in network tab, detect and display "Private MAC" addresses/labels

RFC7042 section 2.1 defines the “Local bit”: when the bit is set
(first octet bit 1, value 0x02), the identifier is not a globally
assigned EUI-48 address but a locally administered one. Modern mobile
operating systems, including iOS and Android, use locally-administered
(randomized) MACs as part of their anti-tracking mechanisms.

Labeling these addresses helps administrators understand which clients
are using private/randomized identifiers and avoid misinterpreting
them as hardware-assigned vendor MACs.

Signed-off-by: Robin Getz <rgetz503@gmail.com>

Author: rgetz

scripts/js/network.js

@@ -183,6 +183,12 @@ $(() => {
         $("td:eq(1)", row).html(
           utils.escapeHtml(data.hwaddr) + "<br>" + utils.escapeHtml(data.macVendor)
         );
+      } else if (data.hwaddr && data.hwaddr.includes(":")) {
+        const firstOctet = Number.parseInt(data.hwaddr.split(":")[0], 16);
+        // Check whether the 2 (0x02) bit is set using arithmetic to avoid bitwise operators:
+        if (Math.floor(firstOctet / 2) % 2 === 1) {
+          $("td:eq(1)", row).html(utils.escapeHtml(data.hwaddr) + "<br>Private MAC");
+        }
       }
 
       // Make mock MAC addresses italics and add title