[RFC] place to put bridge-netfilter specific data in the skbuff

[Bart De Schuymer <bart.de.schuymer@pandora.be>]

Hello netfilter team and others,

DaveM suggested I talk to you (netfilter team) about this.

What's bridge-netfilter: the mapping of the IPv4 onto the bridge hooks, to 
make a powerful bridging firewall.

The problem: in the current br-nf patch we add 3 fields to the skbuff, which 
is (as expected) not acceptable. So we need to find a way to solve this.

We cannot use the control buffer to save this data because tcp uses it while 
we still need the brnf data.

The solution I like best (and David seems to not mind) is adding one pointer 
to a struct nf_bridge_info in the skbuff. So, adding one new member.

Another suggestion by David is this:

struct nf_ct_info {
	union {
		struct nf_conntrack *master;
		struct nf_bridge_info *brinfo;
	} u;
};

But I don't think this will not work because master will be in use while we 
need brinfo.

So another solution could be this:

struct nf_ct_info {
		struct nf_conntrack *master;
		struct nf_bridge_info *brinfo;
};

But I don't know anything about the intricacies of adding this.

Do you have any other suggestions? Comments? Help?
The current patch was already posted on lkml so I won't repeat it.

Also, could you have a look at the current patch, to spot any other 
obstacles/things you don't like?
The patch is available at:
http://users.pandora.be/bart.de.schuymer/ebtables/br-nf/bridge-nf-0.0.10-dev-pre1-against-2.5.42.diff
There is a little text file explaining the source code more in-depth here:
http://users.pandora.be/bart.de.schuymer/ebtables/br-nf/bridge-nf-0.0.10-dev-pre1-against-2.5.39-comments.txt
A high-level explanation of what we're doing is here:
http://users.pandora.be/bart.de.schuymer/ebtables/br_fw_ia/br_fw_ia.html


Another question:
I've been told it is the general concensus that this bridge firewall should be 
compiled in the kernel if CONFIG_NETFILTER=y. Or should it be a user option? 
It is predicted that using a user option will give alot of questions about 
the bridge firewall not working.
Do you have any strong opinion about this?

-- 
cheers,
Bart