Re: nmap errors on *BSDs (noted on NetBSD and MacOSX, so far) (traceroute)

[David Fifield <david () bamsoftware com>]

On Tue, Mar 23, 2010 at 04:16:18PM -0600, David Fifield wrote:
> On Tue, Mar 23, 2010 at 11:07:46PM +0100, Patrik Karlsson wrote:
> > Hmm, I just ran nmap with the traceroute option on Snow Leopard.
> > I'm seeing a single hop for any host I'm scanning:
> >
> > sudo ./nmap -sn --traceroute scanme.insecure.org
> >
> > Starting Nmap 5.21 ( http://nmap.org ) at 2010-03-23 23:03 CET
> > Warning: Unable to open interface vboxnet0 -- skipping it.
> > Nmap scan report for scanme.insecure.org (64.13.134.52)
> > Host is up (0.0027s latency).
> > rDNS record for 64.13.134.52: scanme.nmap.org
> >
> > TRACEROUTE (using port 80/tcp)
> > HOP RTT     ADDRESS
> > 1   3.27 ms scanme.nmap.org (64.13.134.52)
> >
> > Nmap done: 1 IP address (1 host up) scanned in 0.04 seconds
>
> Try with --packet-trace to see what's going on. Probably your first-hop
> router is resetting outgoing TTLs to some fixed value.

It's going to look like the r17036 I just committed was related to this,
but it's not.

------------------------------------------------------------------------
r17036 | david | 2010-03-23 17:30:36 -0600 (Tue, 23 Mar 2010) | 9 lines

In traceroute, separate the directly connected targets from the rest
before starting. There is a special function that does a trace of
directly connected targets without sending any packets, just by filling
in one hop directly to the target. The traceroute code was only checking
whether the first target in the group was directly connected, and if it
was, it assumed all of them were. Now it filters the list into two and
calls traceroute_direct on one and traceroute_remote on the other.
Fyodor discovered this problem today.

------------------------------------------------------------------------

If this was happening to you, you wouldn't have had the TRACEROUTE line
in the output.

David Fifield
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