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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 219</span><hr><div class="refentry"><a name="sd_bus_negotiate_fds"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_bus_negotiate_fds, sd_bus_negotiate_timestamps, sd_bus_negotiate_creds — Control feature negotiation on bus connections</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <systemd/sd-bus.h></pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_bus_negotiate_fds</b>(</code></td><td>sd_bus *<var class="pdparam">bus</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">b</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_bus_negotiate_timestamp</b>(</code></td><td>sd_bus *<var class="pdparam">bus</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">b</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_bus_negotiate_creds</b>(</code></td><td>sd_bus *<var class="pdparam">bus</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">b</var>, </td></tr><tr><td> </td><td>uint64_t <var class="pdparam">flags</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm139677995179312"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_bus_negotiate_fds()</code> controls whether
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file descriptor passing shall be negotiated for the specified bus
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connection. It takes a bus object and a boolean, which, when true,
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enables file descriptor passing, and, when false, disables it. Note
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that not all transports and servers support file descriptor
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passing. To find out whether file descriptor passing is available
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after negotiation, use
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<a href="sd_bus_can_send.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_can_send</span>(3)</span></a>
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and pass <code class="constant">SD_BUS_TYPE_UNIX_FD</code>. Note that file
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descriptor passing is always enabled for both sending and
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receiving or for neither, but never only in one direction. By
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default, file descriptor passing is negotiated for all
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connections.</p><p>Note that when bus activation is used, it is highly
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recommended to set the <code class="option">AcceptFileDescriptors=</code>
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setting in the <code class="filename">.busname</code> unit file to the same
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setting as negotiated by the program ultimately activated. By
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default, file descriptor passing is enabled for both.</p><p><code class="function">sd_bus_negotiate_timestamps()</code> controls
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whether implicit sender timestamps shall be attached automatically
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to all incoming messages. Takes a bus object and a boolean, which,
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when true, enables timestamping, and, when false, disables it. If
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this is disabled,
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<a href="sd_bus_message_get_monotonic_usec.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_message_get_monotonic_usec</span>(3)</span></a>,
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<a href="sd_bus_message_get_realtime_usec.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_message_get_realtime_usec</span>(3)</span></a>,
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<a href="sd_bus_message_get_seqno.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_message_get_seqno</span>(3)</span></a>
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fail with <code class="constant">-ENODATA</code> on incoming messages. Note
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that not all transports support timestamping of messages. On local
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transports, the timestamping is applied by the kernel and cannot
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be manipulated by userspace. By default, message timestamping is
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not negotiated for all connections.</p><p><code class="function">sd_bus_negotiate_creds()</code> controls
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whether implicit sender credentials shall be attached
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automatically to all incoming messages. Takes a bus object, a
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boolean indicating whether to enable or disable the credential
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parts encoded in the bit mask value argument. Note that not all
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transports support attaching sender credentials to messages, or do
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not support all types of sender credential parameters, or might
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suppress them under certain circumstances for individual
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messages. On local transports, the sender credentials are attached
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by the kernel and cannot be manipulated by userspace. By default,
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no sender credentials are attached.</p><p>The <code class="function">sd_bus_negotiate_fds()</code> function may
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be called only before the connection has been started with
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<a href="sd_bus_start.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_start</span>(3)</span></a>. Both
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<code class="function">sd_bus_negotiate_timestamp()</code> and
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<code class="function">sd_bus_negotiate_creds()</code> also may be called
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after a connection has been set up. Note that when operating on a
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connection that is shared between multiple components of the same
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program (for example via
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<a href="sd_bus_default.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_default</span>(3)</span></a>)
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it is highly recommended to only enable additional per message
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metadata fields, but never disable them again, in order not to
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disable functionality needed by other components.</p></div><div class="refsect1"><a name="idm139677999065888"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>On success, these functions returns 0 or a
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positive integer. On failure, they return a negative errno-style
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error code.</p></div><div class="refsect1"><a name="idm139677999064560"></a><h2 id="Errors">Errors<a class="headerlink" title="Permalink to this headline" href="#Errors">¶</a></h2><p>Returned errors may indicate the following problems:</p><div class="variablelist"><dl class="variablelist"><dt id="-EPERM"><span class="term"><code class="constant">-EPERM</code></span><a class="headerlink" title="Permalink to this term" href="#-EPERM">¶</a></dt><dd><p>The bus connection has already been started.</p></dd></dl></div></div><div class="refsect1"><a name="idm139677999061552"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p><code class="function">sd_bus_negotiate_fs()</code> and the other
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functions described here are available as a shared library, which
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can be compiled and linked to with the
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<code class="constant">libsystemd</code> <a href="http://linux.die.net/man/1/pkg-config"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
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file.</p></div><div class="refsect1"><a name="idm139677999058016"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
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<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
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<a href="sd-bus.html"><span class="citerefentry"><span class="refentrytitle">sd-bus</span>(3)</span></a>,
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<a href="sd_bus_start.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_start</span>(3)</span></a>,
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<a href="sd_bus_message_can_send.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_message_can_send</span>(3)</span></a>,
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<a href="sd_bus_message_get_monotonic_usec.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_message_get_monotonic_usec</span>(3)</span></a>,
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<a href="sd_bus_message_get_creds.html"><span class="citerefentry"><span class="refentrytitle">sd_bus_message_get_creds</span>(3)</span></a>,
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<a href="systemd.busname.html"><span class="citerefentry"><span class="refentrytitle">systemd.busname</span>(5)</span></a>
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</p></div></div></body></html>
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