[RFC]: xfrm by mark

[jamal <hadi@cyberus.ca>]

Hi,

While catching up with old netdev threads I noticed this one:
http://marc.info/?l=linux-netdev&m=125621829709171&w=2
I had a chat with Timo and he is too busy on other things at
the moment. I have some cycles to burn and would like to pursue
this unless there is objection to the general idea. I am interested
because I would like to see most of the net stack capable of 
reference by mark. I am posting this so i can get a general
pulse before i go off coding.

Approach:
- introduce attribute XFRMA_MARK
- both SPD and SAD will have new entries ->mark
- by default mark is 0, so backward compat for 
control add/get/del as well as fast path lookup continues.
I dont plan to touch pfkey i.e anything injected by pfkey
will use default mark of 0.
- a sysctl to turn off this feature doesnt seem necessary
since the cycles added by the fast path lookup dont seem
to be much more..

Timo, please chime in with anything i may have missed.


cheers,
jamal