Re: [gupnp] handling of sequence numbers in gupnp-service-proxy.c

On Wed, Mar 25, 2009 at 8:29 PM, Sven Neumann <s neumann phase-zero de> wrote:
> Hi,
> On Wed, 2009-03-25 at 20:04 +0200, Zeeshan Ali (Khattak) wrote:
>> > If we receive messages out-of-order, does that really mean that we have
>> > missed a message? Isn't it possible that the message order is changed
>> > due to asynchronous code?
>>   No, that will only happen because of some bug in libsoup since
>> SoupServer is guaranteed to call the server_handler for each message
>> synchronously as they arrive (assuming they are on the same
>> connection, which afaik is true in our case). I am telling you this
>> after confirming my assumption with Dan Winship on IRC.
> The sender in our case is an AVTransportService implemented by means of
> GUPnPService. So I guess we can assume that we are one the same
> connection. I can also rule out thread issues, all calls to
> gupnp_service_notify() are done from idle handlers in the main-loop.
> I know that usually an AVTransportService only has one evented variable.
> But the spec doesn't forbid that another evented variable is added for
> which notifications can be requested, does it?

  No, AFAIK you can have as many custom state variable and actions as you like.

>> > In the cases where we observed this, the
>> > Service sent out a LastChange event immidiately followed by much simpler
>> > notification event. It looks like the notification event arrived at the
>> > ServiceProxy before the LastChange event.
>>    Then there must be a bug in libsoup?
> I guess we will have to do some more debugging then. Perhaps I can make
> up a simple test case to illustrate the problem.

  That would be nice.

> For now we have removed the code in GUPnPServiceProxy that discards the
> message. IMO it is completely spec conformant to do that. It doesn't
> state that the message has to be discarded, does it?

  No, AFAICT it doesn't. I think such a patch should be welcomed. BTW,
please send patches to gssdp, gupnp and gupnp-media-renderer to
bugzilla. Otherwise they might get forgotten since I don't have write
access to these repos and the guys who do are extremely busy these
days in other stuff.


Zeeshan Ali (Khattak)
FSF member#5124
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