[dpdk-dev] [Bug 345] rte_hash returns invalid key if the number of entries is not a power of 2

[bugzilla at dpdk.org]

https://bugs.dpdk.org/show_bug.cgi?id=345

            Bug ID: 345
           Summary: rte_hash returns invalid key if the number of entries
                    is not a power of 2
           Product: DPDK
           Version: 19.08
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: other
          Assignee: dev at dpdk.org
          Reporter: barbette at kth.se
  Target Milestone: ---

Hi all,

rte_hash_create will silently augment the number of entries (N) to the next
power of 2 value.

Per the documentation, the return values of "rte_hash_lookup" or "rte_hash_add"
is "[... or] a positive value that can be used by the caller as an offset into
an array of user data. This value is unique for this key.".
Which may lead to a segmentation fault, as the user allocated only N entries
and not next_pow2(N). And there is no means to recover what is the "final"
number of entries (next_pow2(N)).

I would suggest to at least update the documentation. One way to really fix
this would be to let the user get the actual number of entries, or fail if the
value is not a power of 2.

Tom

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