Re: Dealing with aggregated packets

[Ivan Nardi <nardi.ivan () gmail com>]

Hi

I work with sctp pcaps very often and I have always found that Wireshark
doesn't handle them in a practical way
The far biggest issue is the display filter logic

As a workaround, I have to externally pre-process the traces and "de-chunk"
the sctp packets: when every sctp packet contains only one chunk everything
works like a charm, as usual

> From a user point of view, I would like an improvement in the display
filters:
* you should be able to match a specific sub-packet. I mean, when the
filter is something like "sccp.xxx == AAAA && gsm_a.yyyy == BBBB" I do
expect the matched fields to be on the same sub-packet, not on different
chunks of the same sctp packet. AFAIK one way to achieve this goal is
forcing all protocol fields above sctp (or any other "aggregating"
protocol) to be per sub-packets, not per packets (as today). In this way,
there shouldn't be multiple fields anymore
* when there is a display filter (involving sub-protocol fields), only
matching sub-packets should be visualized in the packet list
* you should be able to export only visualized sub-packets in a valid file.
Just my 2 cents, based on my personal workflow

I fully understand that my wish-list requires a huge amount of work;
improving only the visual representation of the packets/sub-packet should
be an important step forward anyway

I don't have the expertize to write GUI or "core" code, but I am more than
willing to test any solutions

Thank you very much for bringing up this topic

Ivan

On Mon, 2 Jul 2018 21:19 Darien Spencer, <cusneud () mail com> wrote:

> Hey devs
> There's something that has been bothering me in my wireshark experience
> and I wanted to bring to discussion
> *Some protocols can aggregate several payloads *such as *SCTP and TCP*
> Viewing those in wireshark could be difficult if many payloads are present.
> Specificly *the Info column gets long quickly *(assuming fences are used)
>
> Here is an example - the info column of a SCTP packet with 6 payloads:
> https://i.imgur.com/GeA2WmU.png
>
> It can be challenging to spot a specific packets in those overpopulated
> info columns
> further more, once you find the right packet by the info column you are
> served with your next challenge -
> finding which of the aggregated packets in the protocol tree is the one
> you are looking for.
>
> I was thinking about introducing a newer concept to wireshark in the form
> of *"sub-packets"*
> Maybe that's a cosmetic feature to add to the Qt GUI and maybe it required
> some changes to the dissection engine. I'm not familiar enought with the
> GUI to tell.
> What I had in mind is an option to 'expend' a packet in the main view so
> its aggregated sub packets are seen in a tree under it
> Here's a mock hoping it's get the idea across:
> https://i.imgur.com/WfSvg6x.png
>
> I can imagine how this might require a change to the way info is saved in
> the dissectors.
>
>
> Does anyone else feel this is an issue when analysing traffic?
> Is this a feature fitting the GUI/User experience guidelines of wireshark?
>
> Cheers,
> Darien
>
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