Bug#905503: networkd doesn't like fritzbox' IPv6 announcement, interface degraded

[Marc Haber]

fixed 905503 237-3~bpo9+1
fixed 905503 239-7

On Sun, Aug 05, 2018 at 03:49:37PM +0200, Marc Haber wrote:
> In the next days, I hope I will be able to reproduce this in a simpler
> test machine and then check whether the issue is still present in buster
> or sid. Sadly, it is becoming increasingly painful to run
> systemd-networkd in stretch.

I was able to reproduce this issue in stretch on an amd64 VM with the
following networkd configuration:


[Match]
Name=e*

[Network]
DHCP=Yes

The Fritzbox assigns and IPv4 address and announces an IPv6 prefix. WIth
the systemd in stretch, networkctl hangs at "degraded/failed", while the
systemd 237-3 from stretch-backports and systemd 239-7 works, resulting
in the following network configuration:

2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 52:54:00:a8:3e:97 brd ff:ff:ff:ff:ff:ff
    inet 192.168.252.99/24 brd 192.168.252.255 scope global dynamic ens3
       valid_lft 861566sec preferred_lft 861566sec
    inet6 2001:db8:3022:4100:5054:ff:fea8:3e97/64 scope global mngtmpaddr noprefixroute dynamic 
       valid_lft 6880sec preferred_lft 3280sec
    inet6 fe80::5054:ff:fea8:3e97/64 scope link 
       valid_lft forever preferred_lft forever


default via 192.168.252.254 dev ens3 proto dhcp src 192.168.252.99 metric 1024 
192.168.252.0/24 dev ens3 proto kernel scope link src 192.168.252.99 
192.168.252.254 dev ens3 proto dhcp scope link src 192.168.252.99 metric 1024 

2001:db8:3022:4100::/64 dev ens3 proto ra metric 1024  pref medium
2001:db8:3022:4100::/56 via fe80::cece:1eff:x:y dev ens3 proto ra metric 1024  pref medium
fe80::/64 dev ens3 proto kernel metric 256  pref medium
default via fe80::cece:1eff:x:y dev ens3 proto ra metric 1024  mtu 1492 pref medium

The Fritzbox is an extremely common DSL router in middle europe, and
dual-stack networking is becoming increasingly common. Deutsche Telekom
and 1&1, two of Germany's largest ISPs for consumer DSL, both provide
dual-stacked Internet. This issue should be addressed in stretch.

I'll keep the test VM around for a few months, so that I can test
tentative fixes.

Greetings
Marc

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