Possible bug with IPv6 ICMPv6 handling

[Doug Hardie]

On 21 August 2009, at 11:33, David Horn wrote:

> 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 ?

7.2 and 7.0.

> Did you try the -v parameter to ping6 to display non-echo responses ?
> (man ping6)

No - didn't notice that in either the ping or ping6 man pages before.

>
> 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.

No firewall involved.
>
> Good Luck.

It would appear that this is an error, but in ping and not ping6.   
Both of their man pages have exactly the same comment for -v.   
However, ping does show things like Host down etc without the -v  
argument.  Ping6 works per the man page and does not.  I don't think  
that this is worth a PR though.  Thanks for the help.

>
> --Dave
>