introduce 'weave stop'

which, as well as stopping&removing the weave container also clears
the UDP connection tracking for the weave port, without which UDP
connections to a quickly (<3min) re-started weave would fail.

Fixes #18

README.md

@@ -30,8 +30,15 @@ To run weave on a host, you need to install...
           https://raw.githubusercontent.com/zettio/weave/master/weaver/weave
         sudo chmod a+x /usr/local/bin/weave
 
-3. ethtool. On many systems that is installed already; if not then
-grab it via your favourite package manager.
+3. (recommended) ethtool. On many systems this is installed already;
+   if not then grab it via your favourite package manager. On some
+   systems, weave application container networking may not operate
+   correctly unless ethtool is available.
+
+4. (optional) conntrack. Install this via your favourite package
+   manager. Without conntrack, the weave network may not re-establish
+   itself fully when individual weave instances are stopped (with
+   `weave stop`) and restarted quickly (typically within ~3 minutes).
 
 ## Example
 
@@ -286,12 +293,11 @@ the partition heals.
 
 The weave container is very light-weight - just over 8MB image size
 and a few 10s of MBs of runtime memory - and disposable. I.e. should
-weave ever run into difficulty, one can simply bounce the weave
-container (though note
-[issue #18](https://github.com/zettio/weave/issues/18)). Application
-containers do *not* have to be restarted in that event, and indeed may
-not even experience a temporary connectivity failure if the weave
-container is restarted quickly enough.
+weave ever run into difficulty, one can simply stop it (with `weave
+stop`) and restart it. Application containers do *not* have to be
+restarted in that event, and indeed may not even experience a
+temporary connectivity failure if the weave container is restarted
+quickly enough.
 
 ## Troubleshooting
 

weaver/weave

@@ -6,6 +6,7 @@ usage() {
     echo "weave launch <ipaddr>/<subnet> [-passwd <passwd>] <peer_host> ..."
     echo "weave run    <ipaddr>/<subnet> <docker run args> ..."
     echo "weave expose <ipaddr>/<subnet>"
+    echo "weave stop"
     exit 1
 }
 
@@ -14,16 +15,15 @@ usage() {
     exit 1
 }
 
-[ $# -gt 1 ] || usage
+[ $# -gt 0 ] || usage
 
 BRIDGE=weave
 CONTAINER_IFNAME=ethwe
 MTU=65535
 
 COMMAND=$1
-IPADDR=$2
 
-shift 2
+shift 1
 
 create_bridge() {
     [ ! -d /sys/class/net/$BRIDGE ] && {
@@ -50,6 +50,9 @@ setup_masquerading() {
 
 case "$COMMAND" in
     launch)
+        [ $# -gt 0 ] || usage
+        IPADDR=$1
+        shift 1
         create_bridge
         setup_masquerading
         # We set the router name to the bridge mac since that is
@@ -64,18 +67,35 @@ case "$COMMAND" in
         IFACE=eth0
         ;;
     run)
+        [ $# -gt 0 ] || usage
+        IPADDR=$1
+        shift 1
         create_bridge
         CONTAINER=$(docker run -d "$@")
         echo $CONTAINER
         IFACE=$CONTAINER_IFNAME
         ;;
     expose)
+        [ $# -gt 0 ] || usage
+        IPADDR=$1
+        shift 1
         if ! ip addr list dev $BRIDGE | grep -qF $IPADDR
         then
             ip addr add dev $BRIDGE $IPADDR
         fi
         exit 0
         ;;
+    stop)
+        docker kill weave > /dev/null
+        docker rm weave > /dev/null
+        if command -v conntrack >/dev/null 2>&1
+        then
+            conntrack -D -p udp --dport 6783 >/dev/null 2>&1
+        else
+            echo "Cannot find conntrack; please install it. Continuing without it." >&2
+        fi
+        exit 0
+        ;;
     *)
         echo "Unknown weave command '$COMMAND'"
         usage
@@ -114,7 +134,7 @@ if command -v ethtool >/dev/null 2>&1
 then
     ip netns exec $NSPID ethtool -K $IFACE tx off > /dev/null
 else
-    echo "Cannot find ethtool; continuing without it" >&2
+    echo "Cannot find ethtool; please install it. Continuing without it." >&2
 fi
 
 [ -f /var/run/netns/$NSPID ] && rm -f /var/run/netns/$NSPID