Re: Fedora 32 rpc.gssd misbehavior

[Chuck Lever <chuck.lever@oracle.com>]

> On Jul 29, 2020, at 1:19 PM, Chuck Lever <chuck.lever@oracle.com> wrote:
> 
> Hi!
> 
> I recently updated my test systems from EL7 to Fedora 32, and
> NFSv4.0 with Kerberos has stopped working.
> 
> I mount with "klimt.ib" as before. The client workload stops
> dead when the server tries to perform its first CB_RECALL.
> 
> I added some client instrumentation:
> 
>   kernel: NFSv4: Callback principal (nfs@klimt.ib.1015granger.net) does not match acceptor (nfs@klimt.ib).
>   kernel: NFS: NFSv4 callback contains invalid cred
> 
> I boosted gssd verbosity, and it says:
> 
>   rpc.gssd[986]: doing downcall: lifetime_rec=72226 acceptor=nfs@klimt.ib
> 
> But it knows the full hostname for the server:
> 
>   rpc.gssd[986]: Full hostname for 'klimt.ib' is 'klimt.ib.1015granger.net'
> 
> 
> The acceptor appears to come from the Kerberos library. Shouldn't
> it be canonicalized? If so, should the Kerberos library do it, or
> should gssd? Since this behavior appeared after an upgrade, I
> suspect a Kerberos library regression. But it could be config-
> related, since both systems were re-imaged from the ground up.
> 
> Also noticing some other problems on the server (missing hostname
> strings in debug messages, sssd_kcm infinite loops, and gssd
> sending garbage to the client after the NULL request that
> establishes the callback context).
> 
> But let's look at the client acceptor problem first.

I believe I found the problem.

8bffe8c5ec1a ("gssd: add /etc/nfs.conf support") added a number of gssd config
options to /etc/nfs.conf, including "avoid-dns". The default setting of avoid-
dns is 1. When I set this option on my client system explicitly to 0, NFSv4.0
with Kerberos works again.

Is there a reason the default setting is 1?


--
Chuck Lever