Subject: Re: unaligned access in in_delayed_cksum()
To: Jason R Thorpe <>
From: Manuel Bouyer <>
List: tech-net
Date: 09/30/2002 12:28:10
On Sun, Sep 29, 2002 at 05:32:32PM -0700, Jason R Thorpe wrote:
> On Sun, Sep 29, 2002 at 06:16:51PM +0200, Manuel Bouyer wrote:
>  > First I have a question: are hadware-assised checksums supposed to work
>  > with VLAN ? I found nothing in the code that could pass ec_capenable
> That really depends on the interface.  I suppose we need another cap flag
> for it.

Maybe private to the ethernet/vlan interface. It's just if_vlan which needs
this to decide if he should inherit the *csum flags or not.

> For example, interfaces which do VLAN encap/decap in hardware can generally
> also do the checksum offload.  Other interfaces, like the Intel i8254x, can
> do the checksum offload even if it's not doing the VLAN encap/decap, because
> the driver tells it explicitly where in the frame to start the checksum
> (actually, it looks like I need to add VLAN support to the wm driver's
> checksum offload :-)

I suspect the tigon can do it as well but I didn't check.

>  [...]
> This is a little surprising -- if the interface doesn't have any addresses,
> what is it doing sending out packets?

the vlan interfaces. I had ti0 up with vlan interfaces attached to it.
Then I went on trying checksum offload, I wanted to enable it on ti0 and
then on the vlans. But as soon as I enabled it on ti0 I got the panic.
enabling *csum on ti0 and vlans before assigning IPs to the vlan works.

Manuel Bouyer, LIP6, Universite Paris VI.