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Date:      Fri, 16 Nov 2001 17:23:21 -0800 (PST)
From:      Julian Elischer <julian@elischer.org>
To:        Luigi Rizzo <rizzo@aciri.org>
Cc:        Peter Wemm <peter@wemm.org>, Julian Elischer <julian@vicor-nb.com>, current@FreeBSD.ORG, net@FreeBSD.ORG, wollman@FreeBSD.ORG
Subject:   Re: re-entrancy and the IP stack.
Message-ID:  <Pine.BSF.4.21.0111161711470.6632-100000@InterJet.elischer.org>
In-Reply-To: <20011116170214.A86121@iguana.aciri.org>

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On Fri, 16 Nov 2001, Luigi Rizzo wrote:

> > so far there hasn't been a lot of suggestion as to how the goal can be
> > achieved however..
> 
> i actually suggested one i.e. have explicit pointers
> to metadata area(s) in the pkthdr. I think you forget the
> most fundamental feature which is performance.
> This is way more important than flexibility i think.

Which is the reason that this problem exists..
no-one ever thinks that people will want to do things different
to what they want to do at the time they write it..

Flexibility is I think much more important than you suggest.
Wouldn't it have made it easier for you if there had been a flexible
method to pass such information available?
The m_aux field sounds right to me.

Alternatively, the ability to define a separate
data area in an M_HDR mbuf..
(There's a lot of wasted space there in M_EXT packets.)

[normal header][pkthdr][METADATA][normal_data]

The metadata would be there regardless of whether the 
M_EXT flag was set or not.



> 
> > things it should be:
> > 
> > 1/ flexible

I.e Don't screw over Luigi's NEXT project, Dummynet2.

> > 2/ queueable

I want to let dummynet2 do queuing of packets and keep my 'class'
information with each packet.

> > 3/ transparent to 3rd party code that doesn't know about it.

I don't want My module to have to know about the stuff Dummynet2
is storing with the packet, and I don't want dummynet2
to need to know what I have stashed in there..

4/ Self-descriptive:
If I free a packet, I shouldn't produce a leak of some other
items somewhere else. (they should describe how they should be freed!)


> 
> 	cheers
> 	luigi
> 


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