charon-nm: Prevent NM from changing the default route

This is not required as we install our own (narrow) route(s) in our own
routing table. This should allow split tunneling if configured on the
gateway.

src/charon-nm/nm/nm_service.c

@@ -121,6 +121,14 @@ static void signal_ipv4_config(NMVPNPlugin *plugin,
 	g_value_set_uint(val, me->get_address(me).len * 8);
 	g_hash_table_insert(config, NM_VPN_PLUGIN_IP4_CONFIG_PREFIX, val);
 
+	/* prevent NM from changing the default route. we set our own route in our
+	 * own routing table
+	 */
+	val = g_slice_new0(GValue);
+	g_value_init(val, G_TYPE_BOOLEAN);
+	g_value_set_boolean(val, TRUE);
+	g_hash_table_insert(config, NM_VPN_PLUGIN_IP4_CONFIG_NEVER_DEFAULT, val);
+
 	val = handler_to_val(handler, INTERNAL_IP4_DNS);
 	g_hash_table_insert(config, NM_VPN_PLUGIN_IP4_CONFIG_DNS, val);