I happened to get to talk to Wes about this, and his answer was basically that these things were not meant to be mixed in this way. I have since changed my code to use netsnmp_register_scalar when I want to shadow a scalar, and that works fine.
Bill On Wed, Nov 9, 2022 at 8:36 AM Bill Fenner <fen...@gmail.com> wrote: > Hi, > > I have a MIB module that uses netsnmp_register_scalar() which realloc's > the given root oid to have one more space in it, so that > the netsnmp_scalar_helper_handler can use that space to store the ".0" > instance during the handling of a request. > > This all works fine, until we register an instance for the same object via > netsnmp_register_instance() - or, really, until that instance gets > unregistered, via unregister_mib_context(). At this point, we go back to > calling the scalar handler for that object, but, due to the duplicate > registration, that scalar handler's registration has been duplicated via > netsnmp_subtree_split. Understandably, when netsnmp_subtree_split > duplicates an OID, it doesn't add the magic extra space that the scalar > helper needs, so after this registration and unregistration, the scalar > helper starts stomping on memory it doesn't own. > > Is anyone familiar enough with this code to be able to suggest a way > forward? If the scalar helper wants an extra oid's worth of memory in the > rootoid pointer, it's almost like netsnmp_subtree_split needs to know that > (e.g., a helper can provide its own implementation of snmp_duplicate_objid)? > > Thanks, > Bill > >
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