netplan link-local address handling isue (missing ipv6 link-local address after interface flush)

[Robert Socha]

After:

>apt-get update & apt-get dist-upgrade & reboot

>lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.1 LTS
Release: 18.04
Codename: bionic

Simple network configuration:

>cat /etc/netplan/network.yaml

network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s3:
      dhcp4: false
      link-local: [ ipv4, ipv6 ]
      critical: true
      addresses: [ 192.168.10.20/24 ]
      gateway4: 192.168.10.254
      nameservers:
                addresses: [ 8.8.8.8 ]

After system reboot

>ip addr
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 08:00:27:d0:16:63 brd ff:ff:ff:ff:ff:ff
    inet 169.254.123.211/16 brd 169.254.255.255 scope link enp0s3
       valid_lft forever preferred_lft forever
    inet 192.168.10.20/24 brd 192.168.10.255 scope global enp0s3
       valid_lft forever preferred_lft forever
    inet6 fe80::a00:27ff:fed0:1663/64 scope link
       valid_lft forever preferred_lft forever

looks ok.

route table:
>ip route
default via 192.168.10.254 dev enp0s3 proto static
default dev enp0s3 proto static scope link metric 2048
169.254.0.0/16 dev enp0s3 proto kernel scope link src 169.254.123.211
192.168.10.0/24 dev enp0s3 proto kernel scope link src 192.168.10.20

Don't know what is this second default route for?

After interface flush:

>ip addr flush dev enp0s3
>netplan apply

2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 08:00:27:d0:16:63 brd ff:ff:ff:ff:ff:ff
    inet 169.254.123.211/16 brd 169.254.255.255 scope link enp0s3
       valid_lft forever preferred_lft forever
    inet 192.168.10.20/24 brd 192.168.10.255 scope global enp0s3
       valid_lft forever preferred_lft forever

missing ipv6 link-local address (and it's takes few seconds to bring up ipv4 link-local address up again).

Works after:
ip link set down enp0s3
netplan apply

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.