Added support for RFC 8203 in notification decoder

protocols/bgp/packet/bgp.go

@@ -50,6 +50,10 @@ const (
 	InvalidNetworkField       = 10
 	MalformedASPath           = 11
 
+	// Notification Msg Subcodes
+	AdministrativeShutdown = 2
+	AdministrativeReset    = 4
+
 	// Attribute Type Codes
 	OriginAttr     = 1
 	ASPathAttr     = 2

protocols/bgp/packet/decoder.go

@@ -114,7 +114,7 @@ func decodeNotificationMsg(buf *bytes.Buffer) (*BGPNotification, error) {
 			return invalidErrCode(msg)
 		}
 	case Cease:
-		if msg.ErrorSubcode != 0 {
+		if !(msg.ErrorSubcode == 0 || msg.ErrorSubcode == AdministrativeShutdown || msg.ErrorSubcode == AdministrativeReset) {
 			return invalidErrCode(msg)
 		}
 	default: