installer: add disable IPv6

Author: FooDeas

CHANGELOG.md

@@ -6,6 +6,7 @@
 - support boot or/and install from USB mass storage
 - added or changed configuration variables
   - `release` is set to "stretch" by default
+  - disable IPv6
 
 **Bugfixes:**
 

doc/INSTALL_CUSTOM.md

@@ -82,6 +82,7 @@
 | `ip_broadcast` | `0.0.0.0` |  | Broadcast address |
 | `ip_gateway` | `0.0.0.0` |  | Gateway address (e.g. 192.168.2.1) |
 | `ip_nameservers` |  |  | DNS nameservers (e.g. 8.8.8.8) |
+| `ip_ipv6` | `1` | `0`/`1` | Set to "0" to disable IPv6. |
 
 ## Localization
 

scripts/opt/raspberrypi-ua-netinst/install.sh

@@ -62,6 +62,7 @@ variables_reset() {
 	ip_broadcast=
 	ip_gateway=
 	ip_nameservers=
+	ip_ipv6=
 	drivers_to_load=
 	online_config=
 	gpu_mem=
@@ -137,6 +138,7 @@ variables_set_defaults() {
 	variable_set "ip_netmask" "0.0.0.0"
 	variable_set "ip_broadcast" "0.0.0.0"
 	variable_set "ip_gateway" "0.0.0.0"
+	variable_set "ip_ipv6" "1"
 	variable_set "hdmi_tv_res" "1080p"
 	variable_set "hdmi_monitor_res" "1024x768"
 	variable_set "hdmi_disable_overscan" "0"
@@ -1202,6 +1204,7 @@ echo "  keyboard_layout = ${keyboard_layout}"
 echo "  locales = ${locales}"
 echo "  system_default_locale = ${system_default_locale}"
 echo "  wlan_country = ${wlan_country}"
+echo "  ip_ipv6 = ${ip_ipv6}"
 echo "  cmdline = ${cmdline}"
 echo "  drivers_to_load = ${drivers_to_load}"
 echo "  gpu_mem = ${gpu_mem}"
@@ -1614,6 +1617,12 @@ echo "OK"
 
 # networking
 echo -n "  Configuring network settings... "
+
+if [ "${ip_ipv6}" = "0" ]; then
+	mkdir -p /rootfs/etc/sysctl.d
+	echo "net.ipv6.conf.all.disable_ipv6 = 1" > /rootfs/etc/sysctl.d/01-disable-ipv6.conf
+fi
+
 touch /rootfs/etc/network/interfaces || fail
 # lo interface may already be there, so first check for it
 if ! grep -q "auto lo" /rootfs/etc/network/interfaces; then