UCT/IB/MLX5: Avoid caching AH for UD/DC connect - #11833
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UD mlx5 and DC connect extract the resolved AV bytes from a device-cached AH, which can retain a stale MAC once the peer's IP-to-MAC mapping changes. Create this AH uncached and destroy it right after copying out the AV, matching the fix already applied to the RC DevX QP-connect path. DC's pure-grant reply still relies on the cached AH; left unchanged for now, with a TODO to move it to the same uncached helper.
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🤖 Starting review — findings will be posted here when done. |
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Optional (non-blocking): was this validated on RoCE hardware? The stale-L2-address case that motivates the fix is RoCE-specific, and there's no regression test — worth confirming the AV extraction path still behaves on a real RoCE device. |
brminich
approved these changes
Aug 26, 2026
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What?
UD mlx5 and DC connect no longer use cached address handle (AH). The shared
uct_ud_mlx5_iface_get_av()helper now creates a temporary, uncached AH just to extract the AV bytes, then destroys it right away.Why?
The cached AH is keyed by resolved LID/GID and has no reliable invalidation path, so a peer's stale L2 address could keep being reused. The AH is only needed transiently here to read its AV bytes.
How?
uct_ud_mlx5_iface_get_av()does not go through the cached AH store anymore. This single shared helper covers both callers: UD mlx5 connect and DC connect.Connection matching and
is_connected()already compared the resolved LID/GID/QPN params, not the AH itself, so nothing else needed to change there. DC's pure-grant reply still uses the cached path, left as a follow-up TODO since it could have performance implications.