local bin = require "bin"
local ipOps = require "ipOps"
local nmap = require "nmap"
local stdnse = require "stdnse"
local tab = require "tab"
local table = require "table"

description = [[
Discovers hosts and routing information from devices running RIPng on the
LAN by sending a broadcast RIPng Request command and collecting any responses.
]]

---
-- @usage
-- nmap --script broadcast-ripng-discover
--
-- @output
-- | broadcast-ripng-discover: 
-- |   fe80::a00:27ff:fe9a:880c
-- |     route                       metric  next hop
-- |     fe80:470:0:0:0:0:0:0/64     1       
-- |     fe80:471:0:0:0:0:0:0/64     1       
-- |_    fe80:472:0:0:0:0:0:0/64     1       
--
-- @args broadcast-ripng-discover.timeout sets the connection timeout
--       (default: 5s)

author = "Patrik Karlsson"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"broadcast", "safe"}


prerule = function() return ( nmap.address_family() == "inet6" ) end

RIPng = {

	-- Supported RIPng commands
	Command = {
		Request = 1,
		Response = 2,
	},
	
	-- Route table entry
	RTE = {
	
		-- Creates a new Route Table Entry
		-- @param prefix string containing the ipv6 route prefix
		-- @param tag number containing the route tag
		-- @param prefix_len number containing the length in bits of the
		--        signifcant part of the prefix
		-- @param metric number containing the current metric for the
		--        destination
		new = function(self, prefix, tag, prefix_len, metric)
			local o = {
				prefix = prefix,
				tag = tag,
				prefix_len = prefix_len,
				metric = metric
			}
			setmetatable(o, self)
			self.__index = self
			return o
		end,
		
		-- Parses a byte string and creates an instance of RTE
		-- @param data string of bytes
		-- @return rte instance of RTE
		parse = function(data)
			local rte = RIPng.RTE:new()
			local pos, ip
			
			pos, ip, rte.tag, rte.prefix_len, rte.metric = bin.unpack(">A16SCC", data)
			ip = select(2, bin.unpack("B" .. #ip, ip))
			rte.prefix = ipOps.bin_to_ip(ip)
			return rte
		end,
		
		-- Converts a RTE instance to string
		-- @return string of bytes to send to the server
		__tostring = function(self)
			local ipstr = ipOps.ip_to_str(self.prefix)
			assert(16 == #ipstr, "Invalid IPv6 address encountered")
			return bin.pack(">ASCC", ipstr, self.tag, self.prefix_len, self.metric)
		end,
	
		
	},
		
	-- The Request class contains functions to build a RIPv2 Request
	Request = {
	
		-- Creates a new Request instance
		--
		-- @param command number containing the RIPv2 Command to use
		-- @return o instance of request
		new = function(self, entries)
			local o = { 
				command 	= 1,
				version 	= 1,
				entries		= entries,
			}
			setmetatable(o, self)
			self.__index = self
			return o
		end,
    
		-- Converts the whole request to a string
		__tostring = function(self)
			local RESERVED = 0
			local str = bin.pack(">CCS", self.command, self.version, RESERVED)
			for _, rte in ipairs(self.entries) do
				str = str .. tostring(rte)
			end
			return str
		end,

	},
	
	-- A RIPng Response
	Response = {
		
		-- Creates a new Response instance
		-- @return o new instance of Response
		new = function(self)
			local o = {	}
			setmetatable(o, self)
			self.__index = self
			return o
		end,
		
		-- Creates a new Response instance based on a string of bytes
		-- @return resp new instance of Response
		parse = function(data)
			local resp = RIPng.Response:new()
			local pos, _
			
			pos, resp.command, resp.version, _ = bin.unpack(">CCS", data)
			resp.entries = {}
			while( pos < #data ) do
				local e = RIPng.RTE.parse(data:sub(pos))
				table.insert(resp.entries, e)
				pos = pos + 20
			end
			
			return resp
		end,		
	}
}

local function fail(err) return ("\n  ERROR: %s"):format(err or "") end

-- Parses a RIPng response
-- @return ret string containing the routing table
local function parse_response(resp)
	local next_hop
	local result = tab.new(3)
	tab.addrow(result, "route", "metric", "next hop")
	for _, rte in pairs(resp.entries or {}) do
		-- next hop information is specified in a separate RTE according to
		-- RFC 2080 section 2.1.1
		if ( 0xFF == rte.metric ) then
			next_hop = rte.prefix
		else
			tab.addrow(result, ("%s/%d"):format(rte.prefix, rte.prefix_len), rte.metric, next_hop or "")
		end
	end
	return tab.dump(result)
end

action = function()

	local req = RIPng.Request:new( { RIPng.RTE:new("0::", 0, 0, 16) } )	
	local host, port = "FF02::9", { number = 521, protocol = "udp" }
	local iface = nmap.get_interface()
	local timeout = stdnse.parse_timespec(stdnse.get_script_args(SCRIPT_NAME..".timeout"))
	timeout = (timeout or 5) * 1000

	local sock = nmap.new_socket("udp")
	sock:bind(nil, 521)
	sock:set_timeout(timeout)

	local status = sock:sendto(host, port, tostring(req))
		
	-- do we need to add the interface name to the address?
	if ( not(status) ) then
		if ( not(iface) ) then
			return fail("Couldn't determine what interface to use, try supplying it with -e")
		end
		status = sock:sendto(host .. "%" .. iface, port, tostring(req))
	end
	
	if ( not(status) ) then
		return fail("Failed to send request to server")
	end

	local responses = {}
	while(true) do
		local status, data = sock:receive()
		if ( not(status) ) then
			break
		else
			local status, _, _, rhost = sock:get_info()
			if ( not(status) ) then
				rhost = "unknown"
			end
			responses[rhost] = RIPng.Response.parse(data)
		end
	end
	
	local result = {}
	for ip, resp in pairs(responses) do
		stdnse.print_debug(ip, resp)
		table.insert(result, { name = ip, parse_response(resp) } )
	end
	return stdnse.format_output(true, result)
end