Use of call_dissector ?

Question

I am total newbie in wireshark plugin development and i was curious about precise use case of this function , some "packet-xx.c" don't use it and some use it but still i am not able to make out difference. I am under impression that even if we don't use it , dissectors get called by default from epan/dissectors for all basic protocols.Please point some source file for more understanding of this function.

Accepted Answer

In general, the "call_dissector()" function is called whenever a dissector knows that it's payload is of a certain type for which wireshark has a dissector.

For instance, in the http-dissector, many different types of payload might be encountered. Depending on the type of data, the http-dissestor will call the appropriate (sub-)dissector.

An example is when the http dissector encounters a base64-encoded kerberos object. It will then decode the object first and then hand it over to the kerberos dissector for further dissection:

kerberos_tvb = base64_to_tvb(tvb, line + 9); /* skip 'Kerberos ' which is 9 chars */
add_new_data_source(pinfo, kerberos_tvb, "Kerberos Data");
call_dissector(gssapi_handle, kerberos_tvb, pinfo, tree);