Re: iptables and INVALID packet filtering.
- To: Matthew Babcock <MBabcock@AandRSecurity.com>
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- Subject: Re: iptables and INVALID packet filtering.
- From: Pascal Hambourg <email@example.com>
- Date: Thu, 02 May 2013 00:17:07 +0200
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Matthew Babcock a écrit :
> Please excuse the delayed response.
> To answer your question, no I cannot, yet.
> However, I can demonstrate iptables following what the "state" be on UDP
> packets using DNS.
> You should see as I do, that the UDP DNS request are logged under the
> state NEW, and that the response was logged under the state ESTABLISHED.
Nothing new here. UDP possible states are :
- NEW for a datagram creating a new connection or belonging to a
"connection" which has seen traffic only in one direction ;
- ESTABLISHED for a datagram belonging to a "connection" which has seen
traffic in both directions ;
- RELATED when a conntrack helper expects a UDP datagram related to an
existing connection (e.g. TFTP or SIP).
Note that this is not specific to UDP, conntrack does the same with all
> I consider this, iptables differentiating between "New" and
> "Established" UDP "connections", reason to extrapolate that iptables can
> follow state in UDP packets such as flagging on "Invalid" or out of
> state UDP packets.
UDP is connectionless by nature, so how would you define the INVALID
state of a UDP datagram ?
> I aim to try and create an "Invalid" UDP state packet. I will follow up
> if I try regardless of the outcome.
Good luck. I meant it.