ethercatctl: allow to use the network device name instead of mac address

In the /etc/ethercat.conf file, the MASTERX_DEVICE string is given as a
mac address or a wildcard. When we want to deploy the (same) software (image)
to a bunch of different hardware, and these computers do have more than one
interface that matches the driver, we need a way to define the device by
network interface name. This allows to also define the network device by name
(e.g. eth0, eno1, ...)

Signed-off-by: Matthias Schoepfer <m.schoepfer@rethinkrobotics.com>

script/ethercatctl.in

@@ -37,6 +37,7 @@ LSMOD=/sbin/lsmod
 MODPROBE=/sbin/modprobe
 RMMOD=/sbin/rmmod
 MODINFO=/sbin/modinfo
+IP=/bin/ip
 
 ETHERCAT=@bindir@/ethercat
 
@@ -55,13 +56,19 @@ fi
 #------------------------------------------------------------------------------
 
 parse_mac_address() {
+    local DEVICENAMETOMAC
     if [ -z "${1}" ]; then
         MAC=""
-    elif echo "${1}" | grep -qE '^([0-9a-fA-F]{2}:){5}[0-9a-fA-F]{2}$'; then
+    elif echo ${1} | grep -qE '^([0-9a-fA-F]{2}:){5}[0-9a-fA-F]{2}$'; then
         MAC=${1}
     else
-        echo Invalid MAC address \""${1}"\" in ${ETHERCAT_CONFIG}
-        exit 1
+	DEVICENAMETOMAC=$("${IP}" address show dev "${1}" | awk '/link\/ether/ { print $2; }')
+	if echo "${DEVICENAMETOMAC}" | grep -qE '^([0-9a-fA-F]{2}:){5}[0-9a-fA-F]{2}$'; then
+	    MAC=${DEVICENAMETOMAC}
+	else
+            echo Invalid MAC address \""${1}"\" in ${ETHERCAT_CONFIG}
+            exit 1
+	fi
     fi
 }