[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: ssh_select possible improvement?

Hi Andreas,

I am actually using channel_poll() in other place, but not in this case.
The reason is that ssh_select() is the only function that can put a
channel and a normal system file descriptor together in one select()
call. This way the function will return when either the server side or
the client side has data, which cannot be done with channel_poll().

I did some initial analysis on v0-4 branch, and I can confirm that 0.4.4
is the last release that works fine with ssh_select(); 0.4.5 and later
(including current latest v0-4 commit) all has this problem. I will try
to figure it out which commit exactly break the behavior.

I know that you are moving fast towards 0.5 and avoid changes in 0.4,
but unfortunately version 0.4.5 got into Debian Squeeze, and Squeeze was
already freezed, so no way to upgrade to 0.5 for it...

Anyway, if no one cares about ssh_select(), I guess I am the only one
left to fix it... :)


On Sun, 2010-09-19 at 19:15 +0200, Andreas Schneider wrote:
> On Sunday, September 19, 2010 18:38:20 you wrote:
> > Hi,
> Hi Vic,
> > Recently I just noticed that when I use libssh to establish a ssh shell
> > connection to the server, key strokes have a latency. I checked the code
> > and was able to confirm that this is ssh_select() problem.
> well the ssh_select functions is something we ignored for a long time and we 
> still try to avoid it. It has more bugs than what you describe. I suggest to 
> use channel_poll() instead.
> > The scenario is that: I have a local file descriptor from a terminal pty
> > (which receives key strokes) and a ssh channel (which receives data from
> > server). This is a very typical ssh shell session. So I pass the fd and
> > the channel to ssh_select() with 1 second timeout. However, if I press a
> > key, ssh_select will not return immediately, but will only return until
> > the timeout is passed. If I set timeout to 10 seconds, I will get a huge
> > latency.
> > 
> > I am using 0.4.5 (debian squeeze) version, but if you think 0.4.6 could
> > make any difference, I can try. Please give me some hint before I
> > actually dig into it. Thanks.
> Nobody touched this code since a long time. I think it needs to be rewritten 
> completely cause it misses a lot of things.
> Could you use channel_poll()?
> 	-- andreas

Re: ssh_select possible improvement?Vic Lee <llyzs@xxxxxxx>
ssh_select possible improvement?Vic Lee <llyzs@xxxxxxx>
Re: ssh_select possible improvement?Andreas Schneider <asn@xxxxxxxxxxxx>
Archive administrator: postmaster@lists.cynapses.org