Bugs item #2141548, was opened at 2008-10-02 04:11
Message generated for change (Settings changed) made by bagder
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=703942&aid=2141548&group_id=125852
Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: None
Group: None
>Status: Closed
>Resolution: Wont Fix
Priority: 3
Private: No
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Daniel Stenberg (bagder)
Summary: libssh2_poll detects data on channel, but no data available
Initial Comment:
I've got a small home-brewed SSH client and I've encountered a problem in the library with libssh2_poll() when checking for data on a channel.
Simply put, here's the setup. I have a thread that polls for data on a channel every few usec. When the libssh2_poll function detects data available to be read on the channel I'm interested in, I immediately try to read from that channel. Trouble is, if its a small piece of data that I'm expecting, the read fails while subsequent polls still think that there is data there.
So In my SSH client with a pty, I do something like hit the "z" key. This should send a single character over the lines to the remote SSH server plus any SSH/TCP/IP.... overhead. Now the remote SSH server will echo back the key plus any additional terminal formatting.
As soon as I hit my "z" key, libssh2_poll alerts me that data is available to be read from the channel, but attempting to read from the channel doesn't read any data...polling keeps saying theres data, I read nothing... repeat a lot of times...
If I keep hitting keystrokes, eventually the channel read picks up the data. So it seems like libssh2 holds onto small packets for some reason.
----------------------------------------------------------------------
Comment By: Daniel Stenberg (bagder)
Date: 2009-04-05 20:18
Message:
libssh2_poll() seems to be fundamentally flawed.
I suggest we just call it deprecated and tell people to use poll()
instead!
Can you (or anyone else) provide a use case where the normal poll() or
select() isn't good enough or better?
----------------------------------------------------------------------
Comment By: Paul Thomas (thomaspu)
Date: 2008-10-02 04:22
Message:
I think the problem stems around line 1525 of channel.c. Looks like if we
call the channel_read function, we expect to read data from a call to
libssh2_packet_read() and if we don't read anything from that function
call, we don;t read anything period. However, the code doesn't check the
packet list to see if there's packets in it waiting to be read.
----------------------------------------------------------------------
Comment By: Paul Thomas (thomaspu)
Date: 2008-10-02 04:12
Message:
This one was written up by me, I just forgot to log in again!
----------------------------------------------------------------------
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=703942&aid=2141548&group_id=125852
------------------------------------------------------------------------------
This SF.net email is sponsored by:
High Quality Requirements in a Collaborative Environment.
Download a free trial of Rational Requirements Composer Now!
http://p.sf.net/sfu/www-ibm-com
_______________________________________________
libssh2-devel mailing list
libssh2-devel_at_lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/libssh2-devel
Received on 2009-04-15