Documentation in Example does not match newer opendkim.

[seriv]

From man opendkim.conf for opendkim-2.11.0-0.36.el9.x86_64:

       Socket (string)
              Specifies  the  socket  that  should  be established by the filter to receive connections from
              sendmail(8) in order to provide service.  socketspec is in one of two forms: local:path, which
              creates  a  UNIX domain socket at the specified path, or inet:port[@host] or inet6:port[@host]
              which creates a TCP socket on the specified port and in the specified protocol family.  If the
              host  is  not given as either a hostname or an IP address, the socket will be listening on all
              interfaces.  A literal IP address must be enclosed in square brackets.  This option is  manda‐
              tory either in the configuration file or on the command line.

while basic example has:

  class { '::opendkim':
    socket        => 'inet:8891@127.0.0.1',

It should be changed to socket => 'inet:8891@[127.0.0.1]'.

Following the basic example resulted in working opendkim, but with often lines in the logs:

... opendkim[811]: OpenDKIM Filter: accept() returned invalid socket (Numerical result out of range), try again