From 41ca314cc2fafaaa9089438bdfd24880bafa9079 Mon Sep 17 00:00:00 2001
From: Mark Andrews <marka@isc.org>
Date: Thu, 22 Dec 2011 23:43:52 +0000
Subject: [PATCH] 3260.   [bug]           "rrset-order cyclic" could appears to
 not rotate                         for some query patterns.  [RT #27170]

---
 CHANGES         |  3 +++
 lib/dns/rbtdb.c | 12 +++++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/CHANGES b/CHANGES
index ab6060de47..500853a5a2 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+3260.	[bug]		"rrset-order cyclic" could appears to not rotate
+			for some query patterns.  [RT #27170]
+
 	--- 9.9.0rc1 released ---
 
 3259.	[bug]		named-compilezone: Suppress "dump zone to <file>"
diff --git a/lib/dns/rbtdb.c b/lib/dns/rbtdb.c
index d4e7316dc3..c346118c55 100644
--- a/lib/dns/rbtdb.c
+++ b/lib/dns/rbtdb.c
@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: rbtdb.c,v 1.323 2011/12/07 22:21:05 marka Exp $ */
+/* $Id: rbtdb.c,v 1.324 2011/12/22 23:43:52 marka Exp $ */
 
 /*! \file */
 
@@ -2744,6 +2744,14 @@ zone_zonecut_callback(dns_rbtnode_t *node, dns_name_t *name, void *arg) {
 	return (result);
 }
 
+static inline unsigned int
+prand(isc_uint32_t val) {
+	val ^= val >> 16;
+	val ^= val >> 8;
+	val ^= val >> 4;
+	return (val & 0xf);
+}
+
 static inline void
 bind_rdataset(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
 	      rdatasetheader_t *header, isc_stdtime_t now,
@@ -2783,6 +2791,8 @@ bind_rdataset(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
 	raw = (unsigned char *)header + sizeof(*header);
 	rdataset->private3 = raw;
 	rdataset->count = header->count++;
+	/* Add a weak pseudo random value [0..15]. */
+	header->count += prand(header->count);
 	if (rdataset->count == ISC_UINT32_MAX)
 		rdataset->count = 0;