Re: [Wireshark-dev] XXXX: avoid appending xxxx multiple times to frame.protocols field

[Pascal Quantin]

Hi Guy,

Le 5 oct. 2017 23:20, "Guy Harris"  a écrit :

A given frame's dissection can have multiple packets for a given protocol,
if, at any protocol layer, a PDU can contain multiple PDUs for the next
layer above it (or parts of multiple PDUs, as with byte-stream protocols
such as TCP).

Some recent changes have been submitted to fix that for particular
protocols.

However, the underlying problem is that frame.protocols is intended to be a
set (in which a given item can occur only once) rather than a bag (in which
a given item can occur multiple times).  Perhaps it should be implemented
as a set, with uniqueness enforced, so that individual dissectors don't
need to keep from putting another  in the bag if there's already one
there?


What I like also with frame.protocols field is that it shows the protocol
encapsulation order within the packet. So in case of an IP packet
encapsulated inside a protocol running in top of IP, I think it makes sense
to display up twice. Changing it to a set would lose this property.

The problem with S1AP and Co is that it uses some dissector tables
internally to decode the fields, leading to fake multiple occurrences
within frame.protocols field. By the way, I realize that the pino
functionality introduced by Michael might have been used here also instead
of the simple patch I did. It might be an opportunity for me to see how
this pino stuff behaves exactly ;)

Cheers,
Pascal.
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[Wireshark-dev] XXXX: avoid appending xxxx multiple times to frame.protocols field

[Guy Harris]

A given frame's dissection can have multiple packets for a given protocol, if, 
at any protocol layer, a PDU can contain multiple PDUs for the next layer above 
it (or parts of multiple PDUs, as with byte-stream protocols such as TCP).

Some recent changes have been submitted to fix that for particular protocols.

However, the underlying problem is that frame.protocols is intended to be a set 
(in which a given item can occur only once) rather than a bag (in which a given 
item can occur multiple times).  Perhaps it should be implemented as a set, 
with uniqueness enforced, so that individual dissectors don't need to keep from 
putting another  in the bag if there's already one there?
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