Bug#878162: fixed in systemd 232-25+deb9u2

[Johan Wassberg]

On Sat, 10 Mar 2018 23:13:21 -0800 Rob Leslie <rob at mars.org> wrote:
> The fix for this bug broke the IPv6 networking on one of my systems.
> 
> When the RA does not include any MTU information, this patch causes no IPv6 default route to be added at all, leaving the system without IPv6 connectivity. The journal in this case shows:
> 
>   systemd-networkd[397]: eno1: Failed to get default router MTU from RA: No data available
> 
> A workaround is to add MTU information to the RA from the router, but I don’t think this should be necessary.

We can confirm that the change broke IPv6 on all our updated Stretch
machines:

2018-03-13T08:25:24.671634+01:00 machine.example.com systemd-networkd[286]: ens192: Failed to get default router MTU from RA: No data available

```
$ sysctl -a |grep "accept_ra = "
net.ipv6.conf.all.accept_ra = 1
net.ipv6.conf.default.accept_ra = 1
net.ipv6.conf.ens192.accept_ra = 0
net.ipv6.conf.lo.accept_ra = 1
```

The sysctl output shows that "accept_ra" is enabled for all entries except
for the first physical interface.

Manually setting "accept_ra" to "1" allows us to get a default route,
but restarting systemd-networkd changes it back to 0.

-- 
jocar