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Diffstat (limited to 'lib/ssh/doc/src/ssh_channel.xml')
| -rw-r--r-- | lib/ssh/doc/src/ssh_channel.xml | 288 |
1 files changed, 153 insertions, 135 deletions
diff --git a/lib/ssh/doc/src/ssh_channel.xml b/lib/ssh/doc/src/ssh_channel.xml index a52a6a115e..429ef3c849 100644 --- a/lib/ssh/doc/src/ssh_channel.xml +++ b/lib/ssh/doc/src/ssh_channel.xml @@ -23,69 +23,84 @@ The Initial Developer of the Original Code is Ericsson AB. </legalnotice> <title>ssh_channel</title> + <prepared></prepared> + <docno></docno> + <date></date> + <rev></rev> </header> <module>ssh_channel</module> <modulesummary>-behaviour(ssh_channel). </modulesummary> <description> <p>SSH services (clients and servers) are implemented as channels - that are multiplexed over an SSH connection and communicates via + that are multiplexed over an SSH connection and communicates over the <url href="http://www.ietf.org/rfc/rfc4254.txt"> SSH Connection Protocol</url>. This module provides a callback API - that takes care of generic channel aspects such as flow control - and close messages and lets the callback functions take care of + that takes care of generic channel aspects, such as flow control + and close messages. It lets the callback functions take care of the service (application) specific parts. This behavior also ensures that the channel process honors the principal of an OTP-process so that it can be part of a supervisor tree. This is a requirement of channel processes implementing a subsystem that will be added to - the SSH applications supervisor tree. + the <c>ssh</c> applications supervisor tree. </p> - <note> <p>When implementing a SSH subsystem use the - <c>-behaviour(ssh_daemon_channel).</c> instead of <c>-behaviour(ssh_channel).</c> - as the only relevant callback functions for subsystems are - init/1, handle_ssh_msg/2, handle_msg/2 and terminate/2, so the ssh_daemon_channel - behaviour is limited version of the ssh_channel behaviour. - </p> </note> + <note><p>When implementing an <c>ssh</c> subsystem, use + <c>-behaviour(ssh_daemon_channel)</c> instead of <c>-behaviour(ssh_channel)</c>. + The reason is that the only relevant callback functions for subsystems are + <c>init/1</c>, <c>handle_ssh_msg/2</c>, <c>handle_msg/2</c>, and <c>terminate/2</c>. + So, the <c>ssh_daemon_channel</c> behaviour is a limited version of the + <c>ssh_channel</c> behaviour. + </p></note> </description> <section> - <title>DATA TYPES </title> + <title>DATA TYPES</title> - <p>Type definitions that are used more than once in this module - and/or abstractions to indicate the intended use of the data - type:</p> + <p>Type definitions that are used more than once in this module, + or abstractions to indicate the intended use of the data + type, or both:</p> - <p><c>boolean() = true | false </c></p> - <p><c>string() = list of ASCII characters</c></p> - <p><c>timeout() = infinity | integer() - in milliseconds.</c></p> - <p><c>ssh_connection_ref() - opaque to the user returned by - ssh:connect/3 or sent to an SSH channel process</c></p> - <p><c>ssh_channel_id() = integer() </c></p> - <p><c>ssh_data_type_code() = 1 ("stderr") | 0 ("normal") are - currently valid values see <url href="http://www.ietf.org/rfc/rfc4254.txt">RFC 4254 </url> section 5.2.</c></p> + <taglist> + <tag><c>boolean()</c></tag> + <item><p>= <c>true | false</c></p></item> + <tag><c>string()</c></tag> + <item><p>= list of ASCII characters</p></item> + <tag><c>timeout()</c></tag> + <item><p>= <c>infinity | integer()</c> in milliseconds</p></item> + <tag><c>ssh_connection_ref()</c></tag> + <item><p>Opaque to the user, returned by + <c>ssh:connect/3</c> or sent to an SSH channel process</p></item> + <tag><c>ssh_channel_id()</c></tag> + <item><p>= <c>integer()</c></p></item> + <tag><c>ssh_data_type_code()</c></tag> + <item><p>= <c>1</c> ("stderr") | <c>0</c> ("normal") are + the valid values, + see <url href="http://www.ietf.org/rfc/rfc4254.txt">RFC 4254</url> + Section 5.2</p></item> + </taglist> </section> <funcs> <func> <name>call(ChannelRef, Msg) -></name> <name>call(ChannelRef, Msg, Timeout) -> Reply | {error, Reason}</name> - <fsummary> Makes a synchronous call to a channel.</fsummary> + <fsummary>Makes a synchronous call to a channel.</fsummary> <type> <v>ChannelRef = pid() </v> - <d>As returned by start_link/4 </d> - <v>Msg = term() </v> - <v>Timeout = timeout() </v> - <v>Reply = term() </v> - <v>Reason = closed | timeout </v> + <d>As returned by <c>start_link/4</c></d> + <v>Msg = term()</v> + <v>Timeout = timeout()</v> + <v>Reply = term()</v> + <v>Reason = closed | timeout</v> </type> <desc> <p>Makes a synchronous call to the channel process by sending - a message and waiting until a reply arrives or a timeout - occurs. The channel will call <seealso marker = + a message and waiting until a reply arrives, or a time-out + occurs. The channel calls <seealso marker = "#Module:handle_call-3">Module:handle_call/3</seealso> - to handle the message. If the channel process does not exist + to handle the message. If the channel process does not exist, <c>{error, closed}</c> is returned. </p> </desc> @@ -96,14 +111,14 @@ <fsummary>Sends an asynchronous message to the channel ChannelRef and returns ok.</fsummary> <type> - <v>ChannelRef = pid() </v> - <d>As returned by start_link/4 </d> - <v>Msg = term() </v> + <v>ChannelRef = pid()</v> + <d>As returned by <c>start_link/4</c></d> + <v>Msg = term()</v> </type> <desc> <p>Sends an asynchronous message to the channel process and returns ok immediately, ignoring if the destination node or - channel process does not exist. The channel will call + channel process does not exist. The channel calls <seealso marker = "#Module:handle_cast-2">Module:handle_cast/2</seealso> to handle the message. </p> @@ -112,31 +127,32 @@ <func> <name>enter_loop(State) -> _ </name> - <fsummary> Makes an existing process an ssh_channel process. </fsummary> + <fsummary>Makes an existing process an ssh_channel process.</fsummary> <type> - <v> State = term() - as returned by <seealso marker = "#init-1">ssh_channel:init/1</seealso></v> + <v>State = term() - as returned by + <seealso marker = "#init-1">ssh_channel:init/1</seealso></v> </type> <desc> - <p> Makes an existing process an <c>ssh_channel</c> - process. Does not return, instead the calling process will - enter the <c>ssh_channel</c> process receive loop and become an - <c>ssh_channel process.</c> The process must have been started using - one of the start functions in proc_lib, see <seealso - marker="stdlib:proc_lib">proc_lib(3)</seealso>. The - user is responsible for any initialization of the process - and needs to call <seealso marker = "#init-1">ssh_channel:init/1</seealso> + <p>Makes an existing process an <c>ssh_channel</c> + process. Does not return, instead the calling process + enters the <c>ssh_channel</c> process receive loop and become an + <c>ssh_channel process</c>. The process must have been started using + one of the start functions in <c>proc_lib</c>, see the <seealso + marker="stdlib:proc_lib">proc_lib(3)</seealso> manual page in <c>stdlib</c>. + The user is responsible for any initialization of the process + and must call <seealso marker = "#init-1">ssh_channel:init/1</seealso>. </p> </desc> </func> <func> <name>init(Options) -> {ok, State} | {ok, State, Timeout} | {stop, Reason} </name> - <fsummary> Initiates a ssh_channel process.</fsummary> + <fsummary>Initiates an <c>ssh_channel</c> process.</fsummary> <type> <v>Options = [{Option, Value}]</v> <v>State = term()</v> - <v>Timeout = timeout() </v> - <v>Reason = term() </v> + <v>Timeout = timeout()</v> + <v>Reason = term()</v> </type> <desc> <p> @@ -144,48 +160,47 @@ </p> <taglist> <tag><c><![CDATA[{channel_cb, atom()}]]></c></tag> - <item>The module that implements the channel behaviour.</item> + <item><p>The module that implements the channel behaviour.</p></item> <tag><c><![CDATA[{init_args(), list()}]]></c></tag> - <item> The list of arguments to the callback module's - init function.</item> + <item><p>The list of arguments to the <c>init</c> function of the callback module.</p></item> <tag><c><![CDATA[{cm, connection_ref()}]]></c></tag> - <item> Reference to the ssh connection as returned by <seealso - marker="ssh#connect-3">ssh:connect/3</seealso></item> + <item><p>Reference to the <c>ssh</c> connection as returned by <seealso + marker="ssh#connect-3">ssh:connect/3</seealso></p></item> <tag><c><![CDATA[{channel_id, channel_id()}]]></c></tag> - <item> Id of the SSH channel.</item> + <item><p>Id of the <c>ssh</c> channel.</p></item> </taglist> <note><p>This function is normally not called by the - user. The user only needs to call if for some reason the + user. The user only needs to call if the channel process needs to be started with help of <c>proc_lib</c> instead of calling <c>ssh_channel:start/4</c> or - <c>ssh_channel:start_link/4</c> </p> + <c>ssh_channel:start_link/4</c>.</p> </note> </desc> </func> <func> <name>reply(Client, Reply) -> _</name> - <fsummary>Send a reply to a client.</fsummary> + <fsummary>Sends a reply to a client.</fsummary> <type> <v>Client - opaque to the user, see explanation below</v> <v>Reply = term()</v> </type> <desc> - <p>This function can be used by a channel to explicitly send a + <p>This function can be used by a channel to send a reply to a client that called <c>call/[2,3]</c> when the reply cannot be defined in the return value of <seealso marker ="#Module:handle_call-3">Module:handle_call/3</seealso>.</p> <p><c>Client</c> must be the <c>From</c> argument provided to the callback function <c>handle_call/3</c>. <c>Reply</c> is an arbitrary term, - which will be given back to the client as the return value of - <seealso marker="#call-2">ssh_channel:call/[2,3].</seealso>></p> + which is given back to the client as the return value of + <seealso marker="#call-2">ssh_channel:call/[2,3].</seealso></p> </desc> </func> @@ -193,24 +208,25 @@ <name>start(SshConnection, ChannelId, ChannelCb, CbInitArgs) -> </name> <name>start_link(SshConnection, ChannelId, ChannelCb, CbInitArgs) -> {ok, ChannelRef} | {error, Reason}</name> - <fsummary> Starts a processes that handles a SSH channel. </fsummary> + <fsummary>Starts a process that handles an SSH channel.</fsummary> <type> <v>SshConnection = ssh_connection_ref()</v> - <v>ChannelId = ssh_channel_id() </v> - <d> As returned by cannot be defined in the return value of - <seealso marker ="ssh_connection#session_channel/2">ssh_connection:session_channel/[2,4]</seealso></d> + <v>ChannelId = ssh_channel_id()</v> + <d>As returned by + <seealso marker ="ssh_connection#session_channel/2"> + ssh_connection:session_channel/[2,4]</seealso>.</d> <v>ChannelCb = atom()</v> - <d> The name of the module implementing the service specific parts + <d>Name of the module implementing the service-specific parts of the channel.</d> <v>CbInitArgs = [term()]</v> - <d>Argument list for the init function in the callback module. </d> + <d>Argument list for the <c>init</c> function in the callback module.</d> <v>ChannelRef = pid()</v> </type> <desc> - <p>Starts a processes that handles an SSH channel. It will be - called internally by the SSH daemon or explicitly by the SSH - client implementations. The behavior will set the - <c>trap_exit</c> flag to true. + <p>Starts a process that handles an SSH channel. It is + called internally, by the <c>ssh</c> daemon, or explicitly by the <c>ssh</c> + client implementations. The behavior sets the + <c>trap_exit</c> flag to <c>true</c>. </p> </desc> </func> @@ -219,19 +235,19 @@ <section> <marker id="cb_timeouts"></marker> - <title> CALLBACK TIMEOUTS</title> + <title>CALLBACK TIME-OUTS</title> - <p>The timeout values that may be returned by the callback functions - has the same semantics as in a <seealso marker="stdlib:gen_server">gen_server</seealso> - If the timeout occurs <seealso marker="#Module:handle_msg-2">handle_msg/2</seealso> - will be called as <c>handle_msg(timeout, State). </c></p> + <p>The time-out values that can be returned by the callback functions + have the same semantics as in a <seealso marker="stdlib:gen_server">gen_server</seealso>. + If the time-out occurs, <seealso marker="#Module:handle_msg-2">handle_msg/2</seealso> + is called as <c>handle_msg(timeout, State)</c>.</p> </section> <funcs> <func> <name>Module:code_change(OldVsn, State, Extra) -> {ok, NewState}</name> - <fsummary> Converts process state when code is changed.</fsummary> + <fsummary>Converts process state when code is changed.</fsummary> <type> <v>OldVsn = term()</v> <d>In the case of an upgrade, <c>OldVsn</c> is <c>Vsn</c>, and @@ -241,31 +257,31 @@ <c>Module</c>. If no such attribute is defined, the version is the checksum of the BEAM file.</d> <v>State = term()</v> - <d>The internal state of the channel.</d> + <d>Internal state of the channel.</d> <v>Extra = term()</v> - <d>Passed as-is from the <c>{advanced,Extra}</c> + <d>Passed “as-is” from the <c>{advanced,Extra}</c> part of the update instruction.</d> </type> <desc> - <p> Converts process state when code is changed.</p> + <p>Converts process state when code is changed.</p> - <p>This function is called by a client side channel when it - should update its internal state during a release - upgrade/downgrade, i.e. when the instruction - <c>{update,Module,Change,...}</c> where - <c>Change={advanced,Extra}</c> is given in the <c>appup</c> - file. See <seealso marker="doc/design_principles:release_handling#instr">OTP - Design Principles</seealso> for more information. + <p>This function is called by a client-side channel when it + is to update its internal state during a release + upgrade or downgrade, that is, when the instruction + <c>{update,Module,Change,...}</c>, where + <c>Change={advanced,Extra}</c>, is given in the <c>appup</c> + file. For more information, refer to Section 9.11.6 + Release Handling Instructions in the + <seealso marker="doc/design_principles:release_handling#instr">System Documentation</seealso>. </p> <note><p>Soft upgrade according to the OTP release concept is not straight forward for the server side, as subsystem - channel processes are spawned by the SSH application and - hence added to its supervisor tree. It could be possible to - upgrade the subsystem channels, when upgrading the user - application, if the callback functions can handle two - versions of the state, but this function can not be used in - the normal way.</p> + channel processes are spawned by the <c>ssh</c> application and + hence added to its supervisor tree. The subsystem channels can + be upgraded when upgrading the user application, if the callback + functions can handle two versions of the state, but this function + cannot be used in the normal way.</p> </note> </desc> @@ -274,30 +290,30 @@ <func> <name>Module:init(Args) -> {ok, State} | {ok, State, timeout()} | {stop, Reason}</name> - <fsummary> Makes necessary initializations and returns the + <fsummary>Makes necessary initializations and returns the initial channel state if the initializations succeed.</fsummary> <type> - <v> Args = term() </v> - <d> Last argument to ssh_channel:start_link/4.</d> - <v> State = term() </v> - <v> Reason = term() </v> + <v>Args = term()</v> + <d>Last argument to <c>ssh_channel:start_link/4</c>.</d> + <v>State = term()</v> + <v>Reason = term()</v> </type> <desc> - <p> Makes necessary initializations and returns the initial channel + <p>Makes necessary initializations and returns the initial channel state if the initializations succeed. </p> - <p>For more detailed information on timeouts see the section - <seealso marker="#cb_timeouts">CALLBACK TIMEOUTS</seealso>. </p> + <p>For more detailed information on time-outs, see Section + <seealso marker="#cb_timeouts">CALLBACK TIME-OUTS</seealso>. </p> </desc> </func> <func> <name>Module:handle_call(Msg, From, State) -> Result</name> - <fsummary> Handles messages sent by calling - <c>ssh_channel:call/[2,3]</c></fsummary> + <fsummary>Handles messages sent by calling + <c>ssh_channel:call/[2,3]</c>.</fsummary> <type> <v>Msg = term()</v> - <v>From = opaque to the user should be used as argument to + <v>From = Opaque to the user, is to be used as argument to ssh_channel:reply/2</v> <v>State = term()</v> <v>Result = {reply, Reply, NewState} | {reply, Reply, NewState, timeout()} @@ -311,15 +327,15 @@ <p>Handles messages sent by calling <seealso marker="#call-2">ssh_channel:call/[2,3]</seealso> </p> - <p>For more detailed information on timeouts see the section - <seealso marker="#cb_timeouts">CALLBACK TIMEOUTS</seealso>. </p> + <p>For more detailed information on time-outs,, see Section + <seealso marker="#cb_timeouts">CALLBACK TIME-OUTS</seealso>.</p> </desc> </func> <func> <name>Module:handle_cast(Msg, State) -> Result</name> - <fsummary> Handles messages sent by calling - <c>ssh_channel:cact/2</c></fsummary> + <fsummary>Handles messages sent by calling + <c>ssh_channel:cact/2</c>.</fsummary> <type> <v>Msg = term()</v> <v>State = term()</v> @@ -329,11 +345,11 @@ <v>Reason = term()</v> </type> <desc> - <p> Handles messages sent by calling - <c>ssh_channel:cast/2</c> + <p>Handles messages sent by calling + <c>ssh_channel:cast/2</c>. </p> - <p>For more detailed information on timeouts see the section - <seealso marker="#cb_timeouts">CALLBACK TIMEOUTS</seealso>. </p> + <p>For more detailed information on time-outs, see Section + <seealso marker="#cb_timeouts">CALLBACK TIME-OUTS</seealso>.</p> </desc> </func> @@ -341,33 +357,33 @@ <name>Module:handle_msg(Msg, State) -> {ok, State} | {stop, ChannelId, State}</name> - <fsummary> Handle other messages than SSH connection protocol, - call or cast messages sent to the channel.</fsummary> + <fsummary>Handles other messages than SSH connection protocol, + call, or cast messages sent to the channel.</fsummary> <type> <v>Msg = timeout | term()</v> <v>ChannelId = ssh_channel_id()</v> <v>State = term() </v> </type> <desc> - <p>Handle other messages than ssh connection protocol, call or + <p>Handles other messages than SSH Connection Protocol, call, or cast messages sent to the channel. </p> - <p> Possible erlang 'EXIT'-messages should be handled by this - function and all channels should handle the following message.</p> + <p>Possible Erlang 'EXIT' messages is to be handled by this + function and all channels are to handle the following message.</p> <taglist> <tag><c><![CDATA[{ssh_channel_up, ssh_channel_id(), ssh_connection_ref()}]]></c></tag> - <item>This is the first messages that will be received by - the channel, it is sent just before the <seealso + <item><p>This is the first message that the channel receives. + It is sent just before the <seealso marker="#init-1">ssh_channel:init/1</seealso> function - returns successfully. This is especially useful if the + returns successfully. This is especially useful if the server wants to send a message to the client without first receiving a message from it. If the message is not - useful for your particular scenario just ignore it by - immediately returning {ok, State}. - </item> + useful for your particular scenario, ignore it by + immediately returning <c>{ok, State}</c>. + </p></item> </taglist> </desc> </func> @@ -375,42 +391,44 @@ <func> <name>Module:handle_ssh_msg(Msg, State) -> {ok, State} | {stop, ChannelId, State}</name> - <fsummary> Handles ssh connection protocol messages. </fsummary> + <fsummary>Handles <c>ssh</c> connection protocol messages.</fsummary> <type> - <v>Msg = <seealso marker="ssh_connection"> ssh_connection:event() </seealso> </v> + <v>Msg = ssh_connection:event()</v> <v>ChannelId = ssh_channel_id()</v> <v>State = term()</v> </type> <desc> - <p> Handles SSH connection protocol messages that may need - service specific attention. + <p>Handles SSH Connection Protocol messages that may need + service-specific attention. For details, + see <seealso marker="ssh_connection"> ssh_connection:event()</seealso>. </p> - <p> The following message is completely taken care of by the - SSH channel behavior</p> + <p>The following message is taken care of by the + <c>ssh_channel</c> behavior.</p> <taglist> <tag><c><![CDATA[{closed, ssh_channel_id()}]]></c></tag> - <item> The channel behavior will send a close message to the - other side if such a message has not already been sent and - then terminate the channel with reason normal.</item> + <item><p>The channel behavior sends a close message to the + other side, if such a message has not already been sent. + Then it terminates the channel with reason <c>normal</c>.</p></item> </taglist> </desc> </func> <func> <name>Module:terminate(Reason, State) -> _</name> - <fsummary> </fsummary> + <fsummary>Does cleaning up before channel process termination. +</fsummary> <type> <v>Reason = term()</v> <v>State = term()</v> </type> <desc> <p>This function is called by a channel process when it is - about to terminate. Before this function is called <seealso + about to terminate. Before this function is called, <seealso marker="ssh_connection#close-2"> ssh_connection:close/2 - </seealso> will be called if it has not been called earlier. - This function should do any necessary cleaning + </seealso> is called, if it has not been called earlier. + This function does any necessary cleaning up. When it returns, the channel process terminates with reason <c>Reason</c>. The return value is ignored. </p> |