Wireshark · Wireshark-dev: Re: [Wireshark-dev] Using "ip.id" for dissector_add

[Lars Friedrichs <larsfriedrichs@xxxxxx>]

Hi Abhik,

thanks for the reply but at least looking at packet-sctp doesn't help me
here. I see that it uses "ip.proto" but that is not what I need since
the protocol does not rely on the "ip.proto" field but on "ip.id".
Yust to get this straight:
A protocol registers its header fields, shouldn't all these fields be
possible to be added a subdissector to? Maybe anyone can explain line
697 of packet.c to me:
    g_assert(sub_dissectors);
As I am not used to C I would read that line as if it tries to get some
assumptions about "sub_dissectors" straight. I hoped it would be the
following lines:
    switch (sub_dissectors->type) {

    case FT_UINT8:
    case FT_UINT16:
    case FT_UINT24:
    case FT_UINT32:
...
        break;
...
    default:
        /*
         * But you can't do a port lookup in any other types
         * of tables.
         */
        g_assert_not_reached();
    }
would the failing be done by the last line? So the g_assert above fails
because of the following code? Because that code would mean to me that
if the sub_dissector that was found has non of the given types it would
fail. But I checked the type of the ip.id field - it is FT_UINT16 and so
it is in the list and so it should not fail.
Something may be wrong with my eyes or my understanding of things here.
Could anybody help me clear that up?

Thanks,
Lars


Abhik Sarkar schrieb:
> Hi Lars,
>
> Perhaps the table you are looking for is "ip.proto". Check packet-sctp
> for example.
>
> Good luck!
> Abhik.
>
>