My previous post appeared in a strange format in the mailing list
archive. I guess I should have sent it in plain text. Here is is again.
I hope this is more readable.
-- Troy
==============================
Greetings.
How well is libssh2 supposed to work in multithreaded programs?
I'm using version libssh2-0.15-20070524, which is relatively recent. I
built it on Solaris 9 with the C compiler from Sun Studio 11.
Attached is a little program based on the example that demonstrates a
problem I have encountered. I build this program with Sun Studio 11's
C++ compiler because my goal is to use libssh2 in a C++ application.
The problem is that I can only establish an sftp session if I do it in
the main thread.
When I run the program with no command line parameters, it correctly
establishes an sftp session to a Solaris 10 server that is running the
Sun-provided sshd (which is a version of OpenSSH sshd). When I run the
program with a command line parameter, the program invokes the libssh2
calls in a different thread. In this case, it fails to establish an sftp
session.
I'm sure that I have read somewhere in the mailing list or discussion
forums that someone is using libssh2 and sftp in multithreaded
applications. It seems like I must be doing something wrong.
When my test program fails, it appears that the call to
_libssh2_channel_read(channel, (char *)buffer, 4) at line 235 of sftp.c
is returning -1 instead of the expected value of 4.
Does anyone have any suggestions?
Here is a portion of the output when it fails:
...
[libssh2] SFTP Subsystem: Initializing SFTP subsystem
[libssh2] Connection: Allocated new channel ID#0
[libssh2] Connection: Opening Channel - win 65536 pack 16384
=> libssh2_packet_write plain (24 bytes)
0000: 5a 00 00 00 07 73 65 73 73 69 6f 6e 00 00 00 00 Z....session....
0010: 00 01 00 00 00 00 40 00 ......@.
=> libssh2_packet_write send() (68 bytes)
0000: 9c b2 9e 42 71 e6 b4 a5 2b d3 8c 5b df c3 cc 4f ...Bq...+..[...O
0010: 0e ea b1 12 95 55 69 98 2f 03 16 2f e8 b5 22 e9 .....Ui./../..".
0020: ea 26 35 05 14 c4 31 47 a7 7b 97 0a 34 27 e5 da .&5...1G.{..4'..
0030: dd 6f 4f 07 e8 4a 80 b1 f3 1e a2 e9 df 68 ff cd .oO..J.......h..
0040: 14 11 cd ea ....
[libssh2] Transport: Looking for packet of type: 91
[libssh2] Transport: Looking for packet of type: 92
=> libssh2_packet_read() raw (52 bytes)
0000: b5 7c 2d dd b9 18 2b 86 6a 8a f0 0e 03 f5 0e 57 .|-...+.j......W
0010: ce 13 19 cb 45 41 8e c6 17 7c 29 36 06 06 d7 63 ....EA...|)6...c
0020: 16 d3 a8 b1 16 6a 00 f8 c1 0f 46 fe 21 48 24 69 .....j....F.!H$i
0030: 6e 90 b1 91 n...
=> libssh2_packet_read() plain (17 bytes)
0000: 5b 00 00 00 00 00 00 00 00 00 00 00 00 00 00 80 [...............
0010: 00 .
[libssh2] Transport: Packet type 91 received, length=17
[libssh2] Transport: Looking for packet of type: 91
[libssh2] Connection: Connection Established - ID: 0/0 win: 0/65536
pack: 32768/16384
[libssh2] Connection: starting request(subsystem) on channel 0/0,
message=sftp
=> libssh2_packet_write plain (27 bytes)
0000: 62 00 00 00 00 00 00 00 09 73 75 62 73 79 73 74 b........subsyst
0010: 65 6d ff 00 00 00 04 73 66 74 70 em.....sftp
=> libssh2_packet_write send() (68 bytes)
0000: 93 7f aa 1f ba 1c 9f 34 95 f3 27 e0 64 6f da 82 ......4..'.do..
0010: 9c 4a a2 c8 16 dc ad 35 53 2b ad 39 8e 61 3d 13 .J.....5S+.9.a=.
0020: 6e 54 41 cd 58 8b 43 35 1b 69 ca b7 3c d3 1d b8 nTA.X.C5.i..<...
0030: c4 b7 0f 5e 8c 51 0b 64 ad dc f0 63 39 86 31 87 ...^.Q.d...c9.1.
0040: a9 f4 48 2b ..H+
[libssh2] Transport: Looking for packet of type: 99
[libssh2] Transport: Looking for packet of type: 100
=> libssh2_packet_read() raw (88 bytes)
0000: 46 25 6e 00 52 76 d6 3f dd 7b ed 57 49 af b1 ae F%n.Rv.?.{.WI...
0010: dc 78 19 b2 9a 53 d7 53 3a 54 be 46 11 f4 e4 eb .x...S.S:T.F....
0020: a8 6f 70 72 83 9e 96 46 eb c6 37 19 9c 7b c5 39 .opr...F..7..{.9
0030: c4 82 d0 f0 2f 5a 30 73 e6 e6 8c e8 9d 4f 35 5e ..../Z0s.....O5^
0040: 1e e1 02 a0 6d 70 95 71 4c f7 83 8a 7e f8 19 6c ....mp.qL...~..l
0050: f7 b7 13 1a aa 60 1d 9d .....`..
=> libssh2_packet_read() plain (9 bytes)
0000: 5d 00 00 00 00 00 02 00 00 ]........
[libssh2] Transport: Packet type 93 received, length=9
[libssh2] Connection: Window adjust received for channel 0/0, adding
131072 bytes, new window_size=131072
=> libssh2_packet_read() plain (5 bytes)
0000: 63 00 00 00 00 c....
[libssh2] Transport: Packet type 99 received, length=5
[libssh2] Transport: Looking for packet of type: 99
[libssh2] Connection: Setting blocking mode on channel 0/0 to 1
[libssh2] Connection: Setting channel 0/0 handle_extended_data mode to 1
[libssh2] SFTP Subsystem: Sending FXP_INIT packet advertising version 3
support
[libssh2] Connection: Setting blocking mode on channel 0/0 to 1
[libssh2] Connection: Writing 9 bytes on channel 0/0, stream #0
[libssh2] Connection: Sending 9 bytes on channel 0/0, stream_id=0
=> libssh2_packet_write plain (18 bytes)
0000: 5e 00 00 00 00 00 00 00 09 00 00 00 05 01 00 00 ^...............
0010: 00 03 ..
=> libssh2_packet_write send() (52 bytes)
0000: ea 1c ae ba cd e8 ac f6 66 c2 00 8c 99 6c f3 e2 ........f....l..
0010: b5 3f 86 5a b7 02 e3 5b f2 78 fa 86 c4 61 98 88 .?.Z...[.x...a..
0020: ab 71 db 20 5b 44 00 bc 17 95 86 5e c2 a1 17 83 .q. [D.....^....
0030: be 7a a6 f4 .z..
[libssh2] Connection: Setting blocking mode on channel 0/0 to 1
[libssh2] SFTP Subsystem: Requiring 2 packet
[libssh2] SFTP Subsystem: Asking for 2 packet
[libssh2] SFTP Subsystem: Waiting for packet: will block
[libssh2] Connection: Setting blocking mode on channel 0/0 to 1
[libssh2] Connection: Attempting to read 4 bytes from channel 0/0 stream
#0
[libssh2] Connection: Setting blocking mode on channel 0/0 to 0
[libssh2] Failure Event: -30 - Timeout waiting for FXP packet
[libssh2] Failure Event: -30 - Timeout waiting for response from SFTP
subsystem
[libssh2] Connection: Freeing channel 0/0 resources
[libssh2] Connection: Closing channel 0/0
=> libssh2_packet_write plain (5 bytes)
0000: 61 00 00 00 00 a....
=> libssh2_packet_write send() (36 bytes)
0000: 4f 89 cb 97 da 37 be 42 ab 63 ed 83 a9 76 26 fd O....7.B.c...v&.
0010: d1 c6 45 d9 e6 0c 01 88 89 e3 2b 38 60 d3 cf 81 ..E.......+8`...
0020: 95 8e 7c 35 ..|5
[libssh2] Connection: Setting blocking mode on channel 0/0 to 1
Here is the program:
#include <iostream>
#include <netinet/in.h>
#include <sys/socket.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include "libssh2.h"
#include "libssh2_sftp.h"
void
try_sftp()
{
std::cout << "**** try_sftp started" << std::endl;
int sock;
struct sockaddr_in sin;
sock = socket(AF_INET, SOCK_STREAM, 0);
sin.sin_family = AF_INET;
sin.sin_port = htons(22);
// 172.28.15.12 = 0xAC1C0F0C
sin.sin_addr.s_addr = htonl(0xAC1C0F0C);
if (connect(sock,
(struct sockaddr*)(&sin),
sizeof(struct sockaddr_in)) != 0)
{
std::cerr << "**** failed to connect!" << std::endl;
return;
}
LIBSSH2_SESSION *session;
session = libssh2_session_init();
if (libssh2_session_startup(session, sock))
{
std::cerr << "**** failed to establish SSH session" <<
std::endl;
return;
}
libssh2_trace(session, 255);
char userid[] = "troyg";
char password[] = "troyg.1";
if (libssh2_userauth_password(session, userid, password))
{
std::cerr << "**** authentication by password failed" <<
std::endl;
goto shutdown;
}
else
{
std::cout << "**** successfully authenticated as user " <<
userid << std::endl;
}
LIBSSH2_SFTP *sftp;
sftp = libssh2_sftp_init(session);
if (sftp)
{
std::cout << "**** established SFTP session." << std::endl;
}
else
{
std::cerr << "**** failed to establish SFTP session." <<
std::endl;
goto shutdown;
}
shutdown_ftp:
if (libssh2_sftp_shutdown(sftp) == 0)
{
std::cout << "**** terminated SFTP session." << std::endl;
}
else
{
std::cerr << "**** failed to terminate SFTP session." <<
std::endl;
}
shutdown:
libssh2_session_disconnect(session, "Normal Shutdown, Thank you for
playing");
libssh2_session_free(session);
close(sock);
}
void *
thread_main(void *)
{
try_sftp();
return NULL;
}
int
main( int argc, char *argv[] )
{
if (argc > 1)
{
pthread_t threadID;
pthread_create(&threadID, NULL, thread_main, NULL);
sleep(10000);
}
else
{
try_sftp();
}
return 0;
}
Thanks in advance for any help you can offer.
Troy Gutjahr
Staff Engineer
Tellabs Inc.
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Received on 2007-06-01