I am trying to get X11 forwarding working and it appears that the right support 
is in libssh, but the docs are not clear as to how to make it work.

Below is the code and the resulting libssh log. Xclock does execute but I do 
not see the UI display on the remote computer. There is a note in the docs 
about seeting the DISPLAY variable, but I'm not sure where to set it. I tried 
using ssh_channel_request_env but that does not work. I'm not even sure if this 
is the issue. Any help would be appreciated.

If I start an SSH session using "ssh -X", set the DISPLAY variable in the shell 
and then start xclock it works as expected. This is what I want to accomplish 
with libssh.


m_channel = ssh_channel_new(m_session);
ssh_channel_open_session(m_channel);
ssh_channel_request_x11(m_channel, 1, NULL, NULL, 0);
ssh_channel_request_exec(m_channel, "xclock");
ssh_channel x11_channel = ssh_channel_accept_x11(m_channel, 3000);


[2017/02/11 09:23:47.520517, 2] ssh_connect:  libssh 0.7.2 (c) 2003-2014 Aris 
Adamantiadis, Andreas Schneider, and libssh contributors. Distributed under the 
LGPL, please refer to COPYING file for information about your rights, using 
threading threads_noop
[2017/02/11 09:23:47.528022, 2] ssh_socket_connect:  Nonblocking connection 
socket: 472
[2017/02/11 09:23:47.528022, 2] ssh_connect:  Socket connecting, now waiting 
for the callbacks to work
[2017/02/11 09:23:47.528522, 1] socket_callback_connected:  Socket connection 
callback: 1 (0)
[2017/02/11 09:23:47.535528, 1] ssh_client_connection_callback:  SSH server 
banner: SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.1
[2017/02/11 09:23:47.535528, 1] ssh_analyze_banner:  Analyzing banner: 
SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.1
[2017/02/11 09:23:47.535528, 1] ssh_analyze_banner:  We are talking to an 
OpenSSH client version: 7.2 (70200)
[2017/02/11 09:23:47.638095, 2] ssh_packet_dh_reply:  Received SSH_KEXDH_REPLY
[2017/02/11 09:23:47.641598, 2] ssh_client_curve25519_reply:  SSH_MSG_NEWKEYS 
sent
[2017/02/11 09:23:47.641598, 2] ssh_packet_newkeys:  Received SSH_MSG_NEWKEYS
[2017/02/11 09:23:47.643599, 2] ssh_packet_newkeys:  Signature verified and 
valid
[2017/02/11 09:23:47.691131, 2] channel_open:  Creating a channel 43 with 64000 
window and 32768 max packet
[2017/02/11 09:23:47.788195, 2] ssh_packet_global_request:  Received 
SSH_MSG_GLOBAL_REQUEST packet
[2017/02/11 09:23:47.788696, 2] ssh_packet_global_request:  UNKNOWN 
SSH_MSG_GLOBAL_REQUEST hostkeys...@openssh.com 0
[2017/02/11 09:23:47.788696, 1] ssh_packet_process:  Couldn't do anything with 
packet type 80
[2017/02/11 09:23:47.788696, 2] ssh_packet_channel_open_conf:  Received a 
CHANNEL_OPEN_CONFIRMATION for channel 43:0
[2017/02/11 09:23:47.788696, 2] ssh_packet_channel_open_conf:  Remote window : 
0, maxpacket : 32768
[2017/02/11 09:23:47.789196, 2] channel_request:  Channel request x11-req 
success
[2017/02/11 09:23:47.789696, 2] channel_rcv_change_window:  Adding 2097152 
bytes to channel (43:0) (from 0 bytes)
[2017/02/11 09:23:47.789696, 2] channel_request:  Channel request exec success


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