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

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Message-id: <170622264103.21664.16941742935452333478@noble.neil.brown.name>
Date: Fri, 26 Jan 2024 09:44:01 +1100
From: "NeilBrown" <neilb@...e.de>
To: "Chuck Lever III" <chuck.lever@...cle.com>
Cc: "Jeff Layton" <jlayton@...nel.org>,
 "Lorenzo Bianconi" <lorenzo@...nel.org>,
 "Linux NFS Mailing List" <linux-nfs@...r.kernel.org>,
 "Lorenzo Bianconi" <lorenzo.bianconi@...hat.com>,
 "Jakub Kicinski" <kuba@...nel.org>, "Simon Horman" <horms@...nel.org>,
 "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>
Subject: Re: [PATCH v6 3/3] NFSD: add write_ports to netlink command

On Thu, 25 Jan 2024, Chuck Lever III wrote:
> 
> 
> > On Jan 24, 2024, at 6:24 AM, Jeff Layton <jlayton@...nel.org> wrote:
> > 
> > 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.
> 
> Tearing down a listener that was created that way would be a
> use case for:

Only if it was actually useful.
Have you *ever* wanted to do that?  Or heard from anyone else who did?

NeilBrown


> 
> > Do we ever want/need to remove listening sockets?
> > Normal practice when making any changes is to stop and restart where
> > "stop" removes all sockets, unexports all filesystems, disables all
> > versions.
> 
> 
> 
> --
> Chuck Lever
> 
> 
>