Hi Maxime,
Thanks for the patches.
For patches 2 and 3 introducing unit tests
Acked-by: Vladimir Medvedkin <[email protected]>
For patch 1, 4 and 5,
I think both implementations are over-complicated.
I suggest more optimal implementation for the count_empty_levels() (from
the patch 1/5):
here is a draft based on your 1/5:
https://patches.dpdk.org/project/dpdk/patch/[email protected]/
This implementation can be backported. The function logically belongs to
trie.c, since it reflects its specifics, and not to the RIB library as
it's more generic.
You may take this patch and integrate it into v2 replacing your 1/5.
On 5/22/2026 3:58 PM, Maxime Leroy wrote:
This v1 supersedes the earlier RFC. The RFC dropped rsvd_tbl8s and
used tbl8_pool_pos in the pre-check, which loses the worst-case
envelope: a compressed /48 under a /28 allocates zero tbl8s but must
reserve the boundaries the /48 would need if the /28 is later
removed (DEL forces mid-flight decompression in modify_dp() with no
rollback).
This v1 keeps rsvd_tbl8s and computes it the way dir24_8 already
does for IPv4. dir24_8 counts /24 supernets that contain at least
one /25..32 prefix: that count is invariant under unrelated RIB
changes, so the counter cannot drift. trie6 has the same need at
13 levels instead of 1 (byte boundaries 24, 32, ..., 120), so v1
counts, for each L in that set, the /L supernets containing at
least one prefix with depth > L. ADD/DEL pairs are symmetric by
construction.
Patch 1 is the minimal self-contained fix (Fixes: + Cc: stable).
Patches 2-3 add the reproducer and extended regression tests.
Patches 4-5 are an optimization (not for stable): valid_descendants
in rte_rib6 + single-descent helper, so trie_modify() walks once
instead of up to 13 times per ADD/DEL.
Validated on a live BGP router (grout + FRR, 127 IPv6 prefixes):
RSVD_TBL8 returned to its pre-cycle value after a zebra-kill /
reconverge cycle.
Maxime Leroy (5):
fib6: fix tbl8 reservation drift in trie
test/fib6: add reproducer for tbl8 reservation drift
test/fib6: extended drift test cases
rib: track valid descendant count per node
fib6: speed up tbl8 reservation accounting
app/test/test_fib6.c | 335 ++++++++++++++++++++++++++++++++++++++++
app/test/test_rib6.c | 92 +++++++++++
lib/fib/trie.c | 47 +-----
lib/rib/rib6_internal.h | 37 +++++
lib/rib/rte_rib6.c | 80 ++++++++++
5 files changed, 552 insertions(+), 39 deletions(-)
create mode 100644 lib/rib/rib6_internal.h
---
v1:
* Keep rsvd_tbl8s; recompute it via topology-stable empty-supernet
count (dir24_8 pattern at 13 levels) instead of RIB-derived
depth_diff.
* Drop RFC patch 3/3 (no longer needed).
* Add extended regression tests.
* Add patches 4-5: RIB valid_descendants + single-descent helper
(optional perf optimization; not for stable).
* Production-validated on a live BGP router.
--
2.43.0
--
Regards,
Vladimir
