Re: When is the preference variable updated?

[Paul Offord <Paul.Offord () advance7 com>]

Hi Pascal,

You are right – it got called twice without the preference value being set and then the third time it was.  Thanks to 
you both for your help, it’s saved me a lot of time.

Best regards…Paul

From: wireshark-dev-bounces () wireshark org [mailto:wireshark-dev-bounces () wireshark org] On Behalf Of Pascal Quantin
Sent: 12 November 2015 14:53
To: Developer support list for Wireshark <wireshark-dev () wireshark org>
Subject: Re: [Wireshark-dev] When is the preference variable updated?



2015-11-12 15:48 GMT+01:00 Paul Offord <Paul.Offord () advance7 com<mailto:Paul.Offord () advance7 com>>:
Hi Pascal,

I wondered if that would be the case but it doesn’t seem to be set when I enter the handoff code.  My handoff looks 
like this:

proto_reg_handoff_tmsvc(void)
{
               dissector_handle_t dissect_tmsvc_handle;
               HANDLE h_thread;

               if (tmsvc_port > 0) {
                              dissect_tmsvc_handle = create_dissector_handle(dissect_tmsvc, proto_tmsvc);

                              register_postdissector(dissect_tmsvc_handle);

                              h_thread = create_service_thread();
               }

               return;
}

I’ve checked the value of tmsvc_port with a breakpoint set on the if statement and it’s still 0 at this point.  It is 
set to the saved preference 8989 by the time of the first call to my dissector.

I notice that Anders has given me a slightly different solution and so I’ll take a look at that next.

Anders' solution should be the same as mine (or maybe I was not clear): proto_reg_handoff_tmsvc should be given as 
parameter to perfs_register_protocol and you will see that this function starts being called several times (so you 
should probably ensure that your code is called only once).


Thanks and regards…Paul



From: wireshark-dev-bounces () wireshark org<mailto:wireshark-dev-bounces () wireshark org> 
[mailto:wireshark-dev-bounces () wireshark org<mailto:wireshark-dev-bounces () wireshark org>] On Behalf Of Pascal 
Quantin
Sent: 12 November 2015 14:15
To: Developer support list for Wireshark <wireshark-dev () wireshark org<mailto:wireshark-dev () wireshark org>>
Subject: Re: [Wireshark-dev] When is the preference variable updated?



2015-11-12 15:07 GMT+01:00 Paul Offord <Paul.Offord () advance7 com<mailto:Paul.Offord () advance7 com>>:
Hi,

Frankly I feel a bit stupid asking this but I've been trying to figure it out for about 6 hours and I think I need 
help.  I have a dissector which I register like this:

static int tmsvc_port = 0;

void
proto_register_tmsvc(void)
{
    module_t *tmsvc_module;

    proto_tmsvc = proto_register_protocol("TM Syncro Service",
                                          "TmSyncro",
                                          "tmsvc");

    tmsvc_module = prefs_register_protocol(proto_tmsvc, NULL);

    prefs_register_uint_preference(tmsvc_module, "port",
                                   "TmSyncro service port",
                                   "When set to a value greater than 0 the TmSyncro service is started and accessible 
via the port number"
                                   10,
                                   &tmsvc_port);

}

Immediately after the prefs_register_uint_preference call I check the tmsvc_port value and its still 0 (and I've tried 
other initialisation values and they remain unchanged).  I was expecting tmsvc_port to be set to the value I last set 
by editing the preferences through the Wireshark menu system.

If I check with Menu -> Edit -> Preferences -> Protocols -> TmSyncro sure enough the value I last set is there.

When does my variable get updated?  Or alternatively, how can I retrieve the saved preference value?

Thanks and regards...Paul

Hi Paul,
the variable should be set according to the preference content when the  proto_reg_handoff_tmsvc function (that you 
register thanks to the prefs_register_protocol function) is called. Alternatively (if you do not need the reg_handoff 
function at all) the variable should be set when your dissector code is called.
Best regards,
Pascal.

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