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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /Documentation/kdbus/kdbus.endpoint.xml
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+<?xml version='1.0'?> <!--*-nxml-*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<refentry id="kdbus.endpoint">
+
+ <refentryinfo>
+ <title>kdbus.endpoint</title>
+ <productname>kdbus.endpoint</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>kdbus.endpoint</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>kdbus.endpoint</refname>
+ <refpurpose>kdbus endpoint</refpurpose>
+ </refnamediv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>
+ Endpoints are entry points to a bus (see
+ <citerefentry>
+ <refentrytitle>kdbus.bus</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>).
+ By default, each bus has a default
+ endpoint called 'bus'. The bus owner has the ability to create custom
+ endpoints with specific names, permissions, and policy databases
+ (see below). An endpoint is presented as file underneath the directory
+ of the parent bus.
+ </para>
+ <para>
+ To create a custom endpoint, open the default endpoint
+ (<literal>bus</literal>) and use the
+ <constant>KDBUS_CMD_ENDPOINT_MAKE</constant> ioctl with
+ <type>struct kdbus_cmd</type>. Custom endpoints always have a policy
+ database that, by default, forbids any operation. You have to explicitly
+ install policy entries to allow any operation on this endpoint.
+ </para>
+ <para>
+ Once <constant>KDBUS_CMD_ENDPOINT_MAKE</constant> succeeded, the new
+ endpoint will appear in the filesystem
+ (<citerefentry>
+ <refentrytitle>kdbus.bus</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>), and the used file descriptor will manage the
+ newly created endpoint resource. It cannot be used to manage further
+ resources and must be kept open as long as the endpoint is needed. The
+ endpoint will be terminated as soon as the file descriptor is closed.
+ </para>
+ <para>
+ Endpoint names may be chosen freely except for one restriction: the name
+ must be prefixed with the numeric effective UID of the creator and a dash.
+ This is required to avoid namespace clashes between different users. When
+ creating an endpoint, the name that is passed in must be properly
+ formatted or the kernel will refuse creation of the endpoint. Example:
+ <literal>1047-my-endpoint</literal> is an acceptable name for an
+ endpoint registered by a user with UID 1047. However,
+ <literal>1024-my-endpoint</literal> is not, and neither is
+ <literal>my-endpoint</literal>. The UID must be provided in the
+ user-namespace of the bus.
+ </para>
+ <para>
+ To create connections to a bus, use <constant>KDBUS_CMD_HELLO</constant>
+ on a file descriptor returned by <function>open()</function> on an
+ endpoint node. See
+ <citerefentry>
+ <refentrytitle>kdbus.connection</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>
+ for further details.
+ </para>
+ </refsect1>
+
+ <refsect1>
+ <title>Creating custom endpoints</title>
+ <para>
+ To create a new endpoint, the
+ <constant>KDBUS_CMD_ENDPOINT_MAKE</constant> command is used. Along with
+ the endpoint's name, which will be used to expose the endpoint in the
+ <citerefentry>
+ <refentrytitle>kdbus.fs</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>,
+ the command also optionally takes items to set up the endpoint's
+ <citerefentry>
+ <refentrytitle>kdbus.policy</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>.
+ <constant>KDBUS_CMD_ENDPOINT_MAKE</constant> takes a
+ <type>struct kdbus_cmd</type> argument.
+ </para>
+ <programlisting>
+struct kdbus_cmd {
+ __u64 size;
+ __u64 flags;
+ __u64 return_flags;
+ struct kdbus_item items[0];
+};
+ </programlisting>
+
+ <para>The fields in this struct are described below.</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><varname>size</varname></term>
+ <listitem><para>
+ The overall size of the struct, including its items.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>flags</varname></term>
+ <listitem><para>The flags for creation.</para>
+ <variablelist>
+ <varlistentry>
+ <term><constant>KDBUS_MAKE_ACCESS_GROUP</constant></term>
+ <listitem>
+ <para>Make the endpoint file group-accessible.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>KDBUS_MAKE_ACCESS_WORLD</constant></term>
+ <listitem>
+ <para>Make the endpoint file world-accessible.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>KDBUS_FLAG_NEGOTIATE</constant></term>
+ <listitem>
+ <para>
+ Requests a set of valid flags for this ioctl. When this bit is
+ set, no action is taken; the ioctl will return
+ <errorcode>0</errorcode>, and the <varname>flags</varname>
+ field will have all bits set that are valid for this command.
+ The <constant>KDBUS_FLAG_NEGOTIATE</constant> bit will be
+ cleared by the operation.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>return_flags</varname></term>
+ <listitem><para>
+ Flags returned by the kernel. Currently unused and always set to
+ <constant>0</constant> by the kernel.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>items</varname></term>
+ <listitem>
+ <para>
+ The following items are expected for
+ <constant>KDBUS_CMD_ENDPOINT_MAKE</constant>.
+ </para>
+ <variablelist>
+ <varlistentry>
+ <term><constant>KDBUS_ITEM_MAKE_NAME</constant></term>
+ <listitem>
+ <para>Contains a string to identify the endpoint name.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>KDBUS_ITEM_NAME</constant></term>
+ <term><constant>KDBUS_ITEM_POLICY_ACCESS</constant></term>
+ <listitem>
+ <para>
+ These items are used to set the policy attached to the
+ endpoint. For more details on bus and endpoint policies, see
+ <citerefentry>
+ <refentrytitle>kdbus.policy</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ <para>
+ Unrecognized items are rejected, and the ioctl will fail with
+ <varname>errno</varname> set to <varname>EINVAL</varname>.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Updating endpoints</title>
+ <para>
+ To update an existing endpoint, the
+ <constant>KDBUS_CMD_ENDPOINT_UPDATE</constant> command is used on the file
+ descriptor that was used to create the endpoint, using
+ <constant>KDBUS_CMD_ENDPOINT_MAKE</constant>. The only relevant detail of
+ the endpoint that can be updated is the policy. When the command is
+ employed, the policy of the endpoint is <emphasis>replaced</emphasis>
+ atomically with the new set of rules.
+ The command takes a <type>struct kdbus_cmd</type> argument.
+ </para>
+ <programlisting>
+struct kdbus_cmd {
+ __u64 size;
+ __u64 flags;
+ __u64 return_flags;
+ struct kdbus_item items[0];
+};
+ </programlisting>
+
+ <para>The fields in this struct are described below.</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><varname>size</varname></term>
+ <listitem><para>
+ The overall size of the struct, including its items.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>flags</varname></term>
+ <listitem><para>
+ Unused for this command.
+ <constant>KDBUS_FLAG_NEGOTIATE</constant> is accepted to probe for
+ valid flags. If set, the ioctl will return <errorcode>0</errorcode>,
+ and the <varname>flags</varname> field is set to
+ <constant>0</constant>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>return_flags</varname></term>
+ <listitem><para>
+ Flags returned by the kernel. Currently unused and always set to
+ <constant>0</constant> by the kernel.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>items</varname></term>
+ <listitem>
+ <para>
+ The following items are expected for
+ <constant>KDBUS_CMD_ENDPOINT_UPDATE</constant>.
+ </para>
+ <variablelist>
+ <varlistentry>
+ <term><constant>KDBUS_ITEM_NAME</constant></term>
+ <term><constant>KDBUS_ITEM_POLICY_ACCESS</constant></term>
+ <listitem>
+ <para>
+ These items are used to set the policy attached to the
+ endpoint. For more details on bus and endpoint policies, see
+ <citerefentry>
+ <refentrytitle>kdbus.policy</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>.
+ Existing policy is atomically replaced with the new rules
+ provided.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>KDBUS_ITEM_NEGOTIATE</constant></term>
+ <listitem><para>
+ With this item, programs can <emphasis>probe</emphasis> the
+ kernel for known item types. See
+ <citerefentry>
+ <refentrytitle>kdbus.item</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>
+ for more details.
+ </para></listitem>
+ </varlistentry>
+ </variablelist>
+ <para>
+ Unrecognized items are rejected, and the ioctl will fail with
+ <varname>errno</varname> set to <constant>EINVAL</constant>.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Return value</title>
+ <para>
+ On success, all mentioned ioctl commands return <errorcode>0</errorcode>;
+ on error, <errorcode>-1</errorcode> is returned, and
+ <varname>errno</varname> is set to indicate the error.
+ If the issued ioctl is illegal for the file descriptor used,
+ <varname>errno</varname> will be set to <constant>ENOTTY</constant>.
+ </para>
+
+ <refsect2>
+ <title>
+ <constant>KDBUS_CMD_ENDPOINT_MAKE</constant> may fail with the
+ following errors
+ </title>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>EINVAL</constant></term>
+ <listitem><para>
+ The flags supplied in the <type>struct kdbus_cmd</type>
+ are invalid.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>EINVAL</constant></term>
+ <listitem><para>
+ Illegal combination of <constant>KDBUS_ITEM_NAME</constant> and
+ <constant>KDBUS_ITEM_POLICY_ACCESS</constant> was provided.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>EEXIST</constant></term>
+ <listitem><para>
+ An endpoint of that name already exists.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>EPERM</constant></term>
+ <listitem><para>
+ The calling user is not privileged. See
+ <citerefentry>
+ <refentrytitle>kdbus</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>
+ for information about privileged users.
+ </para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect2>
+
+ <refsect2>
+ <title>
+ <constant>KDBUS_CMD_ENDPOINT_UPDATE</constant> may fail with the
+ following errors
+ </title>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>EINVAL</constant></term>
+ <listitem><para>
+ The flags supplied in <type>struct kdbus_cmd</type>
+ are invalid.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>EINVAL</constant></term>
+ <listitem><para>
+ Illegal combination of <constant>KDBUS_ITEM_NAME</constant> and
+ <constant>KDBUS_ITEM_POLICY_ACCESS</constant> was provided.
+ </para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect2>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <simplelist type="inline">
+ <member>
+ <citerefentry>
+ <refentrytitle>kdbus</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>
+ </member>
+ <member>
+ <citerefentry>
+ <refentrytitle>kdbus.bus</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>
+ </member>
+ <member>
+ <citerefentry>
+ <refentrytitle>kdbus.endpoint</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>
+ </member>
+ <member>
+ <citerefentry>
+ <refentrytitle>kdbus.fs</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>
+ </member>
+ <member>
+ <citerefentry>
+ <refentrytitle>kdbus.item</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>
+ </member>
+ <member>
+ <citerefentry>
+ <refentrytitle>kdbus.message</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>
+ </member>
+ <member>
+ <citerefentry>
+ <refentrytitle>kdbus.name</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>
+ </member>
+ <member>
+ <citerefentry>
+ <refentrytitle>kdbus.pool</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </citerefentry>
+ </member>
+ </simplelist>
+ </refsect1>
+</refentry>