Make --open imply --defeat-rst-ratelimit

CHANGELOG

@@ -1,5 +1,9 @@
 # Nmap Changelog ($Id$); -*-text-*-
 
+o The --open option now implies --defeat-rst-ratelimit. This may result in
+  inaccuracies in the numbers of "Not shown:" closed and filtered ports, but
+  only in situations where it also speeds up scan times. [Daniel Miller]
+
 o Fix reverse DNS on Windows which was failing with the message "mass_dns:
   warning: Unable to determine any DNS servers." This was because the interface
   GUID comparison needed to be done case-insensitive. [Robert Croteau]

nmap.cc

@@ -769,6 +769,8 @@ void parse_options(int argc, char **argv) {
             error("Warning: You specified a highly aggressive --min-hostgroup.");
         } else if (strcmp(long_options[option_index].name, "open") == 0) {
           o.setOpenOnly(true);
+          // If they only want open, don't spend extra time (potentially) distinguishing closed from filtered.
+          o.defeat_rst_ratelimit = 1;
         } else if (strcmp(long_options[option_index].name, "scanflags") == 0) {
           o.scanflags = parse_scanflags(optarg);
           if (o.scanflags < 0) {

output.cc

@@ -655,8 +655,12 @@ void printportoutput(Target *currenths, PortList *plist) {
     prevstate = istate;
   }
 
-  if (prevstate != PORT_UNKNOWN)
+  if (prevstate != PORT_UNKNOWN) {
     log_write(LOG_PLAIN, "\n");
+    if (o.defeat_rst_ratelimit) {
+      log_write(LOG_PLAIN, "Some closed ports may be reported as filtered due to --defeat-rst-ratelimit\n");
+    }
+  }
 
   if (o.reason)
     print_state_summary(plist, STATE_REASON_FULL);