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Date:   Fri, 28 Aug 2020 16:01:31 +0200
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     "S.V.R.Anand" <anandsvr@...c.ac.in>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: packet deadline and process scheduling

On Fri, Aug 28, 2020 at 10:51 AM S.V.R.Anand <anandsvr@...c.ac.in> wrote:
>
> There is an active Internet draft "Packet Delivery Deadline time in
> 6LoWPAN Routing Header"
> (https://datatracker.ietf.org/doc/draft-ietf-6lo-deadline-time/) which
> is presently in the RFC Editor queue and is expected to become an RFC in
> the near future. I happened to be one of the co-authors of this draft.
> The main objective of the draft is to support time sensitive industrial
> applications such as Industrial process control and automation over IP
> networks.  While the current draft caters to 6LoWPAN networks, I would
> assume that it can be extended to carry deadline information in other
> encapsulations including IPv6.
>
> Once the packet reaches the destination at the network stack in the
> kernel, it has to be passed on to the receiver application within the
> deadline carried in the packet because it is the receiver application
> running in user space is the eventual consumer of the data. My mail below is for
> ensuring passing on the packet sitting in the socket interface to the
> user receiver application process in a timely fashion with the help of
> OS scheduler. Since the incoming packet experieces variable delay, the
> remaining time left before deadline approaches too varies. There should
> be a mechanism within the kernel, where network stack needs to
> communicate with the OS scheduler by letting the scheduler know the
> deadline before user application socket recv call is expected to return.
>
> Anand
>
>
> On 20-08-28 10:14:13, Eric Dumazet wrote:
> >
> >
> > On 8/27/20 11:45 PM, S.V.R.Anand wrote:
> > > Hi,
> > >
> > > In the control loop application I am trying to build, an incoming message from
> > > the network will have a deadline before which it should be delivered to the
> > > receiver process. This essentially calls for a way of scheduling this process
> > > based on the deadline information contained in the message.
> > >
> > > If not already available, I wish to  write code for such run-time ordering of
> > > processes in the earlist deadline first fashion. The assumption, however
> > > futuristic it may be, is that deadline information is contained as part of the
> > > packet header something like an inband-OAM.
> > >
> > > Your feedback on the above will be very helpful.
> > >
> > > Hope the above objective will be of general interest to netdev as well.
> > >
> > > My apologies if this is not the appropriate mailing list for posting this kind
> > > of mails.
> > >
> > > Anand
> > >
> >
> > Is this described in some RFC ?
> >
> > If not, I guess you might have to code this in user space.

Could ingress redirect to an IFB device with FQ scheduler work for
ingress EDT? With a BPF program at ifb device egress hook to read
the header and write skb->tstamp.

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