RE: [Bluez-devel] Rfcomm Use Count

[Marcel Holtmann <marcel@holtmann.org>]

Hi Daryl,

> > > I may not have been clear about my thoughts on 
> > rfcomm_sock_cleanup_listen().
> > > If bluez_accept_dequeue() did return sockets regardless of 
> > state, then
> > > rfcomm_sock_cleanup_listen() should work (unless calling 
> > close on an already
> > > closed socket causes trouble). When it calls 
> > rfcomm_sock_kill(), sock_put()
> > > gets called which calls destruct() which should decrement 
> > the use count.
> > 
> > The ...cleanup_listen() kicks in when you stop the listening 
> > server, but
> > that is far too late. The problematic part already happened. 
> > We close a
> > connection that wasn't accepted. We must fix it there and not 
> > afterwards
> > like somekind of garbage collection. This is the kernel and not some
> > weird Jave/C++ code.
> 
> With my suggestion above the condition would be handled by either accept()
> or cleanup_listen(), whichever is called first. Though I guess you could
> still consider that to be garbage collection.

when it is handled in ..cleanup_listen() then it gets handled when you
kill the server process. I think this is far too late, because you can
have more than one connection attempts in between. We must handle this
when we close the connection.

> > > What if bluez_accept_dequeue() called sk->shutdown() on 
> > sockets which are
> > > already closed in the accept queue?
> > 
> > I am not sure about the side effects, but this can be a 
> > solution. What I
> > think is that setting the socket to BT_CLOSED is wrong. Maybe using
> > BT_DISCONN is better, but this involves changing the state machine.
> 
> Calling sk->shutdown() is bluez_accept_dequeue() would be virtually the same
> timing (i.e. garbage collecting likeness) as the suggestion above (returning
> the closed socket in ...accept_dequeue). It would happen only when accept()
> or cleanup_listen() are called.

This is correct and so I don't really like this approach. I think there
is a simply logic mistake in the closing path of the RFCOMM code.

Regards

Marcel




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