[AFS3-std] Callback Extended Information Draft 4

[Jeffrey Hutzelman]

--On Wednesday, May 14, 2008 05:36:42 PM -0400 Matt Benjamin 
<matt@linuxbox.com> wrote:

> Create AFSExtendedCallbackV2, which aggregates an AFSExtendedCallbackV1,
> and then adds new members.  Create ExtendedCallbackV2 taking
> AFSExtendedCallbackV2 as argument.

Oh, you don't need to do that.  You _can_ gracefully extend the union, as 
long as you are willing to accept that calls made using a discriminator not 
known to the server you are calling will abort with RXGEN_SS_UNMARSHALL. 
This is the moral equivalent of a call to an RPC not supported by the 
server aborting with RXGEN_OPCODE, and is perfectly acceptable, given that 
you shouldn't be sending notifications with unknown types anyway.

-- Jeff