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Date:      Tue, 30 Jan 2007 20:18:20 +0100
From:      Erik Norgaard <norgaard@locolomo.org>
To:        Erik Norgaard <norgaard@locolomo.org>
Cc:        FreeBSD Questions <questions@freebsd.org>
Subject:   Re: Negation in tables for packet filter
Message-ID:  <45BF99FC.3080002@locolomo.org>
In-Reply-To: <45BCAC1F.80701@locolomo.org>
References:  <45BCAC1F.80701@locolomo.org>

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I got this response off-list:
Lowell Gilbert wrote:

 > Erik Norgaard <norgaard@locolomo.org> writes:
 >
 >> table <internet> const { !0/8 !10/8 !127/8 !169.254/16 !172.16/12 \
 >>                    !192.0.2/24 !192.168/16 !198.18/15 !224/4 !240/4 }
 >
 > Think about it; this matches *everything*.  All possible packets are
 > in either !10/8 or !127/8.  etc.

This is clear if tables are a simple or'ing of the entries, but the 
documentation is somewhat confusing, they give this example 
(http://www.openbsd.org/faq/pf/tables.html):

<quote>
   table <goodguys> { 172.16.0.0/16, !172.16.1.0/24, 172.16.1.100 }

   block in on dc0 all
   pass  in on dc0 from <goodguys> to any

* 172.16.50.5 - narrowest match is 172.16.0.0/16; packet matches the
   table and will be passed
* 172.16.1.25 - narrowest match is !172.16.1.0/24; packet matches an
   entry in the table but that entry is negated (uses the "!" modifier);
   packet does not match the table and will be blocked
* 172.16.1.100 - exactly matches 172.16.1.100; packet matches the
   table and will be passed
* 10.1.4.55 - does not match the table and will be blocked
</quote>

so maybe I should add 0/0 to the above list?

Thanks, Erik
-- 
Ph: +34.666334818                      web: http://www.locolomo.org

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