Comment 0 for bug 1862232

1) ubuntu version
# lsb_release -rd
Description: Ubuntu 18.04.3 LTS
Release: 18.04

2) package version
# apt-cache policy systemd
systemd:
  Installed: 237-3ubuntu10.31
  Candidate: 237-3ubuntu10.31
  Version table:
 *** 237-3ubuntu10.31 500
        500 http://mirrors.digitalocean.com/ubuntu bionic-updates/main amd64 Packag
es
        100 /var/lib/dpkg/status
     237-3ubuntu10.29 500
        500 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
     237-3ubuntu10 500
        500 http://mirrors.digitalocean.com/ubuntu bionic/main amd64 Packages

3) I expect the network to come online correctly regardless of how long the hostname is. This is what happens with both 14.0 and 19.0 (I tested the same behavior with both of them).

4) the external network interface fails to be configured and is stuck in a (pending) state as reported by networkctl status -a

setting the hostname:

# hostnamectl set-hostname asdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdf

after rebooting the machine, it no longer has network access.

# journalctl
Feb 06 19:29:41 asdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdf systemd[1]: Starting Wait for Network to be Configured...
Feb 06 19:29:41 asdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdf systemd-networkd[605]: eth0: Link state is up-to-date
Feb 06 19:29:41 asdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdf systemd-networkd[605]: eth0: found matching network '/run/systemd/network/10-netplan-eth0.network'
Feb 06 19:29:41 asdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdf systemd-networkd[605]: sd-netlink: callback failed: Invalid argument
Feb 06 19:29:41 asdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdf systemd-networkd[605]: lo: Link state is up-to-date

# networkctl status -a:
● 1: lo
       Link File: /lib/systemd/network/99-default.link
    Network File: n/a
            Type: loopback
           State: carrier (unmanaged)
         Address: 127.0.0.1
                  ::1

● 2: eth0
       Link File: /run/systemd/network/10-netplan-eth0.link
    Network File: /run/systemd/network/10-netplan-eth0.network
            Type: ether
           State: off (pending)
            Path: pci-0000:00:03.0
          Driver: virtio_net
          Vendor: Red Hat, Inc.
           Model: Virtio network device
      HW Address: ae:4d:91:1c:e8:86
             DNS: 67.207.67.3
                  67.207.67.2

and to bring up the network correctly, set the hostname to something shorter

# hostnamectl set-hostname asdf
# systemctl restart systemd-networkd
# networkctl status -a
● 1: lo
       Link File: /lib/systemd/network/99-default.link
    Network File: n/a
            Type: loopback
           State: carrier (unmanaged)
         Address: 127.0.0.1
                  ::1

● 2: eth0
       Link File: /run/systemd/network/10-netplan-eth0.link
    Network File: /run/systemd/network/10-netplan-eth0.network
            Type: ether
           State: routable (configured)
            Path: pci-0000:00:03.0
          Driver: virtio_net
          Vendor: Red Hat, Inc.
           Model: Virtio network device
      HW Address: ae:4d:91:1c:e8:86
         Address: 10.17.0.5
                  157.245.210.250
                  fe80::ac4d:91ff:fe1c:e886
         Gateway: 157.245.208.1 (ICANN, IANA Department)
             DNS: 67.207.67.3
                  67.207.67.2