noel 2003/06/18 23:15:11
Modified: src/java/org/apache/james/dnsserver Tag: branch_2_1_fcs
DNSServer.java
Log:
Added randomization for MX records
Revision Changes Path
No revision
No revision
1.9.4.7 +22 -6 jakarta-james/src/java/org/apache/james/dnsserver/DNSServer.java
Index: DNSServer.java
===================================================================
RCS file:
/home/cvs/jakarta-james/src/java/org/apache/james/dnsserver/DNSServer.java,v
retrieving revision 1.9.4.6
retrieving revision 1.9.4.7
diff -u -r1.9.4.6 -r1.9.4.7
--- DNSServer.java 17 Jun 2003 21:58:23 -0000 1.9.4.6
+++ DNSServer.java 19 Jun 2003 06:15:11 -0000 1.9.4.7
@@ -355,13 +355,29 @@
return answers;
}
- private static class MXRecordComparator
- implements Comparator {
-
+ /* RFC 2821 section 5 requires that we sort the MX records by their
+ * preference, and introduce a randomization. This Comparator does
+ * comparisons as normal unless the values are equal, in which case
+ * it "tosses a coin", randomly speaking.
+ *
+ * This way MX record w/preference 0 appears before MX record
+ * w/preference 1, but a bunch of MX records with the same preference
+ * would appear in different orders each time.
+ *
+ * Reminder for maintainers: the return value on a Comparator can
+ * be counter-intuitive for those who aren't used to the old C
+ * strcmp function:
+ *
+ * < 0 ==> a < b
+ * = 0 ==> a = b
+ * > 0 ==> a > b
+ */
+ private static class MXRecordComparator implements Comparator {
+ private final static Random random = new Random();
public int compare (Object a, Object b) {
- MXRecord ma = (MXRecord)a;
- MXRecord mb = (MXRecord)b;
- return ma.getPriority () - mb.getPriority ();
+ int pa = ((MXRecord)a).getPriority();
+ int pb = ((MXRecord)b).getPriority();
+ return (pa == pb) ? (512 - random.nextInt(1024)) : pa - pb;
}
}
}
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
