function port_permitted($port_id, $device_id = null)
{
    global $permissions;
    if (!is_numeric($device_id)) {
        $device_id = get_device_id_by_port_id($port_id);
    }
    if ($_SESSION['userlevel'] >= '5') {
        $allowed = true;
    } else {
        if (device_permitted($device_id)) {
            $allowed = true;
        } else {
            if ($permissions['port'][$port_id]) {
                $allowed = true;
            } else {
                $allowed = false;
            }
        }
    }
    return $allowed;
}

function port_permitted($port_id, $device_id = NULL)
{
    global $permissions;
    if (!is_numeric($device_id)) {
        $device_id = get_device_id_by_port_id($port_id);
    }
    if ($_SESSION['userlevel'] >= "5") {
        $allowed = TRUE;
    } elseif (device_permitted($device_id)) {
        $allowed = TRUE;
    } elseif ($permissions['port'][$port_id]) {
        $allowed = TRUE;
    } else {
        $allowed = FALSE;
    }
    return $allowed;
}

<?php

if ($vars['tab'] == 'port' && is_numeric($vars['device']) && port_permitted($vars['port'])) {
    $check_device = get_device_id_by_port_id($vars['port']);
    $permit_ports = 1;
}
if (!is_numeric($vars['device'])) {
    $vars['device'] = device_by_name($vars['device']);
}
if (device_permitted($vars['device']) || $check_device == $vars['device']) {
    $selected['iface'] = 'selected';
    $tab = str_replace('.', '', mres($vars['tab']));
    if (!$tab) {
        $tab = 'overview';
    }
    $select[$tab] = 'active';
    $device = device_by_id_cache($vars['device']);
    $attribs = get_dev_attribs($device['device_id']);
    $entity_state = get_dev_entity_state($device['device_id']);
    // print_r($entity_state);
    $pagetitle[] = $device['hostname'];
    if ($config['os'][$device['os']]['group']) {
        $device['os_group'] = $config['os'][$device['os']]['group'];
    }
    echo '<div class="panel panel-default">';
    echo '<table class="device-header-table" style="margin: 0px 7px 7px 7px;" cellspacing="0" class="devicetable" width="99%">';
    require 'includes/device-header.inc.php';
    echo '</table>';
    echo '</div>';
    if (device_permitted($device['device_id'])) {
        echo '<ul class="nav nav-tabs">';

    print_error('<h4>No device specified</h4>
                   A valid device was not specified in the URL. Please retype and try again.');
    return;
}
// Allow people to see this page if they have permission to see one of the ports, but don't show them tabs.
$permit_tabs = array();
if ($vars['tab'] == "port" && is_numeric($vars['device']) && (isset($vars['port']) || isset($vars['ifdescr']))) {
    // If we've been given a 'ifdescr' variable, try to work out the port_id from this
    if (!is_numeric($vars['port']) && !empty($vars['ifdescr'])) {
        $ifdescr = base64_decode($vars['ifdescr']);
        if (!$ifdescr) {
            $ifdescr = $vars['ifdescr'];
        }
        $vars['port'] = get_port_id_by_ifDescr($vars['device'], $ifdescr);
    }
    if (port_permitted($vars['port']) && $vars['device'] == get_device_id_by_port_id($vars['port'])) {
        $permit_tabs['ports'] = TRUE;
    }
}
if ($vars['tab'] == "health" && is_numeric($vars['id']) && isset($vars['id'])) {
    if (is_entity_permitted($vars['id'], 'sensor')) {
        $permit_tabs['health'] = TRUE;
    }
}
// print_vars($permit_tabs);
// If there is no valid device specified in the URL, generate an error.
if (!isset($cache['devices']['id'][$vars['device']]) && !count($permit_tabs)) {
    print_error('<h4>No valid device specified</h4>
                  A valid device was not specified in the URL. Please retype and try again.');
    return;
}