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Message-ID: <20230210134416.0391f272@kernel.org>
Date: Fri, 10 Feb 2023 13:44:16 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Chuck Lever III <chuck.lever@...cle.com>
Cc: Paolo Abeni <pabeni@...hat.com>,
Eric Dumazet <edumazet@...gle.com>,
"open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
"hare@...e.com" <hare@...e.com>,
David Howells <dhowells@...hat.com>,
Benjamin Coddington <bcodding@...hat.com>,
Olga Kornievskaia <kolga@...app.com>,
"jmeneghi@...hat.com" <jmeneghi@...hat.com>
Subject: Re: [PATCH v3 1/2] net/handshake: Create a NETLINK service for
handling handshake requests
On Fri, 10 Feb 2023 19:04:34 +0000 Chuck Lever III wrote:
> >> v2 of the series used generic netlink for the downcall piece.
> >> I can convert back to using generic netlink for v4 of the
> >> series.
> >
> > Would you be able to write the spec for it? I'm happy to help with that
> > as I mentioned.
>
> I'm coming from an RPC background, we usually do start from an
> XDR protocol specification. So, I'm used to that, and it might
> give us some new ideas about protocol correctness or
> simplification.
Nice, our thing is completely homegrown and unprofessional.
Hopefully it won't make you run away.
> Point me to a sample spec or maybe a language reference and we
> can discuss it further.
There are only two specs so far in net-next:
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/tree/Documentation/netlink/specs
Neither of these is great (fou is a bit legacy, and ethtool is not
fully expressed), a better example may be this one which is pending
in the bpf-next tree:
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/Documentation/netlink/specs/netdev.yaml
There is a JSON schema spec (which may be useful for checking available
fields quickly):
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/tree/Documentation/netlink/genetlink.yaml
And (uncharacteristically?), docs:
https://docs.kernel.org/next/userspace-api/netlink/index.html
> > Perhaps you have the user space already hand-written
> > here but in case the mechanism/family gets reused it'd be sad if people
> > had to hand write bindings for other programming languages.
>
> Yes, the user space implementation is currently hand-written C,
> but it can easily be converted to machine-generated if you have
> a favorite tool to do that.
I started hacking on a code generator for C in net-next in
tools/net/ynl/ynl-gen-c.py but it's likely bitrotted already.
I don't actually have a strong user in C to justify the time
investment. All the cool kids these days want to use Rust or Go
(and the less cool C++). For development I use Python
(tools/net/ynl/cli.py tools/net/ynl/lib/).
It should work fairly well for generating the kernel bits
(uAPI header, policy and op tables).
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