Re: [RFC PATCH 1/4] fib: add multi-VRF support

["Medvedkin, Vladimir" <vladimir.medvedkin@intel.com>]

Hi Konstantin,

On 3/23/2026 3:48 PM, Konstantin Ananyev wrote:
>
>> Add VRF (Virtual Routing and Forwarding) support to the IPv4
>> FIB library, allowing multiple independent routing tables
>> within a single FIB instance.
>>
>> Introduce max_vrfs and vrf_default_nh fields in rte_fib_conf
>> to configure the number of VRFs and per-VRF default nexthops.
> Thanks Vladimir, allowing multiple VRFs per same LPM table will
> definitely be a useful thing to have.
> Though, I have the same concern as Maxime:
> memory requirements are just overwhelming.
> Stupid q - why just not to store a pointer to a vector of next-hops
> within the table entry?

Am I understand correctly, a vector with max_number_of_vrfs entries and 
use vrf id to address a nexthop?
Yes, this may work.
But, if we are going to do an extra memory access, I'd better to 
maintain an internal hash table with 5 byte keys {24_bits_from_LPM, 
16_bits_vrf_id} to retrieve a nexthop.

> And we can provide to the user with ability to specify custom
> alloc/free function for these vectors.
> That would help to avoid allocating huge chunks of memory at startup.
> I understand that it will be one extra memory dereference,
> but probably it will be not that critical in terms of performance .
> Again for bulk function  we might be able to pipeline lookups and
> de-references and hide that extra load latency.
>
>> Add four new experimental APIs:
>> - rte_fib_vrf_add() and rte_fib_vrf_delete() to manage routes
>>    per VRF
>> - rte_fib_vrf_lookup_bulk() for multi-VRF bulk lookups
>> - rte_fib_vrf_get_rib() to retrieve a per-VRF RIB handle
>>
>> Signed-off-by: Vladimir Medvedkin <vladimir.medvedkin@intel.com>
>> ---
>>   lib/fib/dir24_8.c        | 241 ++++++++++++++++------
>>   lib/fib/dir24_8.h        | 255 ++++++++++++++++--------
>>   lib/fib/dir24_8_avx512.c | 420 +++++++++++++++++++++++++++++++--------
>>   lib/fib/dir24_8_avx512.h |  80 +++++++-
>>   lib/fib/rte_fib.c        | 158 ++++++++++++---
>>   lib/fib/rte_fib.h        |  94 ++++++++-
>>   6 files changed, 988 insertions(+), 260 deletions(-)
>>
<snip>

-- 
Regards,
Vladimir