Hi,
I having a problem with libssh2_channel_read hanging when there is no data to read.
I am using visual c++ 2010 Express and the libssh2 1.2.7 compiled using mingw.
This is what I have done:
1. Created a socket to the host (socket is blocked I/O)
2. Start a session
3. Authenticate user
4. Start a channel
5. Request pty (vanilla)
6. libssh2_channel_exec("passwd")
Read from the channel(after changing to non-block) as follows (I got most of the code from ssh2_exec example):
static int waitsocket(int socket_fd, LIBSSH2_SESSION *sessioni, int timetowait)
{
struct timeval timeout;
int rc;
fd_set fd;
fd_set *writefd = NULL;
fd_set *readfd = NULL;
int dir;
timeout.tv_sec = timetowait;
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 ssh2_read(SOCKET sock, LIBSSH2_SESSION *session, LIBSSH2_CHANNEL *channel, char *buffer, int bufsize, int timeout) {
int rc;
char *p;
u_long mode = 1;
int status;
int size;
/* non blocking */
status=ioctlsocket (sock, FIONBIO, &mode);
if (status!=0) return -1;
p=buffer;
size=bufsize;
*p=0;
for( ;; )
{
do
{
rc = libssh2_channel_read( channel, p, size);
if( rc > 0 )
{
p+=rc;
size-=rc;
}
else {
fprintf(stderr, "libssh2_channel_read returned %d\n", rc);
if (rc!=0) return -2;
}
}
while( rc > 0 );
if( rc == LIBSSH2_ERROR_EAGAIN ) rc=waitsocket(sock, session, timeout);
else break;
}
/* non blocking */
mode=0;
status=ioctlsocket (sock, FIONBIO, &mode);
if (status!=0) return -1;
*p=0;
return 0;
}
Using trace code I found out that I have got from the remote host a prompt to key in the
exisiting password. The code is hanging at libssh2_channel_read(). I am expecting that the read
should come back with 0 bytes read. The waitsocket() code never gets run.
Can someone please help me and tell me how I can fix this problem?
ps. I did try to turn on debugging:
./configure -enable_debugging
and make a call to libssh2_trace(session,~0);
but nothing came out on stderr
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Received on 2011-03-08