confd: allow setting factory hostname from qemu_fw_cfg

This patch adds support for overriding the default hostname generation
on Qemu systems with the /sys/firmware/qemu_fw_cfg/by_name/opt/hostname
file.  E.g., virtual Infamy test systems using Qeneth.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/confd/bin/gen-hostname

@@ -1,38 +1,29 @@
 #!/bin/sh
-
+# Generate ietf-system.yang hostname based on:
+#  1. Command line argument + MAC suffix
+#  2. Specific hostname from qemu_fw_cfg, from Qeneth
+#  3. /etc/hostname from squashfs + MAC suffix
+#
 set -e
 
-base_mac_lowest_physical()
+gen()
 {
-    ip -d -j link show | jq -r '
-         .[] |
-         select(.link_type == "ether") |
-         select(has("linkinfo") | not) | .address' \
-    | sort | head -n 1
-}
+    base_mac=$(jq -r '.["mac-address"]' /run/system.json)
+    if [ -z "$base_mac" ] || [ "$base_mac" = "null" ]; then
+	base_mac=00:00:00:00:00:00
+    fi
 
-source_base_mac()
-{
-    # TODO: Source the base MAC from the vital product data memory, if
-    # available.
-    # base_mac=$(base_mac_vpd)
-    # [ "$base_mac" ] && return
-
-    base_mac=$(base_mac_lowest_physical)
-    [ "$base_mac" ] && return
-
-    base_mac=00:00:00:00:00:00
+    echo "$1-$(echo $base_mac | tail -c 9 | tr ':' '-')"
 }
 
 if [ "$1" ]; then
-    sysname="$1"
+    sysname=$(gen "$1")
+elif [ -f "/sys/firmware/qemu_fw_cfg/by_name/opt/hostname/raw" ]; then
+    sysname="$(cat /sys/firmware/qemu_fw_cfg/by_name/opt/hostname/raw)"
 else
-    sysname="$(cat /etc/hostname)"
+    sysname=$(gen "$(cat /etc/hostname)")
 fi
 
-source_base_mac
-sysname="${sysname}-$(echo $base_mac | tail -c 9 | tr ':' '-')"
-
 cat <<EOF
 {
   "ietf-system:system": {