From a87cc5c3b15be2bd47c51c74fce9ec88fe0bfd6f Mon Sep 17 00:00:00 2001
From: Bryan Boreham <bjboreham@gmail.com>
Date: Tue, 25 Aug 2015 11:09:16 +0100
Subject: [PATCH] Get the proxy to re-attach the weave router if it sees it
 restart

---
 proxy/proxy.go                            | 18 ++++++++++++++++
 test/640_proxy_restart_reattaches_test.sh |  8 ++++++--
 weave                                     | 25 +++++++++++++++++++++++
 3 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/proxy/proxy.go b/proxy/proxy.go
index 1ab70579..77cc7ca9 100644
--- a/proxy/proxy.go
+++ b/proxy/proxy.go
@@ -305,6 +305,8 @@ func (proxy *Proxy) ContainerStarted(ident string) {
 	// If this was a container we modified the entrypoint for, attach it to the network
 	if containerShouldAttach(container) {
 		proxy.attach(container, true)
+	} else if containerIsWeaveRouter(container) {
+		proxy.attachRouter(container)
 	}
 	proxy.notifyWaiters(container.ID)
 }
@@ -313,6 +315,10 @@ func containerShouldAttach(container *docker.Container) bool {
 	return len(container.Config.Entrypoint) > 0 && container.Config.Entrypoint[0] == weaveWaitEntrypoint[0]
 }
 
+func containerIsWeaveRouter(container *docker.Container) bool {
+	return strings.HasPrefix(container.Config.Image, "weaveworks/weave")
+}
+
 func (proxy *Proxy) createWait(r *http.Request, ident string) {
 	proxy.Lock()
 	ch := make(chan struct{})
@@ -386,6 +392,18 @@ func (proxy *Proxy) attach(container *docker.Container, orDie bool) error {
 	return nil
 }
 
+func (proxy *Proxy) attachRouter(container *docker.Container) error {
+	Log.Infof("Attaching weave router container")
+	args := []string{"attach-router"}
+	if _, stderr, err := callWeave(args...); err != nil {
+		Log.Warningf("Attaching container %s to weave network failed: %s", container.ID, string(stderr))
+		return errors.New(string(stderr))
+	} else if len(stderr) > 0 {
+		Log.Warningf("Attaching container %s to weave network: %s", container.ID, string(stderr))
+	}
+	return nil
+}
+
 func (proxy *Proxy) weaveCIDRs(networkMode string, env []string) ([]string, error) {
 	if networkMode == "host" || strings.HasPrefix(networkMode, "container:") {
 		return nil, fmt.Errorf("the container was created with the '--net=%s'", networkMode)
diff --git a/test/640_proxy_restart_reattaches_test.sh b/test/640_proxy_restart_reattaches_test.sh
index ff02e678..6bdd65ec 100755
--- a/test/640_proxy_restart_reattaches_test.sh
+++ b/test/640_proxy_restart_reattaches_test.sh
@@ -13,13 +13,18 @@ check_attached() {
 
 start_suite "Proxy restart reattaches networking to containers"
 
-weave_on $HOST1 launch
+WEAVE_DOCKER_ARGS=--restart=always WEAVEPROXY_DOCKER_ARGS=--restart=always weave_on $HOST1 launch
 proxy_start_container          $HOST1 -e WEAVE_CIDR=$C2/24 -di --name=c2 --restart=always -h $NAME
 proxy_start_container_with_dns $HOST1 -e WEAVE_CIDR=$C1/24 -di --name=c1 --restart=always
 
 proxy docker_on $HOST1 restart -t=1 c2
 check_attached
 
+# Restart weave router
+docker_on $HOST1 restart weave
+sleep 1
+check_attached
+
 # Kill outside of Docker so Docker will restart it
 run_on $HOST1 sudo kill -KILL $(docker_on $HOST1 inspect --format='{{.State.Pid}}' c2)
 sleep 1
@@ -34,7 +39,6 @@ assert_raises "proxy exec_on $HOST1 c3 $CHECK_ETHWE_UP"
 # Restart docker itself, using different commands for systemd- and upstart-managed.
 run_on $HOST1 sh -c "command -v systemctl >/dev/null && sudo systemctl restart docker || sudo service docker restart"
 sleep 1
-weave_on $HOST1 launch
 check_attached
 
 end_suite
diff --git a/weave b/weave
index d560c278..b89f0173 100755
--- a/weave
+++ b/weave
@@ -685,6 +685,10 @@ setup_router_iface_bridge() {
         echo "Perhaps you are running the docker daemon with container networking disabled (-b=none)." >&2
         return 1
     fi
+    # No-op if already attached
+    if netnsenter ip link show $CONTAINER_IFNAME >/dev/null 2>&1 ; then
+        return 0
+    fi
     connect_container_to_bridge $CONTAINER_IFNAME &&
         netnsenter ethtool -K eth0 tx off >/dev/null &&
         netnsenter ip link set $CONTAINER_IFNAME up
@@ -1467,6 +1471,17 @@ launch_router() {
         --dns-effective-listen-address $DOCKER_BRIDGE_IP \
         ${NETHOST_OPT:+$DNS_ROUTER_OPTS} $NO_DNS_OPT \
         --docker-api "unix:///var/run/docker.sock" "$@")
+}
+
+# Recreate the parameter values that are set when the router is first launched
+fetch_router_args() {
+    IPRANGE=$(docker inspect -f '{{.Args}}' $1 | grep -o -e '-ipalloc-range [^ ]*')
+    # This doesn't get back the right syntax, but it's enough for our purposes
+    DNS_PORT_MAPPING=$(docker inspect -f '{{with index .HostConfig.PortBindings "53/udp"}}{{.}}{{end}}' $1)
+}
+
+attach_router() {
+    ROUTER_CONTAINER=$1
     with_container_netns_or_die $ROUTER_CONTAINER setup_router_iface_$BRIDGE_TYPE
     err_msg=$(death_msg $CONTAINER_NAME)
     container_ip $CONTAINER_NAME "$err_msg" "$err_msg" || return 1
@@ -1643,14 +1658,24 @@ case "$COMMAND" in
         check_not_running $PROXY_CONTAINER_NAME $BASE_EXEC_IMAGE
         COMMON_ARGS=$(common_launch_args "$@")
         launch_router "$@"
+        attach_router $CONTAINER_NAME
         launch_proxy  $COMMON_ARGS
         ;;
     launch-router)
         deprecation_warnings "$@"
         check_not_running $CONTAINER_NAME $BASE_IMAGE
         launch_router "$@"
+        attach_router $CONTAINER_NAME
         echo $ROUTER_CONTAINER
         ;;
+    attach-router)
+        deprecation_warnings "$@"
+        check_running $CONTAINER_NAME
+        enforce_docker_bridge_addr_assign_type
+        create_bridge
+        fetch_router_args $CONTAINER_NAME
+        attach_router $CONTAINER_NAME
+        ;;
     launch-proxy)
         deprecation_warnings "$@"
         check_not_running $PROXY_CONTAINER_NAME $BASE_EXEC_IMAGE