Issue in syncprov findcsn code

[Pierangelo Masarati <ando@sys-net.it>]

Not sure this is a bug, but I'm curious... I hit this while checking for 
ITS#5661.  The code below is from HEAD's syncprov.c:613 (not changed 
recently; pardon any unintended line wrapping):

<snip>
again:
        switch( mode ) {
        case FIND_MAXCSN:
                cf.f_choice = LDAP_FILTER_GE;
                /* If there are multiple CSNs, use the one with our 
serverID */
                for ( i=0; i<si->si_numcsns; i++) {
                        if ( slap_serverID == si->si_sids[i] ) {
                                maxid = i;
                                break;
                        }
                }
</snip>

When run by a consumer, with no serverID set (and thus slap_serverID == 
0), it causes the consumer to use the contextCSN with SID == "000" 
instead of the most recent one.  As a consequence, if one searches the 
contextCSN within that consumer, slapo-syncprov's syncprov_operational() 
causes only that value to be returned, instead of all contextCSNs. After 
the consumer is restarted, all values are correctly returned.  To reproduce:

- populate a DSA (SIDs in CSNs will default to "000")

- turn it into a (multi)master by adding the serverID statement (with 
SID > "000") and so

- perform a modification (so that the most recent contextCSN will have 
SID != "000")

- create a consumer (no serverID statement, so that it defaults to 
"000") and let it pull data from the producer

- search the contextCSN of the consumer

I'm not sure this is a bug; it might be harmless, apart from being 
definitely misleading.  There might be multiple solutions:

- don't let syncprov_operational() muck with contextCSN that way

- make syncprov_findcsn() search the newest contextCSN instead of the 
one with its SID

- initialize slapd_serverID with some SID_UNDEFINED in order to take the 
action above only when SID is not defined

p.


Ing. Pierangelo Masarati
OpenLDAP Core Team

SysNet s.r.l.
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