X11 forwarding request failed on channel 0

Question

$ ssh -Xvv remote_host outputs

....
debug1: channel 0: new [client-session]
debug2: channel 0: send open
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: exec
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: Remote: /home/user/.ssh/authorized_keys:8: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
debug1: Remote: /home/user/.ssh/authorized_keys:8: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
debug2: channel_input_open_confirmation: channel 0: callback start
debug2: x11_get_proto: /usr/bin/xauth  list unix:16.0 2>/dev/null
debug1: Requesting X11 forwarding with authentication spoofing.
debug2: channel 0: request x11-req confirm 1
debug2: fd 3 setting TCP_NODELAY
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 1
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8
debug2: channel 0: request env confirm 0
debug2: channel 0: request shell confirm 1
debug2: channel_input_open_confirmation: channel 0: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel_input_status_confirm: type 100 id 0
X11 forwarding request failed on channel 0
debug2: channel_input_status_confirm: type 99 id 0
debug2: PTY allocation request accepted on channel 0
debug2: channel 0: rcvd adjust 2097152
debug2: channel_input_status_confirm: type 99 id 0
debug2: shell request accepted on channel 0

Tried also -Y. Doesn't work.

I confirmed that X11 forwarding is allowed on the server side. $grep X11 /etc/ssh/sshd_config gave

X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes

I have searched other posts related to X11 forwarding request failed on channel 0 and found no help info.

Answer 1

I had a similar issue on Devuan (fork of Debian without systemd).

I found a solution on an Arch Wiki.

Edit /etc/ssh/sshd_config (on the server side) and set:

AddressFamily inet

The default is AddressFamily any but this does not seem to supply an inet (ipv4) socket.

On my system I noted in /var/log/auth.log:

sshd[9184]: error: Failed to allocate internet-domain X11 display socket.

After the above change to sshd_config and service ssh restart the X11 forwarding worked for me.