From owner-freebsd-hackers@FreeBSD.ORG  Sat Mar 15 07:47:47 2014
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Message-ID: <532405B7.2020007@gmail.com>
Date: Sat, 15 Mar 2014 11:18:07 +0330
From: Hooman Fazaeli <hoomanfazaeli@gmail.com>
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To: Rui Paulo <rpaulo@FreeBSD.org>
Subject: Re: mbuf question
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On 3/15/2014 5:09 AM, Rui Paulo wrote:
> On 14 Mar 2014, at 06:20, Hooman Fazaeli <hoomanfazaeli@gmail.com> wrote:
>
>> Hi list,
>>
>> Is it safe to use m->m_pktdat area to store some arbitrary data about packets allocated as mbuf+cluster pair?
> No, because m_pktdat is really MH_databuf which is part of a union with MH_ext which is set when you allocate an mbuf cluster.
>
> --
> Rui Paulo
>
>
>
Thanks for the point.
I simply overlooked the fact that MH_dat is a union, not a struct.
What about the area started at (m->m_ext + 1) whose size is (MHLEN - sizeof(struct m_ext))?
Is there any known uses of this area in the stack?

-- 

Best regards.
Hooman Fazaeli