proxy interceptors implicitly modify arguments, instead of returning them

proxy/client.go

@@ -27,7 +27,7 @@ func newClient(dial func() (net.Conn, error), i interceptor) *client {
 }
 
 func (c *client) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	req, err := c.InterceptRequest(r)
+	err := c.InterceptRequest(r)
 	if err == docker.ErrNoSuchImage {
 		http.NotFound(w, r)
 		return
@@ -47,13 +47,13 @@ func (c *client) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	client := httputil.NewClientConn(conn, nil)
 	defer client.Close()
 
-	resp, err := client.Do(req)
+	resp, err := client.Do(r)
 	if err != nil && err != httputil.ErrPersistEOF {
 		http.Error(w, fmt.Sprintf("Could not make request to target: %v", err), http.StatusInternalServerError)
 		Warning.Print("Error forwarding request: ", err)
 		return
 	}
-	resp, err = c.InterceptResponse(resp)
+	err = c.InterceptResponse(resp)
 	if err != nil {
 		http.Error(w, "Unable to intercept response", http.StatusInternalServerError)
 		Warning.Print("Error intercepting response: ", err)

proxy/create_container_interceptor.go

@@ -21,36 +21,36 @@ type createContainerRequestBody struct {
 	MacAddress string             `json:"MacAddress,omitempty" yaml:"MacAddress,omitempty"`
 }
 
-func (i *createContainerInterceptor) InterceptRequest(r *http.Request) (*http.Request, error) {
+func (i *createContainerInterceptor) InterceptRequest(r *http.Request) error {
 	body, err := ioutil.ReadAll(r.Body)
 	if err != nil {
-		return nil, err
+		return err
 	}
 	r.Body.Close()
 
 	container := createContainerRequestBody{}
 	if err := json.Unmarshal(body, &container); err != nil {
-		return nil, err
+		return err
 	}
 
 	if _, ok := weaveCIDRsFromConfig(container.Config); ok {
 		container.HostConfig.VolumesFrom = append(container.HostConfig.VolumesFrom, "weaveproxy")
 		if err := i.setWeaveWaitEntrypoint(container.Config); err != nil {
-			return nil, err
+			return err
 		}
 		if err := i.setWeaveDNS(&container); err != nil {
-			return nil, err
+			return err
 		}
 	}
 
 	newBody, err := json.Marshal(container)
 	if err != nil {
-		return nil, err
+		return err
 	}
 	r.Body = ioutil.NopCloser(bytes.NewReader(newBody))
 	r.ContentLength = int64(len(newBody))
 
-	return r, nil
+	return nil
 }
 
 func (i *createContainerInterceptor) setWeaveWaitEntrypoint(container *docker.Config) error {
@@ -100,6 +100,6 @@ func (i *createContainerInterceptor) setWeaveDNS(container *createContainerReque
 	return nil
 }
 
-func (i *createContainerInterceptor) InterceptResponse(r *http.Response) (*http.Response, error) {
-	return r, nil
+func (i *createContainerInterceptor) InterceptResponse(r *http.Response) error {
+	return nil
 }

proxy/interceptor.go

@@ -3,17 +3,17 @@ package proxy
 import "net/http"
 
 type interceptor interface {
-	InterceptRequest(*http.Request) (*http.Request, error)
-	InterceptResponse(*http.Response) (*http.Response, error)
+	InterceptRequest(*http.Request) error
+	InterceptResponse(*http.Response) error
 }
 
 type nullInterceptor struct {
 }
 
-func (i nullInterceptor) InterceptRequest(r *http.Request) (*http.Request, error) {
-	return r, nil
+func (i nullInterceptor) InterceptRequest(r *http.Request) error {
+	return nil
 }
 
-func (i nullInterceptor) InterceptResponse(r *http.Response) (*http.Response, error) {
-	return r, nil
+func (i nullInterceptor) InterceptResponse(r *http.Response) error {
+	return nil
 }

proxy/start_container_interceptor.go

@@ -16,15 +16,15 @@ type startContainerInterceptor struct {
 	withDNS bool
 }
 
-func (i *startContainerInterceptor) InterceptRequest(r *http.Request) (*http.Request, error) {
-	return r, nil
+func (i *startContainerInterceptor) InterceptRequest(r *http.Request) error {
+	return nil
 }
 
-func (i *startContainerInterceptor) InterceptResponse(r *http.Response) (*http.Response, error) {
+func (i *startContainerInterceptor) InterceptResponse(r *http.Response) error {
 	containerID := ""
 	if subs := containerIDRegexp.FindStringSubmatch(r.Request.URL.Path); subs == nil {
 		Warning.Printf("No container id found in request with path %s", r.Request.URL.Path)
-		return r, nil
+		return nil
 	} else {
 		containerID = subs[1]
 	}
@@ -32,13 +32,13 @@ func (i *startContainerInterceptor) InterceptResponse(r *http.Response) (*http.R
 	container, err := i.client.InspectContainer(containerID)
 	if err != nil {
 		Warning.Printf("Error inspecting container %s: %v", containerID, err)
-		return r, nil
+		return nil
 	}
 
 	cidrs, ok := weaveCIDRsFromConfig(container.Config)
 	if !ok {
 		Debug.Print("No Weave CIDR, ignoring")
-		return r, nil
+		return nil
 	}
 	Info.Printf("Container %s was started with CIDR \"%s\"", containerID, strings.Join(cidrs, " "))
 	args := []string{"attach"}
@@ -46,7 +46,7 @@ func (i *startContainerInterceptor) InterceptResponse(r *http.Response) (*http.R
 	args = append(args, containerID)
 	if _, err := callWeave(args...); err != nil {
 		Warning.Printf("Attaching container %s to weave failed: %v", containerID, err)
-		return r, nil
+		return nil
 	}
-	return r, nil
+	return nil
 }