UDP, TCP, and NAT (was Thomas is a doodoo head)

[Thomas Charron]

On 7/13/07, Thomas Charron <twaffle at gmail.com> wrote:
> > >>   By your own statement, explain then why NAT routers need to do
> > >> 'funny things' with very basic UDP based services, like DNS.
> > >   They don't.  I have never had to do application-layer inspection
> > > with DNS.  Nor NTP.  Fire up WireShark and look at the packets if you
> > > don't believe me.
> > ... and correlate what you see with WireShark to what the Linux
> > NetFilter source does.  Find me any code that does anything beyond
> > port number rewriting just to make DNS work, and I'll gladly eat crow
> > (provided you provide sanitary, cooked crow meat for me to eat).
>   You are correct, Linux NetFilter *does* operate in the case of DNS
> as you say.  But others do not, and will actually maintain state
> information based on the serial number of the DNS request contained
> inside the UDP packet.

  Clarification.  When I sent that, I knew it sounded wrong.  I meant
NOT the request 'serial number' but the request sequence number.

-- 
-- Thomas