[netconf] Re: Default statements on udp-client-server groupings

[Andy Bierman <[e-mail]>]

On Tue, Sep 10, 2024 at 9:28 AM Kent Watsen <[e-mail]> wrote:

>
> How is this any different than Call Home, which has default port
> assignments?
>
>
> Exactly, it seems that UDP-notif should have a port assignment.
>
>
> The grouping should not have a default port, but the uses-stmt for the
> udp-notif service should add one.
>
>
> The configuration data model for Call Home is in the NC/RC-client-server
> drafts.  Yes, they “refine” the default as expected.  Here’s an example:
>
>              uses tcpc:tcp-client-grouping {
>                refine "remote-port" {
>                  default "4336";
>                  description
>                    "The RESTCONF server will attempt to
>                     connect to the IANA-assigned well-known
>                     port for 'restconf-ch-tls' (4336) if no
>                     value is specified.";
>                }
>              }
>
> Note that this grouping does NOT refine the “local-port” from
> the tcp-client-grouping, since its default value is fine.
>
>
> And here is the “base” grouping:
>
>      leaf remote-port {
>        type inet:port-number;
>        default "0”;                          <--  THIS IS THE LINE BEING
> CONTESTED
>        description                                    ^— it seems 50/50
> if useful, but it doesn’t harm either, does it?
>          "The IP port number for the remote peer to establish a
>           connection with.  An invalid default value is used
>           so that importing modules may 'refine' it with the
>           appropriate default port number value.";
>      }
>      leaf local-port {
>        if-feature "local-binding-supported";
>        type inet:port-number;
>        default "0";                          <—  AND THIS LINE ALSO
>        description                                    ^— this seems like
> a *good* value for all services, e.g., universal behavior
>          "The local IP port number to bind to for when connecting
>           to the remote peer.  The port number '0', which is the
>           default value, indicates that any available local port
>           number may be used.";
>      }
>
>
>

default "0" should be removed.
Using zero as a special value to mean "not set"  is a common hack, but not
good practice in YANG.


> Kent // contributor
>
>
Andy