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

[Maximiliano Sandoval <m.sandoval@proxmox.com>]

Fiona Ebner <f.ebner@proxmox.com> writes:

> 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.

Running into timeouts is a very common issue in Enterprise support, I do
have a strong preference for keeping it as explicit as possible.

>> +        # - 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.

OK!

>>          $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;
>>      }

-- 
Maximiliano