linux-kernel - Re: [Nbd] [PATCH 2/2] nbd: Disallow ioctls on disconnected block device

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Date:	Sat, 16 Jul 2016 10:32:11 +0100
From:	Alex Bligh <alex@...x.org.uk>
To:	Pranay Srivastava <pranjas@...il.com>
Cc:	Alex Bligh <alex@...x.org.uk>,
	Markus Pargmann <mpa@...gutronix.de>,
	"nbd-general@...ts.sourceforge.net" 
	<nbd-general@...ts.sourceforge.net>, Wouter Verhelst <w@...r.be>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Nbd] [PATCH 2/2] nbd: Disallow ioctls on disconnected block device

On 16 Jul 2016, at 08:42, Pranay Srivastava <pranjas@...il.com> wrote:

> So instead can't we put a mechanism in place for network address + mac
> to be same
> for allowing clients to reconnect? Do let me know if this is not of concern.

MAC address?! nbd clients connect over IP, and if a router reboots
between them, you could easily see two packets from the same client
come from different MAC addresses. Similarly all clients not on
the same L2 network will carry the same MAC address. So MAC address
is a very poor indicator of 'same client'.

IP address is also a poor indicator (think NAT) but is substantially
less bad.

-- 
Alex Bligh