Hi List!
I've looked at the README.developer file to understand, how to call a
subdissector from another one.
Some of the documentation on this topic seems to be out of date, "1.8
Calling Other Dissector" gives an example from packet-ipx.c,
but that does no longer reflect the current implementation in this file.
As it also is hard to understand how things have to be done, I would
like to correct/update/enhance the docs on this topic.
Could someone correct me on the following understanding:
In the upper layer dissector, the proto_reg_handoff_xy() function has to
register the upper dissector at the lower one. This is done by first
create a dissector_handle_t using create_dissector_handle() and then do
a dissector_add() to a specific lower layer protocol field (typically an
identifier of the upper layer protocol). Except from the
README.developer skeleton code:
void
proto_reg_handoff_PROTOABBREV(void)
{
dissector_handle_t PROTOABBREV_handle;
PROTOABBREV_handle = create_dissector_handle(dissect_PROTOABBREV,
proto_PROTOABBREV);
dissector_add("PARENT_SUBFIELD", ID_VALUE, PROTOABBREV_handle);
}
In the lower layer code, the dissector will create a new tvb using
tvb_new_subset(), and then call the upper layer dissector using
call_dissector()
The only thing still missing in my understanding is the data_handle in
the call to call_dissector(). At various places I've found:
data_handle = find_dissector("data");
but what's the use of this "data"?
Regards, ULFL
