[dpdk-dev] [RFC] Add RIB library

[Bruce Richardson]

On Tue, Jul 11, 2017 at 07:33:04PM +0000, Medvedkin Vladimir wrote:
> Hi,
> 
> I want to introduce new library for ip routing lookup that have some advantages
> over current LPM library. In short:
>      - Increases the speed of control plane operations against lpm such as
>        adding/deleting routes
>      - Adds abstraction from dataplane algorythms, so it is possible to add
>        different ip route lookup algorythms such as DXR/poptrie/lpc-trie/etc
>        in addition to current dir24_8
>      - It is possible to keep user defined application specific additional
>        information in struct rte_rib_v4_node which represents route entry.
>        It can be next hop/set of next hops (i.e. active and feasible),
>        pointers to link rte_rib_v4_node based on some criteria (i.e. next_hop),
>        plenty of additional control plane information.
>      - For dir24_8 implementation it is possible to remove rte_lpm_tbl_entry.depth
>        field that helps to save 6 bits.
>      - Also new dir24_8 implementation supports different next_hop sizes
>        (1/2/4/8 bytes per next hop)
> 
> It would be nice to hear your opinion. The draft is below.
> 
> Medvedkin Vladimir (1):
>   lib/rib: Add Routing Information Base library
> 

On reading this patch and then having discussion with you offline, it
appears there are two major new elements in this patchset:

1. a re-implementation of LPM, with the major advantage of having a
flexible data-size
2. a separate control plane structure that is designed to fit on top off
possibly multiple lookup structures for the data plane

Is this correct?

For the first part, I don't think we should carry about two separate LPM
implementations, but rather look to take the improvements in your
version back into the existing lib. [Or else replace the existing one,
but I prefer pulling the new stuff into it, so as to keep backward
compatibility]

For the second part, perhaps you could expand a bit more on the thought
here, and explain what all different data plane implementations would
fit under it. Would, for instance a hash-lookup work? In that case, what
would the data plane APIs be, and the control plane ones.

Thanks,
/Bruce