trusty (3) ssh_connection.3erl.gz
NAME
ssh_connection - This module provides API functions to send SSH Connection Protocol
events to the other side of an SSH channel.
DESCRIPTION
The SSH Connection Protocol is used by clients and servers (i.e. SSH channels) to communicate over the
SSH connection. The API functions in this module sends SSH Connection Protocol events that are received
as messages by the remote channel. In the case that the receiving channel is an Erlang process the
message will be on the following format {ssh_cm, ssh_connection_ref(), ssh_event_msg()}. If the
ssh_channel behavior is used to implement the channel process these will be handled by handle_ssh_msg/2 .
DATA TYPES
Type definitions that are used more than once in this module and/or abstractions to indicate the intended
use of the data type:
boolean() = true | false
string() = list of ASCII characters
timeout() = infinity | integer() - in milliseconds.
ssh_connection_ref() - opaque to the user returned by ssh:connect/3 or sent to an SSH channel processes
ssh_channel_id() = integer()
ssh_data_type_code() = 1 ("stderr") | 0 ("normal") are currently valid values see RFC 4254 section 5.2.
ssh_request_status() = success | failure
event() = {ssh_cm, ssh_connection_ref(), ssh_event_msg()}
ssh_event_msg() = data_events() | status_events() | terminal_events()
data_events() :
{data, ssh_channel_id(), ssh_data_type_code(), binary() = Data}:
Data has arrived on the channel. This event is sent as result of calling
ssh_connection:send/[3,4,5]
{eof, ssh_channel_id()}:
Indicates that the other side will not send any more data. This event is sent as result of calling
ssh_connection:send_eof/2
status_events() :
{signal, ssh_channel_id(), ssh_signal()}:
A signal can be delivered to the remote process/service using the following message. Some systems
will not support signals, in which case they should ignore this message. There is currently no
funtion to generate this event as the signals refered to are on OS-level and not something
generated by an Erlang program.
{exit_signal, ssh_channel_id(), string() = ExitSignal, string() = ErrorMsg, string() =
LanguageString}:
A remote execution may terminate violently due to a signal then this message may be received. For
details on valid string values see RFC 4254 section 6.10. Special case of the signals mentioned
above.
{exit_status, ssh_channel_id(), integer() = ExitStatus}:
When the command running at the other end terminates, the following message can be sent to return
the exit status of the command. A zero 'exit_status' usually means that the command terminated
successfully. This event is sent as result of calling ssh_connection:exit_status/3
{closed, ssh_channel_id()}:
This event is sent as result of calling ssh_connection:close/2 Both the handling of this event and
sending of it will be taken care of by the ssh_channel behavior.
terminal_events() :
Channels implementing a shell and command execution on the server side should handle the following
messages that may be sent by client channel processes.
Note:
Events that includes a WantReply expects the event handling process to call
ssh_connection:reply_request/4 with the boolean value of WantReply as the second argument.
{env, ssh_channel_id(), boolean() = WantReply, string() = Var, string() = Value}:
Environment variables may be passed to the shell/command to be started later. This event is sent
as result of calling ssh_connection:setenv/5
{pty, ssh_channel_id(), boolean() = WantReply, {string() = Terminal, integer() = CharWidth, integer()
= RowHeight, integer() = PixelWidth, integer() = PixelHight, [{atom() | integer() = Opcode, integer()
= Value}] = TerminalModes}}:
A pseudo-terminal has been requested for the session. Terminal is the value of the TERM environment
variable value (e.g., vt100). Zero dimension parameters must be ignored. The character/row
dimensions override the pixel dimensions (when nonzero). Pixel dimensions refer to the drawable
area of the window. The Opcode in the TerminalModes list is the mnemonic name, represented as an
lowercase erlang atom, defined in RFC 4254 section 8, or the opcode if the mnemonic name is not
listed in the RFC. Example OP code: 53, mnemonic name ECHO erlang atom: echo. There is currently no
API function to generate this event.
{shell, boolean() = WantReply}:
This message will request that the user's default shell be started at the other end. This event is
sent as result of calling ssh_connection:shell/2
{window_change, ssh_channel_id(), integer() = CharWidth, integer() = RowHeight, integer() = PixWidth,
integer() = PixHeight}:
When the window (terminal) size changes on the client side, it MAY send a message to the server
side to inform it of the new dimensions. There is currently no API function to generate this event.
{exec, ssh_channel_id(), boolean() = WantReply, string() = Cmd}:
This message will request that the server starts execution of the given command. This event is
sent as result of calling ssh_connection:exec/4
EXPORTS
adjust_window(ConnectionRef, ChannelId, NumOfBytes) -> ok
Types:
ConnectionRef = ssh_connection_ref()
ChannelId = ssh_channel_id()
NumOfBytes = integer()
Adjusts the SSH flowcontrol window. This shall be done by both client and server side channel
processes.
Note:
Channels implemented with the ssh_channel behavior will normaly not need to call this function as
flow control will be handled by the behavior. The behavior will adjust the window every time the
callback handle_ssh_msg/2 has returned after processing channel data
close(ConnectionRef, ChannelId) -> ok
Types:
ConnectionRef = ssh_connection_ref()
ChannelId = ssh_channel_id()
A server or client channel process can choose to close their session by sending a close event.
Note:
This function will be called by the ssh_channel behavior when the channel is terminated see
ssh_channel(3erl) so channels implemented with the behavior should not call this function
explicitly.
exec(ConnectionRef, ChannelId, Command, TimeOut) -> ssh_request_status()
Types:
ConnectionRef = ssh_connection_ref()
ChannelId = ssh_channel_id()
Command = string()
Timeout = timeout()
Should be called by a client channel process to request that the server starts execution of the
given command, the result will be several messages according to the following pattern. Note that
the last message will be a channel close message, as the exec request is a one time execution that
closes the channel when it is done.
N x {ssh_cm, ssh_connection_ref(), {data, ssh_channel_id(), ssh_data_type_code(), binary() =
Data}} :
The result of executing the command may be only one line or thousands of lines depending on
the command.
0 or 1 x {ssh_cm, ssh_connection_ref(), {eof, ssh_channel_id()}}:
Indicates that no more data will be sent.
0 or 1 x {ssh_cm, ssh_connection_ref(), {exit_signal, ssh_channel_id(), string() = ExitSignal,
string() = ErrorMsg, string() = LanguageString}}:
Not all systems send signals. For details on valid string values see RFC 4254 section 6.10
0 or 1 x {ssh_cm, ssh_connection_ref(), {exit_status, ssh_channel_id(), integer() =
ExitStatus}}:
It is recommended by the ssh connection protocol that this message shall be sent, but that may
not always be the case.
1 x {ssh_cm, ssh_connection_ref(), {closed, ssh_channel_id()}}:
Indicates that the ssh channel started for the execution of the command has now been shutdown.
exit_status(ConnectionRef, ChannelId, Status) -> ok
Types:
ConnectionRef = ssh_connection_ref()
ChannelId = ssh_channel_id()
Status = integer()
Should be called by a server channel process to sends the exit status of a command to the client.
reply_request(ConnectionRef, WantReply, Status, ChannelId) -> ok
Types:
ConnectionRef = ssh_connection_ref()
WantReply = boolean()
Status = ssh_request_status()
ChannelId = ssh_channel_id()
Sends status replies to requests where the requester has stated that they want a status report e.i
. WantReply = true, if WantReply is false calling this function will be a "noop". Should be
called while handling an ssh connection protocol message containing a WantReply boolean value.
send(ConnectionRef, ChannelId, Data) ->
send(ConnectionRef, ChannelId, Data, Timeout) ->
send(ConnectionRef, ChannelId, Type, Data) ->
send(ConnectionRef, ChannelId, Type, Data, TimeOut) -> ok | {error, timeout} | {error, closed}
Types:
ConnectionRef = ssh_connection_ref()
ChannelId = ssh_channel_id()
Data = binary()
Type = ssh_data_type_code()
Timeout = timeout()
Should be called by client- and server channel processes to send data to each other.
send_eof(ConnectionRef, ChannelId) -> ok | {error, closed}
Types:
ConnectionRef = ssh_connection_ref()
ChannelId = ssh_channel_id()
Sends eof on the channel ChannelId.
session_channel(ConnectionRef, Timeout) ->
session_channel(ConnectionRef, InitialWindowSize, MaxPacketSize, Timeout) -> {ok, ssh_channel_id()} |
{error, Reason}
Types:
ConnectionRef = ssh_connection_ref()
InitialWindowSize = integer()
MaxPacketSize = integer()
Timeout = timeout()
Reason = term()
Opens a channel for an SSH session. The channel id returned from this function is the id used as
input to the other funtions in this module.
setenv(ConnectionRef, ChannelId, Var, Value, TimeOut) -> ssh_request_status()
Types:
ConnectionRef = ssh_connection_ref()
ChannelId = ssh_channel_id()
Var = string()
Value = string()
Timeout = timeout()
Environment variables may be passed before starting the shell/command. Should be called by a
client channel processes.
shell(ConnectionRef, ChannelId) -> ssh_request_status()
Types:
ConnectionRef = ssh_connection_ref()
ChannelId = ssh_channel_id()
Should be called by a client channel process to request that the user's default shell (typically
defined in /etc/passwd in UNIX systems) shall be executed at the server end.
subsystem(ConnectionRef, ChannelId, Subsystem, Timeout) -> ssh_request_status()
Types:
ConnectionRef = ssh_connection_ref()
ChannelId = ssh_channel_id()
Subsystem = string()
Timeout = timeout()
Should be called by a client channel process for requesting to execute a predefined subsystem on
the server.