2nd try. . .

/etc/inc/util.inc:
- arp_get_mac_by_ip() updated to support IPv6
- attempt at code streamline

/usr/local/www/services_dhcp_edit.php:
- streamline code, now just a simple call to arp_get_mac_by_ip()

(cherry picked from commit dd83f869b79a858bd74c7a8bb4adcd49217445b0)

2 files changed, 18 insertions, 23 deletions

diff --git a/src/etc/inc/util.inc b/src/etc/inc/util.inc
index 8d8a083..418ad51 100644
--- a/src/etc/inc/util.inc
+++ b/src/etc/inc/util.inc
@@ -1848,22 +1848,25 @@ function alias_expand_urltable($name) {
 	return null;
 }
 
-/* obtain MAC address given an IP address by looking at the ARP table */
+/* obtain MAC address given an IP address by looking at the ARP/NDP table */
 function arp_get_mac_by_ip($ip) {
-	mwexec("/sbin/ping -c 1 -t 1 " . escapeshellarg($ip), true);
-	$arpoutput = "";
-	exec("/usr/sbin/arp -n " . escapeshellarg($ip), $arpoutput);
-
-	if ($arpoutput[0]) {
-		$arpi = explode(" ", $arpoutput[0]);
-		$macaddr = $arpi[3];
+	unset($arp_ndp_output);
+	switch (is_ipaddr($ip)) {
+		case 4:
+			mwexec("/sbin/ping -c 1 -t 1 " . escapeshellarg($ip), true);
+			exec("/usr/sbin/arp -n " . escapeshellarg($ip) . " | /usr/bin/awk '{print $4}'", $arp_ndp_output);
+			break;
+		case 6:
+			mwexec("/sbin/ping6 -c 1 -X 1 " . escapeshellarg($ip), true);
+			exec("/usr/sbin/ndp -n " . escapeshellarg($ip) . " | /usr/bin/tail -n+2 | /usr/bin/awk '{print $2}'", $arp_ndp_output);
+			break;
+	}
+	if ($arp_ndp_output[0]) {
+		$macaddr = $arp_ndp_output[0];
 		if (is_macaddr($macaddr)) {
 			return $macaddr;
-		} else {
-			return false;
 		}
 	}
-
 	return false;
 }
 
diff --git a/src/usr/local/www/services_dhcp_edit.php b/src/usr/local/www/services_dhcp_edit.php
index 02ac9d9..22bfbcf 100644
--- a/src/usr/local/www/services_dhcp_edit.php
+++ b/src/usr/local/www/services_dhcp_edit.php
@@ -405,18 +405,8 @@ if ($_POST) {
 // Get our MAC address
 $ip = $_SERVER['REMOTE_ADDR'];
 
-switch (is_ipaddr($ip)) {
-	case 4:
-		$mymac = exec("/usr/sbin/arp -an | grep '('{$ip}')' | head -n 1 | cut -d' ' -f4");
-		$mymac = str_replace("\n", "", $mymac);
-        break;
-    case 6:
-		$mymac = exec("/usr/sbin/ndp -na | /usr/bin/grep '{$ip}' | /usr/bin/head -n 1 | /usr/bin/awk '{ print $2 }'");
-		$mymac = str_replace("\n", "", $mymac);
-		break;
-	default:
-		unset($mymac);
-}
+unset($mymac);
+$mymac = arp_get_mac_by_ip($ip);
 
 $iflist = get_configured_interface_with_descr();
 $ifname = '';
@@ -444,6 +434,7 @@ $macaddress = new Form_Input(
 	$pconfig['mac'],
 	['placeholder' => 'xx:xx:xx:xx:xx:xx']
 );
+
 $btnmymac = new Form_Button(
 	'btnmymac',
 	'Copy My MAC',
@@ -452,6 +443,7 @@ $btnmymac = new Form_Button(
 	);
 
 $btnmymac->setAttribute('type','button')->removeClass('btn-primary')->addClass('btn-success btn-sm');
+
 $group = new Form_Group('MAC Address');
 $group->add($macaddress);
 if (!empty($mymac)) {