Re: Best algorithmic way to implement MPTCP sequence number space analysis ?

[Evan Huus <eapache () gmail com>]

You should just be able to call `epan_get_frame_ts` and pass it
`pinfo->epan` plus your frame number.

On Thu, Oct 8, 2015 at 4:26 PM, Matt <mattator () gmail com> wrote:
> I managed to get the interval tree working with only a few
> modifications to the core R/B tree.
>
> I now would like to compute the sequence number inter arrival times
> (multipath may provoke more out of order hence it is a metric of
> interest). To do that I need to get access to the time arrival of a
> specific frame (i.e., I know the frame number) from packet-tcp.c.
> For instance I have a packet with Sequence Number (=SN) 100 in packet
> 5 and I know that SN 99 is in packet 2 or in packet 8 (out of order)
> and I would like to compute the delta time of arrival between the 2
> packets.
>
> I found the frame_data_sequence_find() function but it expects a list
> of frames as first parameter. Any idea how to retrieve that list from
> packet-tcp.c ?
>
> Regards
>
>
> 2015-10-02 18:11 GMT+02:00 Matt <mattator () gmail com>:
> > Hi,
> >
> > (Question is at the end, I start with an Multipath TCP introduction (MPTCP) ).
> > I would be interested in adding MPTCP sequence number analysis to
> > wireshark, similar to what is done with TCP but taking into account
> > MPTCP specifics:
> > - MPTCP sequence number is 64 bits.
> > - MPTCP uses a global sequence number (SN) space and maps this global
> > SN to a TCP SN. For instance, an MPTCP socket wants to send the bytes
> > 1 to 10. It may send 6 bytes on TCP subflow 1 and the 4 other bytes on
> > another subflow 2. On each subflow (=TCP connection), it will send a
> > mapping (via a TCP option called DSS=Data Sequence Signaling) saying
> > for instance
> > on subflow 1 I map MPTCP global SN 1-6 to local subflow SN 21-26,
> > on subflow 2 I map MPTCP global SN 7-10 to local TCP SN 60-63.
> >
> > Keeping track of those DSS options/mappings would help analyzing the
> > behavior of an MPTCP connection:
> > - does it duplicate some packets over different paths (<=> do some DSS
> > overlap on different subflows?)
> > - it would allow to generate an MPTCP RTT/application latency since
> > striping packets over several paths is likely to increase the
> > application latency
> > - also allow to deduce if we've captured all subflows or if there are
> > holes in the MPTCP sequence number (maybe one subflow was emitting on
> > the wifi interface and we didn't capture it)
> > etc...
> >
> > Now here is my problem: what datastructure should I use to achieve
> > what I previously describe in a way that could be accepted upstream ?
> > or to put it differently how to retrieve a list of ranges (MPTCP start
> > SN and end SN) from another SN range ? The interval tree sounds like a
> > good solution (http://www.geeksforgeeks.org/interval-tree/) but I
> > wonder if there is any advice on an alternate solution ? or ways to
> > build the tree efficiently (like disabling rotations and balancing the
> > tree only at the end or stuff like that, I am not an algorithmic
> > expert).
> >
> > In any case, I plan to add an option to turn this DSS analysis on/off.
> >
> > Regards
> >
> > Matt
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