Added method LDAPObject.supported_ldap_version()

[Michael <mi...@st...>]

HI!

I've committed a method LDAPObject.supported_ldap_version() to
Lib/ldap/ldapobject.py in CVS.

See the code snippet below. Please comment whether you find it
useful or annoying. Personally I'm using this code in web2ldap for
quite some while now and it seems to work with LDAP servers from
several vendors.

Hmm, I also thought about placing something like this in
LDAPObject.bind() to avoid an extra BindRequest. But this might be
too much hidden magic.

Ciao, Michael.

--------------------------------------------------------------------------
  def supported_ldap_version(self):
    """
    supported_ldap_version() -> int
    Tries to negotiate the highest supported protocol version.
    First this method binds anonymously with LDAPv3. If
    that fails with info field 'version not supported' the
    connection is completely dropped and re-openend like described
    in RFC2251.

    Mainly this is useful when connecting to a LDAP server without
    prior knowledge. If you know the highest protocol version
    supported by your server you won't need this method.
    Caveat is that it sends an extra BindRequest to the server and
    it does not work if the server does not allow anonymous bind
    or mandates SASL bind.
    
    The result of this method is an integer containing
    the negotiated protocol version.
    """
    # Try to set protocol version
    self.set_option(ldap.OPT_PROTOCOL_VERSION,ldap.VERSION3)
    # first try LDAPv3 bind
    try:
      # Try to bind to provoke error reponse at this very time
      # if protocol version is not supported
      self.bind_s('','',ldap.AUTH_SIMPLE)
    except ldap.PROTOCOL_ERROR,e:
      # Make sure that error just happened because of wrong
      # protocol version
      if hasattr(e,'args') and \
         type(e.args)==type(()) and \
         type(e.args[0])==type({}) and \
         e.args[0].get('info','').lower()=='version not supported':
        # Drop connection completely
        self.unbind_s() ; del self._l
        # Reconnect to host
        self._l = self._ldap_call(_ldap.initialize,self._uri)
        # Switch to new connection to LDAPv2
        self.set_option(ldap.OPT_PROTOCOL_VERSION,ldap.VERSION2)
      else:
        # Raise any other error exception
        raise e
      # Set currently determined protocol version
      protocol_version = ldap.VERSION2
    else:
      protocol_version = ldap.VERSION3
    return protocol_version