netdev - Re: [devel-ipsec] [RFC ipsec-next 4/8] iptfs: sysctl: allow configuration of global default values

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Date: Sun, 12 Nov 2023 05:28:16 -0500
From: Christian Hopps <chopps@...n.net>
To: Michael Richardson <mcr@...delman.ca>
Cc: Christian Hopps <chopps@...pps.org>, devel@...ux-ipsec.org,
 netdev@...r.kernel.org, Christian Hopps <chopps@...n.net>
Subject: Re: [devel-ipsec] [RFC ipsec-next 4/8] iptfs: sysctl: allow
 configuration of global default values

Michael Richardson <mcr@...delman.ca> writes:

> [[PGP Signed Part:Signature made by expired key 7002AEC2CCD88043 Michael Richardson <mcr+china@...delman.ca>]]
>
>>>>>> Christian Hopps <chopps@...n.net> writes:
> Christian Hopps via Devel <devel@...ux-ipsec.org> wrote:
>     > Add sysctls for the changing the IPTFS default SA values.
>
> Add sysctls for the changing the IPTFS default SA values.
>
> +xfrm_iptfs_idelay - UNSIGNED INTEGER
> +        The default IPTFS initial output delay. The initial output delay is the
> +        amount of time prior to servicing the output queue after queueing the
> +        first packet on said queue.
>
> I'm guessing this is in miliseconds, but the documentation here does not say.

It's microseconds actually, thanks for noticing this. Drop timer is the same.

> +xfrm_iptfs_rewin - UNSIGNED INTEGER
> +        The default IPTFS reorder window size. The reorder window size dictates
> +        the maximum number of IPTFS tunnel packets in a sequence that may arrive
> +        out of order.
> +
> +        Default 3.
>
> Why three?
> Is there some experimental reason to pick three?

B/c I had no idea what the right value was (guesses but no data), and so I asked the TCP guys at IETF and that's what the TCP guys told me they used. :)

> It seems that maybe the reorder window size could have been a per-SA attribute.

All of these are per-SA values. These sysctl variables adjust the defaults assigned to an SA when the user does not specify a value.

> I read through the rest of the patches, and they seem great, but I didn't
> read with a lot of comprehension.  I found the explanatory comments and
> diagrams very well done!

Thanks, :)
Chris.