Destroy connect scan probes that aren't otherwise handled (thereby closing the

socket). It's possible to get an EHOSTUNREACH or EHOSTDOWN (and possibly other
errors) against a nonexistent LAN host and formerly the socket wasn't closed.
This allowed Nmap's internal count of sockets to be less that the true count of
open sockets. It would eventually try to open too many sockets and quit with
the message

Socket creation in sendConnectScanProbe: Too many open files (24)

Be aware that in this message 24 is the errno, not the number of open files.

scan_engine.cc

@@ -2798,6 +2798,8 @@ static UltraProbe *sendConnectScanProbe(UltraScanInfo *USI, HostScanStats *hss,
         hss->destroyAllOutstandingProbes();
     } else if (!USI->ping_scan && port_state != PORT_UNKNOWN) {
       ultrascan_port_probe_update(USI, hss, probeI, port_state, &USI->now);
+    } else {
+      hss->destroyOutstandingProbe(probeI);
     }
     probe = NULL;
   }