ssh_handle_key_exchange timeout in some machine

[312 <moan1223@xxxxxxx>]

Dear libssh developer,


I found that only when some client, ssh_handle_key_exchange function will timeout.
For example, 
If I started a ssh sever and connect the server by 'ssh myuser@10.104.196.18 -P 6990'
The server output log like this. Because I know little about libssh internal, so I cannot find why 
this only happened on some ssh clients. And I have no idea on how to further debug this issue.
I need someone to give me some clues. Thanks.
~~~
[zhengjie@localhost examples]$ sudo ./ssh_server_fork --ecdsakey=/etc/ssh/ssh_host_ecdsa_key   -d ~/.ssh/id_dsa -r /etc/ssh/ssh_host_rsa_key -p 6990 -v 10.104.196.18
[2017/10/14 11:48:28.545161, 3] packet_send2:  packet: wrote [len=28,padding=11,comp=16,payload=16]
[2017/10/14 11:48:28.545897, 3] ssh_socket_pollcallback:  Received POLLOUT in connecting state
[2017/10/14 11:48:28.546206, 3] ssh_socket_unbuffered_write:  Enabling POLLOUT for socket
[2017/10/14 11:48:38.556532, 3] ssh_handle_key_exchange:  ssh_handle_key_exchange: current state : 2


[2017/10/14 11:48:38.556640, 3] ssh_socket_unbuffered_write:  Enabling POLLOUT for socket
[2017/10/14 11:48:38.556671, 3] packet_send2:  packet: wrote [len=28,padding=11,comp=16,payload=16]
start to bindbegin to fork[2017/10/14 11:51:06.217847, 3] packet_send2:  packet: wrote [len=28,padding=11,comp=16,payload=16]
[2017/10/14 11:51:06.218884, 3] ssh_socket_pollcallback:  Received POLLOUT in connecting state
[2017/10/14 11:51:06.220702, 3] ssh_socket_unbuffered_write:  Enabling POLLOUT for socket
[2017/10/14 11:51:16.229942, 3] ssh_handle_key_exchange:  ssh_handle_key_exchange: current state : 2


[2017/10/14 11:51:16.230105, 3] ssh_socket_unbuffered_write:  Enabling POLLOUT for socket
[2017/10/14 11:51:16.230134, 3] packet_send2:  packet: wrote [len=28,padding=11,comp=16,payload=16]
start to bindbegin to forkstart to bindbegin to fork[2017/10/14 11:51:31.926009, 3] packet_send2:  packet: wrote [len=28,padding=11,comp=16,payload=16]
[2017/10/14 11:51:31.926863, 3] ssh_socket_pollcallback:  Received POLLOUT in connecting state
[2017/10/14 11:51:31.927066, 3] ssh_socket_unbuffered_write:  Enabling POLLOUT for socket
[2017/10/14 11:51:41.938226, 3] ssh_handle_key_exchange:  ssh_handle_key_exchange: current state : 2


[2017/10/14 11:51:41.938326, 3] ssh_socket_unbuffered_write:  Enabling POLLOUT for socket
[2017/10/14 11:51:41.938352, 3] packet_send2:  packet: wrote [len=28,padding=11,comp=16,payload=16]
start to bindbegin to forkstart to bindbegin to forkstart to bindbegin to fork
^C[zhengjie@localhost examples]$ sudo ./ssh_server_fork --ecdsakey=/etc/ssh/ssh_host_ecdsa_key   -d ~/.ssh/id_dsa -r /etc/ssh/ssh_host_rsa_key -p 6990 -v 10.104.196.18
[2017/10/14 11:55:49.005142, 3] packet_send2:  packet: wrote [len=28,padding=11,comp=16,payload=16]
[2017/10/14 11:55:49.006125, 3] ssh_socket_pollcallback:  Received POLLOUT in connecting state
[2017/10/14 11:55:49.007918, 3] ssh_socket_unbuffered_write:  Enabling POLLOUT for socket
[2017/10/14 11:55:59.017861, 3] ssh_handle_key_exchange:  ssh_handle_key_exchange: current state : 2


[2017/10/14 11:55:59.018245, 3] ssh_socket_unbuffered_write:  Enabling POLLOUT for socket
[2017/10/14 11:55:59.018275, 3] packet_send2:  packet: wrote [len=28,padding=11,comp=16,payload=16]
start to bindbegin to fork


~~~


Best Regards
Zhengjie