netdev - Re: [RFC 0/2] Delayed binding of UDP sockets for Quic per-connection sockets

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Message-ID: <fb15e4df-83c6-2c32-c3c3-392d2e66a378@gmail.com>
Date:   Sun, 4 Nov 2018 10:58:43 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Jana Iyengar <jri.ietf@...il.com>, Ian Swett <ianswett@...gle.com>
Cc:     Christoph Paasch <cpaasch@...le.com>,
        willemdebruijn.kernel@...il.com, netdev@...r.kernel.org,
        lhedstrom@...le.com
Subject: Re: [RFC 0/2] Delayed binding of UDP sockets for Quic per-connection
 sockets

On 11/04/2018 02:45 AM, Jana Iyengar wrote:
> I think SO_TXTIME solves the most egregious problem I have with using sched_fq for QUIC. That's a great help, so thank you!
> 
> That said, as Ian says, SO_TXTIME does not allow for the flow isolation properties of sched_fq, which would be a nice secondary benefit. I suspect that can also be done in a similar manner to SO_TXTIME -- by attaching an opaque label to each sendmsg which is used by sched_fq to determine the flow. Is that feasible?

The plan is to have flow isolation, without having to change applications to provide a flow identifier,
since we can not trust user applications anyway.

FQ will perform a proper flow dissection for packets sent over unconnected UDP sockets.

FQ has two parts [1], one being used by locally generated packets (local TCP stack),
one being used in forwarding workloads.

The patch which I will send shortly (when net-next reopens)
will only make sure FQ does not use skb->sk as a flow identifier
if the socket is not a connected one.

[1] See commit 06eb395fa9856b5a87cf7d80baee2a0ed3cdb9d7 for some details.