Improve MAC address detection and fix incorrect hostname on non-managed devices

Author: Gold856

photon-core/src/main/java/org/photonvision/common/dataflow/networktables/NetworkTablesManager.java

@@ -253,14 +253,22 @@ private void checkHostnameAndCameraNames() {
         String mac = NetworkUtils.getMacAddress();
         if (!mac.equals(currentMacAddress)) {
             logger.debug("MAC address changed! New MAC address is " + mac + ", was " + currentMacAddress);
+            kCoprocTable.getSubTable(currentMacAddress).getEntry("hostname").unpublish();
+            kCoprocTable.getSubTable(currentMacAddress).getEntry("cameraNames").unpublish();
             currentMacAddress = mac;
         }
-        if (mac.isEmpty()) {
+        if (mac.equals("00-00-00-00-00-00")) {
             logger.error("Cannot check hostname and camera names, MAC address is not set!");
             return;
         }
 
-        String hostname = ConfigManager.getInstance().getConfig().getNetworkConfig().hostname;
+        var config = ConfigManager.getInstance().getConfig();
+        String hostname;
+        if (config.getNetworkConfig().shouldManage) {
+            hostname = config.getNetworkConfig().hostname;
+        } else {
+            hostname = CameraServerJNI.getHostname();
+        }
         if (hostname == null || hostname.isEmpty()) {
             logger.error("Cannot check hostname and camera names, hostname is not set!");
             return;

photon-core/src/main/java/org/photonvision/common/networking/NetworkUtils.java

@@ -17,7 +17,9 @@
 
 package org.photonvision.common.networking;
 
+import edu.wpi.first.networktables.NetworkTableInstance;
 import java.io.IOException;
+import java.net.InetAddress;
 import java.net.NetworkInterface;
 import java.util.ArrayList;
 import java.util.List;
@@ -218,40 +220,54 @@ public static String getIPAddresses(String iFaceName) {
         return String.join(", ", addresses);
     }
 
+    /**
+     * Gets a MAC address of a network interface. On devices where networking is managed by
+     * PhotonVision, this will return the MAC address of the configured interface. Otherwise, this
+     * will attempt to search for the network interface in current use and use that interface's MAC
+     * address, and if that fails, it will return a MAC address from the first network interface with
+     * a MAC address, as sorted by {@link NetworkInterface#networkInterfaces()}.
+     *
+     * @return The MAC address.
+     */
     public static String getMacAddress() {
         var config = ConfigManager.getInstance().getConfig().getNetworkConfig();
-        if (config.networkManagerIface == null || config.networkManagerIface.isBlank()) {
-            // This is a silly heuristic to find a network interface that PV might be using. It looks like
-            // it works pretty well, but Hyper-V adapters still show up in the list. But we're using MAC
-            // address as a semi-unique identifier, not as a source of truth, so this should be fine.
-            // Hyper-V adapters seem to show up near the end of the list anyways, so it's super likely
-            // we'll find the right adapter anyways
-            try {
+        try {
+            // Not managed? See if we're connected to a network. General assumption is one interface in
+            // use at a time
+            if (config.networkManagerIface == null || config.networkManagerIface.isBlank()) {
+                // Use NT client IP address to find the interface in use
+                if (!config.runNTServer) {
+                    var conn = NetworkTableInstance.getDefault().getConnections();
+                    if (conn.length > 0 && !conn[0].remote_ip.equals("127.0.0.1")) {
+                        var addr = InetAddress.getByName(conn[0].remote_ip);
+                        return formatMacAddress(NetworkInterface.getByInetAddress(addr).getHardwareAddress());
+                    }
+                }
+                // Connected to a localhost server or we are the server? Try resolving ourselves. Only
+                // returns a localhost address when there's no other interface available
+                byte[] mac =
+                        NetworkInterface.getByInetAddress(InetAddress.getLocalHost()).getHardwareAddress();
+                if (mac != null) {
+                    return formatMacAddress(mac);
+                }
+                // Fine. Just find something with a MAC address
                 for (var iface : NetworkInterface.networkInterfaces().toList()) {
-                    if (iface.isUp() && !iface.isVirtual() && !iface.isLoopback()) {
-                        byte[] mac = iface.getHardwareAddress();
-                        if (mac == null) {
-                            logger.error("No MAC address found for " + iface.getDisplayName());
-                        }
-                        return formatMacAddress(mac);
+                    if (iface.isUp() && iface.getHardwareAddress() != null) {
+                        return formatMacAddress(iface.getHardwareAddress());
                     }
                 }
-            } catch (Exception e) {
-                logger.error("Error getting MAC address:", e);
-            }
-            return "";
-        }
-        try {
-            byte[] mac = NetworkInterface.getByName(config.networkManagerIface).getHardwareAddress();
-            if (mac == null) {
-                logger.error("No MAC address found for " + config.networkManagerIface);
-                return "";
+            } else { // Managed? We should have a working interface available
+                byte[] mac = NetworkInterface.getByName(config.networkManagerIface).getHardwareAddress();
+                if (mac != null) {
+                    return formatMacAddress(mac);
+                } else {
+                    logger.error("No MAC address found for " + config.networkManagerIface);
+                }
             }
-            return formatMacAddress(mac);
         } catch (Exception e) {
-            logger.error("Error getting MAC address for " + config.networkManagerIface, e);
-            return "";
+            logger.error("Error getting MAC address", e);
         }
+        return "00-00-00-00-00-00";
     }
 
     private static String formatMacAddress(byte[] mac) {