)
-            [ $# -gt 1 ] || usage
-            DNS_SERVER="$2"
-            shift
-            ;;
-        --searchpath)
-            [ $# -gt 1 ] || usage
-            SEARCHPATH="$2"
-            shift
-            ;;
         --app.*)
             if echo "$1" | grep "=" 1>/dev/null; then
                 ARG_NAME=$(echo "$1" | sed 's/\-\-app\.\([^=]*\)=\(.*\)/\1/')
@@ -73,15 +107,34 @@ while true; do
     shift
 done
 
+if is_running $WEAVE_CONTAINER_NAME; then
+    container_ip $WEAVE_CONTAINER_NAME
+    PROBE_ARGS="$PROBE_ARGS -weave.router.addr=$CONTAINER_IP"
+    weave_expose
+
+    DOCKER_BRIDGE_IP=$(docker_bridge_ip)
+    echo "Weave container detected at $CONTAINER_IP, Docker bridge at $DOCKER_BRIDGE_IP"
+
+    echo "domain $DOMAIN" >/etc/resolv.conf
+    echo "search $DOMAIN" >>/etc/resolv.conf
+    echo "nameserver $DOCKER_BRIDGE_IP" >>/etc/resolv.conf
+
+    IP_ADDRS=$(find /sys/class/net -type l | xargs -n1 basename | grep -vE 'docker|veth|lo' | \
+        xargs -n1 ip addr show | grep inet | awk '{ print $2 }' | grep -oE "$IP_REGEXP")
+    CONTAINER=$(docker inspect --format='{{.Id}}' weavescope)
+    if [ -z "$IP_ADDRS" ]; then
+        echo "Could not determine local IP address; Weave DNS integration will not work correctly."
+        exit 1
+    else
+        for ip in $IP_ADDRS; do
+            weave --local dns-add $ip $CONTAINER -h $HOSTNAME.$DOMAIN
+        done
+    fi
+fi
+
 echo "$APP_ARGS" >/etc/weave/scope-app.args
 echo "$PROBE_ARGS" >/etc/weave/scope-probe.args
 
-if [ -n "$DNS_SERVER" -a -n "$SEARCHPATH" ]; then
-    echo "domain $SEARCHPATH" >/etc/resolv.conf
-    echo "search $SEARCHPATH" >>/etc/resolv.conf
-    echo "nameserver $DNS_SERVER" >>/etc/resolv.conf
-fi
-
 # End of the command line can optionally be some
 # addresses of apps to connect to, for people not
 # using Weave DNS. We stick these in /etc/weave/apps