Re: [MPTCP] [Weekly meetings] MoM - 26th of July 2018

Re: [MPTCP] [Weekly meetings] MoM - 26th of July 2018

[Mat Martineau]

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On Thu, 26 Jul 2018, Matthieu Baerts wrote:

> Netdev's debriefing:
>    - we got good feedbacks:
>        - people want to have MPTCP upstream and are supportive (Tom
> Herbert and Eric Dumazet)
>        - some concerns about not modifying binaries and still use MPTCP
> (without LD_PRELOAD), something possible with mptcp_trunk.
>        - there were some discussions/reminders about using per cgroups
> ebpf hooks (e.g. for API extension):
>            - BPF/netdev background:
> http://vger.kernel.org/netconf2018_files/AlexeiStarovoitov_netconf2018.pdf

Regarding this BPF / cgroup idea (thank you, David Ahern), here's a link 
to similar functionality implemented for the connect() call:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d74bad4e74ee373787a9ae24197c17b7cdc428d5

The equivalent would be something that could run early to override the 
proto value (or any other parameters) for any socket() call in a 
particular cgroup.

BPF_CGROUP_INET_SOCK_CREATE exists, but it runs at the end of 
inet_create() (too late to override the protocol).

--
Mat Martineau
Intel OTC

[MPTCP] [Weekly meetings] MoM - 26th of July 2018

[Matthieu Baerts]

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Hello,

We just had our 15th meeting with Mat, Ossama, Peter (Intel OTC),
Christoph (Apple) and myself (Tessares).

Thanks again for this new good meeting!



Here are the minutes of the meeting:



Linux Plumber:
    - we sent a proposition of talk but no news
    - now a 2-days track
    - there are new announcements on the list (new talks accepted)



mptcp_net-next:
    - new patches (3) are coming from mptcp_trunk (and applied)
    - sync with net-next done by Mat
    - Christoph will look at upstreaming MPTCPv1 (first on mptcp_trunk)



Netdev's debriefing:
    - we got good feedbacks:
        - people want to have MPTCP upstream and are supportive (Tom
Herbert and Eric Dumazet)
        - some concerns about not modifying binaries and still use MPTCP
(without LD_PRELOAD), something possible with mptcp_trunk.
        - there were some discussions/reminders about using per cgroups
ebpf hooks (e.g. for API extension):
            - BPF/netdev background:
http://vger.kernel.org/netconf2018_files/AlexeiStarovoitov_netconf2018.pdf
    - skb buff: we got advises from Eric Dumazet: add a pointer at the
end is no longer costly (see the next topic)
    - changes in TCP stack: we didn't got propositions/discussions about
that, what we could do then:
        - either propose code change (RFC)
        - having other possibilities to talk about architecture
        - RFC about a design/API (internal API first before exposing
that to userspace)
            - for the userspace API, it could be nice to expose subflows
or only a part of them (err queue, send queue info)



Mat and Peter's patches:
    - can be updated after Eric Dumazet comments:
        - it is fine to add a few bytes *as long as we don't touch them*
(not to affect cache misses)
        - "size doesn't matter"... he said (somehow)
        - Mat: could still be good to check if we need a separated queue
        - Christoph: callback + memory generator:
            - could be good in case of splitting (tcp_fragment: to point
to the same memory if it is linked to the same DSS)
            - should be ok for the incoming and outgoing path
    - TODO: write in the wiki a design based on Eric's idea (adding a
few bytes at the end of the SKB is OK)
        - Mat will start that and share the wiki page.

Next steps:
    - Peter: working on MP_JOIN stuff
    - Christoph: MPTCPv1 + bug fixes + test mptcp_net-next
    - Mat: new design + new test setup between two VMs but difficult to
track regression (for mptcp_net-next)
    - Matth: use recent kernel and try to test mptcp_net-next with our
test-suite. + update netlink code after that.
    - Ossama: more debugging on userspace code



Next meeting:
    - We propose to have it next Wednesday this time to have more people
available, the 1st of August then. Usual time 9am PDT - 16:00 UTC (9am
PDT, 6pm CEST)
    - Still open to everyone!
    - https://annuel2.framapad.org/p/mptcp_upstreaming_20180801



Feel free to comment on these points and propose new ones for the next
meeting!



Talk to you next week,
Matthieu
-- 
Matthieu Baerts | R&D Engineer
matthieu.baerts(a)tessares.net
Tessares SA | Hybrid Access Solutions
www.tessares.net
1 Avenue Jean Monnet, 1348 Louvain-la-Neuve, Belgium

-- 


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