On Mon, 2018-09-24 at 11:38 +0200, Jakub Hrozek wrote:
> > On 21 Sep 2018, at 20:36, [email protected] wrote:
> > 
> > For our case, say we have a set of groups abcd..1, abcd..2 etc, all
> > with the same GID. I would expect the first lookup (e.g. abcd..1)
> > to put an entry in the cache. If there is then a lookup by GID,
> > (getent group <GID>) it would return this entry. However a lookup
> > by name (e.g. abcd..2) would have to query LDAP, right? Then what
> > happens, does this new data overwrite the old GID entry in the
> > cache? Or is there some bug whereby sometimes a duplicate entry
> > gets made? Why is there a check for duplicates when a GID is looked
> > up as opposed to when an entry is placed in the cache?
> 
> I’m not so sure it would be a good idea to support this, honestly.
> What do you suggest would then be returned for lookups by GID
> (getgrgid 1234) if there are multiple entries with GID=1234 in the
> cache? Just let the first match win? I know this is what nss_ldap
> does, whatever is returned from LDAP is then passed on to NSS, but
> I’m mostly concerned about consistency, suppose a first machine does
> getent group abcd..1, another one does geten group abcd..2. Then you
> get a different result on each machine for by-GID request..

For groups I would expect us to merge memberships in rfc2307 mode, and
keeping the alphabetically "smaller" name as the group name for
predictability.
For RFC 2307bis it may be a little harder because of nested membership
stuff, that needs a little bit more thinking.
Maybe allow it only for RFC2307 trees ?

> LDAP also doesn’t guarantee any ordering of results AFAIK (even
> though in practice I’ve seen the replies are quite consistent), so
> it’s even not guaranteed to always receive the same answer for the
> by-GID LDAP search..
> 
> btw it’s a good question to ask why isn’t the check done on saving
> the group. I thought it was and I see code that checks for ID
> uniqueness and even a test..

In current code, saving would override data as if the group was renamed
changed I think ?

Simo.

-- 
Simo Sorce
Sr. Principal Software Engineer
Red Hat, Inc
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