Re: TCP_CONNTRACK_ESTABLISHED 5days

[Mogens Valentin <monz@danbbs.dk>]

Taylor, Grant wrote:
>> Moritz, thanks for pointing that out.
>> Your suggested 10 minutes seems a bit short, though..
> 
> 
> I would not set ip_conntrack_tcp_timeout_established to any thing lower 
> than tcp_fin_timeout.  I would be tempted to set 
> ip_conntrack_tcp_timeout_established to approximately double what 
> tcp_fin_timeout is set to.  I don't know of any reason that conntrack 
> would need to keep things for twice tcp_fin_timeout, but I'd rather be 
> safe than sorry.  Besides even double of tcp_fin_timeout is CONSIDERABLY 
> less than 5 days.

Hmm, dunno if various distros set tcp_fin_timeout differently.
With 2.6.10, it's 60 secs (not a distro kernel, and I didn't set this).
Are you saying that Mouritz' 10mins will in some (distro?) cases violate
   ip_conntrack_tcp_timeout_established >= tcp_fin_timeout * 2 ?


Anyway, /usr/src/linux/Documentation/filesystems/proc.txt says

tcp_fin_timeout
---------------
The length of time in seconds it takes to receive a final FIN before the 
socket is always closed.  This is strictly a violation of the TCP
specification, but required to prevent denial-of-service attacks.


I'm having trouble understanding the 'strictly a violation' part.
Is it a (iana) crime to define tcp_fin_timeout?

-- 
Kind regards,
Mogens Valentin