问题
I'm implementing VNC connection for xen VM in my app. In order to connect I have to forward the port as XenServer accept only local connection. I do it like this:
ssh -L 5903:localhost:5903 root@192.168.1.4
After it a can connect my VNC to localhost with corresponding port. But I have to frequently reconnect to different hosts, and using bash is not a good idea as I have a windows build also. Installing ssh-client is not always possible.
I read http://api.libssh.org/stable/libssh_tutor_forwarding.html and tried to test it.
ssh_channel forwarding_channel;
forwarding_channel = ssh_channel_new(session);
int rc = channel_open_forward(forwarding_channel,
"192.168.1.4", 5903,
"localhost", 5903);
if (rc != SSH_OK)
{
ssh_channel_free(forwarding_channel);
return rc;
}
for(;;)
{
usleep(100000);
}
The tunnel itself is created, according to status. But I can see no ports listening via netstat. What I'm doing wrong and is it possible at all?
Update:
Here is resulted code that seems to work properly using libssh
int32_t forward_port (ssh_session session, char *remote_host, int32_t remote_port, int32_t local_port)
{
int32_t server_sock = 0;
int32_t client_sock = -1;
struct sockaddr_in client_name;
socklen_t client_name_len = sizeof client_name;
char buf[4096] = {0};
server_sock = server_startup(local_port);
client_sock = accept(server_sock,
(struct sockaddr *)&client_name,
&client_name_len);
if (client_sock == -1)
{
perror("Error on accept");
return SSH_ERROR;
}
int32_t client_port = ntohs(client_name.sin_port);
int32_t size_recv, nwritten, nread = 0;
uint8_t data[4096];
fcntl(client_sock, F_SETFL, O_NONBLOCK);
/* */
ssh_channel forwarding_channel;
forwarding_channel = ssh_channel_new(session);
int rc = channel_open_forward(forwarding_channel,
remote_host, remote_port,
"127.0.0.1", client_port);
if (rc != SSH_OK)
{
ssh_channel_free(forwarding_channel);
close(client_sock);
close(server_sock);
return rc;
}
while(!ssh_channel_is_eof (forwarding_channel))
{
if((size_recv = recv(client_sock, data, sizeof data, MSG_DONTWAIT) ) < 0)
{
if((nread = ssh_channel_read_nonblocking(forwarding_channel, data, sizeof data, 0))>0)
{
if(write(client_sock,data,nread)<0)
{
perror("Error writing to socket");
close(client_sock);
close(server_sock);
ssh_channel_free(forwarding_channel);
return SSH_ERROR;
}
}
}
else if (!size_recv)
{
puts("Local client disconnected, exiting");
goto exit;
}
nwritten = channel_write(forwarding_channel, data, size_recv);
if (size_recv != nwritten)
{
ssh_channel_free(forwarding_channel);
return SSH_ERROR;
}
}
exit:
close(client_sock);
close(server_sock);
ssh_channel_free(forwarding_channel);
return SSH_OK;
}
回答1:
ssh_channel_open_forward documentation
## Warning ##
This function does not bind the local port and does not automatically forward the content of a socket to the channel. You still have to use channel_read and channel_write for this.
来源:https://stackoverflow.com/questions/18811781/c-can-i-forward-port-for-external-application-with-libssh