Re: ping6 with ipv4 mapped ipv6 address

[Ignatios Souvatzis <ignatios%cs.uni-bonn.de@localhost>]

Hello,

On Fri, Jan 06, 2012 at 07:42:08PM +0530, Ritesh Agrawal wrote:

> Do you think it is not allowed to do ping6 for IPv4 mapped IPv6 address?

Yes, I think so.

You should be aware that IPv4 mapped IPv6 is still IPv4 - it's only
presented in a IPv6-resembling text format (or actually, when calling
your operating system's libraries or kernel, binary socket address
format.)

For dual-protocol applications this is no problem - they know how
to switch (implicitly, when using the right (modern) library calls). 

However, ping6 (and traceroute6) don't only use the modern calls, but
also some very special ones; while old ping and traceroute for IPv4 
need to hand-craft the IPv4 packets. (They use very special packets
after all!

It would be quite some effort to unify those programs with the IPv4
counterparts; and this would hide the differences which really are
there. Given that those are _analysis_ tools, not user applications, I
think that's not only acceptable, but even slightly better so (no
danger to confuse a working v6 with a broken v4 connectivity or
vice versa).

I understand this is a matter of taste.

Regards,
        -is