openssh unix dev - May 2008 - "ServerAliveInterval" and "ServerAliveCountMax" doesnt work in openssh50?

Hi OpenSSH team,

We found that openssh5.0 has a bug with the "ServerAliveInterval" and
"ServerAliveCountMax" options.

This function doesnt work at all, which means when the Maxtime reached, the ssh
will not kill the connection and prompt the infomation "Connection
Timedout" as it used to do.

 

We built the openssh5.0p1 code on the a Linux box,  and use the following
configruation, and reproduced on it.

 

Following is the experiment i did on my Ubuntu Linux box. 

 

In Terminal 1:

root at sway-desktop:~# uname -aLinux sway-desktop 2.6.22-14-generic #1 SMP Sun
Oct 14 23:05:12 GMT 2007 i686 GNU/Linux

root at sway-desktop:~# cat /ssh_config   Protocol 2   HashKnownHosts yes  
ServerAliveInterval 5   ServerAliveCountMax 1      #This tells the ssh to close
the connection after 5*1 = 5 seconds  if no data has been received from the
server.

 

root at sway-desktop:~# ps -ef|grep sshdroot      5415     1  0 14:21 ?       
00:00:00 /home/sway/openssh-5.0p1/sshd -p 5555

root at sway-desktop:~# cd /home/sway/openssh-5.0p1root at
sway-desktop:/home/sway/openssh-5.0p1# /ssh -F /ssh_config 192.168.37.131 -p
5555root at 192.168.37.131's password:Last login: Sun May  4 14:22:20 2008
from qianbo-desktop.localroot at sway-desktop:

 

 

In termial 2:

root at sway-desktop:~# ps -ef|grep sshd

root      5415     1  0 14:21 ?        00:00:00 /home/sway/openssh-5.0p1/sshd -p
5555

root      5832  5415  0 14:34 ?        00:00:00 sshd: root at pts/0

root at sway-desktop:~# kill -19 5832                     // 19 means SIGSTOP

 

I waited more than 10 miniutes, the ssh still  hangs there without giving any
information about "Connection timeout"...

 

So i sent a SIGCONT to the sshd server, and the ssh come back alive.

We debugged into the code, found out that everytime the ssh did check the
variable "keep_alive_timeouts" with the ServerAliveCountMax value
after ServerAliveInterval seconds to see if keep_alive_timeouts >
ServerAliveCountMax, if so , ssh will close the connection and give the
"connection timeout" information, else it will increment the
keep_alive_timeouts by 1.

After Checking, ssh will jump into the "packet_read_poll_seqnr(u_int32_t
*seqnr_p)" function, and there it will reset the keep_alive_timeouts
variable to "0" again which actually caused the problem.
Can you check if it is a bug with openssh50's code or not?Thanks very much.
 
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