Re: Calling a dissector: Type for data parameter

[Anders Broman <a.broman58 () gmail com>]

Hi,
Yes the method is fragile. At the time of development I think it was
proposed to pass a struct containing a string and the void pointer where
the string could be used as a identifier. But that was voted down.
Regards
Anders

Den lör 29 maj 2021 09:26Guy Harris <gharris () sonic net> skrev:

> On May 29, 2021, at 12:12 AM, Anders Broman <a.broman58 () gmail com> wrote:
>
> > Shouldn't the caller be calling with the right data type or NULL? So a
> bug in the MQTT disector?
>
> How can the MQTT dissector determine what the right data type *is* -
> especially given that the dissectors aren't wired in, there's a UAT
> preference that lets the user configure it.
>
> This is where the current mechanism for passing data between dissectors
> goes crashing to the ground.
>
> MQTT passes a topic string, which is just a string, to the dissectors it
> calls.
>
> JSON expects to be passed a pointer to an http_message_info_t.
>
> JSON registers its non-heuristic dissector by name, and allows it to be
> used with Decode As... for UDP ports.
>
> It might *look* safe if you check the UDP dissector and the dissectors
> that use "media_type" and "grpc_message_type", but the "registers its
> non-heuristic dissector by name" mean there are no guarantees, given that
> another dissector that passes a pointer to something *other* than an
> http_message_info_t to dissectors that are specified by name in a UAT.
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