linux-kernel - Re: [RFC PATCH 32/33] Add the Xen virtual network device driver.

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Message-Id: <1153226379.5283.51.camel@jzny2>
Date:	Tue, 18 Jul 2006 08:39:39 -0400
From:	jamal <hadi@...erus.ca>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Chris Wright <chrisw@...s-sol.org>, linux-kernel@...r.kernel.org,
	virtualization@...ts.osdl.org, xen-devel@...ts.xensource.com,
	Jeremy Fitzhardinge <jeremy@...p.org>, Andi Kleen <ak@...e.de>,
	Andrew Morton <akpm@...l.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Zachary Amsden <zach@...are.com>,
	Ian Pratt <ian.pratt@...source.com>,
	Christian Limpach <Christian.Limpach@...cam.ac.uk>,
	netdev@...r.kernel.org
Subject: Re: [RFC PATCH 32/33] Add the Xen virtual network device driver.

On Tue, 2006-18-07 at 12:27 +0200, Arjan van de Ven wrote:

> 
> Hmmm maybe it's me, but something bugs me if a NIC driver is going to
> send IP level ARP packets... that just feels very very wrong and is a
> blatant layering violation.... 

It is but the bonding driver has been setting precedence for years now
on sending ARPs from a driver;->
It does make a lot of sense to put it in user space. More interesting
policies may include sending more than just ARPs and once you hard-code
in the kernel you loose that flexibility.

> shouldn't the ifup/ifconfig scripts just
> be fixed instead if this is critical behavior?
> 

I dont think the ifup/ifconfig provide operational status (i.e link
up/down) - or do they? If they can be made to invoke scripts in such
a case then we are set.

Note: you will get netlink events when devices are created or devices
change their admin (via ifconfig) or operational (link down/up) status.
[Try running "ip monitor" to see]

One could write a little daemon that reacts to these specific events.
The problem has been some people claiming that daemons are a bad idea
from a usability perspective. Patrick has mentioned he may be working on
a daemon in user space that does exactly that. The other alternative is
to do the udev thing and have the kernel invoke a script whenever an
event of interest happens.

cheers,
jamal

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