Re: [PATCH storage v4 2/2] nfs: use rpcinfo as a showmount fallback for nfs3

[Fiona Ebner <f.ebner@proxmox.com>]

Am 06.07.26 um 4:37 PM schrieb Maximiliano Sandoval:
> The check_connection call must succeed in order for the NFS storage to
> be activated. In a setup in which the NFS server does not list exports
> and which only supports NFSv3 this would result in the storage not being
> usable (not without manually mounting the NFS share and using a
> Directory storage instead). We add a fallback check with rpcinfo for
> this case.
> 
> The rpcinfo check was replaced with showmount in f8b0d82f. At the time
> the rationale was that rpcinfo did not have support for ipv6
> connections, which does not hold anymore.
> 
> In order to not break compatibility with setups that already activate
> correctly, we add a rpcinfo check as a fallback for NFSv3-only setups
> only after the showmount command fails.
> 
> Signed-off-by: Maximiliano Sandoval <m.sandoval@proxmox.com>
> ---
>  src/PVE/Storage/NFSPlugin.pm | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/src/PVE/Storage/NFSPlugin.pm b/src/PVE/Storage/NFSPlugin.pm
> index 56dbd9ec..4fe7695a 100644
> --- a/src/PVE/Storage/NFSPlugin.pm
> +++ b/src/PVE/Storage/NFSPlugin.pm
> @@ -198,6 +198,11 @@ sub check_connection {
>          # no exports are listed
>          $cmd = $nfs_get_rpcinfo_command->($server, '4');
>      } else {
> +        # FIXME: PVE 10: Consider switching to rpcinfo altogether.
> +        # There are some potential pitfalls:
> +        # - Some NFSv3 servers might only support UDP (cf. RFC 1813, Section 2.3)
> +        # - The two timeouts add up to a potential worst-case scenario of 20 seconds

This is not a pitfall for to the switch to rpcinfo, but related to your
current implementation with showmount+rpcinfo. It's rather easy to spot,
so not sure it needs a comment in the code. I'd rather have it in the
commit message.

> +        # - Some NFSv4-only servers might not have rpcbind as described at commit acff8954

This is already addressed by the current implementation. If you want to
add such a comment, it should rather be in the fallback branch for v4.

>          $cmd = ['/sbin/showmount', '--no-headers', '--exports', $server];
>      }
>  
> @@ -214,6 +219,12 @@ sub check_connection {
>              return 0 if $port == 0;
>  
>              return PVE::Network::tcp_ping($server, $port, 2);
> +        } else {
> +            $cmd = $nfs_get_rpcinfo_command->($server, '3');
> +            eval {
> +                run_command($cmd, timeout => 10, outfunc => sub { }, errfunc => sub { });
> +            };
> +            return 1 if !$@;
>          }
>          return 0;
>      }