Hello Olivier,
I attempted to recreate the issue with latest Ganesha code. It works fine for me.
$ rpm -qa | grep ganesha
gpfs.pm-ganesha-10.0.0-1.el8.x86_64
nfs-ganesha-gpfs-4-dev.7.el8.x86_64
nfs-ganesha-gpfs-debuginfo-4-dev.7.el8.x86_64
nfs-ganesha-selinux-4-dev.7.el8.noarch
nfs-ganesha-utils-debuginfo-4-dev.7.el8.x86_64
nfs-ganesha-4-dev.7.el8.x86_64
nfs-ganesha-debuginfo-4-dev.7.el8.x86_64
nfs-ganesha-utils-4-dev.7.el8.x86_64
[root@ganeshanode1 2020_03_04-12:42:50 fs1]$ ganesha_stats enable client_all_ops
Successfully enabled statistics counting
[root@ganeshanode1 2020_03_04-12:43:02 fs1]$ ganesha_stats list_clients
Timestamp: Wed Mar 4 12:43:33 2020606796548 nsecs
Client List:
Address: ::ffff:127.0.0.1
NFSv3 stats available: 0
MNT stats available: 0
NLM4 stats available: 0
RQUOTA stats available: 0
NFSv4.0 stats available 0
NFSv4.1 stats available: 0
NFSv4.2 stats available: 0
9P stats available: 0
Address: ::ffff:192.168.122.1
NFSv3 stats available: 1
MNT stats available: 1
NLM4 stats available: 0
RQUOTA stats available: 0
NFSv4.0 stats available 0
NFSv4.1 stats available: 0
NFSv4.2 stats available: 0
9P stats available: 0
[root@ganeshanode1 2020_03_04-12:43:33 fs1]$ ganesha_stats client_all_ops ::ffff:192.168.122.1
Client last active at: Wed Mar 4 12:43:15 202096989749 nsecs
NFSv3 Operations
Op Name total errors dups
LOOKUP 2 0 0
ACCESS 1 0 0
CREATE 1 0 0
MKDIR 3 0 0
No NLMv4 activity
No NFSv4 activity
No NFSv4 compound ops
My client is RHEL 8. I tried with IPV6 enabled & disabled mode. It works fine.
$ cat /etc/redhat-release
Red Hat Enterprise Linux release 8.0 (Ootpa)