Add CHANGELOG entry for UDP payloads and add guidelines for payloads to

payloads.cc.

CHANGELOG

@@ -1,5 +1,12 @@
 # Nmap Changelog ($Id$); -*-text-*-
 
+o For some UDP ports, Nmap will now send a protocol-specific payload
+  that is more likely to get a response than an empty packet is. This
+  improves the effectiveness of probes to those ports for host
+  discovery, and also makes an open port more likely to be classified
+  open rather than open|filtered. The ports and payloads are defined
+  in payload.cc. [David]
+
 o Fixed two memory leaks in ncat_posix.c and a bug where an open file was not
   being closed in libdnet-stripped/src/intf.c [Josh Marlow]
 

payload.cc

@@ -103,6 +103,10 @@ extern NmapOps o;
 
   s = eval('"' + raw_input().replace('"', '\\"') + '"')
   print '"' + "".join(c.isalnum() and c or "\\%03o" % ord(c) for c in s) + '"'
+
+  These payloads are sent with every host discovery or port scan probe. Only
+  include payloads that are unlikely to crash services, trip IDS alerts, or
+  change state on the server.
 */
 
 static const char payload_DNSStatusRequest[] =