#!/usr/bin/lua
--[[

	Part of AREDN® -- Used for creating Amateur Radio Emergency Data Networks
	Copyright (C) 2023 Tim Wilkinson
	See Contributors file for additional contributors

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation version 3 of the License.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program.  If not, see <http://www.gnu.org/licenses/>.

	Additional Terms:

	Additional use restrictions exist on the AREDN® trademark and logo.
		See AREDNLicense.txt for more info.

	Attributions to the AREDN® Project must be retained in the source code.
	If importing this code into a new or existing project attribution
	to the AREDN® project must be added to the source code.

	You must not misrepresent the origin of the material contained within.

	Modified versions must be modified to attribute to the original source
	and be marked in reasonable ways as differentiate it from the original
	version

--]]

require("uci")
require("aredn.olsr")

local dns_file = "/tmp/dnsmasq.d/supernode.conf"

local c = uci.cursor()

-- Supernodes themselves dont need supernode nameservers
if c:get("aredn", "@supernode[0]", "enable") == "1" then
    os.exit(0)
end

-- Ignore supernodes?
if c:get("aredn", "@supernode[0]", "support") == "0" then
	os.exit(0)
end

-- Find the closest supernode to use as a nameserver
local sn = {}
for _, hna in ipairs(aredn.olsr.getOLSRHNA())
do
	if hna.genmask == 8 and hna.destination == "10.0.0.0" then
		sn[hna.gateway] = true
		break
	end
end
local best = { destination = nil, etx = 99999999 }
for _, route in ipairs(aredn.olsr.getOLSRRoutes())
do
	if sn[route.destination] and route.etx < best.etx then
		best = route
	end
end
if not best.destination then
	os.exit(0)
end

-- Update the dns and restart network if necessary
local dns = "#" .. best.destination .. "\nserver=/local.mesh/" .. best.destination .. "\nrev-server=10.0.0.0/8," ..best.destination .. "\nrev-server=172.31.0.0/16," .. best.destination .. "\nrev-server=172.30.0.0/16," .. best.destination .. "\n"
local odns = ""
local f = io.open(dns_file)
if f then
	odns = f:read("*a")
	f:close()
end
if odns ~= dns then
	f = io.open(dns_file, "w+")
	if f then
		f:write(dns)
		f:close()
		os.execute("/etc/init.d/dnsmasq restart")
	end
end