netdev - Re: dhcp client packet sniffing...

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Message-ID: <1270737440.1872.93.camel@sakura.staff.proxad.net>
Date:	Thu, 08 Apr 2010 16:37:20 +0200
From:	Maxime Bizon <mbizon@...ebox.fr>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: dhcp client packet sniffing...

On Thu, 2010-04-08 at 22:27 +0800, Herbert Xu wrote:

> Oh and if anybody is doing any user-space hacking, this is what you
> could do: AF_PACKET is only necessary when you're waiting for a
> response from the server.  So you could close the socket after a
> lease has been acquired, and reopen it the next time you need
> to communicate with a server.

That's already what some clients do (at least udhcpc from busybox)

The packet socket is only needed during "init_selecting", "init_reboot",
"requesting" and "rebinding" state.

For "bound" or "requesting" state (in which you spend most of the time),
the packet socket is not needed and a standard AF_INET dgram socket can
be used instead.

You can't close the socket while bound since you can receive DHCPINFORM
anytime.

-- 
Maxime

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