netdev - Re: [PATCH net-next] net/vxlan: Avoid unaligned access in vxlan_build

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Message-ID: <20160920190929.57ddaeb0@griffin>
Date:   Tue, 20 Sep 2016 19:09:29 +0200
From:   Jiri Benc <jbenc@...hat.com>
To:     Sowmini Varadhan <sowmini.varadhan@...cle.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        hannes@...essinduktion.org, aduyck@...antis.com,
        daniel@...earbox.net, pabeni@...hat.com
Subject: Re: [PATCH net-next] net/vxlan: Avoid unaligned access in
 vxlan_build_skb()

On Tue, 20 Sep 2016 18:43:33 +0200, Jiri Benc wrote:
> On Tue, 20 Sep 2016 12:31:08 -0400, Sowmini Varadhan wrote:
> > The vxlan header is after the ethernet header (14 bytes),
> > IP header (20 bytes, assuming no options) and udp header (8 bytes).
> 
> If the VXLAN header is not aligned to 4 bytes, then IP header is not
> aligned to 4 bytes, too, and you have greater problems than just VXLAN.

...which is indeed the case. Sorry, I guess I'm too much focused on
VXLAN-GPE nowadays and I missed that we're building this before the
inner Ethernet header.

But the point stands, we have much greater problems here than VXLAN.
And I don't think that wrapping all IP address accesses into
get/put_unaligned all around the stack is the solution.

 Jiri