ITS#8204 Remove bias towards the first record in RFC2782 shuffle implementation.

Prior to this change, given two records of weight 1 the algorithm would
return them in the order (0,1) with 100% probability instead of the
desired 50%. This was due to an off-by-one error in the range test.

srv_rand() returns a float in the range [0.0, 1.0[, so r is an integer in the
range [0, total[. The correct probability for record 0 to be chosen is
a[0].weight/total, not (a[0].weight+1)/total.

diff --git a/libraries/libldap/dnssrv.c b/libraries/libldap/dnssrv.c
index 10f179dc2e23e5af14732512e2579f98ef29f9b4..1503c068b6b88d03303568ab718ec8fee9ba803b 100644 (file)
--- a/libraries/libldap/dnssrv.c
+++ b/libraries/libldap/dnssrv.c
@@ -234,7 +234,7 @@ static void srv_shuffle(srv_record *a, int n) {
                r = srv_rand() * total;
                for (j=0; j<p; j++) {
                        r -= a[j].weight;
-                       if (r <= 0) {
+                       if (r < 0) {
                                if (j) {
                                        srv_record t = a[0];
                                        a[0] = a[j];