nfsv4 client/server protocol prob err=10020

[Martin Laabs]

Hello,

I currently try to set up a nfsv4 network at home. I have a server which 
acts as KDC and kerberos server (I know the security advices to not do 
that) and also as NFSv4 server.
On the server I have the following lines in my rc.conf

#NFS stuff
rpcbind_enable="YES"
nfsv4_server_enable="YES"
nfsuserd_enable="YES"
mountd_enable="YES"
mountd_flags="-r"
gssd_enable="YES"

#kerberos
kerberos5_server_enable="YES"
kadmind5_server_enable="YES"


on the client:

nfsuserd_enable="YES"
nfscbd_enable="YES"


I also set  vfs.usermount=1 to mount the nfs as regular user that has a 
kerberos principal. Beside the user principal I also created a 
nfs/pc.martinlaabs.de principal for the client and exported it to the 
client krb5.keytab.

The exports at the server side contains:

V4: /usr/home -sec=krb5p pc.martinlaabs.de

As user on my client I run  mount_nfs -o tcp,nfsv4,sec=krb5p server:/ mnt 
which returns only a warning that mount can not update mounttab which is OK.
However - if I access the mnt directory I get the following error:

bash:~$ ls mnt
ls: mnt: Input/output error

In the system message buffer I find the following message:

nfsv4 client/server protocol prob err=10020

As far as I know error 10020 means NFS4ERR_NOFILEHANDLE. I sometimes also 
get the following message:

nfscl: consider increasing kern.ipc.maxsockbuf

But increasing does not affect the 10020 error.

On the server I can not find any log entries.
Can anyone interpret the error message and/or tell me what to do to get the 
nfs service working?

Thank you,
  Martin Laabs

PS: I use ipv6 for the nfs/kerberos stuff only.