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Re: vioif(4) ipv6 issues?

In article <>,
Staffan Thomén  <> wrote:
>Staffan Thomén wrote:
>> Greg Troxel wrote:
>>> Jeff Rizzo<> writes:
>>>> I just noticed that a host of mine running as a Xen guest is not
>>>> getting (or maybe just sending) ipv6 packets correctly. It's running
>>>> pretty much the same as some physical hosts, and the only difference I
>>>> can see is the Xen (and vioif) aspect.
>>> Are you using a bridge for xvifN.0 on the dom0?
>>> Try using ping6 to the link-local (fe80::) addresses. Remember to use
>>> %ifname as it appears in ifconfig (other end's address, your ifname).
>>> Try running tcpdump in promiscuous mode on both ends. That can hide
>>> some mcast programming/filtering bugs to help diagnosis.
>>> First, ping the ll address of the xvif from the domU, and vice versa.
>> The tone I imagined in your email seems to suggest that you know why
>> this is happening.
>> I am seeing this exact problem on my Xen setup, it's a NetBSD 7.1 dom0
>> with 7.1 domU:s using xvif linked to the real wm with a bridge. The
>> domUs sometimes become completely unresponsive on ipv6, but then
>> recover. ipv4 seems completely unaffected.
>> Sometimes the dom0 is also unresponsive on v6.
>> It seems to happen as the domUs are idle, with little to no traffic,
>> because one of the VMs host my (v6) irc session and it has stayed up for
>> 30+ days.
>Following up on my own mail here, sorry.
>I did some investigation and noticed that listing the entries in NDP on my v6 
>gateway showed the nonresponsive (xen domU) hosts as having expired. This 
>would explain the unresponsiveness.
>Next I dumped the traffic going through the dom0's interface, and saw the 
>gateway querying ff02::<eui64> of the expired hosts repeatedly but not getting 
>a reply (this seems like a fallback broadcast).
>So I looked a little closer, and my domU:s were using dhcpcd to handle ipv6, 
>so I put 'ipv4only' in dhcpcd.conf, set net.inet6.ip6.accept_rtadv to 1 in 
>sysctl, enabled rtsold and restarted networking. Voila, the problem went away 
>I'm guessing this is a bug in dhcpcd and that it doesn't reply to neighbour 
>solicitation queries properly when there's a transparent hop like bridge(4) in 
>the network. The expire times seem to become very short (looks like 60 
>seconds) where hosts directly connected get 24 hours.
>Maybe this can help the OP.

I don't know if it is related to the hop, but there was a bug in dhcpcd
responding that was fixed...


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