Pablo Neira Ayuso [off-list ref] wrote:

quoted

If I understand correctly, the connection tracking netlink interface
is an exception here because it has its own handling of dealing with
congestion ("more reliable"?) so you need to disable the "default
congestion control"?

In conntrack, you have to combine NETLINK_NO_ENOBUFS with
NETLINK_BROADCAST_ERROR, then it's the kernel turns on the "more
reliable" event delivery.

The "more reliable" event delivery guarantees that the kernel will
deliver at least the DESTROY notification (connection close).

If the userspace program is stuck, kernel has to hold on the expired
entries.  Eventually conntrack stops accepting new connections because
the table is full.

So this feature can't be recommended as a best-practice for conntrack
either.