Re: UDP traceroute does not work to google.com

[David Fifield <david () bamsoftware com>]

On Wed, Jan 07, 2015 at 01:05:20PM +0000, Sriram Rajan wrote:
> Hi Daniel & Nmap-dev,
>
> You were right about the unprivileged option. However, I could not get the
> traceroute over UDP with these options below. It still does a traceroute over
> ICMP.  Any means of restricing this to UDP in nmap ?
>
> $ sudo nmap -v -n -PU -Pn -sn  --traceroute google.com
>
> Starting Nmap 6.47 ( http://nmap.org ) at 2015-01-07 12:51 UTC
> ...(truncated)....
>
> TRACEROUTE (using proto 1/icmp)
> ...
> I have seen UDP here once. But the proto has been stuck at icmp since.

Unfortunately you can't directly control the probe that Nmap uses for
traceroute. It uses the "best" probe it has discovered during scanning
of the host so far (i.e., TCP SYN, UDP). It uses ICMP if it doesn't have
any information about responsive probes. Because you turned off both
host discovery and port scanning with -Pn -sn, Nmap has no information
about responsive probes and it uses the default ICMP for traceroute.

Try these options. They are not guaranteed to work (it depends on what
probes the target responds to).
        $ sudo nmap -v -n -PU -sn --traceroute <target>
        $ sudo nmap -v -n -PU -sU --traceroute <target>

David Fifield
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