Some of the collisions that are occuring are due to flowtable lookups
that succeed but have an invalid lle - typically because the L2 adjacency
lookup hasn't completed. This would lead to a follow-up insert which
would then fail (ie, collision) and the code would fall through to doing
a slow-path L2/L3 lookup in the netinet/netinet6 code.
This patch simply aborts storing a new flowtable entry if the lle isn't
yet valid.
Whilst I'm here, add a new pcpu counter for the item so the number of
failures can be tracked separately from generic "collisions."
Reviewed by: glebius
MFC after: 10 days
Sponsored by: Netflix, Inc.
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