It should be possible to get the whole round trip path with the
following:
host1: traceroute -g host2 host1
which traceroutes to the originator, but insists on the target as a
loose source route. None of this seems to work quite right on the
loom cluster however, but I didn't try very hard.
Andy
> Ok, here's the crazy idea of the day (abusing IP is much more fun than
> making slides):
>
> Modifying Kenichi's lsping to differentiate forward from reverse
> paths.
>
> Ok, so first, the target host has to forward LSR IP packets. I think
> Kenichi found that about 10% of the servers he surveyed would do this
> (surprising, but apparently true). Ok, now traceroute from the source
> to the target, and report the routers traversed and the final hop count
> as finalTtl.
>
> Now, set ttl to FinalTtl + 1, and send the packet from the source "back
> to the source", but loose source routed via the target. It will get to
> the target and then will return back towards the source, but will only
> go one hop before ttl is decremented to 0 and an ICMP error will be
> returned.... to the source from the offending router. In this way, one
> can implement "reverse traceroute" that gets the list of hosts traversed
> in the "reverse" direction.
>
> Anyone (Kenichi?) interesting in trying to get this to work?
>
> - Stefan
>
>
>
-- //------------------------------------------------------------------------- // Andy Collins -- KC6YEY acollins@cs.washington.edu // Graduate Student, University of Washington // Ford Pinto Rule: // Never buy a car that has a wick. // (collection last updated by Don Woods) //-------------------------------------------------------------------------