[Pkg-libvirt-maintainers] Bug#923249: Bug#923249: libvirt0: libvirt sets disable_ipv6 on bridge, entirely breaking internal IPv6 networking

[Guido Günther]

Hi,
On Mon, Feb 25, 2019 at 02:25:57PM +0100, Ralf Jung wrote:
> Package: libvirt0
> Version: 5.0.0-1
> Severity: grave
> Justification: renders package unusable
> 
> Dear Maintainer,
> 
> After a recent upgrade, IPv6 communication between a virtual router and another
> virtual client over an isolated network stopped working. I am seeing the rotuer
> advertisments sent by the router on vnet0, which is attached to the bridge
> virbr1, but when I capture packages on the bridge, the IPv6 traffic is gone.  It
> just took me several hours of debugging to realize that the reason for this is
> that /proc/sys/net/ipv6/conf/virbr1/disable_ipv6 is set to 1.  After setting it
> to 0, IPv6 is working as expected now.
> 
> This is a regression, IPv6 used to work between virtual clients just fine
> without having to manually fiddle with the network configuration.

I'm not near a ipv6 setup atm but according to the git logs nothing
changed in that area for quite some time. Please indicate which version
you updated from so it's easier to check for related changes and also
provide details about your setup (preferably network XML and domain XML).

There were some ipv6 related changes with firewalld though which might be worth
investigating.
 -- Guido