Call underlying bev ctrl SET_FD on filtered bufferevents If a bufferevent_filter is set on an underlying bufferevent which has ctrl functions, bufferevent_filter needs to handle this. For now I have added just BEV_CTRL_SET_FD, since this is needed for bufferevent_sock to assign file descriptors to the proper bufferevent_read/write callbacks. A good example of the problem can be found in issue #237 https://github.com/libevent/libevent/issues/237