From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: Getting a NIC's MTU size
Date: Thu, 20 Feb 2014 13:45:04 -0500 (EST)
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From: David Howells <dhowells@redhat.com>
Date: Thu, 20 Feb 2014 17:30:23 +0000

> David Miller <davem@davemloft.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?

If the dst is valid and you have a reference to it, dst->dev is good.