Date: Mon, 10 Feb 1997 09:43:12 -0500 (EST) From: Robert Shady <rls@mail.id.net> To: julian@whistle.com (Julian Elischer) Cc: rls@mail.id.net, tiller@connectnet.com, FreeBSD-Questions@freebsd.org, FreeBSD-ISP@freebsd.org Subject: Re: Packet filtering help please Message-ID: <199702101443.JAA27415@server.id.net> In-Reply-To: <32FD37FA.41C67EA6@whistle.com> from Julian Elischer at "Feb 8, 97 06:35:38 pm"
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> > Also remember that the numbers are the 'rules numbers', they are
> > parsed from highest to lowest, and everyone must be different.
> > In the above example, it starts our like this
> >
> > RULE #
> > ======
> > 65536 deny ip from any to any (Don't let ANYONE into this box by default)
> > 10000 allow ip from all to all (Now allow EVERYONE into this box by default)
> > 1000 deny ip from a.a.a.a (Now just deny people from a.a.a.a)
> >
> > And you could add...
> >
> > 999 deny ip from b.b.b.b (Now deny people from a.a.a.a & b.b.b.b)
>
> Boy is that confusing!
> 1/ there can be more than one rule with ths same number.. ordering of
> such rules is undefined.
> 2/ the rules are parsed LOWEST to HIGHEST..
>
> the rules are interpretted with an implied "OTHERWISE go on to the next
> rule".
>
> while (rules to do) {
> if (condition of next rule is true) {
> if (rule is deny)
> return FALSE;
> else /* rule is accept */
> return TRUE;
> }
> rule++; /* move on to next rule */
> }
>
>
> in other words the set above are:
>
>
> 1000 If it's our pesky friend block it and go get the next packet.
> otherwise, go on to the next rule.
> 10000 Allow all packets not already thrown out.
> 65535 *never reached *
I stand corrected...
-- Rob
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