> On Feb 5, 2024, at 11:17 AM, Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> 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=dns -- Chuck Lever
