Bugs item #2785173, was opened at 2009-05-01 19:42
Message generated for change (Settings changed) made by bagder
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Category: API
Group: None
>Status: Closed
Resolution: Fixed
Priority: 5
Private: No
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Daniel Stenberg (bagder)
Summary: channel_read returns LIBSSH2_ERROR_EAGAIN, no data on socket
Initial Comment:
While using libssh2_channel_read_ex(), I found that when the last of the data
has been read, the libssh2_channel_read_ex() may return LIBSSH2_ERROR_EAGAIN,
but a poll() on the socket times out (eventually). I diagnosed this as packets
(channel eof and channel close) in memory, but not processed, so
libssh2_channel_eof() remains false. Root caused as a "single shot" call to
_libssh2_transport_read() in channel_read(). No call to
_libssh2_transport_read() should be made unless the caller continues to call
the function until it returns a non-positive value (0 or negative). This will
prevent it from leaving unprocessed buffers in memory.
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Comment By: Daniel Stenberg (bagder)
Date: 2009-05-01 21:07
Message:
Ok, now I understand you perfectly and I also see that you're entirely
correct. This actually means we can simplify the channel_read() function
since we can do the transport_read() loop the same way independent of the
state at the top of the function.
See the commit I just did. Please verify this and tell me if it fixes your
problem!
Thanks a lot. If you tell me your real name, I'll give you proper credit
in the changelog etc.
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Comment By: Nobody/Anonymous (nobody)
Date: 2009-05-01 20:49
Message:
The transport function did not return EAGAIN. It processed a full packet
(fullpacket()), and returned the result (the packet type). Because
_libssh2_transport_read() returns after processing just one packet,
additional packets may be waiting (in memory) to be processed by future
calls to _libssh2_transport_read(). To resolve this I changed
channel_read() in channel.c (around line 1777):
Was:
rc = _libssh2_transport_read(session);
Now:
rc = 1;
while (rc > 0)
rc = _libssh2_transport_read(session);
----------------------------------------------------------------------
Comment By: Daniel Stenberg (bagder)
Date: 2009-05-01 20:19
Message:
This explanation is not clear to me. If the reason for the
LIBSSH2_ERROR_EAGAIN is a "single shot" call to _libssh2_transport_read()
in channel_read() then didn't that transport function return EAGAIN? If so,
what good would adding a loop do?
Or perhaps put in another way: can you please provide a patch showing what
you suggest?
----------------------------------------------------------------------
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=703942&aid=2785173&group_id=125852
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