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From: Martin Wege <martin.l.wege@gmail.com>
Date: Tue, 21 May 2024 10:32:00 +0200
Message-ID: <CANH4o6NtVdF1p1fkW-uiCkm7RAcwGzhSxt5sFkz45LqbJhZd0Q@mail.gmail.com>
Subject: Re: NFSv4 referrals - custom (non-2049) port numbers in fs_locations?
To: Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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Good morning!

What is the status here?

Thanks,
Martin

On Mon, Feb 5, 2024 at 8:53=E2=80=AFPM Chuck Lever III <chuck.lever@oracle.=
com> wrote:
>
>
>
> > On Feb 5, 2024, at 11:17=E2=80=AFAM, Trond Myklebust <trondmy@hammerspa=
ce.com> wrote:
> >
> > On Mon, 2024-02-05 at 15:13 +0000, Chuck Lever III wrote:
> >>
> >>
> >> A DNS label is just a hostname (fully-qualified or not). It
> >> never includes a port number.
> >>
> >> According to RFC 8881, fs_location4's server field can contain:
> >>
> >>  - A DNS label (no port number; 2049 is assumed)
> >>
> >>  - An IP presentation address (no port number; 2049 is assumed)
> >>
> >>  - a universal address
> >>
> >> A universal address is an IP address plus a port number. Therefore
> >> a universal address is the only way an alternate port can be
> >> communicated in an NFSv4 referral.
> >
> > That's not strictly true. RFC8881 has little to say about how you are
> > to go about using the DNS hostname provided by fs_locations4. There is
> > just some non-normative and vague language about using DNS to look up
> > the addresses.
> >
> > The use of DNS service records do allow you to look up the full IP
> > address and port number (i.e. the equivalent of a universal address)
> > given a fully qualified hostname and a service. While we do not use the
> > hostname that way in the Linux NFS client today, I see nothing in the
> > spec that would appear to disallow it at some future time.
>
> We absolutely could do that. But first a service name would need to be
> reserved, yes?
>
> https://www.iana.org/assignments/service-names-port-numbers/service-names=
-port-numbers.xhtml?search=3Ddns
>
>
> --
> Chuck Lever
>
>