Make code coverage work through the proxy

Previously, the proxy would run the weave script in ways that did
not run the weaver executable.  Now they can.  This is a problem because
of the contortions involved in using golang's code coverage support
in the integration tests, which require the weaver command line args to
be slightly mangled.

proxy/common.go

@@ -24,15 +24,28 @@ var (
 
 func callWeave(args ...string) ([]byte, []byte, error) {
 	args = append([]string{"--local"}, args...)
-	Log.Debug("Calling weave", args)
 	cmd := exec.Command("./weave", args...)
 	cmd.Env = []string{
 		"PATH=/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
 		"PROCFS=/hostproc",
 	}
-	if bridge := os.Getenv("DOCKER_BRIDGE"); bridge != "" {
-		cmd.Env = append(cmd.Env, fmt.Sprintf("DOCKER_BRIDGE=%s", bridge))
+
+	propagateEnv := func(key string) {
+		if val := os.Getenv(key); val != "" {
+			cmd.Env = append(cmd.Env, fmt.Sprintf("%s=%s", key, val))
+		}
 	}
+
+	propagateEnv("DOCKER_BRIDGE")
+
+	// Propogage WEAVE_DEBUG, to make debugging easier.
+	propagateEnv("WEAVE_DEBUG")
+
+	// This prevents the code coverage contortions in our
+	// integration test suite breaking things.
+	propagateEnv("COVERAGE")
+
+	Log.Debug("Calling weave args: ", args, "env: ", cmd.Env)
 	var stdout, stderr bytes.Buffer
 	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr

proxy/proxy.go

@@ -436,13 +436,15 @@ func (proxy *Proxy) getDNSDomain() (domain string) {
 	}
 
 	weaveContainer, err := proxy.client.InspectContainer("weave")
-	if err != nil ||
-		weaveContainer.NetworkSettings == nil ||
-		weaveContainer.NetworkSettings.IPAddress == "" {
-		return
+	var weaveIP string
+	if err == nil && weaveContainer.NetworkSettings != nil {
+		weaveIP = weaveContainer.NetworkSettings.IPAddress
+	}
+	if weaveIP == "" {
+		weaveIP = "127.0.0.1"
 	}
 
-	url := fmt.Sprintf("http://%s:%d/domain", weaveContainer.NetworkSettings.IPAddress, router.HTTPPort)
+	url := fmt.Sprintf("http://%s:%d/domain", weaveIP, router.HTTPPort)
 	resp, err := http.Get(url)
 	if err != nil || resp.StatusCode != http.StatusOK {
 		return

weave

@@ -1381,6 +1381,8 @@ launch_proxy() {
         -e PROCFS=/hostproc \
         -e WEAVE_CIDR=none \
         -e DOCKER_BRIDGE \
+        -e WEAVE_DEBUG \
+        -e COVERAGE \
         --entrypoint=/home/weave/weaveproxy \
         $WEAVEPROXY_DOCKER_ARGS $EXEC_IMAGE $COVERAGE_ARGS $PROXY_ARGS)
     wait_for_status $PROXY_CONTAINER_NAME http_call_unix $PROXY_CONTAINER_NAME status.sock