tunneldigger: add package for establishing L2TPv3 tunnels over UDP

In the previous commit we already added tunneldigger-broker. Add the
corresponding client.

This PR is just a refactoring of the already existing opkg package from
wlanslovenija [0].

[0] - https://github.com/wlanslovenija/firmware-packages-opkg/tree/master/net/tunneldigger

Signed-off-by: Nick Hainke <vincent@systemli.org>

net/tunneldigger/Makefile

@@ -0,0 +1,57 @@
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=tunneldigger
+PKG_RELEASE:=1
+
+PKG_SOURCE_URL:=https://github.com/wlanslovenija/tunneldigger.git
+PKG_SOURCE_PROTO:=git
+PKG_SOURCE_VERSION:=4f72b30578ac3dbc5482f4a54054bf870355bdf5
+PKG_MIRROR_HASH:=babc71c757b757026f63e298bd4bd0edceae220827fff5cfad0af3f04ed529c7
+
+PKG_MAINTAINER:=Nick Hainke <vincent@systemli.org>
+PKG_LICENSE:=AGPL-3.0
+PKG_LICENSE_FILES:=COPYING
+
+include $(INCLUDE_DIR)/package.mk
+include $(INCLUDE_DIR)/cmake.mk
+
+CMAKE_SOURCE_SUBDIR:=client
+
+define Package/tunneldigger
+  SECTION:=net
+  CATEGORY:=Network
+  DEPENDS:= \
+	+kmod-l2tp \
+	+kmod-l2tp-ip \
+	+kmod-l2tp-eth \
+	+libnl-tiny \
+	+libpthread \
+	+librt
+  TITLE:=L2TPv3 tunneling via UDP
+  URL:=https://github.com/wlanslovenija/tunneldigger
+endef
+
+TARGET_CFLAGS += \
+	-I$(STAGING_DIR)/usr/include/libnl-tiny \
+	-I$(STAGING_DIR)/usr/include \
+	-DLIBNL_TINY
+
+define Package/tunneldigger/description
+Tunneldigger is a simple VPN tunneling solution based on the Linux kernel
+support for L2TPv3 tunnels over UDP.
+endef
+
+define Package/tunneldigger/conffiles
+/etc/config/tunneldigger
+endef
+
+define Package/tunneldigger/install
+	$(INSTALL_DIR) $(1)/usr/bin
+	$(INSTALL_BIN) $(PKG_BUILD_DIR)/tunneldigger $(1)/usr/bin/tunneldigger
+	$(INSTALL_DIR) $(1)/etc/init.d
+	$(INSTALL_BIN) ./files/tunneldigger.init $(1)/etc/init.d/tunneldigger
+	$(INSTALL_DIR) $(1)/etc/config
+	$(INSTALL_DATA) ./files/config.default $(1)/etc/config/tunneldigger
+endef
+
+$(eval $(call BuildPackage,tunneldigger))

net/tunneldigger/files/config.default

@@ -0,0 +1,8 @@
+config broker
+	list address 'x.y.z.w:8942'
+	list address 'x.y.z.w:53'
+	list address 'x.y.z.w:123'
+	option uuid 'abcd'
+	option interface 'l2tp0'
+	option limit_bw_down '1024'
+	option enabled '0'

net/tunneldigger/files/tunneldigger.init

@@ -0,0 +1,67 @@
+#!/bin/sh /etc/rc.common
+
+. $IPKG_INSTROOT/lib/functions/network.sh
+
+USE_PROCD=1
+START=90
+
+tunnel_id=1
+
+missing() {
+	echo "Not starting tunneldigger - missing $1" >&2
+}
+
+parse_broker() {
+	local section="$1"
+
+	config_get_bool enabled "$section" enabled 1
+	config_get addresses "$section" address
+	config_get uuid "$section" uuid
+	config_get interface "$section" interface
+	config_get limit_bw_down "$section" limit_bw_down
+	config_get hook_script "$section" hook_script
+	config_get bind_interface "$section" bind_interface
+	
+	[ $enabled -eq 0 ] && return
+
+	local broker_opts=""
+	for address in $addresses; do
+		append broker_opts "-b ${address}"
+	done
+
+	[ ! -z "${limit_bw_down}" ] && append broker_opts "-L ${limit_bw_down}"
+	[ ! -z "${hook_script}" ] && append broker_opts "-s ${hook_script}"
+	[ ! -z "${bind_interface}" ] && {
+		# Resolve logical interface name.
+		unset _bind_interface
+		network_get_device _bind_interface "${bind_interface}" || _bind_interface="${bind_interface}"
+		append broker_opts "-I ${_bind_interface}"
+	}
+
+	if [ -z "$uuid" ]; then
+		missing uuid
+		return
+	elif [ -z "$interface" ]; then
+		missing interface
+		return
+	fi
+
+	procd_open_instance "tunneldigger_${tunnel_id}"
+	procd_set_param command "/usr/bin/tunneldigger"
+	procd_append_param command -f
+	procd_append_param command -u "${uuid}"
+	procd_append_param command -i "${interface}"
+	procd_append_param command -t "${tunnel_id}"
+	procd_append_param command ${broker_opts}
+	procd_set_param stdout 1
+	procd_set_param stderr 1
+	procd_set_param respawn
+	procd_close_instance
+
+	let tunnel_id++
+}
+
+start_service() {
+	config_load tunneldigger
+	config_foreach parse_broker broker
+}