netdev - Re: Getting a NIC's MTU size

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Message-ID: <20140220181252.GA15495@order.stressinduktion.org>
Date:	Thu, 20 Feb 2014 19:12:52 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	David Howells <dhowells@...hat.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: Getting a NIC's MTU size

On Thu, Feb 20, 2014 at 05:30:23PM +0000, David Howells wrote:
> David Miller <davem@...emloft.net> wrote:
> 
> > > One further question: If I want to get the MTU size of the NIC through
> > > which packets will go to get to a particular peer, can I do:
> > 
> > As has been suggested or at least hinted to by others, you have to use
> > the route dst's device pointer.
> 
> So I gather.  My query was intended to be about the safety of accessing the
> dst->dev pointer.  Can I just dereference it?  Or do I need to take a lock or
> use RCU?

No, you can just dereference it. dst holds a reference on ->dev, so it
is safe without lock or rcu as long as dst is alive and referenced.

Greetings,

  Hannes

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