CORBA35 — Limitation and ambiguity in the use of BidirectionalOfferPolicy of DENY

Part of this issue has been surfaced in the discussions over the mail list. I now file it as an issue.

The Bi-directional GIOP spec says, "An object reference with a BidirectionalOfferPolicy of DENY must not be invoked over a bi-directional
connection." Satisfying this policy requirement does not close some potential limitation and ambiguity when other policies or policy instances are around.

For example, at the connection initiator side, we may have two object references one of which has BidirectionalOfferPolicy of DENY and the other has BidirectionalOfferPolicy of ALLOW. If these two object references point to the same server, according to spec, we need two connections to the server: one is bi-directional and one is not. However, having a non-bi-directional connection doesn't mean much. For invocations on the object reference with the DENY policy, the server side can always callback using the other bi-directional connection.

There is an argument (by Brian Niebuhr) saying that it's not realistic to both trust and not trust the same server. However, in practice, it's not always possible to tell whether two object references point to the same server or not. Furthermore, the client may decide whether or not to trust the server of an object reference depending on reasons other than the information about the server. For example, the client may decide to use BidirectionalOfferPolicy of ALLOW or DENY according to the source of an object reference.

On the other hand, at the connection acceptor side, things become a little more interesting. For an object reference with BidirectionalAcceptPolicy of ALLOW and effective BidirectionalOfferPolicy of DENY (e.g., the default policy on that ORB), what shall be the proper behavior of the ORB? According to the BidirectionalAcceptPolicy, "the ORB may accept and use any connections that a client has offered as bi-directional." However, shall we let the BidirectionalOfferPolicy of DENY prohibits the use of such a bi-directional connection? Or shall we allow the use of such a bi-directional connection because it's in the "reverse" direction?