[master] default -U to ncpus, not to -n

3471.	[bug]		The number of UDP dispatches now defaults to
			the number of CPUs even if -n has been set to
			a higher value. [RT #30964]

CHANGES

@@ -1,3 +1,7 @@
+3471.	[bug]		The number of UDP dispatches now defaults to
+			the number of CPUs even if -n has been set to
+			a higher value. [RT #30964]
+
 3470.	[bug]		Slave zones could fail to dump when successfully
 			refreshing after an initial failure. [RT #31276]
 

bin/named/main.c

@@ -609,7 +609,9 @@ create_managers(void) {
 #ifdef WIN32
 	ns_g_udpdisp = 1;
 #else
-	if (ns_g_udpdisp == 0 || ns_g_udpdisp > ns_g_cpus)
+	if (ns_g_udpdisp == 0)
+		ns_g_udpdisp = ns_g_cpus_detected;
+	if (ns_g_udpdisp > ns_g_cpus)
 		ns_g_udpdisp = ns_g_cpus;
 #endif
 	isc_log_write(ns_g_lctx, NS_LOGCATEGORY_GENERAL, NS_LOGMODULE_SERVER,

bin/named/named.docbook

@@ -290,9 +290,10 @@
             Use <replaceable class="parameter">#listeners</replaceable>
             worker threads to listen for incoming UDP packets on each
             address.  If not specified, <command>named</command> will
-            use all of the worker threads for this purpose; the
-            <option>-U</option> option allows the number to be
-            decreased but not increased.
+            use the number of detected CPUs.  If <option>-n</option>
+            has been set to a higher value than the number of CPUs,
+            then <option>-U</option> may be increased as high as that
+            value, but no higher.
           </para>
         </listitem>
       </varlistentry>