I have NFSv4 working with an kerberos authentication on my Red Hat 6.1 NFS server. Everything was working properly with the nfs-utils-1.2.3-7.el6.x86_64. When I upgraded it to the nfs-utils-1.2.3-7.el6_1.1.x86_64 rpc.svcgssd stopped work correctly. I didn't change anything on workstations (Fedora 15 and Red Hat 6.1). Just this one package.

After a more detailed investigation I found that rpc.svcgssd caused the problem. When I replace this file - /usr/sbin/rpc.svcgssd with that one from the nfs-utils-1.2.3-7.el6.x86_64 everything is working fine again.

Now I can give you some details about this problem. When I starting my NFSv4 server evetything seems working correctly. But when a client try to mount an NFS volume with the kerberos authentication there apperas an error (without kerberos security everything works fine):

[root@client ~]# mount -t nfs4 -o sec=krb5 nfs.wszib.edu.pl:/ /nfs
mount.nfs4: access denied by server while mounting nfs.wszib.edu.pl:/

On the server I have in /var/log/messages:

Nov 10 20:57:41 nfs rpc.svcgssd[1786]: ERROR: GSS-API: error in gss_export_lucid_sec_context(): GSS_S_NO_CONTEXT (No context has been established) - (0x00007f26)
Nov 10 20:57:41 nfs rpc.svcgssd[1786]: ERROR: failed serializing krb5 context for kernel
Nov 10 20:57:41 nfs rpc.svcgssd[1786]: WARNING: handle_nullreq: serialize_context_for_kernel failed

When I running /usr/sbin/rpc.svcgssd in verbose mode I have:

[root@nfs sbin]# /usr/sbin/rpc.svcgssd -f -vvvv
entering poll
leaving poll
handling null request
sname = nfs/client.wszib.edu.pl.PL
DEBUG: serialize_krb5_ctx: lucid version!
ERROR: GSS-API: error in gss_export_lucid_sec_context(): GSS_S_NO_CONTEXT (No context has been established) - (0x00007f80)
ERROR: failed serializing krb5 context for kernel
WARNING: handle_nullreq: serialize_context_for_kernel failed
sending null reply
...

On the client I have:

[root@client ~]# /usr/sbin/rpc.gssd -f -vvvv
beginning poll
...
handling gssd upcall (/var/lib/nfs/rpc_pipefs/nfs/clnt50)
handle_gssd_upcall: 'mech=krb5 uid=0 enctypes=18,17,16,23,3,1,2 '
handling krb5 upcall (/var/lib/nfs/rpc_pipefs/nfs/clnt50)
process_krb5_upcall: service is '<null>'
Full hostname for 'nfs.wszib.edu.pl' is 'nfs.wszib.edu.pl'
Full hostname for 'client.wszib.edu.pl' is 'client.wszib.edu.pl'
No key table entry found for CLIENT.WSZIB.EDU.PL$@WSZIB.EDU.PL while getting keytab entry for 'CLIENT.WSZIB.EDU.PL$@WSZIB.EDU.PL'
No key table entry found for root/client.wszib.edu.pl.PL while getting keytab entry for 'root/client.wszib.edu.pl.PL'
Success getting keytab entry for 'nfs/client.wszib.edu.pl.PL'
Successfully obtained machine credentials for principal 'nfs/clientwszib.edu.pl.PL' stored in ccache 'FILE:/tmp/krb5cc_machine_WSZIB.EDU.PL'
INFO: Credentials in CC 'FILE:/tmp/krb5cc_machine_WSZIB.EDU.PL' are good until 1320994315
using FILE:/tmp/krb5cc_machine_WSZIB.EDU.PL as credentials cache for machine creds
using environment variable to select krb5 ccache FILE:/tmp/krb5cc_machine_WSZIB.EDU.PL
creating context using fsuid 0 (save_uid 0)
creating tcp client for server nfs.wszib.edu.pl
DEBUG: port already set to 2049
creating context with server nfs.edu.pl
WARNING: Failed to create krb5 context for user with uid 0 for server nfs3.dydaktyka.wszib.edu.pl
WARNING: Failed to create machine krb5 context with credentials cache FILE:/tmp/krb5cc_machine_WSZIB.EDU.PL for server nfs.wszib.edu.pl
WARNING: Machine cache is prematurely expired or corrupted trying to recreate cache for server nfs.wszib.edu.pl

When I had replaced the /usr/sbin/rpc.svcgssd with the previous one from nfs-utils-1.2.3-7.el6.x86_64 and restarted rpcsvcgssd service everything was working fine again.

I don't have any idea what is wrong with the /usr/sbin/rpc.svcgssd and how resolve this problem. The only solution for me is to come back to the previous version of nfs-utils.