Mount protocol/showmount vs NFSv4

[Colin Percival]

Thanks for bringing this to the list, Rick.  (This started with me asking
Rick why unmounting my nfsv4 mount was sending UDP packets.)

On 11/06/16 12:51, Rick Macklem wrote:
> NFSv4 doesn't use the Mount protocol at all and does everything via the NFSv4 protocol
> serviced at port #2049.

It doesn't use the Mount protocol while the filesystem is in use, but our
umount(8) code does send UDP packets (which I understand are for the Mount
protocol) when unmounting an nfsv4 mount.

> I have never done anything about this, since most were still using NFSv3, but it seems
> that maybe something should be done now?
> - What do people think of having a new option on mountd(8) that would be used for
>    NFSv4 only servers that disables servicing of Mount RPCs.

Done in isolation, it seems that this would guarantee that unmounting an
nfsv4 filesystem will result in umount(8) hanging while it waits for
responses to the UDP packets it sends.  So I'd think that we should fix
the client side to stop sending those first?

-- 
Colin Percival
Security Officer Emeritus, FreeBSD | The power to serve
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid