[PATCH net-next] calipso: hash the cache key, not the option start, in calipso_cache_add()

[sashiko-bot at kernel.org]

> calipso_cache_add() stores calipso_ptr + 2 as the cache key, but
> computes entry->hash over calipso_ptr, i.e. starting two bytes earlier
> at the option type and length.  calipso_opt_getattr() looks entries up
> with calipso_cache_check(calipso + 2, calipso[1], ...), which hashes the
> key itself.
> 
> The two hashes only match on a jhash collision, so the CALIPSO label
> cache never hits and every labelled packet takes the full DOI lookup and
> category conversion path.  The memcmp() on the key keeps lookups
> correct, so this is a performance bug only.
> 
> Hash the stored key, as cipso_v4_cache_add() does for CIPSO.
> 
> Fixes: 4fee5242bf41 ("calipso: Add a label cache.")
> Signed-off-by: Joas Antonio dos Santos <joasantonio108 at gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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