Mounting FreeBSD NFSv4 share on Linux using krb5

[Julian Andrej]

Hello,

i'm desperately trying to mount a nfsv4 export from FreeBSD on a Linux
client using sec=krb5.

So my setup is as follows:
FreeBSD host which is the KDC. Linux client which can auth via
kerberos and should be able to mount the nfs share.

Mounting the share with sec=krb5 from FreeBSD on another FreeBSD box
is no problem, but it fails on the linux client. The client fails with

$ sudo mount -t nfs4 -o sec=krb5 ***:/tank/homes mnt -vv
mount.nfs4: timeout set for Mon May  2 15:39:19 2016
mount.nfs4: trying text-based options 'sec=krb5,addr=***,clientaddr=***'
mount.nfs4: mount(2): Input/output error
mount.nfs4: mount system call failed

and on the FreeBSD host i get the message

gssd_pname_to_uid: failed major=0xd0000 minor=-1765328227
gssd_release_name: done major=0x0 minor=0
gssd_release_cred: done major=0x0 minor=0

which translates to KRB5_NO_LOCALNAME. I have the appropriate
principals with nfs/* for the host and client!

I have tried heimdal from base and MIT krb5 from ports. Both show the
same behavior.

The actual kernel log from linux is:
Mai 02 15:37:19 *** kernel: NFS: nfs4_discover_server_trunking
unhandled error -121. Exiting with error EIO

Can anyone guide me to a possible solution here?

Regards
Julian