Same IP is banned multiple times (conflict with Memcache)

To anyone having this issue nowadays, this is due to the following optional configuration suggested by the memcache module :

// Don't bootstrap the database when serving pages from the cache.
$conf['page_cache_without_database'] = TRUE;
$conf['page_cache_invoke_hooks'] = FALSE;

With these options set as suggested, the Drupal IP blocking does not work at all and that is why the IP is added multiple times since there is no check if it already exists in DB prior to adding.

We could have a check like this in the function blockUser() :

      if (!db_query("SELECT * FROM {blocked_ips} WHERE ip = :ip", array(':ip' => $ip))->fetchField()) {
        ...
      }

But such a check is not necessary when the blocking actually works!

Thanks for that great module!