netdev - RE: [PATCH bpf-next 0/2] Introduce TCP_ULP option for bpf

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Message-ID: <61b258ad273a9_6bfb2084d@john.notmuch>
Date:   Thu, 09 Dec 2021 11:27:41 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     Tony Lu <tonylu@...ux.alibaba.com>, ast@...nel.org,
        daniel@...earbox.net, andrii@...nel.org
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: RE: [PATCH bpf-next 0/2] Introduce TCP_ULP option for
 bpf_{set,get}sockopt

Tony Lu wrote:
> This patch set introduces a new option TCP_ULP for bpf_{set,get}sockopt
> helper. The bpf prog can set and get TCP_ULP sock option on demand.
> 
> With this, the bpf prog can set TCP_ULP based on strategies when socket
> create or other's socket hook point. For example, the bpf prog can
> control which socket should use tls or smc (WIP) ULP modules without
> modifying the applications.
> 
> Patch 1 replaces if statement with switch to make it easy to extend.
> 
> Patch 2 introduces TCP_ULP sock option.

Can you be a bit more specific on what ULP you are going to load on
demand here and how that would work? For TLS I can't see how this will
work, please elaborate. Because the user space side (e.g. openssl) behaves
differently if running in kTLS vs uTLS modes I don't think you can
from kernel side just flip it on? I'm a bit intrigued though on what
might happen if we do did do this on an active socket, but seems it
wouldn't be normal TLS with handshake and keys at that point? I'm
not sure we need to block it from happening, but struggling to see
how its useful at the moment.

The smc case looks promising, but for that we need to get the order
correct and merge smc first and then this series.

Also this will need a selftests.

Thanks,
John