Wireshark-bugs: [Wireshark-bugs] [Bug 8178] Multiple requests or responses in a single frame ca

Date: Fri, 14 Jun 2013 01:27:51 +0000

Comment # 13 on bug 8178 from
(In reply to comment #12)
> (In reply to comment #10)
> > It seems to me that there are two separate issues here:
> > 
> > 1. How to usefully filter multiple protocol occurrences in a single frame.
> > 
> > What about a function limit_distance(n, filter) where an n of 0 requires the
> > filter be satisfied in a single subtree, n of 1 allows the engine to travel
> > one level to satisfy the filter, etc.
> 
> I take it that's similar to same_subtree(protocol, filter)?  If so, what
> defines a subtree?  If there are multiple levels at which there are multiple
> higher-level packets per frame, with an n of 0, which of those subtrees
> would be used?

Similar to but more flexible than same_subtree. A subtree in this context is
whatever is registered with proto_register_subtree_array (basically ett_
variables). This has the advantage that it works automatically with existing
dissectors as long as they group tree items under a subtree when they belong
together. For example:

PROTO
|-item1
|-item2
|-subtree
||-item3
||-item4
|-subtree
||-item4
||-item5
||-subtree
|||-item6
|||-item7

These filters would match:
limit_distance(0, item1 && item2)
limit_distance(0, item3 && item4)
limit_distance(0, item4 && item5)
limit_distance(0, item6 && item7)

These would not:
limit_distance(0, item1 && item3)
limit_distance(0, item3 && item5)
limit_distance(0, item4 && item6)

These would match:
limit_distance(1, item1 && item3)
limit_distance(1, item3 && item5)
limit_distance(1, item4 && item6)
limit_distance(2, item1 && item7)

This would not:
limit_distance(1, item1 && item7)

Something about this still doesn't feel quite ideal, but it's a step in the
right direction.


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