netdev - Re: [PATCH v6 3/3] NFSD: add write

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Message-ID: <8fabd83caa0d44369853a4040a89c069f9b0f935.camel@kernel.org>
Date: Wed, 24 Jan 2024 06:24:22 -0500
From: Jeff Layton <jlayton@...nel.org>
To: Lorenzo Bianconi <lorenzo@...nel.org>
Cc: Chuck Lever <chuck.lever@...cle.com>, NeilBrown <neilb@...e.de>, 
	linux-nfs@...r.kernel.org, lorenzo.bianconi@...hat.com, kuba@...nel.org, 
	horms@...nel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v6 3/3] NFSD: add write_ports to netlink command

On Wed, 2024-01-24 at 10:52 +0100, Lorenzo Bianconi wrote:
> [...]
> > 
> > That's a great question. We do need to properly support the -H option to
> > rpc.nfsd. What we do today is look up the hostname or address using
> > getaddrinfo, and then open a listening socket for that address and then
> > pass that fd down to the kernel, which I think then takes the socket and
> > sticks it on sv_permsocks.
> > 
> > All of that seems a bit klunky. Ideally, I'd say the best thing would be
> > to allow userland to pass the sockaddr we look up directly via netlink,
> > and then let the kernel open the socket. That will probably mean
> > refactoring some of the svc_xprt_create machinery to take a sockaddr,
> > but I don't think it looks too hard to do.
> 
> Do we already have a specific use case for it? I think we can even add it
> later when we have a defined use case for it on top of the current series.
> 

Yes:

rpc.nfsd -H makes nfsd listen on a particular address and port. By
passing down the sockaddr instead of an already-opened socket
descriptor, we can achieve the goal without having to open sockets in
userland.

-- 
Jeff Layton <jlayton@...nel.org>