Many protocols contain subtrees, such as a header with various fields that are part of the header, and it’s convenient/logical to group those fields within the header subtree. However, doing so results in a Packet Diagram that only
shows the raw bytes of the subtree rather than the individual fields contained within the subtree.
So either I’m doing something wrong, in which case I welcome any suggestions for improving the display, or there seems to be a current limitation to the way the Packet Diagram behaves with respect to subtrees. Has anyone else noticed
this?
Is there a way to achieve this while still grouping the fields within a subtree?
Not in a subtree currently. If you look around line 600 of ui/qt/packet-diagram.cpp, you'll see that it only groups the top level fields in each protocol.
For the same reason, bitmask fields that are grouped together not in a subtree, using proto_tree_add_bitmask_list()
(like packet-rtp.c#L2072 with octet1_fields), then they are displayed separately (in master, post commit
for bitmask fields that are added with a subtree with proto_tree_add_bitmask() only the top level header
item appears.
There you can see bitmask fields that are displayed properly because there is no subtree.
I agree it would be a nice enhancement to travel down into the children of items that have children, though I imagine
you'd have to take care in some cases; e.g., dissect_e164_msisdn() from packet-e164.[ch] is used a lot in various dissectors,
and has a header that has the entire number, with child that only has the country code (but not a child for the non country code digits).
The simplest way to descend into the subtree for a E.164 number would thus only has an entry for the country code but leave the
other bits blank. Or you could have issues with dealing with overlaps.
John Thacker
