multiple routing tables review patch ready for simple testing.

[Bruce M. Simpson]

John Hay wrote:
> The linux guys seems to have multiple fibs (or whatever they call them)
> which they can chain together by giving them different priorities. The
> effect seems to be that a packet will be matched through the highest
> priority fib to the lowest until a route match is found en then is used.
> Will something like that be possible? I came across that kind of use
> with the olsr guys. They let olsrd twiddle one of the higher priority
> fibs and then put fallback routes in a lower priority fib. That way
> olsrd can override a route (even the default route) and when olsrd
> exists and deltes all its routes, the original ones are still in the
> lower priority fib and will be used.
>   

XORP already does this without relying on any kernel support.

Each routing protocol supplies an origin table of its own. The RIB makes 
the decision on which route to plumb to the kernel based on 
administrative distance. When xorp_olsr exits, its origin table is 
removed, and the winning routes are recalculated.

You don't need to go to the kernel for this sort of thing unless you 
specifically need to implement route policy based on which interface(s) 
a packet came in on.