rootlessport: allow socket paths with more than 108 chars

Creating the rootlessport socket can fail with `bind: invalid argument`
when the socket path is longer than 108 chars. This is the case for
users with a long runtime directory.
Since the kernel does not allow to use socket paths with more then 108
chars use a workaround to open the socket path.

[NO TESTS NEEDED]

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

libpod/networking_slirp4netns.go

@@ -632,16 +632,7 @@ func (c *Container) reloadRootlessRLKPortMapping() error {
 	childIP := getRootlessPortChildIP(c)
 	logrus.Debugf("reloading rootless ports for container %s, childIP is %s", c.config.ID, childIP)
 
-	var conn net.Conn
+	conn, err := openUnixSocket(filepath.Join(c.runtime.config.Engine.TmpDir, "rp", c.config.ID))
-	var err error
-	// try three times to connect to the socket, maybe it is not ready yet
-	for i := 0; i < 3; i++ {
-		conn, err = net.Dial("unix", filepath.Join(c.runtime.config.Engine.TmpDir, "rp", c.config.ID))
-		if err == nil {
-			break
-		}
-		time.Sleep(250 * time.Millisecond)
-	}
 	if err != nil {
 		// This is not a hard error for backwards compatibility. A container started
 		// with an old version did not created the rootlessport socket.

pkg/rootlessport/rootlessport_linux.go

@@ -218,10 +218,20 @@ outer:
 
 	// we only need to have a socket to reload ports when we run under rootless cni
 	if cfg.RootlessCNI {
-		socket, err := net.Listen("unix", filepath.Join(socketDir, cfg.ContainerID))
+		// workaround to bypass the 108 char socket path limit
+		// open the fd and use the path to the fd as bind argument
+		fd, err := unix.Open(socketDir, unix.O_PATH, 0)
 		if err != nil {
 			return err
 		}
+		socket, err := net.ListenUnix("unixpacket", &net.UnixAddr{Name: fmt.Sprintf("/proc/self/fd/%d/%s", fd, cfg.ContainerID), Net: "unixpacket"})
+		if err != nil {
+			return err
+		}
+		err = unix.Close(fd)
+		if err != nil {
+			logrus.Warnf("failed to close the socketDir fd: %v", err)
+		}
 		defer socket.Close()
 		go serve(socket, driver)
 	}