Bug#924575: systemd-networkd doesn't process IPv6 RA properly

[Johan Wassberg]

Package: systemd
Version: 232-25+deb9u9
Severity: important

Dear Maintainer,
this issue is a bit outside my confort zone but I still want to try to
report this bug.

It is probably the same as Launchpad#1800836[0] and according to that
ticket the issue fixed in a new version of systemd. But for all of us
that are stuck with Stretch for some years to come it would be great if
someone could look in to the issue and backport the fix.

The problem seems to be that systemd-networkd doesn't expire or take
note of the RA Default Lifetime.

In older OSes (or Stretch without systemd-networkd) you could see the
expiration of the default route:
```
$ ip -6 r
2001:6b0:5:1568::/64 dev ens192 proto kernel metric 256  expires 2591756sec pref medium
fe80::/64 dev ens192 proto kernel metric 256  pref medium
default via fe80::209:fff:fe09:5 dev ens192 proto ra metric 1024  expires 1556sec pref medium

```
but with systemd-networkd that information is lost:
```
ip -6 r
2001:6b0:5:1219::/64 dev ens33 proto ra metric 1024  pref medium
fe80::/64 dev ens33 proto kernel metric 256  pref medium
default via fe80::209:fff:fe09:5 dev ens33 proto ra metric 1024  mtu 1500 pref medium
```

My quess is that this is not an display issue since we can reproduce the
same behavior as in Launchpad#1800836[0]: Multiple default routes after
a firewall failover. Multiple default routes causes strange connection
errors.

After failover with systemd-networkd:
```
ip -6 r
2001:6b0:5:1219::/64 dev ens33 proto ra metric 1024  pref medium
fe80::/64 dev ens33 proto kernel metric 256  pref medium
default via fe80::209:fff:fe09:5 dev ens33 proto ra metric 1024  mtu 1500 pref medium
default via fe80::724c:a5ff:fe58:42a2 dev ens33 proto ra metric 1024  mtu 1500 pref medium
```

After failover without systemd-networkd:
```
ip -6 r
2001:6b0:5:1568::/64 dev ens192 proto kernel metric 256  expires 2591536sec pref medium
fe80::/64 dev ens192 proto kernel metric 256  pref medium
default via fe80::209:fff:fe09:5 dev ens192 proto ra metric 1024  expires 1336sec pref medium
```

Let me know if there is any other information I can provide to help out.

[0] https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1800836


-- Package-specific info:

-- System Information:
Debian Release: 9.8
  APT prefers stretch-updates-test
  APT policy: (500, 'stretch-updates-test'), (500, 'stretch-security-test'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.9.0-8-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to en_US.UTF-8), LANGUAGE=en_GB:en (charmap=UTF-8) (ignored: LC_ALL set to en_US.UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages systemd depends on:
ii  adduser         3.115
ii  libacl1         2.2.52-3+b1
ii  libapparmor1    2.11.0-3+deb9u2
ii  libaudit1       1:2.6.7-2
ii  libblkid1       2.29.2-1+deb9u1
ii  libc6           2.24-11+deb9u4
ii  libcap2         1:2.25-1
ii  libcryptsetup4  2:1.7.3-4
ii  libgcrypt20     1.7.6-2+deb9u3
ii  libgpg-error0   1.26-2
ii  libidn11        1.33-1
ii  libip4tc0       1.6.0+snapshot20161117-6
ii  libkmod2        23-2
ii  liblz4-1        0.0~r131-2+b1
ii  liblzma5        5.2.2-1.2+b1
ii  libmount1       2.29.2-1+deb9u1
ii  libpam0g        1.1.8-3.6
ii  libseccomp2     2.3.1-2.1+deb9u1
ii  libselinux1     2.6-3+b3
ii  libsystemd0     232-25+deb9u9
ii  mount           2.29.2-1+deb9u1
ii  procps          2:3.3.12-3+deb9u1
ii  util-linux      2.29.2-1+deb9u1

Versions of packages systemd recommends:
ii  dbus            1.10.26-0+deb9u1
ii  libpam-systemd  232-25+deb9u9

Versions of packages systemd suggests:
pn  policykit-1        <none>
pn  systemd-container  <none>
pn  systemd-ui         <none>

Versions of packages systemd is related to:
pn  dracut           <none>
ii  initramfs-tools  0.130
ii  udev             232-25+deb9u9

-- no debconf information