netdev - Re: [RFC PATCH ipsec] xfrm: use the right dev to fill xdst

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Date:	Fri, 5 Apr 2013 15:59:59 +0300
From:	Daniel Baluta <dbaluta@...acom.com>
To:	Steffen Klassert <steffen.klassert@...unet.com>
Cc:	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	herbert@...dor.apana.org.au, davem@...emloft.net,
	netdev@...r.kernel.org
Subject: Re: [RFC PATCH ipsec] xfrm: use the right dev to fill xdst

On Fri, Apr 5, 2013 at 12:46 PM, Steffen Klassert
<steffen.klassert@...unet.com> wrote:
> On Thu, Apr 04, 2013 at 05:12:42PM +0200, Nicolas Dichtel wrote:
>> Commit bc8e4b954e46 (xfrm6: ensure to use the same dev when building a bundle)
>> broke IPsec for IPv4 over IPv6 tunnels (because dev points to an IPv4 only
>> interface, hence in6_dev_get(dev) returns NULL.
>
> Can you give some informations on how to reproduce this? I'm running
> interfamily tunnels on our testing environment and it seems to
> work fine.

I can hit this in our setup while using some internal custom simulated
interfaces.

Anyhow, this should be reproducible with a classic IPv6 IPsec over
IPv4 test.  Please make sure
that the IPv4 interface doesn't have an IPv6 address set up.

Quoting from commit bc8e4b954e46 (xfrm6: ensure to use the same dev
when building a bundle):

-       xdst->u.rt6.rt6i_idev = in6_dev_get(rt->u.dst.dev);
+       xdst->u.rt6.rt6i_idev = in6_dev_get(dev);

dev points to IPv4 endpoint and if it doesn't have an IPv6 address
associated then
in6_dev_get(dev) will return NULL.

>
>>
>> After looking again into commit 25ee3286dcbc ([IPSEC]: Merge common code into
>> xfrm_bundle_create), it seems that previously we were using dev from the route,
>> for both IPv4 and IPv6.
>
> I think this was the right way. We need to attach the dev from the
> corresponding route to the xdst.
>
>>
>> In fact, xfrm_fill_dst() is called during a loop on chained dst, but dev points
>> always to the same device.
>
> The way we do it now can be problematic for tunnel in tunnel scenarios too.
> We assign the dev from the first tunnel route to all the bundle entries,
> this looks really wrong.
>
> I think your patch is correct, but I want understand the breaking
> scenario first.

thanks,
Daniel.
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