interfaces: adhere to DAD during VIP recreation in rc.newwanipv6

PR: https://forum.opnsense.org/index.php?topic=44743.msg225133#msg225133

src/etc/inc/interfaces.inc

@@ -1398,18 +1398,22 @@ function interfaces_vips_configure($interface, $family = null)
 
     $proxyarp = false;
     $pfsync = false;
+    $dad = false;
 
     foreach ($config['virtualip']['vip'] as $vip) {
         if ($vip['interface'] != $interface) {
             continue;
         }
 
-        if ($family === 4 && strpos($vip['subnet'], ':') !== false) {
-            continue;
-        } elseif ($family === 6 && strpos($vip['subnet'], ':') === false) {
+        $inet6 = strpos($vip['subnet'], ':') !== false;
+
+        if (($family === 4 && $inet6) || ($family === 6 && !$inet6)) {
             continue;
         }
 
+        /* XXX trigger DAD only through rc.newwanipv6 explicit call for now */
+        $dad = $dad || ($inet6 && $family === 6);
+
         switch ($vip['mode']) {
             case 'proxyarp':
                 $proxyarp = true;
@@ -1431,6 +1435,10 @@ function interfaces_vips_configure($interface, $family = null)
     if ($proxyarp) {
         interface_proxyarp_configure();
     }
+
+    if ($dad) {
+        waitfordad();
+    }
 }
 
 function interface_ipalias_configure($vip)

src/etc/inc/util.inc

@@ -93,6 +93,14 @@ function waitforpid($pidfile, $timeout = -1)
     return trim(file_get_contents($pidfile));
 }
 
+function waitfordad($grace_period = 1)
+{
+    $dad_delay = (int)get_single_sysctl('net.inet6.ip6.dad_count');
+    if ($dad_delay) {
+        sleep($dad_delay + $grace_period);
+    }
+}
+
 function is_process_running($process)
 {
     exec('/bin/pgrep -anx ' . escapeshellarg($process), $output, $retval);

src/etc/rc.newwanipv6

@@ -68,11 +68,7 @@ if (!$fp || !flock($fp, LOCK_EX | LOCK_NB)) {
 }
 
 /* wait for DAD to complete to avoid discarding tentative address */
-$dad_delay = (int)get_single_sysctl('net.inet6.ip6.dad_count');
-if ($dad_delay) {
-    /* XXX this is also required but missed for IPv6 VIPs created later in the script */
-    sleep($dad_delay + 2);
-}
+waitfordad(2);
 
 /* this may be required to cleanse the DNS information no longer available */
 system_resolver_configure();