Fix for ICMP net unreachable in connect scan

[Richard Moore <rich () westpoint ltd uk>]

First lets configure a host to send some 'weird' responses:

iptables -A INPUT -p TCP --dport 3 -j REJECT --reject-with 
icmp-net-unreachable

nmap will now abort as soon as it scans this port using a connect
scan, see below:

rich@fester:~/nmap-3.81> ./nmap -P0 -sT -p 3,4 pugsley

Starting nmap 3.81 ( http://www.insecure.org/nmap/ ) at 2005-02-09 15:23 GMT
Strange SO_ERROR from connection to 192.168.3.46 (101) -- bailing scan : 
Operation now in progress

The fix is to treat this message as a way of filtering the
port. Patch below against 3.81.

Cheers

Rich.
--
Richard Moore, Principle Software Engineer,
Westpoint Ltd,
Albion Wharf, 19 Albion Street, Manchester, M1 5LN, England
Tel: +44 161 237 1028
Fax: +44 161 237 1031

*** scan_engine.cc      2005-02-09 15:20:25.000000000 +0000
--- /home/rich/xx/nmap-3.81/scan_engine.cc      2005-02-09 15:18:57.000000000 +0000
***************
*** 2167,2179 ****
        case EHOSTUNREACH:
        case ETIMEDOUT:
        case EHOSTDOWN:
          /* It could be the host is down, or it could be firewalled.  We
             will go on the safe side & assume port is closed ... on second
             thought, lets go firewalled! and see if it causes any trouble */
          newstate = PORT_FILTERED;
          break;
        case ENETDOWN:
-       case ENETUNREACH:
        case ENETRESET:
        case ECONNABORTED:
          snprintf(buf, sizeof(buf), "Strange SO_ERROR from connection to %s (%d - '%s') -- bailing scan", 
host->target->targetipstr(), optval, strerror(optval) );
--- 2167,2179 ----
        case EHOSTUNREACH:
        case ETIMEDOUT:
        case EHOSTDOWN:
+       case ENETUNREACH:
          /* It could be the host is down, or it could be firewalled.  We
             will go on the safe side & assume port is closed ... on second
             thought, lets go firewalled! and see if it causes any trouble */
          newstate = PORT_FILTERED;
          break;
        case ENETDOWN:
        case ENETRESET:
        case ECONNABORTED:
          snprintf(buf, sizeof(buf), "Strange SO_ERROR from connection to %s (%d - '%s') -- bailing scan", 
host->target->targetipstr(), optval, strerror(optval) );

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