[dpdk-dev] [RFC] Add RIB library
Bruce Richardson
bruce.richardson at intel.com
Tue Aug 15 10:23:22 CEST 2017
On Tue, Aug 15, 2017 at 01:28:26AM +0300, Vladimir Medvedkin wrote:
> 2017-08-14 13:51 GMT+03:00 Bruce Richardson <bruce.richardson at intel.com>:
>
> > 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?
> >
> 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.
> >
>
> I'm not sure for _all_ data plane implementations, but from my point of
> view compressed prefix trie (rte_rib structure) could be useful at least
> for dir24_8, dxr, bitmap handling. Concerning to hash lookup, it depends on
> algorithm (array of hash tables indexed by mask length, unrolling prefix to
> number of /32).
> Perhaps it is better to waive the abstraction and make LPM as primary
> struct that keeps rte_rib inside (instead of rules_tbl[ ]).
> In that case rte_rib becomes side structure and it's API only for working
> with a trie. LPM's API remains the same (except next_hop size and LPM
> creation).
>
>
What is the advantage of using the rte_rib for control plane access over
the existing rules table structure. Are not the basic operations needed
for adding/removing/looking-up rules supported by both?
/Bruce
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