Re: X11 Forwarding example

[lucky62 <lucky62@xxxxxxxxxx>]

Program was executed with highest log level and this is my observation.

*Seems that after succesful EXEC polling-in is blocked, and incomming 
request SSH_MSG_CHANNEL_OPEN (90) is waiting somewhere in buffer...*

When waiting loop is out, then program calls ssh_channel_free 
(internally ssh_channel_close).
Messages SSH_MSG_CHANNEL_EOF (96) and SSH_MSG_CHANNEL_CLOSE (97) are 
sent, polling is enabled
and simultaneously the incoming message SSH_MSG_CHANNEL_OPEN (90) is 
received.

[2020/11/18 15:13:42.539242, 3] ssh_packet_need_rekey:  packet: [data_rekey_needed=0, out_blocks=44, in_blocks=67
[2020/11/18 15:13:42.539250, 3] ssh_packet_need_rekey:  packet: [data_rekey_needed=0, out_blocks=44, in_blocks=67
[2020/11/18 15:13:42.539259, 2] channel_request:  Channel request*exec success*
*polling is blocked?...****after 5s timeout ssh_channel_free is sending EOF and CLOSE *
[2020/11/18 15:13:53.568543, 3] ssh_packet_need_rekey:  packet: [data_rekey_needed=0, out_blocks=44, in_blocks=67
[2020/11/18 15:13:53.568656, 3] ssh_socket_unbuffered_write:  Enabling POLLOUT for socket

[2020/11/18 15:13:53.568687, 3] packet_send2:  packet: wrote [type=96, len=16, padding_size=10, comp=5, payload=5]
[2020/11/18 15:13:53.568702, 3] ssh_channel_send_eof:*Sent a EOF*  on client channel (43:0)
[2020/11/18 15:13:53.568714, 3] ssh_packet_need_rekey:  packet: [data_rekey_needed=0, out_blocks=44, in_blocks=67

[2020/11/18 15:13:53.568733, 3] packet_send2:  packet: wrote [type=97, len=16, padding_size=10, comp=5, payload=5]
[2020/11/18 15:13:53.568751, 3] ssh_channel_close:*Sent a close*  on client channel (43:0)
[2020/11/18 15:13:53.568769, 4] ssh_socket_pollcallback:  Poll callback on socket 3 (*POLLIN POLLOUT *), out buffer 36

[2020/11/18 15:13:53.568800, 3] ssh_packet_socket_callback:  packet:*read type 90*  [len=48,padding=10,comp=37,payload=37]
[2020/11/18 15:13:53.568816, 3] ssh_packet_process:  Dispatching handler for packet type 90
[2020/11/18 15:13:53.568857, 3] ssh_packet_channel_open:  Clients wants to open a x11 channel
x11callback:
   OrigAddr: |127.0.0.1|
   OrigPort: |55312|
[2020/11/18 15:13:53.568915, 4] ssh_message_channel_request_open_reply_default:  Refusing a channel

So need I call some function to enable polling?
Or is this a library bug?...

Jan


On 18. 11. 2020 16:35, lucky62 wrote:
> really I don't understand... "stdout from remote" ?
>
> I think that X app connected to display (which is set by server when 
> x11 forwarding is requested) will send the output through the x11 channel.
> But this channel still not exists.  It will be created when SSH server 
> will send the x11 channel request.
> In my case this request is detected after 5s delay is out...
>
> Jan
>
>
> On 18. 11. 2020 15:36, Alexander Grotewohl wrote:
> > I believe after you call the exec, and in your code you just wait, 
> > the program should actually be reading stdout from the remote. In 
> > that case, your code would read from there until the x11 
> > programterminated and subsequently the read would fail.
> >
> > Alex
> >
> > --
> > Alexander Grotewohl
> > https://dcclost.com
> >
> > ------------------------------------------------------------------------
> > *From:* lucky62 <lucky62@xxxxxxxxxx>
> > *Sent:* Wednesday, November 18, 2020 8:33:10 AM
> > *To:* libssh@xxxxxxxxxx <libssh@xxxxxxxxxx>
> > *Subject:* Re: X11 Forwarding example
> > Hi,
> >
> > I am trying to create x11 example by myself.
> >
> > I have already created example skeleton with these steps:
> >
> >   *     create the session
> >   *     set callbacks
> >   *     set options (host,...)
> >   *     connect to host
> >   *     authenticate
> >   *     create and open channel
> >   *     send x11-req
> >   *     send exec request (start X app on server)
> >       o here the program is just sleeping for 5 seconds to wait for
> >         server response... (in while loop 5000 x 1ms)
> >
> >
> > This is my x11 callback, which is currently doing nothing - just to 
> > see that is called:
> > static ssh_channel x11_callback( ssh_session session, const char * originator_address, int originator_port, void *userdata ) {
> >     fprintf( stderr, "x11callback:\n" );
> >     fprintf( stderr, "   OrigAddr: |%s|\n", originator_address );
> >     fprintf( stderr, "   OrigPort: |%d|\n", originator_port );
> >     return NULL;
> > }
> >
> > But when exec request is sent to the server and success confirmed 
> > then nothing happens immediately.
> > Program is waiting 5 seconds and x11 callback is called then. Why?
> > [2020/11/18 13:33:12.599888, 3] channel_request:  Sent a SSH_MSG_CHANNEL_REQUEST exec
> > [2020/11/18 13:33:12.602802, 3] ssh_packet_socket_callback:  packet: read type 93 [len=16,padding=6,comp=9,payload=9]
> > [2020/11/18 13:33:12.602862, 3] ssh_packet_process:  Dispatching handler for packet type 93
> > [2020/11/18 13:33:12.602897, 2] channel_rcv_change_window:  Adding 2097152 bytes to channel (43:0) (from 0 bytes)
> > [2020/11/18 13:33:12.602921, 3] ssh_packet_socket_callback:  Processing 36 bytes left in socket buffer
> > [2020/11/18 13:33:12.602944, 3] ssh_packet_socket_callback:  packet: read type 99 [len=16,padding=10,comp=5,payload=5]
> > [2020/11/18 13:33:12.602964, 3] ssh_packet_process:  Dispatching handler for packet type 99
> > [2020/11/18 13:33:12.602985, 3] ssh_packet_channel_success:  Received SSH_CHANNEL_SUCCESS on channel (43:0)
> > [2020/11/18 13:33:12.603006, 3] ssh_packet_need_rekey:  packet: [data_rekey_needed=0, out_blocks=44, in_blocks=67
> > [2020/11/18 13:33:12.603026, 3] ssh_packet_need_rekey:  packet: [data_rekey_needed=0, out_blocks=44, in_blocks=67
> > [2020/11/18 13:33:*12*.603049, 2]*channel_request: Channel request exec success 5 seconds delay... *[2020/11/18 13:33:*17*.603149, 3] ssh_packet_need_rekey:  packet: [data_rekey_needed=0, out_blocks=44, in_blocks=67
> > [2020/11/18 13:33:17.603358, 3] ssh_socket_unbuffered_write:  Enabling POLLOUT for socket
> > [2020/11/18 13:33:17.603381, 3] packet_send2:  packet: wrote [type=96, len=16, padding_size=10, comp=5, payload=5]
> > [2020/11/18 13:33:17.603452, 3] ssh_channel_send_eof:  Sent a EOF on client channel (43:0)
> > [2020/11/18 13:33:17.603486, 3] ssh_packet_need_rekey:  packet: [data_rekey_needed=0, out_blocks=44, in_blocks=67
> > [2020/11/18 13:33:17.603521, 3] packet_send2:  packet: wrote [type=97, len=16, padding_size=10, comp=5, payload=5]
> > [2020/11/18 13:33:17.603543, 3] ssh_channel_close:  Sent a close on client channel (43:0)
> > [2020/11/18 13:33:17.603578, 3] ssh_packet_socket_callback:  packet: read type 90 [len=48,padding=10,comp=37,payload=37]
> > [2020/11/18 13:33:17.603601, 3] ssh_packet_process:  Dispatching handler for packet type 90
> > [2020/11/18 13:33:*17*.603624, 3]*ssh_packet_channel_open: Clients wants to open a x11 channel*
> > x11callback:
> >     OrigAddr: |127.0.0.1|
> >     OrigPort: |55280|
> > [2020/11/18 13:33:17.603672, 3] ssh_packet_need_rekey:  packet: [data_rekey_needed=0, out_blocks=45, in_blocks=70
> > [2020/11/18 13:33:17.603703, 3] packet_send2:  packet: wrote [type=92, len=32, padding_size=14, comp=17, payload=17]
> > [2020/11/18 13:33:17.603733, 3] ssh_packet_need_rekey:  packet: [data_rekey_needed=0, out_blocks=45, in_blocks=69
> > [2020/11/18 13:33:17.603772, 3] ssh_socket_unbuffered_write:  Enabling POLLOUT for socket
> > [2020/11/18 13:33:17.603796, 3] ssh_packet_need_rekey:  packet: [data_rekey_needed=0, out_blocks=46, in_blocks=70
> > [2020/11/18 13:33:17.603831, 3] packet_send2:  packet: wrote [type=1, len=32, padding_size=11, comp=20, payload=20]
> >
> > *How to correctly wait for server response?*
> > Any help is appreciated.
> >
> > thx in advance
> > Jan
> >
> >
> > P.S.: My monolithic program is attached. Many things are hardcoded 
> > (auth, host, ..)
> >        Compiled on my Linux Mint 20 by command: /gcc -o my_x11_client 
> > my_x11_client.c -lssh/