mgw: accept zero-length RTP payload as BFI Mainline OsmoBTS now has an option (rtp continuous-streaming) that causes it to emit an RTP packet every 20 ms without gaps, sending a BFI marker in the form of zero-length RTP payload when it has nothing else to send. These codec-independent BFI markers don't indicate TAF, but this provision is a good start. Accept this BFI packet format in themwi-mgw.

/*
 * This header file defines internal data structures for themwi-rtp-mgr.
 */

struct bind_range_cfg {
	struct in_addr	bind_ip;
	unsigned	port_range_start;
	unsigned	port_range_end;
	unsigned	port_next;
	unsigned	port_tries;
};

struct rtp_one_end {
	int	rtp_fd;
	int	rtcp_fd;
	struct sockaddr_in bound_addr;
};