interfaces.inc, fix mtu setup for vlans, for https://github.com/opnsense/core/issues/1709

src/etc/inc/interfaces.inc

@@ -2517,37 +2517,6 @@ function interface_virtual_create($interface)
     }
 }
 
-function interface_vlan_adapt_mtu($vlanifs, $mtu)
-{
-    global $config;
-
-    if (!is_array($vlanifs)) {
-        return;
-    }
-
-    /* All vlans need to use the same mtu value as their parent. */
-    foreach ($vlanifs as $vlan) {
-        $assignedport = convert_real_interface_to_friendly_interface_name($vlan['vlanif']);
-        if (!empty($assignedport)) {
-            if (!empty($config['interfaces'][$assignedport]['mtu'])) {
-                /*
-                 * XXX: This is really never going to happen just keep the code for safety and readbility.
-                 * It never happens since interface_vlan_mtu_configured finds the biggest mtu on vlans.
-                 * Also if it has a lower mtu configured just respect user choice.
-                 */
-                if (intval($config['interfaces'][$assignedport]['mtu']) > $mtu) {
-                    legacy_interface_mtu($vlan['vlanif'], $mtu);
-                }
-            } else {
-                if (legacy_interface_stats($vlan['vlanif'])['mtu'] != $mtu) {
-                    legacy_interface_mtu($vlan['vlanif'], $mtu);
-                }
-            }
-        } elseif (legacy_interface_stats($vlan['vlanif'])['mtu'] != $mtu) {
-            legacy_interface_mtu($vlan['vlanif'], $mtu);
-        }
-    }
-}
 
 function interface_configure($interface = 'wan', $reloadall = false, $linkupevent = false, $verbose = false)
 {
@@ -2701,34 +2670,27 @@ function interface_configure($interface = 'wan', $reloadall = false, $linkupeven
                 break;
         }
     }
+    $intf_stats = legacy_interface_stats();
     if (!empty($wancfg['mtu'])) {
         if (stristr($realif, "_vlan")) {
-            $assignedparent = convert_real_interface_to_friendly_interface_name($realhwif);
-            if (!empty($assignedparent) && !empty($config['interfaces'][$assignedparent]['mtu'])) {
-                $parentmtu = $config['interfaces'][$assignedparent]['mtu'];
-            } else {
-                $parentmtu = interface_vlan_mtu_configured($realhwif, $wancfg['mtu']);
+            // max mtu to parent
+            $mtu = $wancfg['mtu'] < $intf_stats[$realhwif]['mtu'] ? $wancfg['mtu'] : $intf_stats[$realhwif]['mtu'];
+            if ($mtu != $intf_stats[$realif]['mtu']) {
+                legacy_interface_mtu($realif, $mtu);
             }
+        } elseif ($wancfg['mtu'] != $intf_stats['mtu']) {
+            legacy_interface_mtu($realhwif, $wancfg['mtu']);
+        }
+    }
 
-            if ($wancfg['mtu'] > $parentmtu) {
-                if (legacy_interface_stats($realhwif)['mtu'] != $wancfg['mtu']) {
-                    legacy_interface_mtu($realhwif, $wancfg['mtu']);
-                }
-
-                /* All vlans need to use the same mtu value as their parent. */
-                interface_vlan_adapt_mtu(link_interface_to_vlans($realhwif), $wancfg['mtu']);
-            } else {
-                legacy_interface_mtu($realif, $wancfg['mtu']);
-            }
-        } else {
-            if ($wancfg['mtu'] != legacy_interface_stats($realhwif)['mtu']) {
-                legacy_interface_mtu($realhwif, $wancfg['mtu']);
+    // in case this interface has vlan's configured, make sure none of them has an mtu set higher than it's parent
+    if (!empty($config['vlans']['vlan'])) {
+        $intf_stats = legacy_interface_stats();
+        foreach ($config['vlans']['vlan'] as $vlan) {
+            if ($realhwif == $vlan['if'] && $intf_stats[$realhwif]['mtu'] < $intf_stats[$vlan['vlanif']]['mtu']) {
+                legacy_interface_mtu($vlan['vlanif'], $intf_stats[$realhwif]['mtu']);
             }
-
-            /* This case is needed when the parent of vlans is being configured */
-            interface_vlan_adapt_mtu(link_interface_to_vlans($realif), $wancfg['mtu']);
         }
-        /* XXX: What about gre/gif/lagg/.. ? */
     }
 
     if (does_interface_exist($wancfg['if'])) {