BFD: documentation

Change-Id: I06a23d24340c5527f3848177d2178bf3e55f7614
Signed-off-by: Klement Sekera <ksekera@cisco.com>
diff --git a/src/vnet/bfd/bfd_udp.c b/src/vnet/bfd/bfd_udp.c
index e6dbaab..b3eabc9 100644
--- a/src/vnet/bfd/bfd_udp.c
+++ b/src/vnet/bfd/bfd_udp.c
@@ -12,6 +12,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+/**
+ * @file
+ * @brief BFD UDP transport layer implementation
+ */
 #include <vppinfra/types.h>
 #include <vlibmemory/api.h>
 #include <vlib/vlib.h>