Properly support devices with only one ethernet interface

package/gluon-core/files/lib/gluon/upgrade/core/initial/001-sysconfig

@@ -15,7 +15,14 @@ get_primary_mac() {
     esac
 }
 
+lan_ifname="$(uci get network.lan.ifname)"
+wan_ifname="$(uci get network.wan.ifname)"
+
+if [ -n "$wan_ifname" ]; then
+	[ -z "$lan_ifname" ] || sysconfig_set lan_ifname "$lan_ifname"
+	sysconfig_set wan_ifname "$wan_ifname"
+else
+	sysconfig_set wan_ifname "$lan_ifname"
+fi
 
-sysconfig_set lan_ifname "$(uci get network.lan.ifname)"
-sysconfig_set wan_ifname "$(uci get network.wan.ifname)"
 sysconfig_set primary_mac "$(get_primary_mac)"

package/gluon-mesh-batman-adv/files/lib/gluon/upgrade/mesh-batman-adv/initial/010-mesh

@@ -3,9 +3,16 @@
 . /lib/functions.sh
 . /lib/gluon/functions/sysconfig.sh
 
+lan_ifname="$(sysconfig lan_ifname)"
 
 uci_add network interface client
-uci_set network client ifname "$(sysconfig lan_ifname) bat0"
+
+if [ -n "$lan_ifname" ]; then
+	uci_set network client ifname "$lan_ifname bat0"
+else
+	uci_set network client ifname "bat0"
+fi
+
 uci_set network client type 'bridge'
 uci_set network client proto 'dhcpv6'
 uci_set network client reqprefix 'no'