Mount protocol/showmount vs NFSv4

[Rick Macklem]

Colin Percival wrote:

>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.
Yes, I should have stated this. At least for NFSv4, it would seem that it should not do
any Unmount RPC. For NFSv3 over TCP, maybe it should use TCP instead of UDP.

>> 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?
Yes, the NFSv4 client should be fixed so that it doesn't do Unmount RPCs before
mountd gets changed. (I had thought of this, but neglected to mention it in the first
post. Thanks for bringing this up.)

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