Re: ebt_vnat -- Slapping on a VLAN tag on the bridge

On Friday 19 December 2003 20:59, Kashyap Ashwin wrote:
> Hi,
> This question is related to "Headroom for bridging question". I wrote a new
> target to add a VLAN tag to specified packets. This is how you set the
> rule: # ebtables -t nat -A POSTROUTING -s 00:11:22:33:44:55 -j vnat
> --to-vlan 6
>
> Most of the code was simply copied from ebt_s/dnat both in user and kernel
> code.
>
> This is the problem:
> br_netfilter: Argh!! br_nf_post_routing: bad mac.raw pointer.[eth0][br0]
>
> How do I fix the mismatch between skb->mac.raw and skb->data? I was
> thinking of putting this in the OUTPUT chain instead of postrouting...

skb->mac.raw -= VLAN_HLEN;
skb->nh.raw -= VLAN_HLEN;

I think nat OUTPUT seem most appropriate.

It would be nice if this vnat module were able to
1. change both vlan fields of a vlan packet, this should also be allowed in 
nat PREROUTING.
2. encapsulate the packet in a vlan header (like your code does) and give a 
valid values to the vlan fields.
E.g. -j vnat --vnat-encapsulate adds a vlan header with default values, -j 
vnat --vnat-id id changes the vlan id. --vnat-id together with 
vnat-encapsulate changes the id of the newly added vlan header.
Also, adding the option --vnat-target analogous to --dnat-target is essential.

cheers,
Bart



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