Update README.md

README.md

@@ -2,6 +2,31 @@
 Makefile to generate OpenWrt .opkg packages from official k3s binaries.
 
 ## Usage
+This requires a custom kernel with support for various cgroup, namespaces, vxlan, cfs
+scheduler etc. See here for my openwrt config: https://github.com/5pi-home/openwrt/blob/master/config
+
+### Firewall
+To allow the k3s' flannel bridge to access the internet, configure a interface
+for flannel.1 in uci:
+
+/etc/config/network:
+```
+config interface 'k8s'
+	option proto 'none'
+	option ifname 'flannel.1'
+```
+
+..and assign it to the lan zone:
+```
+config zone
+        option name 'lan'
+        option input 'ACCEPT'
+        option output 'ACCEPT'
+        option forward 'ACCEPT'
+        option network 'lan k8s'
+```
+
+## Building
 Run `make` to build the default version for `x86_64`. You can override ARCH and
 VERSION, e.g `make ARCH=armhf`. See ARCHS and VERSIONS files for available
 architectures and versions.