Wireshark-dev: Re: [Wireshark-dev] Custom item not related to the packet

From: Roland Knall <rknall@xxxxxxxxx>
Date: Wed, 26 May 2021 14:31:11 +0200
The data displayed in the subitem is the one from pt, your data variable which you used to create the new tvb. The hf_item seems to point to a different data structure. How is pt being generated? Are you using the same length and start offset as for the hf item? 

regards
Roland

Am Mi., 26. Mai 2021 um 08:46 Uhr schrieb Antonello Tartamo <antonellotartamo@xxxxxxxxx>:
Hello everyone,
I'm trying to add a custom item which is not strictly related to the packet but it is coming from a processing of a part of the packet.
I've used the following instructions:

                new_tvb = tvb_new_child_real_data(tvb, pt, (guint)16, 16);
                add_new_data_source(pinfo, new_tvb, "processed");

                ti = proto_tree_add_item(data_tree, hf_mp_control_processed, new_tvb, 0, 16, ENC_NA);
                PROTO_ITEM_SET_GENERATED(ti);

hf_mp_control_processed is a set of bytes: 
        { & hf_mp_control_processed ,
          { "mp control processed", "mp.control.processed",
            FT_BYTES, BASE_NONE, 0x0, 0x0,
            NULL, HFILL }
        }

The problem is that when I click on this new item into the Packet Details I see the correct byte values, while in the Packet Bytes view these ones are totally wrong.

Attached image:
image.png
For example the first byte is 0x48 but 0x68 is shown in the Packet Bytes view.

Is there a different way to perform this operation ?

Thanks in advance
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