• Thomas Haller's avatar
    dbus: cache GetConnectionUnixProcessID and GetConnectionUnixUser · e04dc445
    Thomas Haller authored
    We call GetConnectionUnixProcessID and GetConnectionUnixUser *a lot*.
    And we do so synchronously. Both is a problem.
    
    To avoid the first problem, cache the last few requests with each cached
    value being valid for one second.
    
    On a quick test, this saves 98% of the requests:
    
         59 GetConnectionUnixProcessID(*)
       3201 GetConnectionUnixProcessID(*) (served from cache)
         59 GetConnectionUnixUser(*)
       3201 GetConnectionUnixUser(*) (served from cache)
    
    Note that now as we serve requests from the cache, it might be the case
    that the D-Bus endpoint already disconnected. Previously, the request would
    have failed but now we return the cached user-id and process-id. This
    problem is mitigated by only caching the values for up to one second.
    Also, it's not really a problem because we cache sender names. Those
    are supposed to be unique and not repeat. So, even if the peer already
    disconnected, it is still true that the corresponding PID/UID was as
    we have cached it. We don't use this API for checking whether the peer
    is still connected, but what UID/PID it has/had. That answer is still
    correct for the cached value after the peer disconnected.
    e04dc445
nm-auth-subject.c 14.1 KB