netdev - Re: [PATCH net-next 0/6] kcm: Kernel Connection Multiplexor (KCM)

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Date:	Tue, 24 Nov 2015 09:00:41 -0800
From:	Tom Herbert <tom@...bertland.com>
To:	Florian Westphal <fw@...len.de>
Cc:	David Miller <davem@...emloft.net>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Kernel Team <kernel-team@...com>, davejwatson@...com,
	Alexei Starovoitov <alexei.starovoitov@...il.com>
Subject: Re: [PATCH net-next 0/6] kcm: Kernel Connection Multiplexor (KCM)

On Tue, Nov 24, 2015 at 8:25 AM, Florian Westphal <fw@...len.de> wrote:
> David Miller <davem@...emloft.net> wrote:
>> From: Florian Westphal <fw@...len.de>
>> Date: Tue, 24 Nov 2015 16:27:44 +0100
>>
>> > Aside from Hannes comment -- KCM seems to be tied to the TLS work, i.e.
>> > I have the impression that KCM without ability to do TLS in the kernel
>> > is pretty much useless for whatever use case Tom has in mind.
>>
>> I do not get this impression at all.
>>
>> Tom's design document in the final patch looks legitimately what the
>> core use case is.
>
> You mean
> https://patchwork.ozlabs.org/patch/547054/ ?
>
> Its a well-written document, but I don't see how moving the burden of
> locking a single logical tcp connection (to prevent threads from
> reading a partial record) from userspace to kernel is an improvement.
>
> If you really have 100 threads and must use a single tcp connection
> to multiplex some arbitrarily complex record-format in atomic fashion,
> then your requirements suck.
>
Well, this is the sort of thing that multi threaded applications do.

> Now, arguably, maybe the requirements of Toms use case are restricted
> /cannot be avoided.
>
> But that still begs the question: Why should mainline care?
>
I have no idea. I guess it's the same reason that mainline would care
about RDS, iSCSI, FCOE, RMDA, or anything in that nature. No one is
being forced to use any of this.

> Once its in, next step will be 'my single tcp connection that I use
> for multiplexing via KCM now has requirement to use TLS'.
>
> How far are you willing to take the KCM concept?

Obviously we are looking forward TLS+KCM. But it does open up a bunch
of other possibilities.
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