refactor weaveCIDRsFromConfig to return an error message

proxy/create_container_interceptor.go

@@ -46,7 +46,9 @@ func (i *createContainerInterceptor) InterceptRequest(r *http.Request) error {
 		return err
 	}
 
-	if cidrs, ok := i.proxy.weaveCIDRsFromConfig(container.Config, container.HostConfig); ok {
+	if cidrs, err := i.proxy.weaveCIDRsFromConfig(container.Config, container.HostConfig); err != nil {
+		Info.Printf("Ignoring container due to %s", err)
+	} else {
 		Info.Printf("Creating container with WEAVE_CIDR \"%s\"", strings.Join(cidrs, " "))
 		if container.HostConfig == nil {
 			container.HostConfig = &docker.HostConfig{}

proxy/create_exec_interceptor.go

@@ -30,8 +30,10 @@ func (i *createExecInterceptor) InterceptRequest(r *http.Request) error {
 	}
 
 	_, hasWeaveWait := container.Volumes["/w"]
-	cidrs, hasCIDRs := i.proxy.weaveCIDRsFromConfig(container.Config, container.HostConfig)
-	if hasCIDRs && hasWeaveWait {
+	cidrs, err := i.proxy.weaveCIDRsFromConfig(container.Config, container.HostConfig)
+	if err != nil {
+		Info.Printf("Ignoring container %s due to %s", container.ID, err)
+	} else if hasWeaveWait {
 		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/proxy.go

@@ -2,6 +2,7 @@ package proxy
 
 import (
 	"crypto/tls"
+	"errors"
 	"net"
 	"net/http"
 	"net/url"
@@ -22,6 +23,10 @@ var (
 	containerCreateRegexp = regexp.MustCompile("^(/v[0-9\\.]*)?/containers/create$")
 	containerStartRegexp  = regexp.MustCompile("^(/v[0-9\\.]*)?/containers/[^/]*/(re)?start$")
 	execCreateRegexp      = regexp.MustCompile("^(/v[0-9\\.]*)?/containers/[^/]*/exec$")
+
+	ErrInvalidNetworkMode = errors.New("--net option")
+	ErrWeaveCIDRNone      = errors.New("WEAVE_CIDR=none")
+	ErrNoDefaultIPAM      = errors.New("--no-default-ipam option")
 )
 
 type Proxy struct {
@@ -115,28 +120,22 @@ func (proxy *Proxy) ListenAndServe() error {
 	return (&http.Server{Handler: proxy}).Serve(listener)
 }
 
-func (proxy *Proxy) weaveCIDRsFromConfig(config *docker.Config, hostConfig *docker.HostConfig) ([]string, bool) {
-	if !validNetworkMode(hostConfig) {
-		return nil, false
+func (proxy *Proxy) weaveCIDRsFromConfig(config *docker.Config, hostConfig *docker.HostConfig) ([]string, error) {
+	if hostConfig != nil &&
+		hostConfig.NetworkMode != "" &&
+		hostConfig.NetworkMode != "bridge" {
+		return nil, ErrInvalidNetworkMode
 	}
 	for _, e := range config.Env {
 		if strings.HasPrefix(e, "WEAVE_CIDR=") {
 			if e[11:] == "none" {
-				return nil, false
+				return nil, ErrWeaveCIDRNone
 			}
-			return strings.Fields(e[11:]), true
+			return strings.Fields(e[11:]), nil
 		}
 	}
-	return nil, !proxy.NoDefaultIPAM
-}
-
-func validNetworkMode(hostConfig *docker.HostConfig) bool {
-	return networkMode(hostConfig) == "bridge"
-}
-
-func networkMode(hostConfig *docker.HostConfig) string {
-	if hostConfig == nil || hostConfig.NetworkMode == "" {
-		return "bridge"
+	if proxy.NoDefaultIPAM {
+		return nil, ErrNoDefaultIPAM
 	}
-	return hostConfig.NetworkMode
+	return nil, nil
 }

proxy/start_container_interceptor.go

@@ -21,13 +21,9 @@ func (i *startContainerInterceptor) InterceptResponse(r *http.Response) error {
 		return err
 	}
 
-	if !validNetworkMode(container.HostConfig) {
-		Debug.Printf("Ignoring container %s with --net=%s", container.ID, networkMode(container.HostConfig))
-		return nil
-	}
-	cidrs, ok := i.proxy.weaveCIDRsFromConfig(container.Config, container.HostConfig)
-	if !ok {
-		Debug.Print("No Weave CIDR, ignoring")
+	cidrs, err := i.proxy.weaveCIDRsFromConfig(container.Config, container.HostConfig)
+	if err != nil {
+		Info.Printf("Ignoring container %s due to %s", container.ID, err)
 		return nil
 	}
 	Info.Printf("Attaching container %s with WEAVE_CIDR \"%s\" to weave network", container.ID, strings.Join(cidrs, " "))