Possible bug with IPv6 ICMPv6 handling

[David Horn]

On Fri, Aug 21, 2009 at 1:55 AM, Doug Hardie<bc979 at lafn.org> wrote:
> I have found what to me seems like a bug with ICMPv6 handling in IPv6.
>  However, before submitting a PR I wanted to check to be sure that its not a
> misunderstanding on my part.
>
> The network setup.  A host (A) connected to a router (B) connected to
> another host (C) on a separate network.  When all are up and running, A can
> ping6 to C and gets a response.  If you power off C and then do the ping
> again, tpcdump on A shows an ICMPv6 destination unreachable datagram
> received from B. However ping6 does not report that back to the user.  A
> ktrace of ping6 shows that it does not receive the ICMPv6 response.  Its my
> understanding that it should and the ping6 code seems to imply that also. Is
> this a bug?
> _______________________________________________

What version of FreeBSD are you using ?
Did you try the -v parameter to ping6 to display non-echo responses ?
(man ping6)

In a similar test I ran, I was able to get the icmp6 host unreachable
message from ping6 -v on my FreeBSD 7.2 box.  (I pinged a non-existent
address/machine off an upstream router)

uname -a
FreeBSD dhorn-bsd 7.2-RELEASE-p2 FreeBSD 7.2-RELEASE-p2 #0: Wed Jun 24
00:57:44 UTC 2009
root at i386-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  i386

dhorn at dhorn-bsd:~> ping6 -v 2001:470:7:584::3
PING6(56=40+8+8 bytes) 2001:470:8:584:20e:cff:xxxx:xxxx --> 2001:470:7:584::3
64 bytes from 2001:470:7:584::1: Destination Host Unreachable
Vr TC  Flow Plen Nxt Hlim
 6 00 00000 0010  3a   3e
2001:470:8:584:20e:cff:xxxx:xxxx->2001:470:7:584::3
ICMP6: type = 128, code = 0

The other thing to potentially look at would be firewall rules, but
that is unlikely if you can see the icmp6 response in tcpdump.

Good Luck.

--Dave