fix: do not proceed with DHCP if no network device with an active link is present

programs/src/dhcp/main.cpp

@@ -250,6 +250,23 @@ extern "C" void _start() {
 
     montauk::service_log("MontaukOS DHCP Client");
 
+    // 0. Check if any device with an up link even exists. 
+    montauk::abi::NetIfInfo ifs[4];
+    int n = montauk::net_interfaces(ifs, 4);
+
+    bool link = false;
+
+    for (int i = 0; i < n; i++) {
+        if (ifs[i].linkUp == true) {
+            link = true;
+        }
+    }
+
+    if (link == false) {
+        montauk::service_log("Unable to locate a network device with an active link.\n");
+        montauk::exit(montauk::StatusCodes::NoDevice);
+    }
+
     // 1. Get MAC address
     montauk::abi::NetCfg origCfg;
     montauk::get_netcfg(&origCfg);