SSH Channels

Functions that manage a channel. More...

Functions

ssh_channel channel_accept_x11 (ssh_channel channel, int timeout_ms)
 Accept an X11 forwarding channel.
int channel_change_pty_size (ssh_channel channel, int cols, int rows)
 Change the size of the terminal associated to a channel.
int channel_close (ssh_channel channel)
 Close a channel.
ssh_channel channel_forward_accept (ssh_session session, int timeout_ms)
 Accept an incoming TCP/IP forwarding channel.
int channel_forward_cancel (ssh_session session, const char *address, int port)
 Sends the "cancel-tcpip-forward" global request to ask the server to cancel the tcpip-forward request.
int channel_forward_listen (ssh_session session, const char *address, int port, int *bound_port)
 Sends the "tcpip-forward" global request to ask the server to begin listening for inbound connections.
void channel_free (ssh_channel channel)
 Close and free a channel.
int channel_get_exit_status (ssh_channel channel)
 Get the exit status of the channel (error code from the executed instruction).
ssh_session channel_get_session (ssh_channel channel)
 Recover the session in which belongs a channel.
int channel_is_closed (ssh_channel channel)
 Check if the channel is closed or not.
int channel_is_eof (ssh_channel channel)
 Check if remote has sent an EOF.
int channel_is_open (ssh_channel channel)
 Check if the channel is open or not.
ssh_channel channel_new (ssh_session session)
 Allocate a new channel.
int channel_open_forward (ssh_channel channel, const char *remotehost, int remoteport, const char *sourcehost, int localport)
 Open a TCP/IP forwarding channel.
int channel_open_session (ssh_channel channel)
 Open a session channel (suited for a shell, not TCP forwarding).
int channel_poll (ssh_channel channel, int is_stderr)
 Polls a channel for data to read.
int channel_read (ssh_channel channel, void *dest, uint32_t count, int is_stderr)
 Reads data from a channel.
int channel_read_buffer (ssh_channel channel, ssh_buffer buffer, uint32_t count, int is_stderr)
 Read data from a channel into a buffer.
int channel_read_nonblocking (ssh_channel channel, void *dest, uint32_t count, int is_stderr)
 Do a nonblocking read on the channel.
int channel_request_env (ssh_channel channel, const char *name, const char *value)
 Set environement variables.
int channel_request_exec (ssh_channel channel, const char *cmd)
 Run a shell command without an interactive shell.
int channel_request_pty (ssh_channel channel)
 Request a PTY.
int channel_request_pty_size (ssh_channel channel, const char *terminal, int col, int row)
 Request a pty with a specific type and size.
int channel_request_send_signal (ssh_channel channel, const char *signal)
 Send a signal to remote process (as described in RFC 4254, section 6.9).
int channel_request_shell (ssh_channel channel)
 Request a shell.
int channel_request_subsystem (ssh_channel channel, const char *subsys)
 Request a subsystem (for example "sftp").
int channel_request_x11 (ssh_channel channel, int single_connection, const char *protocol, const char *cookie, int screen_number)
 Sends the "x11-req" channel request over an existing session channel.
int channel_select (ssh_channel *readchans, ssh_channel *writechans, ssh_channel *exceptchans, struct timeval *timeout)
 Act like the standard select(2) on channels.
int channel_send_eof (ssh_channel channel)
 Send an end of file on the channel.
void channel_set_blocking (ssh_channel channel, int blocking)
 Put the channel into blocking or nonblocking mode.
int channel_write (ssh_channel channel, const void *data, uint32_t len)
 Blocking write on channel.

Detailed Description

Functions that manage a channel.


Function Documentation

ssh_channel channel_accept_x11 ( ssh_channel  channel,
int  timeout_ms 
)

Accept an X11 forwarding channel.

Parameters:
channel An x11-enabled session channel.
timeout_ms Timeout in milli-seconds.
Returns:
Newly created channel, or NULL if no X11 request from the server
int channel_change_pty_size ( ssh_channel  channel,
int  cols,
int  rows 
)

Change the size of the terminal associated to a channel.

Parameters:
channel The channel to change the size.
cols The new number of columns.
rows The new number of rows.
Warning:
Do not call it from a signal handler if you are not sure any other libssh function using the same channel/session is running at same time (not 100% threadsafe).

References buffer_free(), and buffer_new().

int channel_close ( ssh_channel  channel  ) 

Close a channel.

This sends an end of file and then closes the channel. You won't be able to recover any data the server was going to send or was in buffers.

Parameters:
channel The channel to close.
Returns:
SSH_SUCCESS on success
SSH_ERROR on error
See also:
channel_free()
channel_eof()

References channel_send_eof(), ssh_log(), and SSH_LOG_PACKET.

Referenced by channel_free().

ssh_channel channel_forward_accept ( ssh_session  session,
int  timeout_ms 
)

Accept an incoming TCP/IP forwarding channel.

Parameters:
session The ssh session to use.
timeout_ms Timeout in milli-seconds.
Returns:
Newly created channel, or NULL if no incoming channel request from the server
int channel_forward_cancel ( ssh_session  session,
const char *  address,
int  port 
)

Sends the "cancel-tcpip-forward" global request to ask the server to cancel the tcpip-forward request.

Parameters:
session The ssh session to send the request.
address The bound address on the server.
port The bound port on the server.
Returns:
SSH_OK on success
SSH_ERROR on error

References buffer_free(), buffer_new(), string_free(), and string_from_char().

int channel_forward_listen ( ssh_session  session,
const char *  address,
int  port,
int *  bound_port 
)

Sends the "tcpip-forward" global request to ask the server to begin listening for inbound connections.

Parameters:
session The ssh session to send the request.
address The address to bind to on the server. Pass NULL to bind to all available addresses on all protocol families supported by the server.
port The port to bind to on the server. Pass 0 to ask the server to allocate the next available unprivileged port number
bound_port The pointer to get actual bound port. Pass NULL to ignore.
Returns:
SSH_OK on success
SSH_ERROR on error

References buffer_free(), buffer_new(), string_free(), and string_from_char().

void channel_free ( ssh_channel  channel  ) 

Close and free a channel.

Parameters:
channel The channel to free.
Warning:
Any data unread on this channel will be lost.

References buffer_free(), and channel_close().

Referenced by ssh_free().

int channel_get_exit_status ( ssh_channel  channel  ) 

Get the exit status of the channel (error code from the executed instruction).

Parameters:
channel The channel to get the status from.
Returns:
-1 if no exit status has been returned or eof not sent, the exit status othewise.
ssh_session channel_get_session ( ssh_channel  channel  ) 

Recover the session in which belongs a channel.

Parameters:
channel The channel to recover the session from.
Returns:
The session pointer.
int channel_is_closed ( ssh_channel  channel  ) 

Check if the channel is closed or not.

Parameters:
channel The channel to check.
Returns:
0 if channel is opened, nonzero otherwise.
See also:
channel_is_open()
int channel_is_eof ( ssh_channel  channel  ) 

Check if remote has sent an EOF.

Parameters:
channel The channel to check.
Returns:
0 if there is no EOF, nonzero otherwise.

Referenced by ssh_scp_pull_request().

int channel_is_open ( ssh_channel  channel  ) 

Check if the channel is open or not.

Parameters:
channel The channel to check.
Returns:
0 if channel is closed, nonzero otherwise.
See also:
channel_is_closed()
ssh_channel channel_new ( ssh_session  session  ) 

Allocate a new channel.

Parameters:
session The ssh session to use.
Returns:
A pointer to a newly allocated channel, NULL on error.

References buffer_free(), and buffer_new().

int channel_open_forward ( ssh_channel  channel,
const char *  remotehost,
int  remoteport,
const char *  sourcehost,
int  localport 
)

Open a TCP/IP forwarding channel.

Parameters:
channel An allocated channel.
remotehost The remote host to connected (host name or IP).
remoteport The remote port.
sourcehost The source host (your local computer). It's facultative and for logging purpose.
localport The source port (your local computer). It's facultative and for logging purpose.
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.
Returns:
SSH_OK on success
SSH_ERROR on error

References buffer_free(), buffer_new(), string_free(), and string_from_char().

int channel_open_session ( ssh_channel  channel  ) 

Open a session channel (suited for a shell, not TCP forwarding).

Parameters:
channel An allocated channel.
Returns:
SSH_OK on success
SSH_ERROR on error.
See also:
channel_open_forward()
channel_request_env()
channel_request_shell()
channel_request_exec()
int channel_poll ( ssh_channel  channel,
int  is_stderr 
)

Polls a channel for data to read.

Parameters:
channel The channel to poll.
is_stderr A boolean to select the stderr stream.
Returns:
The number of bytes available for reading, 0 if nothing is available or SSH_ERROR on error.
Warning:
When the channel is in EOF state, the function returns SSH_EOF.
See also:
channel_is_eof()

References ssh_handle_packets().

Referenced by channel_read_nonblocking(), ssh_scp_write(), and ssh_select().

int channel_read ( ssh_channel  channel,
void *  dest,
uint32_t  count,
int  is_stderr 
)

Reads data from a channel.

Parameters:
channel The channel to read from.
dest The destination buffer which will get the data.
count The count of bytes to be read.
is_stderr A boolean value to mark reading from the stderr flow.
Returns:
The number of bytes read, 0 on end of file or SSH_ERROR on error.
Warning:
This function may return less than count bytes of data, and won't block until count bytes have been read.
The read function using a buffer has been renamed to channel_read_buffer().

References ssh_log(), and SSH_LOG_PROTOCOL.

Referenced by channel_read_nonblocking(), ssh_scp_leave_directory(), ssh_scp_push_directory(), ssh_scp_push_file(), ssh_scp_read(), ssh_scp_read_string(), and ssh_scp_response().

int channel_read_buffer ( ssh_channel  channel,
ssh_buffer  buffer,
uint32_t  count,
int  is_stderr 
)

Read data from a channel into a buffer.

Parameters:
channel The channel to read from.
buffer The buffer which will get the data.
count The count of bytes to be read. If it is biggerthan 0, the exact size will be read, else (bytes=0) it will return once anything is available.
is_stderr A boolean value to mark reading from the stderr stream.
Returns:
The number of bytes read, 0 on end of file or SSH_ERROR on error.

References buffer_get_len(), ssh_log(), and SSH_LOG_PROTOCOL.

int channel_read_nonblocking ( ssh_channel  channel,
void *  dest,
uint32_t  count,
int  is_stderr 
)

Do a nonblocking read on the channel.

A nonblocking read on the specified channel. it will return <= count bytes of data read atomicly.

Parameters:
channel The channel to read from.
dest A pointer to a destination buffer.
count The count of bytes of data to be read.
is_stderr A boolean to select the stderr stream.
Returns:
The number of bytes read, 0 if nothing is available or SSH_ERROR on error.
Warning:
Don't forget to check for EOF as it would return 0 here.
See also:
channel_is_eof()

References channel_poll(), and channel_read().

int channel_request_env ( ssh_channel  channel,
const char *  name,
const char *  value 
)

Set environement variables.

Parameters:
channel The channel to set the environement variables.
name The name of the variable.
value The value to set.
Returns:
SSH_SUCCESS on success, SSH_ERROR on error.
Warning:
Some environement variables may be refused by security reasons.

References buffer_free(), buffer_new(), string_free(), and string_from_char().

int channel_request_exec ( ssh_channel  channel,
const char *  cmd 
)

Run a shell command without an interactive shell.

This is similar to 'sh -c command'.

Parameters:
channel The channel to execute the command.
cmd The command to execute (e.g. "ls ~/ -al | grep -i reports").
Returns:
SSH_SUCCESS on success, SSH_ERROR on error.
See also:
channel_request_shell()

References buffer_free(), buffer_new(), string_free(), and string_from_char().

int channel_request_pty ( ssh_channel  channel  ) 

Request a PTY.

Parameters:
channel The channel to send the request.
Returns:
SSH_SUCCESS on success, SSH_ERROR on error.
See also:
channel_request_pty_size()

References channel_request_pty_size().

int channel_request_pty_size ( ssh_channel  channel,
const char *  terminal,
int  col,
int  row 
)

Request a pty with a specific type and size.

Parameters:
channel The channel to sent the request.
terminal The terminal type ("vt100, xterm,...").
col The number of columns.
row The number of rows.
Returns:
SSH_SUCCESS on success, SSH_ERROR on error.

References buffer_free(), buffer_new(), string_free(), and string_from_char().

Referenced by channel_request_pty().

int channel_request_send_signal ( ssh_channel  channel,
const char *  signal 
)

Send a signal to remote process (as described in RFC 4254, section 6.9).

Sends a signal 'signal' to the remote process. Note, that remote system may not support signals concept. In such a case this request will be silently ignored. Only SSH-v2 is supported (I'm not sure about SSH-v1).

Parameters:
channel The channel to send signal.
signal The signal to send (without SIG prefix) (e.g. "TERM" or "KILL").
Returns:
SSH_SUCCESS on success, SSH_ERROR on error (including attempt to send signal via SSH-v1 session).

References buffer_free(), buffer_new(), string_free(), and string_from_char().

int channel_request_shell ( ssh_channel  channel  ) 

Request a shell.

Parameters:
channel The channel to send the request.
Returns:
SSH_SUCCESS on success, SSH_ERROR on error.
int channel_request_subsystem ( ssh_channel  channel,
const char *  subsys 
)

Request a subsystem (for example "sftp").

Parameters:
channel The channel to send the request.
subsys The subsystem to request (for example "sftp").
Returns:
SSH_SUCCESS on success, SSH_ERROR on error.
Warning:
You normally don't have to call it for sftp, see sftp_new().

References buffer_free(), buffer_new(), string_free(), and string_from_char().

int channel_request_x11 ( ssh_channel  channel,
int  single_connection,
const char *  protocol,
const char *  cookie,
int  screen_number 
)

Sends the "x11-req" channel request over an existing session channel.

This will enable redirecting the display of the remote X11 applications to local X server over an secure tunnel.

Parameters:
channel An existing session channel where the remote X11 applications are going to be executed.
single_connection A boolean to mark only one X11 app will be redirected.
protocol x11 authentication protocol. Pass NULL to use the default value MIT-MAGIC-COOKIE-1
cookie x11 authentication cookie. Pass NULL to generate a random cookie.
screen_number Screen number.
Returns:
SSH_OK on success
SSH_ERROR on error

References buffer_free(), buffer_new(), string_free(), and string_from_char().

int channel_select ( ssh_channel *  readchans,
ssh_channel *  writechans,
ssh_channel *  exceptchans,
struct timeval *  timeout 
)

Act like the standard select(2) on channels.

The list of pointers are then actualized and will only contain pointers to channels that are respectively readable, writable or have an exception to trap.

Parameters:
readchans A NULL pointer or an array of channel pointers, terminated by a NULL.
writechans A NULL pointer or an array of channel pointers, terminated by a NULL.
exceptchans A NULL pointer or an array of channel pointers, terminated by a NULL.
timeout Timeout as defined by select(2).
Returns:
SSH_SUCCESS operation successful
SSH_EINTR select(2) syscall was interrupted, relaunch the function
int channel_send_eof ( ssh_channel  channel  ) 

Send an end of file on the channel.

This doesn't close the channel. You may still read from it but not write.

Parameters:
channel The channel to send the eof to.
Returns:
SSH_SUCCESS on success
SSH_ERROR on error
See also:
channel_close()
channel_free()

References ssh_log(), and SSH_LOG_PACKET.

Referenced by channel_close().

void channel_set_blocking ( ssh_channel  channel,
int  blocking 
)

Put the channel into blocking or nonblocking mode.

Parameters:
channel The channel to use.
blocking A boolean for blocking or nonblocking.
Bug:
This functionnality is still under development and doesn't work correctly.
int channel_write ( ssh_channel  channel,
const void *  data,
uint32_t  len 
)

Blocking write on channel.

Parameters:
channel The channel to write to.
data A pointer to the data to write.
len The length of the buffer to write to.
Returns:
The number of bytes written, SSH_ERROR on error.
See also:
channel_read()

Referenced by ssh_scp_accept_request(), ssh_scp_deny_request(), ssh_scp_leave_directory(), ssh_scp_pull_request(), ssh_scp_push_directory(), ssh_scp_push_file(), ssh_scp_read(), and ssh_scp_write().

Generated on Mon Jul 5 22:12:40 2010 for libssh by  doxygen 1.6.3