Provide a new nsock_setup_udp function to create a UDP socket without connecting it. Provide an NSE interface to the function. Add broadcast.nse, a script that receives UDP broadcasts with an unconnected socket.

nse_nsock.cc

@@ -727,6 +727,42 @@ int l_get_ssl_certificate (lua_State *L)
 }
 #endif
 
+static int l_setup (lua_State *L)
+{
+  static const int families[] = { AF_INET, AF_INET6 };
+  static const char *const fam_op[] = {"ipv4", "ipv6", NULL};
+  nsock_pool nsp;
+  nse_nsock_udata *nu;
+  const char *proto;
+  int af;
+
+  af = families[luaL_checkoption(L, 2, NULL, fam_op)];
+  proto = luaL_checkstring(L, 3);
+
+  if (strcmp(proto, "udp") != 0)
+    return luaL_argerror(L, 2, "must be \"udp\"");
+
+  nsp = get_pool(L);
+  nu = check_nsock_udata(L, 1, 0);
+
+  nu->nsiod = nsi_new(nsp, NULL);
+  if (nu->source_addr.ss_family != AF_UNSPEC) {
+    nsi_set_localaddr(nu->nsiod, &nu->source_addr, nu->source_addrlen);
+  } else if (o.spoofsource) {
+    struct sockaddr_storage ss;
+    size_t sslen;
+
+    o.SourceSockAddr(&ss, &sslen);
+    nsi_set_localaddr(nu->nsiod, &ss, sslen);
+  }
+  if (o.ipoptionslen)
+    nsi_set_ipoptions(nu->nsiod, o.ipoptions, o.ipoptionslen);
+
+  nsock_setup_udp(nsp, nu->nsiod, callback, nu->timeout, nu, af);
+
+  return yield(L, nu, "SETUP", TO, 0, NULL);
+}
+
 /* Set the local address for socket operations. The two optional parameters
    after the first (which is the socket object) are a string representing a
    numeric address, and a port number. If either optional parameter is omitted
@@ -987,6 +1023,7 @@ LUALIB_API int luaopen_nsock (lua_State *L)
 "return receive_buf;\n";
 
   static const luaL_Reg l_nsock[] = {
+    {"setup", l_setup},
     {"bind", l_bind},
     {"send", l_send},
     {"receive", l_receive},

scripts/broadcast.nse

@@ -0,0 +1,15 @@
+description = ""
+categories = {}
+
+prerule = function() return true end
+
+action = function()
+  local s, status, data
+
+  s = nmap.new_socket()
+  s:bind("255.255.255.255", 67)
+  s:setup("ipv4", "udp")
+  status, data = s:receive()
+
+  return data
+end