[ovs-dev] [mlhash2 1/2] mac-learning: Use random secret in hash function.

[Ben Pfaff]

On Fri, Jul 22, 2011 at 01:36:25PM -0700, Ethan Jackson wrote:
> The mac-learning 'secret' parameter is intended to prevent an
> attacker from turning the mac learning table into a linked list by
> using a known hash function to choose perfectly bad mac entries.
> However, this parameter was not taken into account in most cases.
> 
> Found by inspection.

Looks good.  I think that instead of:

    return hash_2words(hash_bytes(mac, ETH_ADDR_LEN, vlan), ml->secret);

we could just use:

    return hash_bytes(mac, ETH_ADDR_LEN, vlan ^ ml->secret);

and avoid a second hashing step.