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Date:      Thu, 15 Aug 2002 11:38:25 -0700
From:      Luigi Rizzo <rizzo@icir.org>
To:        Julian Elischer <julian@elischer.org>
Cc:        ipfw@FreeBSD.ORG
Subject:   Re: RFC: new mbuf flag bit needed
Message-ID:  <20020815113824.B30190@iguana.icir.org>
In-Reply-To: <Pine.BSF.4.21.0208151042200.27476-100000@InterJet.elischer.org>; from julian@elischer.org on Thu, Aug 15, 2002 at 10:49:22AM -0700
References:  <20020815000720.B24495@iguana.icir.org> <Pine.BSF.4.21.0208151042200.27476-100000@InterJet.elischer.org>

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On Thu, Aug 15, 2002 at 10:49:22AM -0700, Julian Elischer wrote:
...
> A bit to force non testing in a firewall might be useful in other places..
> I'd however like to float an idea that maybe there should be more
> specific bits for input and output processing.

unfortunately bits are a scarce resource in struct m_hdr which we
do not want to change in RELENG_4. Plus, many of the cases you are
mentioning are already taken care of with m_tag/annotations because
you need additional information: e.g.  in the "fwd" you need the
fwd address anyways, same for divert (you need the 'next rule'),
and dummynet when you want multiple passes.

The problem with protocol-specific bits is that you'll end up
overloading them, and once you pass the packets to a multi-protocol
module (such as netgraph, or ipfw2) you are in trouble.
E.g. M_PROTO1 has been overloaded by device drivers to report
some vlan-related info. The other M_PROTO* are all taken by
the KAME code.

	cheers
	luigi

> 
> 
> for example a 'fwd' packet that has been forwarded out from thi input
> filter needs to bypass the output filter.. your bit could be used for
> that. I am just wondering if a separate 
> 'input' and 'output' filtering bit may be a worthwhile aim..
> anyhow these are IP specific items so what I suggest is instead, that we
> define 4 or so "protocol family specific" bits
> that are reserved for protocol use. and allow each protocol family to
> define their own use for them.
> 
> you could then define bits for
> input-filter bypass,
> output filter bypass,
> input-from-divert
> 
> 
> etc.
> 
> 
> 
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