Re: timeout in LDAP access

[Denis Excoffier <cygwin@Denis-Excoffier.org>]

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On 2014-07-09 12:12 Corinna Vinschen wrote:
>> 
>> I have encountered this case in real life. The domain admins have set
>> the trustPosixOffset of the secondary domain to zero. This value is therefore
>> never recorded and the cldap->open occurs again and again.
> 
> Ouch.  Why on earth are admins doing this?  There's no way to
> workaround this reliably.
> 
Reliably i don’t know. I’ve modified uinfo.cc in order that the special value
for td->PosixOffset is no longer 0. Taking into account that LDAP_SERVER_DOWN
is now recognized, my ‘getent passwd’ executes gracefully in 40 minutes
(instead of 60) and ‘getent group’ in 25 minutes (instead of 90). Also quicker
is ‘mkpasswd -d secondary_domain’ of course. Patch attached.

Regards,

Denis Excoffier.


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diff -uNr cygwin-snapshot-20140709-1-o/winsup/cygwin/uinfo.cc cygwin-snapshot-20140709-1-p/winsup/cygwin/uinfo.cc
--- cygwin-snapshot-20140709-1-o/winsup/cygwin/uinfo.cc	2014-07-09 14:10:50.000000000 +0200
+++ cygwin-snapshot-20140709-1-p/winsup/cygwin/uinfo.cc	2014-07-11 13:16:07.671916100 +0200
@@ -35,6 +35,8 @@
 #include "ldap.h"
 #include "cygserver_pwdgrp.h"
 
+#define CYG_LDAP_IMPROBABLE_POSIXOFFSET	1111111111	/* 0 would be too probable */
+
 /* Initialize the part of cygheap_user that does not depend on files.
    The information is used in shared.cc for the user shared.
    Final initialization occurs in uinfo_init */
@@ -853,8 +855,9 @@
 	      tdom[idx].DomainSid = cmalloc_abort(HEAP_BUF, len);
 	      RtlCopySid (len, tdom[idx].DomainSid, td[idx].DomainSid);
 	    }
-	  /* ...and set PosixOffset to 0.  This */
-	  tdom[idx].PosixOffset = 0;
+	  /* ...and set PosixOffset to CYG_LDAP_IMPROBABLE_POSIXOFFSET to mean
+	     that the offset is still to be fetched */
+	  tdom[idx].PosixOffset = CYG_LDAP_IMPROBABLE_POSIXOFFSET;
 	}
       NetApiBufferFree (td);
       tdom_count = tdom_cnt;
@@ -1139,7 +1142,7 @@
 {
   uint32_t id_val;
 
-  if (!td->PosixOffset && !(td->Flags & DS_DOMAIN_PRIMARY) && td->DomainSid)
+  if (td->PosixOffset == CYG_LDAP_IMPROBABLE_POSIXOFFSET && !(td->Flags & DS_DOMAIN_PRIMARY) && td->DomainSid)
     {
       if (cldap->open (NULL) != NO_ERROR)
 	{
@@ -1151,13 +1154,14 @@
 	}
       else
 	id_val = cldap->fetch_posix_offset_for_domain (td->DnsDomainName);
-      if (id_val)
+      if (id_val != CYG_LDAP_IMPROBABLE_POSIXOFFSET)
 	{
 	  td->PosixOffset = id_val;
 	  if (id_val < cygheap->dom.lowest_tdo_posix_offset)
 	    cygheap->dom.lowest_tdo_posix_offset = id_val;
 
 	}
+      debug_printf ("computing PosixOffset for domain %W, found %u", td->DnsDomainName, td->PosixOffset);
     }
   return td->PosixOffset;
 }


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