libpod: Detect whether we have a private UTS namespace on FreeBSD

Right now, we always use a private UTS namespace on FreeBSD. This should
be made optional but implementing that cleanly needs a FreeBSD extension
to the OCI runtime config. The process for that is starting
(https://github.com/opencontainers/tob/pull/133) but in the meantime,
assume that the UTS namespace is private on FreeBSD.

This moves the Linux-specific namespace logic to
container_internal_linux.go and adds a FreeBSD stub.

[NO NEW TESTS NEEDED]

Signed-off-by: Doug Rabson <dfr@rabson.org>

libpod/container.go

@@ -688,15 +688,7 @@ func (c *Container) Hostname() string {
 
 	// if the container is not running in a private UTS namespace,
 	// return the host's hostname.
-	privateUTS := false
-	if c.config.Spec.Linux != nil {
-		for _, ns := range c.config.Spec.Linux.Namespaces {
-			if ns.Type == spec.UTSNamespace {
-				privateUTS = true
-				break
-			}
-		}
-	}
+	privateUTS := c.hasPrivateUTS()
 	if !privateUTS {
 		hostname, err := os.Hostname()
 		if err == nil {

libpod/container_internal_freebsd.go

@@ -392,3 +392,10 @@ func (c *Container) getPlatformRunPath() (string, error) {
 func (c *Container) addMaskedPaths(g *generate.Generator) {
 	// There are currently no FreeBSD-specific masked paths
 }
+
+func (c *Container) hasPrivateUTS() bool {
+	// Currently we always use a private UTS namespace on FreeBSD. This
+	// should be optional but needs a FreeBSD section in the OCI runtime
+	// specification.
+	return true
+}

libpod/container_internal_linux.go

@@ -811,3 +811,16 @@ func (c *Container) addMaskedPaths(g *generate.Generator) {
 		g.AddLinuxMaskedPaths("/sys/devices/virtual/powercap")
 	}
 }
+
+func (c *Container) hasPrivateUTS() bool {
+	privateUTS := false
+	if c.config.Spec.Linux != nil {
+		for _, ns := range c.config.Spec.Linux.Namespaces {
+			if ns.Type == spec.UTSNamespace {
+				privateUTS = true
+				break
+			}
+		}
+	}
+	return privateUTS
+}