Re: [PATCH] wireguard: convert index_hashtable and pubkey_hashtable into rhashtables

From: Hamza Mahfooz
Date: Wed Sep 08 2021 - 21:56:24 EST

Hey Jason,
On Wed, Sep 8 2021 at 01:27:12 PM +0200, Jason A. Donenfeld <Jason@xxxxxxxxx> wrote:
- What's performance like? Does the abstraction of rhashtable
introduce overhead? These are used in fast paths -- for every packet
-- so being quick is important.

Are you familiar with any (micro)benchmarks (for WireGuard) that, you
believe would be particularly informative in assessing the outlined
performance characteristics?

- How does this interact with the timing side channel concerns in the
comment of the file? Will the time required to find an unused index
leak the number of items in the hash table? Do we need stochastic
masking? Or is the construction of rhashtable such that we always get
ball-park same time?

I think the maintainers of rhashtable are best positioned to answer these
questions (I have cc'd them).