Re: XXXX: avoid appending xxxx multiple times to frame.protocols field

[Evan Huus <eapache () gmail com>]

It sounds to me like it shouldn’t be a set or a list, but a tree?

Evan

On Fri, Oct 6, 2017 at 08:17 Michael Mann via Wireshark-dev <
wireshark-dev () wireshark org> wrote:

> There's also this explanation:
> https://www.wireshark.org/lists/wireshark-dev/201701/msg00005.html
>
>
> -----Original Message-----
> From: Pascal Quantin <pascal.quantin () gmail com>
> To: Developer support list for Wireshark <wireshark-dev () wireshark org>
> Sent: Fri, Oct 6, 2017 3:06 am
> Subject: Re: [Wireshark-dev] XXXX: avoid appending xxxx multiple times to
> frame.protocols field
>
> Hi Roland,
>
> 2017-10-06 8:23 GMT+02:00 Roland Knall <rknall () gmail com>:
>
> Personally I think moving to a set would reduce functionality for some
> applications. Industrial ethernet applications for instance heavily rely on
> multiple protocols being transported in single frames multiple times (one
> UDP packet contains a lot of openSAFETY frames, which themselve could
> contain data dissectors).
>
> So -1 for me for moving to a set.
>
>  @Pascal - could you point me in the direction of Michael's change you
> mentioned (pino stuff)?
>
>
> Here it is: https://code.wireshark.org/review/19464
>
>
> On Fri, Oct 6, 2017 at 7:01 AM, Pascal Quantin <pascal.quantin () gmail com>
> wrote:
>
> Hi Guy,
>
> Le 5 oct. 2017 23:20, "Guy Harris" <guy () alum mit edu> 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 XXXX 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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