virtcontainers/utils: Implement function to check vsocks support

Implement function to check if the system has support for vsocks.
This function looks for vsock and vhost-vsock devices returning
true if those exist, otherwise false.

Signed-off-by: Jose Carlos Venegas Munoz <jose.carlos.venegas.munoz@intel.com>
Signed-off-by: Julio Montes <julio.montes@intel.com>

virtcontainers/utils/utils.go

@@ -23,6 +23,12 @@ const fileMode0755 = os.FileMode(0755)
 // See unix(7).
 const MaxSocketPathLen = 107
 
+// VSockDevicePath path to vsock device
+var VSockDevicePath = "/dev/vsock"
+
+// VHostVSockDevicePath path to vhost-vsock device
+var VHostVSockDevicePath = "/dev/vhost-vsock"
+
 // FileCopy copys files from srcPath to dstPath
 func FileCopy(srcPath, dstPath string) error {
 	if srcPath == "" {
@@ -200,3 +206,16 @@ func BuildSocketPath(elements ...string) (string, error) {
 
 	return result, nil
 }
+
+// SupportsVsocks returns true if vsocks are supported, otherwise false
+func SupportsVsocks() bool {
+	if _, err := os.Stat(VSockDevicePath); err != nil {
+		return false
+	}
+
+	if _, err := os.Stat(VHostVSockDevicePath); err != nil {
+		return false
+	}
+
+	return true
+}

virtcontainers/utils/utils_test.go

@@ -294,3 +294,34 @@ func TestBuildSocketPath(t *testing.T) {
 		assert.Equal(d.expected, result)
 	}
 }
+
+func TestSupportsVsocks(t *testing.T) {
+	assert := assert.New(t)
+
+	orgVSockDevicePath := VSockDevicePath
+	orgVHostVSockDevicePath := VHostVSockDevicePath
+	defer func() {
+		VSockDevicePath = orgVSockDevicePath
+		VHostVSockDevicePath = orgVHostVSockDevicePath
+	}()
+
+	VSockDevicePath = "/abc/xyz/123"
+	VHostVSockDevicePath = "/abc/xyz/123"
+	assert.False(SupportsVsocks())
+
+	vSockDeviceFile, err := ioutil.TempFile("", "vsock")
+	assert.NoError(err)
+	defer os.Remove(vSockDeviceFile.Name())
+	defer vSockDeviceFile.Close()
+	VSockDevicePath = vSockDeviceFile.Name()
+
+	assert.False(SupportsVsocks())
+
+	vHostVSockFile, err := ioutil.TempFile("", "vhost-vsock")
+	assert.NoError(err)
+	defer os.Remove(vHostVSockFile.Name())
+	defer vHostVSockFile.Close()
+	VHostVSockDevicePath = vHostVSockFile.Name()
+
+	assert.True(SupportsVsocks())
+}