bootmac: set MAC from serialno or machine-id

Bootmac configures the MAC addresses of WLAN and Bluetooth interfaces at boot.
Bootmac can be invoked in various ways at boot, but currently only udev rules are tested.
Bootmac generates MAC addresses from the `serialno` provided by Android bootloaders
through /proc/cmdline or from /etc/machine-id. The Organizationally Unique Identifier (OUI)
is retrieved from a lookup database macdb by matching deviceinfo_manufacturer
from /etc/deviceinfo with the entries in the database.

bootmac

+#!/bin/sh
+set -e
+
+#
+# Configure WLAN and Bluetooth MAC addresses for SDM845 devices on boot.
+# This script is triggered through an udev rule when the WLAN or Bluetooth
+# interface comes up.
+#
+# Copyright (c) Dylan Van Assche (2022)
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+
+MACDB_PATH="/etc/macdb"
+WLAN_MAC=""
+BT_MAC=""
+WLAN_INTERFACE="wlan0"
+BT_INTERFACE="hci0"
+
+source /etc/deviceinfo
+
+log() {
+    echo "$@" | logger -t "qmac"
+}
+
+mac_generate() {
+    # Try to retrieve the serial number from the cmdline
+    log "retrieving device serial number"
+    SERIAL_NUMBER=$(cat /proc/cmdline | grep -o "serialno.*" | cut -d" " -f1)
+
+    # If the serial number is missing, fallback to /etc/machine-id
+    # While 'machine-id' ensures the MAC address is consistent across reboot,
+    # it will be changed each time the device is flashed since the machine-id
+    # is generated on first boot.
+    if [ -z "$SERIAL_NUMBER" ]; then
+        log "serial number not available, falling back to machine-id"
+        SERIAL_NUMBER=$(cat /etc/machine-id)
+    fi
+
+    if [ -z "$SERIAL_NUMBER" ]; then
+       log "no unique ID available, cannot generate MAC address"
+       exit 1
+    fi
+
+    # Manufacturers get a range of MAC addresses with a prefix called 
+    # Organizationally Unique Identifier (OUI). Read the OUI from /etc/macdb
+    MAC_OUI=$(cat $MACDB_PATH | grep $deviceinfo_manufacturer | cut -f1)
+    MAC_CTRL=$(echo "$SERIAL_NUMBER" | sha256sum | awk '{printf("%010s\n", $1)}')
+    MAC=$(echo "${MAC_OUI:0:6}${MAC_CTRL:0:6}")
+
+    # Generate WLAN from extracted SERIAL_NUMBER
+    # Increment WLAN MAC by 1 to have a valid Bluetooth MAC address
+    log "generating WLAN and Bluetooth MAC addresses"
+    WLAN_MAC=$(echo "$MAC" | sed 's/\(..\)/\1:/g' | sed '$s/:$//')
+    BT_MAC=$(printf "%x\n" $((0x$MAC + 1)) | sed 's/\(..\)/\1:/g' | sed '$s/:$//')
+}
+
+mac_bluetooth() {
+    # Bring Bluetooth down, set the generated MAC and bring it up again
+    log "setting Bluetooth MAC to $BT_MAC"
+    btmgmt -i "$BT_INTERFACE" power off
+    btmgmt -i "$BT_INTERFACE" public-addr $BT_MAC
+    rfkill unblock bluetooth
+    btmgmt -i "$BT_INTERFACE" power on
+}
+
+mac_wlan() {
+    # Bring WLAN down, set the extracted MAC and bring it up again
+    log "setting WLAN MAC to $WLAN_MAC"
+    ip link set dev "$WLAN_INTERFACE" down
+    ip link set dev "$WLAN_INTERFACE" address "$WLAN_MAC"
+    rfkill unblock wlan
+    ip link set dev "$WLAN_INTERFACE" up
+}
+
+log "configuring MAC addresses"
+mac_generate
+mac_wlan
+mac_bluetooth
+log "MAC addresses configured successfully"
+

bootmac.rules

+# 
+# Configure the MAC addresses of the WLAN and Bluetooth interfaces when they appear.
+# Copyright (c) Dylan Van Assche (2022)
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+
+ACTION=="add", SUBSYSTEM=="net", KERNEL=="wlan0", RUN+="/usr/bin/qmac"
+ACTION=="add", SUBSYSTEM=="bluetooth", KERNEL=="hci0", RUN+="/usr/bin/qmac"

macdb

+OUI	MANUFACTURER
+64A2F9	OnePlus
+785364	SHIFT