The systemd bug #3752 was fixed by commit 444b01704648c2f1292531f17c3b8c95bf1a9896 (networkd: configure link even if no routes have been received by dhcp (#6886)] which should be included in Ubuntu 18.04 systemd 237:
$ git tag --contains 444b01704648c2f1292531f17c3b8c95bf1a9896 v236 v237 v238 v239 -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to systemd in Ubuntu. https://bugs.launchpad.net/bugs/1804478 Title: netplan dhcp interface with no default route causes systemd-networkd- wait-online to hang Status in systemd: New Status in systemd package in Ubuntu: Confirmed Bug description: root cause in systemd bug: https://github.com/systemd/systemd/issues/3752 Environment: Ubuntu 18.04 LTS amd64 systemd package version 237-3ubuntu10.9 How to trigger: 1. add netplan interface with dhcpv4 client enabled: enp0s8: addresses: [] dhcp4: true 2. configure dhcp server to NOT give a default route, or any route for that matter 3. reboot 4. systemd-networkd-wait-online will block until dhcp renew is triggered root@sensor1:~# /lib/systemd/systemd-networkd-wait-online --timeout=3 Event loop failed: Connection timed out root@sensor1:~# /lib/systemd/systemd-networkd-wait-online --timeout=3 --ignore=enp0s8 managing: enp0s3 ignoring: lo ignoring: enp0s8 How to fix: Backport upstream changes from systemd (see related systemd ticket). To manage notifications about this bug go to: https://bugs.launchpad.net/systemd/+bug/1804478/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
