[proxy] Set hostname and domainname based on container name, when dns

Had to make the assert_dns_record test helper more robust against
'getent hosts' returning duplicates

proxy/create_container_interceptor.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/fsouza/go-dockerclient"
 	. "github.com/weaveworks/weave/common"
+	"github.com/weaveworks/weave/nameserver"
 )
 
 type createContainerInterceptor struct{ proxy *Proxy }
@@ -43,7 +44,7 @@ func (i *createContainerInterceptor) InterceptRequest(r *http.Request) error {
 		if err := i.setWeaveWaitEntrypoint(container.Config); err != nil {
 			return err
 		}
-		if err := i.setWeaveDNS(&container); err != nil {
+		if err := i.setWeaveDNS(&container, r); err != nil {
 			return err
 		}
 	}
@@ -78,7 +79,7 @@ func (i *createContainerInterceptor) setWeaveWaitEntrypoint(container *docker.Co
 	return nil
 }
 
-func (i *createContainerInterceptor) setWeaveDNS(container *createContainerRequestBody) error {
+func (i *createContainerInterceptor) setWeaveDNS(container *createContainerRequestBody, r *http.Request) error {
 	if !i.proxy.WithDNS {
 		return nil
 	}
@@ -88,6 +89,14 @@ func (i *createContainerInterceptor) setWeaveDNS(container *createContainerReque
 	if len(container.HostConfig.DNSSearch) == 0 {
 		container.HostConfig.DNSSearch = []string{"."}
 	}
+
+	name := r.URL.Query().Get("name")
+	if container.Hostname == "" && name != "" {
+		container.Hostname = name
+		// TODO: Get weaveDNS domain
+		container.Domainname = nameserver.DefaultLocalDomain
+	}
+
 	return nil
 }