aa141517a3
The RTP seq/timestamp extraction in input_udp_recv was disabled since
be32351 (2020) with a "TODO: Figure out why this does not work" comment.
The root cause was a buffer offset bug: recvfrom writes the UDP payload
at recv_buf + ipheader_bytes, but the extraction code read recv_buf[2..7]
— the reserved IP-header prefix area — returning garbage.