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From: Matthieu Baerts <matthieu.baerts@tessares.net>
To: Geliang Tang <geliang.tang@suse.com>, mptcp@lists.linux.dev
Subject: Re: [PATCH mptcp-next v12 08/10] mptcp: add call_me_again flag
Date: Wed, 20 Apr 2022 18:40:00 +0200	[thread overview]
Message-ID: <dd161bcd-2107-ed55-34cf-ce8d7936467b@tessares.net> (raw)
In-Reply-To: <68fa62e5d0ba5fe88f89f6be7923eb952fe3b817.1650430389.git.geliang.tang@suse.com>

Hi Geliang,

On 20/04/2022 06:57, Geliang Tang wrote:
> For supporting a "redundant" packet scheduler in the future, this patch
> adds a flag named call_me_again to indicate that get_subflow() function
> needs to be called again.

If I'm not mistaken, in mptcp.org, there are two functions that can be
modified by a packets scheduler:

  - get_subflow(): return an ssk to where an skb passed in argument will
be sent. A boolean is also passed to inform if it is a zero window test

  - next_segment(): return the next skb to be sent. A parameter called
"reinject" can be set to 3 values: from reinject queue (1), from sent
queue (0), meta-level retransmission for optimisations purposes (-1).

In short, a redundant scheduler will then make sure the same skb is
returned multiple times in next_segment(). (After the first time,
'reinject' is set to -1.)

I understand it is quite different from what we currently have here in
upstream where we don't really have a "next_segment()" that can be
modified by the different schedulers. Having this 'call_me_again'
variable should do the job and it is quite "flexible". At least more
than setting a function parameter. But I don't know if it is a proper
way and if it will fix all situations. I didn't follow the development
on all different packet schedulers in mptcp.org. Maybe we can check with
Christoph if we need to "fix an API".

Cheers,
Matt
-- 
Tessares | Belgium | Hybrid Access Solutions
www.tessares.net

  reply	other threads:[~2022-04-20 16:40 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-20  4:56 [PATCH mptcp-next v12 00/10] BPF packet scheduler Geliang Tang
2022-04-20  4:57 ` [PATCH mptcp-next v12 01/10] mptcp: add struct mptcp_sched_ops Geliang Tang
2022-04-20 16:22   ` Matthieu Baerts
2022-04-20  4:57 ` [PATCH mptcp-next v12 02/10] mptcp: register default scheduler Geliang Tang
2022-04-20  4:57 ` [PATCH mptcp-next v12 03/10] mptcp: add a new sysctl scheduler Geliang Tang
2022-04-20  4:57 ` [PATCH mptcp-next v12 04/10] mptcp: add sched in mptcp_sock Geliang Tang
2022-04-20  4:57 ` [PATCH mptcp-next v12 05/10] mptcp: add get_subflow wrapper Geliang Tang
2022-04-20  4:57 ` [PATCH mptcp-next v12 06/10] mptcp: add bpf_mptcp_sched_ops Geliang Tang
2022-04-20  4:57 ` [PATCH mptcp-next v12 07/10] mptcp: add last_snd write access Geliang Tang
2022-04-20 16:23   ` Matthieu Baerts
2022-04-20 16:44   ` Matthieu Baerts
2022-04-21  6:42   ` kernel test robot
2022-04-20  4:57 ` [PATCH mptcp-next v12 08/10] mptcp: add call_me_again flag Geliang Tang
2022-04-20 16:40   ` Matthieu Baerts [this message]
2022-04-20  4:57 ` [PATCH mptcp-next v12 09/10] selftests: bpf: add bpf_first scheduler Geliang Tang
2022-04-20  4:57 ` [PATCH mptcp-next v12 10/10] selftests: bpf: add bpf_first test Geliang Tang
2022-04-20  5:14   ` selftests: bpf: add bpf_first test: Build Failure MPTCP CI
2022-04-20  6:49   ` selftests: bpf: add bpf_first test: Tests Results MPTCP CI

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