My client, OpenBSD is connected to a VPN, and the server, OpenBSD is also connected to a VPN with the SSH port being forwarded.

I can complete any number of tasks just fine, but if, for example, I tar -xzvf lots-of-files.tar.gz it will display a few and then freeze, requiring me to close my xterm and reconnect and tmux a back into my session. If I try to launch very 'heavy' tui apps like htop all I get is a black screen with a stuck cursor.

Of note, I can still SEND commands while in this state. I can change tmux panes, or I can ctrl+c htop and then reconnect and reattach and all is well.

This VPS is low spec, with only 512mb, but currently it is not doing anything. And doesnt pull more than 10% CPU utilization or more than 100mb of ram utilization.


My wireguard interface and my vio0 interface had mismatched MTU values. I set them all to the same value of 1420 with doas ifconfig $interface mtu 1420 up and that fixed it. Able to run htop and vim and tmux and screen and all that jazz as much as I want now without issue.

  • You might have an issue like a firewall dropping ICMP packets that triggers PMTUD blackhole. Not requiring PMTUD by lowering MTU is an alternate way to solve this.
    – A.B
    Aug 1 at 14:02

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