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Date: Mon, 31 Oct 2011 22:31:25 -0700
From: Julian Elischer <julian@freebsd.org>
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Cc: freebsd-net@freebsd.org
Subject: Re: Undocumented netgraph `cmd' flags ?
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On 10/31/11 4:16 PM, Arnaud Lacombe wrote:
> Hi Julian,
>
> For my information, is it documented anywhere that bit 28[0] and 29[1]
> of Netgraph message's `cmd' shall not be used (the bits, not the
> macros) ?
>
> Thanks,
>   - Arnaud
>
> [0]: NGM_READONLY
> [1]: NGM_HASREPLY
>
Not really sure what you are asking.

NGM_READONLY allows the base system to use a reader lock and not block 
other
traffic while the message is bring processed.
NGM_HASREPLY is not used that I can see in the kernel. It may be a 
historical artifact or
maybe only used in the library as a hint.

It has been so long since I was involved with netgraph (over a decade) 
that I really don't remember.