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Date:      Wed, 27 Nov 2002 16:04:25 -0500 (EST)
From:      Andrew Gallatin <gallatin@cs.duke.edu>
To:        Terry Lambert <tlambert2@mindspring.com>
Cc:        Andrew Gallatin <gallatin@cs.duke.edu>, Robert Watson <rwatson@freebsd.org>, Luigi Rizzo <rizzo@icir.org>, current@freebsd.org
Subject:   Re: mbuf header bloat ?
Message-ID:  <15845.13145.445000.166358@grasshopper.cs.duke.edu>
In-Reply-To: <3DE52F25.61FAB63C@mindspring.com>
References:  <15840.8629.324788.887872@grasshopper.cs.duke.edu> <Pine.NEB.3.96L.1021127095837.43889C-100000@fledge.watson.org> <15844.60298.44810.750373@grasshopper.cs.duke.edu> <3DE5275E.9D3E9F9B@mindspring.com> <15845.10492.726439.227885@grasshopper.cs.duke.edu> <3DE52F25.61FAB63C@mindspring.com>

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Terry Lambert writes:
 > Andrew Gallatin wrote:
 > > Terry Lambert writes:
 > >  > Andrew Gallatin wrote:
 > >  > > What I (as a 3rd party driver author working in a GNUish
 > 
 > "This is how I do it."
 > 
 > > <...>
 > > 
 > >  > > How is one supposed to build a 3rd party module these days?
 > 
 > "How are you supposed to do it?"
 > 
 > >  > One is not.  The vendor supplies only a binary.
 > > 
 > > Damn it Terry,  I AM the vendor.  Somtimes I wonder if you even read
 > > the articles you reply to.   I'm asking how the vendor (me) is
 > > supposed to build a binary module and I gave an example of how currently
 > > do it.
 > 
 > You're the vendor in the first statement, and a consumer in the
 > second.

I"m the vendor in both statements, no matter how you choose to misread
my words.

 > The topic of the post to which you were replying was third party
 > binary compatability.
 > 
 > The answer is that if the structures change, then there is no
 > binary compatability without source code, period.

Yes there is.  You can be binary compatable ONLY with a kernel with
options MAC.

 > It seemed to me that you were assuming access to the source code
 > for consumers of third party modules.
 > 
 > I think the issue that Robert is concerned about is MAC modules
 > that are provided by a third party to a consumer of FreeBSD and
 > the modules, and for which the structure changes and so on can
 > not be permitted.
 > 
 > This mnakes sense, because the MAC code is being developed under
 > a DARPA contract, and it's likely that the module source code and
 > the modules won't be available to the end users, let alone the
 > general public, without some kind of security clearance, and then
 > probably not then.

If you're a vendor of a device which inserts MAC mtags and needs
options MAC, you put this code in your driver:

if (mbstat.m_mhlen != MHLEN) {
   printf("Please rebuild your kernel with 'options MAC'\n");
   goto atach_failed_no_mac;
}

I've already got code like this in my driver to check that m_mclbytes
and m_mlen is what I expect it to be, since people sometimes change
them. 

Drew
   

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