bgp: catch socket error with sendall

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

ryu/services/protocols/bgp/speaker.py

@@ -376,6 +376,8 @@ class BgpProtocol(Protocol, Activity):
         self._sendlock.acquire()
         try:
             self._socket.sendall(msg.serialize())
+        except socket.error as err:
+            self.connection_lost('failed to write to socket')
         finally:
             self._sendlock.release()