NAT keep alive ip_conntrack

Hi @all,

I am writing an application to determine the binding time of Network
Address Translators (NAT) for UDP (using UDP sockets). To verify the
results I'm setting the ip_conntrack_max_udp_timeout and
ip_conntrack_max_udp_timeout_stream values (under /proc/net/ipv4) myself.

I knwo that when a new connection is started, the udp_timeout value is
used and when the connection is assured after having sent “a few”
packets, the udp_timeout_stream value becomes active. What is the number
of packets after which this switching is made? Does anybody know the
algorithm that is used for this switching?

Thanks,

Andreas