Re: IPv6 "is unreachable" route flapping

[Paul Ripke <stix%stix.id.au@localhost>]

On Tue, Mar 10, 2020 at 12:31:57PM +0000, Roy Marples wrote:
> On 09/03/2020 23:03, Paul Ripke wrote:
> > On Mon, Mar 09, 2020 at 10:42:42AM +0000, Roy Marples wrote:
> > > On 09/03/2020 10:28, Paul Ripke wrote:
> > > > Time has passed, and I'm now running netbsd-9 on the orange pi, and
> > > > on the amd64 router. I still see these issues with IPv6 route flaps.
> > > > 
> > > >   From the arm side:
> > > > 
> > > > Mar  9 20:52:20 thing1 dhcpcd[292]: emac0: Router Advertisement from fe80::52e5:49ff:fea6:f5d8
> > > > Mar  9 20:52:20 thing1 dhcpcd[292]: emac0: fe80::52e5:49ff:fea6:f5d8: no longer a default router
> > > 
> > > Well, that's pretty telling.
> > > dhcpcd received a RA with a router lifetime of zero.
> > > It's not that the route is flapping, it's the router saying it's no longer a
> > > default router and should not be used.
> > > dhcpcd is just doing what it's told.
> > > 
> > > The rest of the debug is irrelevant at this point.
> > > 
> > > Is there anything on your router restarting rtadvd as that would trigger the above?
> > 
> > Nothing restarting it, afaik. I do have a /etc/ppp/dhcp6c-script:
> > 
> > ----
> > #!/bin/ksh
> > 
> > IP=$(ifconfig pppoe0 | awk '/inet6/ {print $2}' | cut -d / -f 1)
> > route change -inet6 default "$IP" || route add -inet6 default "$IP"
> > sleep 2 && /etc/rc.d/rtadvd reload
> > ----
> > 
> > And /etc/rtadvd.conf:
> > 
> > ----
> > alc0:\
> >          :maxinterval#300:\
> >          :rltime#3600:
> > ----
> > 
> > I've commented out the SIGHUP, I forget why I added that - lost to the
> > mists of time. Alternately, I see rtadvd has a -C option, but that sounds
> > wrong. I'll see what happens with it commented out.
> 
> You shouldn't need it that reload.
> rtadvd should spot the new/changed prefix via route(4) and do the right thing.
> 
> The -C option is noted as only used for testing clients as I use it from
> time to time to test dhcpcd. Not using it is the right thing to do :)

Thanks, indeed, with the SIGHUP gone, I no longer see those routes
flapping.

Thanks!
-- 
Paul Ripke
"Great minds discuss ideas, average minds discuss events, small minds
 discuss people."
-- Disputed: Often attributed to Eleanor Roosevelt. 1948.