Remmina SPICE SSH Tunnel Bug and a Workaround

I seem to come across the strangest of bugs.

Bug

Remmina SPICE over an SSH tunnel fails to handle keyboard-mouse interactions.

I have set up several virtual machines with desktop operating systems using Libvirt on my primary computer. I can access these virtual machines over the network using Libvirt on my laptop. However, I wanted to use Remmina as the SPICE client since it is more configurable.

All worked well until I tried to access a Manjaro Gnome virtual machine with the SSH tunnel feature on Remmina.

Strangely, the same setup works fine with a Windows virtual machine on the same host.

It also works fine if I open a port on the virtual machine host and access the Manjaro Gnome virtual machine without tunnelling over SSH. However, as soon as I tried to use Remmina’s SSH tunnel feature, I could see the desktop in the virtual machine but not interact with it.

Workaround

Fortunately, Remmina allows you to configure connection profiles to run commands before making a connection and after disconnecting it. It is possible to setup and teardown an SSH tunnel using these options.

I turned off Remmina’s SSH tunnel feature for that problematic profile, and based on the clue I found on Remmina’s wiki, I came up with the following commands.

Before:

/bin/sh -c 'ssh -o ControlMaster=auto -o ControlPath=$HOME/.ssh/remmina-tunnel-%r@%h:%p -4fnN -L 17890:localhost:17890 carrot.local'

After:

/bin/sh -c 'ssh -o ControlMaster=auto -o ControlPath=$HOME/.ssh/remmina-tunnel-%r@%h:%p -4fnN -O exit carrot.local'

In these commands, 17890 is the SPICE port number on the virtual machine and carrot.local is its hostname.

With this workaround, I no longer face the issue where Remmina SPICE over an SSH tunnel fails to handle keyboard-mouse interactions.

Although the workaround solves the problem I was facing, it is anticlimactic not knowing what causes this issue in the first place. Let me know please if you have any ideas.