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It seems to me that (currently) any extension specification must be cognizant of all previous extension specifications and the SEQUENCE numbers they have set aside for their use. It would be better if we could solve this in [LDAPIANA]. I don't know how to do that other than to set up registrations for each protocol type which is extensible. That seems like an ugly task, so hopefully someone else has a better idea.
Jim
>>> Hallvard B Furuseth <h.b.furuseth@usit.uio.no> 11/7/04 4:13:45 PM >>> There are two different ways to extend BindResponse and ModifyRequest. I imagine this may lead to some sort of conflict or at least a rather messy situation, in particular in which order the fields should occur: 1) If one defines a new BindRequest.AuthenticationChoice or ModifyRequest.changes.change.operation, one may need a new matching sequence element in BindResponse or ModifyRequest.changes.change. 2) One may define trailing SEQUENCE elements; [Protocol] section 4 says implementation must ignore unrecognized trailing SEQUENCE elements. I don't know that works when there are several extra SEQUENCE elements present: Will an implementation pick up a known element following an unknown element? Can elements from different specifications be present in any order? Or must all specifications of such elements define where in the SEQUENCE the element occurs in relation to all previous specifications of other elements? If this is not a problem, ignore the rest of this message. Otherwise: One fix might be to define (not in LDAPbis) two extensions to be used with future specifications of Bind authentication choices and Modify operation types: -- appended to BindResponse BindAuthData ::= [something] CHOICE { -- currently no choices are defined } -- appended to ModifyRequest.changes.change ModifyChangeData ::= [something] CHOICE { -- currently no choices are defined } where each CHOICE tag number is reserved for the same BindRequest.AuthenticationChoice tag number and ModifyRequest.changes.change.operation value. If this is desirable, I don't know if such a draft could - or should - be rushed out quickly enough that [protocol] and [ldapiana] can add a (maybe informative) reference to it? For reference, here are the current ASN.1 definitions: BindResponse ::= [APPLICATION 1] SEQUENCE { COMPONENTS OF LDAPResult, serverSaslCreds [7] OCTET STRING OPTIONAL } ModifyRequest ::= [APPLICATION 6] SEQUENCE { object LDAPDN, changes SEQUENCE OF change SEQUENCE { operation ENUMERATED { add (0), delete (1), replace (2) }, modification PartialAttribute } } As far as I can tell there are no other protocol fields with similar troubles, but I make no promises:-) -- Hallvard |