New script broadcast-ospf2-discover. Closes #743

nselib/ipOps.lua

@@ -3,6 +3,7 @@
 --
 -- @copyright Same as Nmap--See https://nmap.org/book/man-legal.html
 
+local math = require "math"
 local stdnse = require "stdnse"
 local string = require "string"
 local table = require "table"
@@ -674,6 +675,32 @@ hex_to_bin = function( hex )
   return status, result
 end
 
+---
+-- Convert a CIDR subnet mask to dotted decimal notation.
+--
+-- @param subnet CIDR string representing the subnet mask.
+-- @usage
+-- local netmask = ipOps.cidr_to_subnet( "/16" )
+-- @return Dotted decimal representation of the suppliet subnet mask (e.g. "255.255.0.0")
+cidr_to_subnet = function( subnet )
+  local bits = subnet:match("/(%d%d)$")
+  if not bits then return nil end
+  return fromdword((0xFFFFFFFF >> tonumber(bits)) ~ 0xFFFFFFFF)
+end
+
+---
+-- Convert a dotted decimal subnet mask to CIDR notation.
+--
+-- @param subnet Dotted decimal string representing the subnet mask.
+-- @usage
+-- local cidr = ipOps.subnet_to_cidr( "255.255.0.0" )
+-- @return CIDR representation of the supplied subnet mask (e.g. "/16").
+subnet_to_cidr = function( subnet )
+  local dword, err = todword(subnet)
+  if not dword then return nil, err end
+  return "/" .. tostring(32 - (math.tointeger(math.log((dword ~ 0xFFFFFFFF) + 1, 2))))
+end
+
 --Ignore the rest if we are not testing.
 if not unittest.testing() then
   return _ENV
@@ -801,5 +828,7 @@ do
   test_suite:add_test(unittest.is_nil(expand_ip("2001:db8::1", "ipv4")),
       "IPv6 to IPv4")
 end
+test_suite:add_test(unittest.equal(cidr_to_subnet("/16"), "255.255.0.0"), "cidr_to_subnet")
+test_suite:add_test(unittest.equal(subnet_to_cidr("255.255.0.0"), "/16"), "subnet_to_cidr")
 
 return _ENV;