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Diffstat (limited to 'lib/ssh/doc/src/ssh_daemon_channel.xml')
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diff --git a/lib/ssh/doc/src/ssh_daemon_channel.xml b/lib/ssh/doc/src/ssh_daemon_channel.xml new file mode 100644 index 0000000000..8b0ff93f5f --- /dev/null +++ b/lib/ssh/doc/src/ssh_daemon_channel.xml @@ -0,0 +1,169 @@ +<?xml version="1.0" encoding="utf-8" ?> +<!DOCTYPE erlref SYSTEM "erlref.dtd"> + +<erlref> + <header> + <copyright> + <year>2009</year> + <year>2016</year> + <holder>Ericsson AB, All Rights Reserved</holder> + </copyright> + <legalnotice> + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + + The Initial Developer of the Original Code is Ericsson AB. + </legalnotice> + <title>ssh_daemon_channel</title> + <prepared></prepared> + <docno></docno> + <date></date> + <rev></rev> + </header> + <module>ssh_daemon_channel</module> + <modulesummary>-behaviour(ssh_daemon_channel). + </modulesummary> + <description> + <p>SSH services (clients and servers) are implemented as channels + 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 for daemons, 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 <c>ssh</c> applications supervisor tree. + </p> + + <note><p>When implementing a client subsystem handler, use + <seealso marker="ssh_channel">-behaviour(ssh_channel)</seealso> instead. + </p> + </note> + + </description> + + <section> + <title>Callback Functions</title> + <p> + The following functions are to be exported from a + <c>ssh_daemon_channel</c> callback module. + </p> + </section> + + <funcs> + <func> + <name>Module:init(Args) -> {ok, State} | {ok, State, timeout()} | + {stop, Reason}</name> + <fsummary>Makes necessary initializations and returns the + initial channel state if the initializations succeed.</fsummary> + <type> + <v>Args = term()</v> + <d>Last argument to <c>start_link/4</c>.</d> + <v>State = term()</v> + <v>Reason = term()</v> + </type> + <desc> + <p>Makes necessary initializations and returns the initial channel + state if the initializations succeed. + </p> + <p>The time-out values that can be returned + 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> + </desc> + </func> + + <func> + <name>Module:handle_msg(Msg, State) -> {ok, State} | + {stop, ChannelId, State}</name> + + <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 = <seealso marker="ssh#type-channel_id">ssh:channel_id()</seealso></v> + <v>State = term() </v> + </type> + <desc> + <p>Handles other messages than SSH Connection Protocol, call, or + cast messages sent to the channel. + </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>{ssh_channel_up, ssh:channel_id(), ssh:connection_ref()}</c></tag> + <item><p>This is the first message that the channel receives. + 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, ignore it by + immediately returning <c>{ok, State}</c>. + </p></item> + </taglist> + </desc> + </func> + + <func> + <name>Module:handle_ssh_msg(Msg, State) -> {ok, State} | {stop, + ChannelId, State}</name> + <fsummary>Handles <c>ssh</c> connection protocol messages.</fsummary> + <type> + <v>Msg = ssh_connection:event()</v> + <v>ChannelId = <seealso marker="ssh#type-channel_id">ssh:channel_id()</seealso></v> + <v>State = term()</v> + </type> + <desc> + <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 taken care of by the + <c>ssh_daemon_channel</c> behavior.</p> + + <taglist> + <tag><c>{closed, ssh:channel_id()}</c></tag> + <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>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 + marker="ssh_connection#close-2"> ssh_connection:close/2 + </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> + </desc> + </func> + + </funcs> + +</erlref> |