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