Hello,
Exec "uptime" on a remote machine (LAN) does not
return the "stdout" output, if "libssh2_channel_read()"
is not called fast enough.
Instead, "libssh2_channel_read()" returns zero.
This issue may be reproduced via the attached c-file.
If the "sleep(3)" right before "libssh2_channel_read()"
is removed, everything works fine.
Libssh2 release 1.1
Thank you very much
Markus
------------------------------------------
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <ctype.h>
#include <libssh2.h>
static int waitsocket(int socket_fd, LIBSSH2_SESSION *session)
{
struct timeval timeout;
int rc;
fd_set fd;
fd_set *writefd = NULL;
fd_set *readfd = NULL;
int dir;
timeout.tv_sec = 10;
timeout.tv_usec = 0;
FD_ZERO(&fd);
FD_SET(socket_fd, &fd);
/* now make sure we wait in the correct direction */
dir = libssh2_session_block_directions(session);
if(dir & LIBSSH2_SESSION_BLOCK_INBOUND)
readfd = &fd;
if(dir & LIBSSH2_SESSION_BLOCK_OUTBOUND)
writefd = &fd;
rc = select(socket_fd + 1, readfd, writefd, NULL, &timeout);
return rc;
}
int main(int argc, char *argv[])
{
const char *remotehost = "192.168.1.69";
const char *commandline = "uptime";
const char *username = "double";
const char *password = "";
unsigned long hostaddr;
int sock, i;
struct sockaddr_in sin;
const char *fingerprint;
LIBSSH2_SESSION *session;
LIBSSH2_CHANNEL *channel;
int rc;
#ifdef WIN32
WSADATA wsadata;
WSAStartup(MAKEWORD(2,0), &wsadata);
#endif
hostaddr = inet_addr( remotehost );
/* Ultra basic "connect to port 22 on localhost"
* Your code is responsible for creating the socket establishing the
* connection
*/
sock = socket(AF_INET, SOCK_STREAM, 0);
sin.sin_family = AF_INET;
sin.sin_port = htons(22);
sin.sin_addr.s_addr = hostaddr;
if (connect(sock, (struct sockaddr*)(&sin), sizeof(struct
sockaddr_in)) != 0) {
fprintf(stderr, "failed to connect!\n");
return -1;
}
/* We set the socket non-blocking. We do it after the connect just to
simplify the example code. */
#ifdef F_SETFL
/* FIXME: this can/should be done in a more portable manner */
rc = fcntl(sock, F_GETFL, 0);
fcntl(sock, F_SETFL, rc | O_NONBLOCK);
#elif defined(HAVE_IOCTLSOCKET)
ioctlsocket(sock, FIONBIO, &flag);
#else
#ifdef WIN32
u_long mode = 1;
ioctlsocket (sock, FIONBIO, &mode);
#else
#error "add support for setting the socket non-blocking here"
#endif
#endif
/* Create a session instance */
session = libssh2_session_init();
if (!session)
return -1;
/* Since we have set non-blocking, tell libssh2 we are non-blocking */
libssh2_session_set_blocking(session, 0);
/* ... start it up. This will trade welcome banners, exchange keys,
* and setup crypto, compression, and MAC layers
*/
while ((rc = libssh2_session_startup(session, sock)) ==
LIBSSH2_ERROR_EAGAIN);
if (rc) {
fprintf(stderr, "Failure establishing SSH session: %d\n", rc);
return -1;
}
/* At this point we havn't yet authenticated. The first thing to do
* is check the hostkey's fingerprint against our known hosts
Your app
* may have it hard coded, may go to a file, may present it to the
* user, that's your call
*/
fingerprint = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_MD5);
fprintf(stderr, "Fingerprint: ");
for(i = 0; i < 16; i++) {
fprintf(stderr, "%02X ", (unsigned char)fingerprint[i]);
}
fprintf(stderr, "\n");
if ( strlen(password) != 0 ) {
/* We could authenticate via password */
while ((rc = libssh2_userauth_password(session, username,
password)) ==
LIBSSH2_ERROR_EAGAIN);
if (rc) {
fprintf(stderr, "Authentication by password failed.\n");
goto shutdown;
}
} else {
/* Or by public key */
while ((rc = libssh2_userauth_publickey_fromfile(session, username,
"/home/double/"
".ssh/id_rsa.pub",
"/home/double/"
".ssh/id_rsa",
password)) ==
LIBSSH2_ERROR_EAGAIN);
if (rc) {
fprintf(stderr, "\tAuthentication by public key failed\n");
goto shutdown;
}
}
libssh2_trace(session, LIBSSH2_TRACE_TRANS | LIBSSH2_TRACE_KEX |
LIBSSH2_TRACE_AUTH | LIBSSH2_TRACE_CONN | LIBSSH2_TRACE_SCP |
LIBSSH2_TRACE_SFTP | LIBSSH2_TRACE_ERROR | LIBSSH2_TRACE_PUBLICKEY );
/* Exec non-blocking on the remove host */
while( (channel = libssh2_channel_open_session(session)) == NULL &&
libssh2_session_last_error(session,NULL,NULL,0) ==
LIBSSH2_ERROR_EAGAIN )
{
waitsocket(sock, session);
}
if( channel == NULL )
{
fprintf(stderr,"Error\n");
exit( 1 );
}
while( (rc = libssh2_channel_exec(channel, commandline)) ==
LIBSSH2_ERROR_EAGAIN )
{
waitsocket(sock, session);
}
if( rc != 0 )
{
fprintf(stderr,"Error\n");
exit( 1 );
}
for( ;; )
{
// loop until we block
int rc;
do
{
char buffer[0x4000];
/* strange thing */
sleep( 3 );
rc = libssh2_channel_read( channel, buffer, sizeof(buffer) );
if( rc > 0 )
{
int i;
for( i=0; i < rc; ++i )
putchar( buffer[i] );
}
}
while( rc > 0 );
// this is due to blocking that would occur otherwise so we loop
on this condition
if( rc == LIBSSH2_ERROR_EAGAIN )
{
waitsocket(sock, session);
}
else if( rc == 0 )
break;
}
int exitcode = 127;
while( (rc = libssh2_channel_close(channel)) == LIBSSH2_ERROR_EAGAIN )
;
if( rc == 0 )
{
//does-not-work if( libssh2_channel_wait_closed(channel) == 0 )
exitcode = libssh2_channel_get_exit_status( channel );
}
printf("\n%d\n", exitcode );
libssh2_channel_free(channel);
channel = NULL;
shutdown:
libssh2_session_disconnect(session,
"Normal Shutdown, Thank you for playing");
libssh2_session_free(session);
#ifdef WIN32
Sleep(1000);
closesocket(sock);
#else
sleep(1);
close(sock);
#endif
fprintf(stderr, "all done\n");
return 0;
}
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <ctype.h>
#include <libssh2.h>
static int waitsocket(int socket_fd, LIBSSH2_SESSION *session)
{
struct timeval timeout;
int rc;
fd_set fd;
fd_set *writefd = NULL;
fd_set *readfd = NULL;
int dir;
timeout.tv_sec = 10;
timeout.tv_usec = 0;
FD_ZERO(&fd);
FD_SET(socket_fd, &fd);
/* now make sure we wait in the correct direction */
dir = libssh2_session_block_directions(session);
if(dir & LIBSSH2_SESSION_BLOCK_INBOUND)
readfd = &fd;
if(dir & LIBSSH2_SESSION_BLOCK_OUTBOUND)
writefd = &fd;
rc = select(socket_fd + 1, readfd, writefd, NULL, &timeout);
return rc;
}
int main(int argc, char *argv[])
{
const char *remotehost = "192.168.1.69";
const char *commandline = "uptime";
const char *username = "double";
const char *password = "";
unsigned long hostaddr;
int sock, i;
struct sockaddr_in sin;
const char *fingerprint;
LIBSSH2_SESSION *session;
LIBSSH2_CHANNEL *channel;
int rc;
#ifdef WIN32
WSADATA wsadata;
WSAStartup(MAKEWORD(2,0), &wsadata);
#endif
hostaddr = inet_addr( remotehost );
/* Ultra basic "connect to port 22 on localhost"
* Your code is responsible for creating the socket establishing the
* connection
*/
sock = socket(AF_INET, SOCK_STREAM, 0);
sin.sin_family = AF_INET;
sin.sin_port = htons(22);
sin.sin_addr.s_addr = hostaddr;
if (connect(sock, (struct sockaddr*)(&sin), sizeof(struct sockaddr_in)) != 0) {
fprintf(stderr, "failed to connect!\n");
return -1;
}
/* We set the socket non-blocking. We do it after the connect just to
simplify the example code. */
#ifdef F_SETFL
/* FIXME: this can/should be done in a more portable manner */
rc = fcntl(sock, F_GETFL, 0);
fcntl(sock, F_SETFL, rc | O_NONBLOCK);
#elif defined(HAVE_IOCTLSOCKET)
ioctlsocket(sock, FIONBIO, &flag);
#else
#ifdef WIN32
u_long mode = 1;
ioctlsocket (sock, FIONBIO, &mode);
#else
#error "add support for setting the socket non-blocking here"
#endif
#endif
/* Create a session instance */
session = libssh2_session_init();
if (!session)
return -1;
/* Since we have set non-blocking, tell libssh2 we are non-blocking */
libssh2_session_set_blocking(session, 0);
/* ... start it up. This will trade welcome banners, exchange keys,
* and setup crypto, compression, and MAC layers
*/
while ((rc = libssh2_session_startup(session, sock)) ==
LIBSSH2_ERROR_EAGAIN);
if (rc) {
fprintf(stderr, "Failure establishing SSH session: %d\n", rc);
return -1;
}
/* At this point we havn't yet authenticated. The first thing to do
* is check the hostkey's fingerprint against our known hosts Your app
* may have it hard coded, may go to a file, may present it to the
* user, that's your call
*/
fingerprint = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_MD5);
fprintf(stderr, "Fingerprint: ");
for(i = 0; i < 16; i++) {
fprintf(stderr, "%02X ", (unsigned char)fingerprint[i]);
}
fprintf(stderr, "\n");
if ( strlen(password) != 0 ) {
/* We could authenticate via password */
while ((rc = libssh2_userauth_password(session, username, password)) ==
LIBSSH2_ERROR_EAGAIN);
if (rc) {
fprintf(stderr, "Authentication by password failed.\n");
goto shutdown;
}
} else {
/* Or by public key */
while ((rc = libssh2_userauth_publickey_fromfile(session, username,
"/home/double/" ".ssh/id_rsa.pub",
"/home/double/" ".ssh/id_rsa",
password)) ==
LIBSSH2_ERROR_EAGAIN);
if (rc) {
fprintf(stderr, "\tAuthentication by public key failed\n");
goto shutdown;
}
}
libssh2_trace(session, LIBSSH2_TRACE_TRANS | LIBSSH2_TRACE_KEX | LIBSSH2_TRACE_AUTH | LIBSSH2_TRACE_CONN | LIBSSH2_TRACE_SCP | LIBSSH2_TRACE_SFTP | LIBSSH2_TRACE_ERROR | LIBSSH2_TRACE_PUBLICKEY );
/* Exec non-blocking on the remove host */
while( (channel = libssh2_channel_open_session(session)) == NULL &&
libssh2_session_last_error(session,NULL,NULL,0) == LIBSSH2_ERROR_EAGAIN )
{
waitsocket(sock, session);
}
if( channel == NULL )
{
fprintf(stderr,"Error\n");
exit( 1 );
}
while( (rc = libssh2_channel_exec(channel, commandline)) == LIBSSH2_ERROR_EAGAIN )
{
waitsocket(sock, session);
}
if( rc != 0 )
{
fprintf(stderr,"Error\n");
exit( 1 );
}
for( ;; )
{
// loop until we block
int rc;
do
{
char buffer[0x4000];
/* strange thing */
sleep( 3 );
rc = libssh2_channel_read( channel, buffer, sizeof(buffer) );
if( rc > 0 )
{
int i;
for( i=0; i < rc; ++i )
putchar( buffer[i] );
}
}
while( rc > 0 );
// this is due to blocking that would occur otherwise so we loop on this condition
if( rc == LIBSSH2_ERROR_EAGAIN )
{
waitsocket(sock, session);
}
else if( rc == 0 )
break;
}
int exitcode = 127;
while( (rc = libssh2_channel_close(channel)) == LIBSSH2_ERROR_EAGAIN )
;
if( rc == 0 )
{
//does-not-work if( libssh2_channel_wait_closed(channel) == 0 )
exitcode = libssh2_channel_get_exit_status( channel );
}
printf("\n%d\n", exitcode );
libssh2_channel_free(channel);
channel = NULL;
shutdown:
libssh2_session_disconnect(session,
"Normal Shutdown, Thank you for playing");
libssh2_session_free(session);
#ifdef WIN32
Sleep(1000);
closesocket(sock);
#else
sleep(1);
close(sock);
#endif
fprintf(stderr, "all done\n");
return 0;
}
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