Fix network connectivity problem for non-root users

If a container was started with a non-root user the container
may not be able to resolve DNS names because of too restrictive
permission in the /etc/resolv.conf container file. This problem
is in how this file gets created in libnetwork and ths PR
attempts to fix the issue by vendoring in the libnetwork code
with the fix.

Signed-off-by: Jana Radhakrishnan <mrjana@docker.com>
Upstream-commit: afd901e408d8d4ed00707c545ae985bc637a1979
Component: engine

components/engine/vendor/src/github.com/docker/libnetwork/endpoint.go

@@ -548,6 +548,11 @@ func (ep *endpoint) updateDNS(resolvConf []byte) error {
 		return err
 	}
 
+	// Change the perms to 0644 since ioutil.TempFile creates it by default as 0600
+	if err := os.Chmod(tmpResolvFile.Name(), 0644); err != nil {
+		return err
+	}
+
 	// write the updates to the temp files
 	if err = ioutil.WriteFile(tmpHashFile.Name(), []byte(newHash), 0644); err != nil {
 		return err

components/engine/vendor/src/github.com/docker/libnetwork/libnetwork_test.go

@@ -1137,6 +1137,16 @@ func TestResolvConf(t *testing.T) {
 		}
 	}()
 
+	finfo, err := os.Stat(resolvConfPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	fmode := (os.FileMode)(0644)
+	if finfo.Mode() != fmode {
+		t.Fatalf("Expected file mode %s, got %s", fmode.String(), finfo.Mode().String())
+	}
+
 	content, err := ioutil.ReadFile(resolvConfPath)
 	if err != nil {
 		t.Fatal(err)