IPv6 broken on Fedora 20?

Hannes Frederic Sowa hannes at stressinduktion.org
Tue Jan 7 12:49:15 CET 2014

On Tue, Jan 07, 2014 at 12:42:43PM +0100, Tore Anderson wrote:
> * Hannes Frederic Sowa
> > It also had some affect of anycast address generation.
> > 
> >> But you are right, essentially it should work but some assumptions were
> >> made in the kernel which should have been checked first.
> > 
> > I guess they're switching back to 64 while suppressing automatically addding
> > prefix routes:
> > 
> >   <http://patchwork.ozlabs.org/patch/307389/>
> > 
> > This feature should also be available in iproute then.
> Could you elaborate on the anycast address generation problem?

Kernel did also install an subnet-all-router anycast address if the
prefixlen was 128. If you have NM and also e.g. libvirt, which may
enable ipv6 forwarding, the same /128 got installed as an anycast address
(see /proc/net/anycast6). I did not see any breakage, but it could defer ndisc

> Reason I'm asking is that even though the patch you linked to allow NM
> to return to adding /64s in the case of SLAAC, there's still DHCPv6
> IA_NA which are always /128, yet possibly in combination with arbitrary
> prefix length onlink routes (if PIO exists in RA with A=0, L=1). I'm
> thinking that perhaps this anycast address generation problem could be
> present in that case too?

Yes it is and I fixed that yesterday. I guess, I should ask that the patch
should be pushed to stable.



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