Error log when trying to find the interface comes without the interface

[manuelbuil]

Environmental Info:
K3s Version:

Node(s) CPU architecture, OS, and Version:

Cluster Configuration:

Describe the bug:

If k3s has problems finding the interface, it fails without specifying what interface it is using:

INFO[0009] Waiting for control-plane node agent startup 
INFO[0010] Waiting to retrieve agent configuration; server is not ready: unable to find interface: route ip+net: no such network interface 

or

WARN[0000] unable to get global unicast ip from interface name: route ip+net: no such network interface 
FATA[0000] invalid node-ip: invalid ip format ''        
FATA[0000] child died: command [k3s server --rootless] exited: exit status 1 
FATA[0000] child exited: exit status 1

This makes debugging difficult

Steps To Reproduce:

• Installed K3s:

Expected behavior:

Logs show the interface

Actual behavior:

Logs don't show the interface

Additional context / logs:

[fmoral2]

Validated on Version:

-$  k3s version v1.28.2+k3s-2a9e8e68 (2a9e8e68)

Environment Details

Infrastructure
Cloud EC2 instance

Node(s) CPU architecture, OS, and Version:
Ubuntu 22.04
Windows 2019

Cluster Configuration:
1 node servers

Steps to validate the fix

1. Install k3s passing the flag for flannel interface with a mock one and another with a non-existing one
2. Check logs of failure
3. Need to find the interface name in the logs

Issue reprodution:

There is no interface named test on the node.

-$ curl https://get.k3s.io | INSTALL_K3S_COMMIT=xxxxxxx  sh -s - server --cluster-init --flannel-iface=test

Sep 27   sh[17555]: Failed to get unit file state for nm-cloud-setup.service: No such file or directory
Sep 27  k3s[17558]: time="2023-09-27T15:37:58Z" level=warning msg="unable to get global unicast ip from interface name: route ip+net: no such network interface"
Sep 27 k3s[17558]: time="2023-09-27T15:37:58Z" level=fatal msg="invalid node-ip: invalid ip format ''"

Validation Results:

There is no interface named test on the node.

-$ curl https://get.k3s.io | INSTALL_K3S_COMMIT=xxxxxxxx  sh -s - server --cluster-init --flannel-iface=test

Sep 27  k3s[18095]: time="2023-09-27T15:39:47Z" level=fatal msg="interface test does not have a correct global unicast ip: route ip+net: no such network interface"
Sep 27 15:39:47 ip-172-31-26-165 systemd[1]: k3s.service: Main process exited, code=exited, status=1/FAILURE




-$ create test interface mock
sudo ip link add name dummy0 type dummy
sudo ip link set dev dummy0 up

-$ curl https://get.k3s.io | INSTALL_K3S_COMMIT=56abe7055fca997daf2bd88e67b1ddcb148c41b9  sh -s - server --cluster-init --flannel-iface=dummy0




Sep 27  k3s[10569]: time="2023-09-27T15:21:07Z" level=fatal msg="interface dummy0 does not have a correct global unicast ip: can't find ip for interface dummy0"