vici: Ensure we read exactly the specified amount of bytes from the socket in Python

recv() will return less bytes than specified (as that's the buffer size)
if not as many are ready to be read from the socket.

src/libcharon/plugins/vici/python/vici/protocol.py

@@ -20,15 +20,22 @@ class Transport(object):
         self.socket.sendall(struct.pack("!I", len(packet)) + packet)
 
     def receive(self):
-        raw_length = self.socket.recv(self.HEADER_LENGTH)
+        raw_length = self._recvall(self.HEADER_LENGTH)
         length, = struct.unpack("!I", raw_length)
-        payload = self.socket.recv(length)
+        payload = self._recvall(length)
         return payload
 
     def close(self):
         self.socket.shutdown(socket.SHUT_RDWR)
         self.socket.close()
 
+    def _recvall(self, count):
+        """Ensure to read count bytes from the socket"""
+        data = b""
+        while len(data) < count:
+            data += self.socket.recv(count - len(data))
+        return data
+
 
 class Packet(object):
     CMD_REQUEST = 0         # Named request message