Re: [PATCH nf-next 3/3] netfilter: bridge: copy back VLAN header for bridge packet queued to userspace

[Florian Westphal <fw@strlen.de>]

stéphane bryant <stephane.ml.bryant@gmail.com> wrote:
> On 01/15/2016 03:04 PM, Florian Westphal wrote:
> > Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> >> For the specific case of nfnetlink_queue, I would expose the vlan
> >> information through a new netlink attribute NFQA_VLAN (similar to what
> >> we do for NFQA_HWADDR for the layer 3).
> > 
> > If we do this I think it does make sense to consider putting
> > the entire L2 mac header under its own attr too.
> > 
> > This is especially good if we'd later add support for NETDEV
> > family.  Since drivers already pull the L2 header userspace
> > would not need to handle arbirary L2 protocols.
> > 
> >>> +				payload += VLAN_HLEN;
> >>> +				payload_len -= VLAN_HLEN;
> >>> +			} else {
> >>> +				entry->skb->vlan_tci &= ~VLAN_TAG_PRESENT;
> >>> +				entry->skb->protocol = veth->h_vlan_proto;
> >>> +			}
> >>> +		}
> >>
> >> I'm awar it's more work, but it would be good to reduce ifdef pollution
> >> by placing all this bridge netfilter code wrapped into functions under
> >> one single ifdef in this file to improve maintainability.
> > 
> > Right, but for anything family specifiy it would be even better to push
> > it into nf afinfo. In case thats too much work or too cumbersome (e.g.
> > because you'd need 12 function arguments ...) then the ifdef-wrapped
> > helper is fine of course.
> 
> As the nf_afinfo saveroute/reroute hooks are called on the original
> packet skb, at a location where netlink attributes are not in existence,
> it only seems possible to use these hooks to hide the L2 code if we
> pull-in/pull out the L2 header into/from the original skb, and forego
> the new attributes -- which is fine by me as it is precisely what i was
> doing in the original patches (albeit in a different location).

Yes.  Problem with push/pull is that it will be impossible to do packet
rewriting of the l2 header since we'd have to pull a different amount.

> If we use new netlink attributes (NFQA_VLAN, NFQA_L2HDR) we will have to
> wrap them in a #ifder helper, it seems.

ifdef helper is fine.
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