Re: connection tracking fails to update udp timer

[Florian Westphal <fw@strlen.de>]

Eray Bilgin <bilgin@eray.ca> wrote:
> i noticed this when my voip phone mysteriously stopped ringing. i use
> a tp-link router as a gateway which i'm certain is running
> linux/netfilters, though i don't know what version. i've observed the
> same problem on my raspberry pi running iptables v1.8.2.
> 
> usually the first thing a sip client does is register with the provider's
> server. this has the effect of punching a hole through any firewalls in
> its path. after that initial registration, my provider keeps the
> connection alive by sending messages every 60 seconds.
> 
> when netfilters sees traffic moving back and forth, the connection should
> transition to the assured state and set the expiration timer to
> nf_conntrack_udp_timeout_stream, which by default is 120 seconds. but in
> this case the timer is reset to nf_conntrack_udp_timeout, which is 30
> seconds. the connection does not appear as "assured".

Replies during first 2 seconds are ignored in order to prevent
DNS requests from triggering assured state + 2m timeout.