Add --proxy option to enable/disable proxy.

Weave Net initially had the ability to start a single component at a time with `launch-proxy` and `launch-router`.
This change enables this again via `--proxy=false` despite the merge of the proxy and the router.
Note that by default:
- `launch` passes `--proxy` which enables the proxy and keeps behaviour consistent with `launch` pre-merge,
- `weaver` defaults `--proxy` to `false` which disables the proxy and keeps behaviour consistent with `weaver` pre-merge (as it was `weaveproxy`'s responsibility).

prog/weaver/main.go

@@ -252,16 +252,18 @@ func main() {
 	}
 	config.ProtocolMinVersion = byte(protocolMinVersion)
 
-	// Start Weave Proxy:
-	proxy, err := weaveproxy.NewProxy(*proxyConfig)
-	if err != nil {
-		Log.Fatalf("Could not start proxy: %s", err)
+	if proxyConfig.Enabled {
+		// Start Weave Proxy:
+		proxy, err := weaveproxy.NewProxy(*proxyConfig)
+		if err != nil {
+			Log.Fatalf("Could not start proxy: %s", err)
+		}
+		defer proxy.Stop()
+		listeners := proxy.Listen()
+		proxy.AttachExistingContainers()
+		go proxy.Serve(listeners)
+		go proxy.ListenAndServeStatus("/home/weave/status.sock")
 	}
-	defer proxy.Stop()
-	listeners := proxy.Listen()
-	proxy.AttachExistingContainers()
-	go proxy.Serve(listeners)
-	go proxy.ListenAndServeStatus("/home/weave/status.sock")
 
 	if pktdebug {
 		networkConfig.PacketLogging = packetLogging{}
@@ -521,6 +523,7 @@ func configureProxy(version string, defaultDockerHost string) *weaveproxy.Config
 		DockerBridge: getenvOrDefault("DOCKER_BRIDGE", "docker0"),
 		DockerHost:   defaultDockerHost,
 	}
+	mflag.BoolVar(&proxyConfig.Enabled, []string{"-proxy"}, false, "instruct Weave Net to start its Docker proxy")
 	mflagext.ListVar(&proxyConfig.ListenAddrs, []string{"H"}, nil, "addresses on which to listen")
 	mflag.StringVar(&proxyConfig.HostnameFromLabel, []string{"-hostname-from-label"}, "", "Key of container label from which to obtain the container's hostname")
 	mflag.StringVar(&proxyConfig.HostnameMatch, []string{"-hostname-match"}, "(.*)", "Regexp pattern to apply on container names (e.g. '^aws-[0-9]+-(.*)$')")

proxy/proxy.go

@@ -50,6 +50,7 @@ func dockerAPIEndpoint(endpoint string) *regexp.Regexp {
 }
 
 type Config struct {
+	Enabled             bool
 	HostnameFromLabel   string
 	HostnameMatch       string
 	HostnameReplacement string

weave

@@ -48,7 +48,7 @@ weave launch        [--password <pass>] [--trusted-subnets <cidr>,...]
                     [--no-restart] [--resume] [--no-discovery] [--no-dns]
                     [--ipalloc-init <mode>]
                     [--ipalloc-range <cidr> [--ipalloc-default-subnet <cidr>]]
-                    [--plugin]
+                    [--plugin=false] [--proxy=false]
                     [-H <endpoint>] [--without-dns] [--no-multicast-route]
                     [--no-rewrite-hosts] [--no-default-ipalloc]
                     [--hostname-from-label <labelkey>]
@@ -1509,7 +1509,8 @@ EOF
         deprecation_warnings "$@"
         check_not_running router $CONTAINER_NAME        $BASE_IMAGE
         check_not_running_plugin_v2
-        launch --plugin "$@"
+        # Plugin and proxy are started by default. Should users additionally pass --plugin=false or --proxy=false, their overrides will take precedence when parsed by Go.
+        launch --plugin --proxy "$@"
         echo "$WEAVE_CONTAINER"
         ;;
     env)