Resuming with Ethernet

February 17, 2019 2-minute read

I had this strange issue on Arch where I would not have internet connection after waking from suspend.

I was suspending the desktop through i3, with

bindsym $mod+bracketright exec --no-startup-id $lock_command && systemctl suspend

in ~/.config/i3/config

When the computer resumes from suspend, it would not be able to connect to the Internet for a while.

tcpdump on my home router (also my DNS/DHCP server) would show no DHCP requests.

dig www.google.com on the computer would just not respond for about 40 seconds, and after 40 seconds, the connection would magically revive itself again.

I looked at systemd-networkd and systemd-resolved but logs and configuration of both of those seemed correct.

I took a while to realize that there was some issue with some component of the network interface on the physical layer, because ip link would show NO-CARRIER.

enp2s0: <NO-CARRIER,BROADCAST,MULTICAST,UP>

There was definitely no wiring issues, since all I did was to suspend and resume the computer.

After following some guides on forums, it appears that a possible workaround would be to stop the interface before suspending and then start it on resume, so here are the systemd service files to make that work:

$ cat /etc/systemd/system/root-suspend.service
[Unit]
Description=Stop network interface before sleep
Before=sleep.target

[Service]
User=root
Type=oneshot
ExecStart=/usr/bin/ip link set enp0s31f6 down
TimeoutSec=0
StandardOutput=syslog

[Install]
WantedBy=sleep.target

$ cat /etc/systemd/system/root-resume.service
[Unit]
Description=Stop network interface before sleep
After=suspend.target

[Service]
User=root
Type=oneshot
ExecStart=/usr/bin/ip link set enp0s31f6 up
TimeoutSec=0
StandardOutput=syslog

[Install]
WantedBy=suspend.target

And we need to enable those two

sudo systemctl enable root-suspend.service
sudo systemctl enable root-resume.service