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

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Date: Wed, 24 Jan 2024 13:55:14 +0000
From: Chuck Lever III <chuck.lever@...cle.com>
To: Jeff Layton <jlayton@...nel.org>, Lorenzo Bianconi <lorenzo@...nel.org>,
        Neil Brown <neilb@...e.de>
CC: 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 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:

> 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