calling another dissector

Question

hey,

I am writing a dissector for netscaler core to core messages. Now this protocol works on top of the Net Scaler Trace layer(nstrace), which is introduced by the netscaler for debugging purposes.

So when I am writing the dissector for core to core, I want to be able to call (nstrace) after that. So how should I code for that??

PLEASE HELP, ANYONE??

Thanks,

Sid

Answer 1

Simple enough:

To call dissector "foo":

Define a global variable

static dissector_handle_t foo_handle;

In your proto_reg_handoff() fcn:
foo_handle = find_dissector("foo");
To actually call the dissector:
foo_tvb = tvb_new_subset(tvb, offset, length, reported_length);
call_dissector(foo_handle, foo_tvb, pinfo, subtree);

Look at any one of the many dissectors which use call_dissector() for examples.

In fact, if you look at packet-nstrace.c you'll see that it calls the "eth_withoutfcs" dissector.

Oops:

Actually: the above won't work. - nstrace isn't a "public" (registered dissector) (so it's not available to be found by find_dissector).

From the code, it looks like nstrace is expected to be and is processed as a thin outer layer which encapsulates ethernet.

So: I'm puzzled when you say the core-to-core protocol runs "on top of" nstrace.

What is the actual sequence of protocols in a frame ?