Intermittent DHCP startup failure during boot due to potential race condition in interface renaming

[Drew Hastings]

The server fails to start its network with DHCP seemingly randomly. It can take a few reboots to bring up the network. This causes issues where automated updates that trigger a reboot cause the server to go offline.

I've attached syslog examples of both success and failure.

My assumption is that the cause of this bug is a race condition where systemd is not waiting on the interface renaming.

Notably, when it boots properly, it says:

"Interface is under renaming, pending initialization."

That message is not logged when it fails.

The server uses cloud-init, and the cloud image provided by Ubuntu.

Another possible explanation is the netplan configuration at /etc/netplan/50-cloud-init.yaml is:

network:
    version: 2
    ethernets:
        eth0:
            dhcp4: true
            match:
                macaddress: 92:00:00:00:43:6a
            set-name: eth0

Maybe set-name is redundant here, but it's the default configuration generated by cloud-init.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: systemd 245.4-4ubuntu3.21
ProcVersionSignature: Ubuntu 5.4.0-164.181-generic 5.4.248
Uname: Linux 5.4.0-164-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.27
Architecture: amd64
CasperMD5CheckResult: skip
Date: Wed Oct 18 16:22:57 2023
Lsusb: Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Lsusb-t: /: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=uhci_hcd/2p, 12M
MachineType: Slicie.com Slicie Cloud Server
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.4.0-164-generic root=UUID=f849f569-82f8-4fc0-9ac6-d4f7f7ef9609 ro console=tty1 console=ttyS0
SourcePackage: systemd
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 04/01/2014
dmi.bios.vendor: SeaBIOS
dmi.bios.version: 1.13.0-1ubuntu1.1
dmi.chassis.type: 1
dmi.chassis.vendor: QEMU
dmi.chassis.version: pc-i440fx-2.1
dmi.modalias: dmi:bvnSeaBIOS:bvr1.13.0-1ubuntu1.1:bd04/01/2014:svnSlicie.com:pnSlicieCloudServer:pvr1.0.0:cvnQEMU:ct1:cvrpc-i440fx-2.1:
dmi.product.name: Slicie Cloud Server
dmi.product.version: 1.0.0
dmi.sys.vendor: Slicie.com