Merge branch '67_attach' of https://github.com/bboreham/weave into bboreham-67_attach

README.md

@@ -221,6 +221,30 @@ will work. And, more interestingly,
 
 will work too, which is talking to a container that resides on $HOST1.
 
+### Attach to already-running containers
+
+If you don't want to start containers via the `weave` script, e.g. because
+you are controlling them as part of some larger orchestration scheme, you can
+attach the weave network to an already-running container. To illustrate, we
+can achieve the same effect as the first example like this:
+
+    host1# C=$(docker run -d -t -i ubuntu)
+    host1# weave attach 10.0.1.1/24 $C
+
+There is a matching `weave detach` command:
+
+    host1# weave detach 10.0.1.1/24 $C
+
+You can detach a container from one subnet and re-attach it to another:
+
+    host1# weave detach 10.0.1.1/24 $C
+    host1# weave attach 10.0.2.1/24 $C
+
+or attach a container to multiple subnets:
+
+    host1# weave attach 10.0.1.1/24 $C
+    host1# weave attach 10.0.2.1/24 $C
+
 ### Service export
 
 Services running in containers on a weave network can be made

weaver/weave

@@ -5,6 +5,8 @@ usage() {
     echo "Usage:"
     echo "weave launch <ipaddr>/<subnet> [-passwd <passwd>] <peer_host> ..."
     echo "weave run    <ipaddr>/<subnet> <docker run args> ..."
+    echo "weave attach <ipaddr>/<subnet> <container_id>"
+    echo "weave detach <ipaddr>/<subnet> <container_id>"
     echo "weave expose <ipaddr>/<subnet>"
     echo "weave hide   <ipaddr>/<subnet>"
     echo "weave status"
@@ -101,7 +103,7 @@ stop_masquerading() {
 }
 
 # the following borrows from https://github.com/jpetazzo/pipework
-configure_container_networking() {
+container_netns_preamble() {
     DOCKERPID=$(docker inspect --format='{{ .State.Pid }}' $1)
     [ "$DOCKERPID" = 0 ] && {
         echo "Container $1 not running." >&2
@@ -111,15 +113,40 @@ configure_container_networking() {
         echo "Container $1 unknown to Docker." >&2
         exit 1
     }
+
     NSPID=$DOCKERPID
 
     [ ! -d /var/run/netns ] && mkdir -p /var/run/netns
     rm -f /var/run/netns/$NSPID
     ln -s /proc/$NSPID/ns/net /var/run/netns/$NSPID
-
-    EXITCODE=1
     LOCAL_IFNAME="v${CONTAINER_IFNAME}pl${NSPID}"
     GUEST_IFNAME="v${CONTAINER_IFNAME}pg${NSPID}"
+
+    return 0
+}
+
+container_netns_cleanup() {
+    rm -f /var/run/netns/$NSPID
+}
+
+# Parameters are container ID, CIDR address
+configure_container_networking() {
+    container_netns_preamble $1
+
+    EXITCODE=1
+
+    # If veth name already exists then assume we set it up already;
+    # just add the IP address
+    if ip link show $LOCAL_IFNAME >/dev/null 2>&1 ; then
+        if ip netns exec $NSPID ip addr add $2 dev $CONTAINER_IFNAME ; then
+            EXITCODE=0
+        else
+            echo "Failed to attach address $2 to container $1" >&2
+        fi
+        container_netns_cleanup
+        return $EXITCODE
+    fi
+
     IP_TMPFILE=/tmp/weave_ip_output_$$
     rm -f $IP_TMPFILE
     if ip link add name $LOCAL_IFNAME mtu $MTU type veth peer name $GUEST_IFNAME mtu $MTU >$IP_TMPFILE 2>&1 ; then
@@ -148,11 +175,35 @@ configure_container_networking() {
     fi
 
     rm -f $IP_TMPFILE
-    rm -f /var/run/netns/$NSPID
+    container_netns_cleanup
 
     return $EXITCODE
 }
 
+# Parameters are container ID, CIDR address, interface-name
+detach() {
+    container_netns_preamble $1
+
+    EXITCODE=1
+    if ip netns exec $NSPID ip addr del $2 dev $CONTAINER_IFNAME ; then
+        # if no inet addresses remain then delete the veth
+        if [ -z "$(ip netns exec $NSPID ip -f inet addr list dev ethwe)" ] ; then
+            if ip link del $LOCAL_IFNAME type veth ; then
+                EXITCODE=0
+            else
+                echo "Failed to delete virtual ethernet device $LOCAL_IFNAME from container $1" >&2
+            fi
+        else
+            EXITCODE=0
+        fi
+    else
+        echo "Failed to detach address $2 from container $1" >&2
+    fi
+
+    container_netns_cleanup
+    return $EXITCODE
+}
+
 case "$COMMAND" in
     launch)
         [ $# -gt 0 ] || usage
@@ -226,6 +277,15 @@ case "$COMMAND" in
         configure_container_networking $CONTAINER $IPADDR $CONTAINER_IFNAME
         echo $CONTAINER
         ;;
+    attach)
+        [ $# -gt 1 ] || usage
+        create_bridge
+        configure_container_networking $2 $1 $CONTAINER_IFNAME
+        ;;
+    detach)
+        [ $# -gt 1 ] || usage
+        detach $2 $1
+        ;;
     expose)
         [ $# -gt 0 ] || usage
         IPADDR=$1