From 2924761826677361fbc8368ea7a354197a507587 Mon Sep 17 00:00:00 2001
From: reubenmiller <reuben.d.miller@gmail.com>
Date: Mon, 9 Dec 2024 09:50:57 +0100
Subject: [PATCH] feat: fallback to mac address of first adapter for the serial
 number

---
 src/scripts.d/50_c8y_Hardware | 45 +++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/src/scripts.d/50_c8y_Hardware b/src/scripts.d/50_c8y_Hardware
index 54b6215..63f159b 100755
--- a/src/scripts.d/50_c8y_Hardware
+++ b/src/scripts.d/50_c8y_Hardware
@@ -68,6 +68,45 @@ hardware_info_container() {
     echo "serialNumber=\"$SERIAL\""
 }
 
+get_mac_address() {
+    SCN=/sys/class/net
+    min=65535
+    arphrd_ether=1
+    ifdev=
+
+    # find iface with lowest ifindex, skip non ARPHRD_ETHER types (lo, sit ...)
+    for dev in "$SCN"/*; do
+        if [ ! -f "$dev/type" ]; then
+            continue
+        fi
+
+        iftype=$(cat "$dev/type")
+        if [ "$iftype" -ne $arphrd_ether ]; then
+            continue
+        fi
+
+        # Skip dummy interfaces
+        if echo "$dev" | grep -q "$SCN/dummy" 2>/dev/null; then
+            continue
+        fi
+
+        idx=$(cat "$dev/ifindex")
+        if [ "$idx" -lt "$min" ]; then
+            min=$idx
+            ifdev=$dev
+        fi
+    done
+
+    if [ -z "$ifdev" ]; then
+        echo "no suitable interfaces found" >&2
+        exit 1
+    else
+        echo "using interface $ifdev" >&2
+        # grab MAC address
+        cat "$ifdev/address"
+    fi
+}
+
 hardware_info_device() {
     MODEL=$(grep Model /proc/cpuinfo | cut -d: -f2- | xargs)
     HARDWARE=$(grep "^Hardware" /proc/cpuinfo | cut -d: -f2- | xargs)
@@ -81,6 +120,12 @@ hardware_info_device() {
         fi
     fi
 
+    if [ -z "$SERIAL" ]; then
+        # TODO: not all cpus have a serial number /proc/cpuinfo
+        # Fallback to using the mac address
+        SERIAL="$(get_mac_address 2>/dev/null)"
+    fi
+
     echo "model=\"$MODEL\""
     echo "revision=\"$HARDWARE-$REVISION\""
     echo "serialNumber=\"$SERIAL\""