[proxy] Add support for WEAVE_CIDR=none

Tells the proxy not to do anything with this container. We set it when
running weaveexec/weave/etc containers, so that the weave script works
through the proxy.

proxy/common.go

@@ -28,13 +28,16 @@ func callWeave(args ...string) ([]byte, error) {
 	return out, err
 }
 
-func weaveCIDRsFromConfig(config *docker.Config) ([]string, bool) {
+func weaveCIDRsFromConfig(config *docker.Config, noDefaultIPAM bool) ([]string, bool) {
 	for _, e := range config.Env {
 		if strings.HasPrefix(e, "WEAVE_CIDR=") {
+			if e[11:] == "none" {
+				return nil, false
+			}
 			return strings.Fields(e[11:]), true
 		}
 	}
-	return nil, false
+	return nil, !noDefaultIPAM
 }
 
 func marshalRequestBody(r *http.Request, body interface{}) error {

proxy/create_container_interceptor.go

@@ -33,7 +33,7 @@ func (i *createContainerInterceptor) InterceptRequest(r *http.Request) error {
 		return err
 	}
 
-	if cidrs, ok := weaveCIDRsFromConfig(container.Config); ok || !i.proxy.NoDefaultIPAM {
+	if cidrs, ok := weaveCIDRsFromConfig(container.Config, i.proxy.NoDefaultIPAM); ok {
 		Info.Printf("Creating container with WEAVE_CIDR \"%s\"", strings.Join(cidrs, " "))
 		if container.HostConfig == nil {
 			container.HostConfig = &docker.HostConfig{}

proxy/create_exec_interceptor.go

@@ -29,7 +29,7 @@ func (i *createExecInterceptor) InterceptRequest(r *http.Request) error {
 		return err
 	}
 
-	if cidrs, ok := weaveCIDRsFromConfig(container.Config); ok || !i.proxy.NoDefaultIPAM {
+	if cidrs, ok := weaveCIDRsFromConfig(container.Config, i.proxy.NoDefaultIPAM); ok {
 		Info.Printf("Exec in container %s with WEAVE_CIDR \"%s\"", container.ID, strings.Join(cidrs, " "))
 		cmd := append(weaveWaitEntrypoint, "-s")
 		options.Cmd = append(cmd, options.Cmd...)

proxy/start_container_interceptor.go

@@ -21,8 +21,8 @@ func (i *startContainerInterceptor) InterceptResponse(r *http.Response) error {
 		return err
 	}
 
-	cidrs, ok := weaveCIDRsFromConfig(container.Config)
-	if !ok && i.proxy.NoDefaultIPAM {
+	cidrs, ok := weaveCIDRsFromConfig(container.Config, i.proxy.NoDefaultIPAM)
+	if !ok {
 		Debug.Print("No Weave CIDR, ignoring")
 		return nil
 	}