Hi,
this is my suggestion to solve https://fedorahosted.org/sssd/ticket/2948 "Handle overriden name of members in the memberUid attribute".
The first two patches are for the IPA provider and make sure that all ghost members in a group get resolved because otherwise we cannot determine if the name is overridden or not. This adds an overhead to group lookups, especially for larger groups but I think it is an requirement which cannot be skipped.
The third patch adds a sysdb call to recursively resolve all user-members of a group. Since the groups in SSSD's cache are hierarchically organized the member attribute only contains direct user and group members. To get all users the group members must be resolved recursively.
Finally the forth patch applies the code-path which is already used for non-default views to the default case as well and adds a new list of members, with correctly overridden names (hopefully :-) which is then used in fill_grmem(). This adds some overhead to the overall group processing in the NSS responder (as can be seen in the test changes because the members are returned in different order in some cases). But I think because the of memory cache this is acceptable and might even help to remove the memberuid attribute in future and make the memberof plugin simpler.
I worked on an alternative approach as well which tried to make the memberof plugin aware of the defaultOverrideName attribute. My wip tree is at https://fedorapeople.org/cgit/sbose/public_git/sssd.git/log/?h=memberof_defa... but so far it does not work properly. Additionally I would prefer to not touch the memberof plugin.
bye, Sumit