problems with complex import/export attributes

Hi,

Yes, I know this is not a RPSL forum, but i think someone
of you could help me ;-)

I found a problem for RPSL parsers conform with RFC2622. In the
RFC2622 (section 6.6) is an example of an import attribute:

 > import: from AS1 action pref = 1; accept as-foo;
 >         except {
 >            from AS2 action pref = 2; accept AS226;
 >            except {
 >               from AS3 action pref = 3; accept {128.9.0.0/16};
 >            }
 >         }

Appendix B "Grammar Rules" describes the syntax like below:

 > ...
 > import_attribute: ATTR_IMPORT
 > | ATTR_IMPORT opt_protocol_from opt_protocol_into import_factor
 >
 > import_expression: import_term
 > | import_term KEYW_REFINE import_expression
 > | import_term KEYW_EXCEPT import_expression
 >
 > import_term: import_factor ';'
 > | '{' import_factor_list '}'
 >
 > import_factor_list: import_factor ';'
 > | import_factor_list import_factor ';'
 >
 > import_factor: import_peering_action_list KEYW_ACCEPT filter
 >
 > import_peering_action_list: KEYW_FROM peering opt_action
 > | import_peering_action_list KEYW_FROM peering opt_action
 >
 > ...

I feel in import_attribute lakes a line like:

 | ATTR_IMPORT opt_protocol_from opt_protocol_into import_expression

and a look into ftp://ftp.isi.edu/ra/RAToolSet/RAToolSet-4.6.3.tar.gz
file src/rpsl/rpsl/rpsl.y agree with me:

 > ...
 > import_attribute: ATTR_IMPORT
 >                   opt_protocol_from opt_protocol_into
 >                   import_expr TKN_EOA {
 >    $$ = changeCurrentAttr(new AttrImport($2, $3, $4));
 > }
 > | ATTR_IMPORT opt_protocol_from opt_protocol_into import_factor TKN_EOA {
 >    PolicyTerm *term = new PolicyTerm;
 >    term->append($4);
 >
 >    $$ = changeCurrentAttr(new AttrImport($2, $3, term));
 > }
 > | ATTR_IMPORT error TKN_EOA {
 >    $$ = $1;
 >    handle_error("Error: from <peering> expected.\n");
 >    yyerrok;
 > }
 > ;
 > ..

OK as so far, but rpslcheck as well as my perl parser module breaks
while parsing the example above ;-(

 > fb at sun5 1315> rpslcheck < example 
 > ...
 > import: from AS1 action pref = 1;
 >         accept as-foo;
 >         except {
 >           from AS2 action pref = 2; accept AS226;
 >            except {
 >            ^^^^^^
 > ***Error: from <peering> expected.
 >             from AS3 action pref = 3; accept {128.9.0.0/16};
 >           }
 >        }
 > ...

For me looks the grammar correct, but my knowledge about automata theory,
languages and computation is worser than my english ;-)

Has anybody a solution for this problem ?


cheers
frank