#206: Calling libssh2_sftp_read multiple times with a reducing buffer size sends
a large amount of outbound packets
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Reporter:
www.google.com/accounts/o8/id?id=aitoawklaurjnhtim8cmypfnamil7ugv00-86qe |
Owner:
Type: defect
| Status: new
Priority: normal
| Milestone:
Component: SFTP
| Version:
Keywords:
| Blocks:
Blocked By:
|
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When I call libssh2_sftp_read multiple times with a reducing buffer size,
the 2nd call takes a long time/hangs and begins sending a large amount of
data to the server. At this point it fills the network socket's send
buffer and then call to libssh2_sftp_read finishes. When calling
libssh2_sftp_close on the file handle, the return code is -7
(LIBSSH2_ERROR_SOCKET_SEND).
This only happens when subsequent calls to libssh2_sftp_read have a
smaller buffer size than the previous call. If the buffer size is the same
or larger there are no problems. A real world example of this is:
1. Open a remote file with a size of 8000 bytes with libssh2_sftp_open
2. First call to libssh2_sftp_read with a buffer size of 8000 returns just
the first 2000 bytes
3. Second call to libssh2_sftp_read with a buffer size of 6000 (8000-2000)
returns 6000 bytes
4. Inspect rate of outbound network traffic and return value of
libssh2_sftp_close
Client Environment:
Source: daily snapshot libssh2-1.2.8-20110113
Compiler: VC2010 (x86) on Windows 7 64-bit
Server Environment:
Ubuntu 10.10 64-bit with openssh-server
Reproducable on:
1. a remote Xen VPS host with 180ms ping
2. VMWare virtualised local host running with < 1 ms ping
Attachments:
Modified example\sftp.c
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Ticket URL: <http://trac.libssh2.org/ticket/206>
libssh2 <http://trac.libssh2.org/>
C library for writing portable SSH2 clients
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