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<refentry id="systemd-socket-proxyd"
          xmlns:xi="http://www.w3.org/2001/XInclude">

        <refentryinfo>
                <title>systemd-socket-proxyd</title>
                <productname>systemd</productname>
                <authorgroup>
                        <author>
                                <contrib>Developer</contrib>
                                <firstname>David</firstname>
                                <surname>Strauss</surname>
                                <email>david@davidstrauss.net</email>
                        </author>
                </authorgroup>
        </refentryinfo>
        <refmeta>
                <refentrytitle>systemd-socket-proxyd</refentrytitle>
                <manvolnum>8</manvolnum>
        </refmeta>
        <refnamediv>
                <refname>systemd-socket-proxyd</refname>
                <refpurpose>Bidirectionally proxy local sockets to another (possibly remote) socket.</refpurpose>
        </refnamediv>
        <refsynopsisdiv>
                <cmdsynopsis>
                        <command>systemd-socket-proxyd</command>
                        <arg choice="opt" rep="repeat"><replaceable>OPTIONS</replaceable></arg>
                        <arg choice="plain"><replaceable>HOST</replaceable>:<replaceable>PORT</replaceable></arg>
                </cmdsynopsis>
                <cmdsynopsis>
                        <command>systemd-socket-proxyd</command>
                        <arg choice="opt" rep="repeat"><replaceable>OPTIONS</replaceable></arg>
                        <arg choice="plain"><replaceable>UNIX-DOMAIN-SOCKET-PATH</replaceable>
                        </arg>
                </cmdsynopsis>
        </refsynopsisdiv>
        <refsect1>
                <title>Description</title>
                <para>
                <command>systemd-socket-proxyd</command> is a generic
                socket-activated network socket forwarder proxy daemon
                for IPv4, IPv6 and UNIX stream sockets. It may be used
                to bi-directionally forward traffic from a local listening socket to a
                local or remote destination socket.</para>

                <para>One use of this tool is to provide
                socket activation support for services that do not
                natively support socket activation. On behalf of the
                service to activate, the proxy inherits the socket
                from systemd, accepts each client connection, opens a
                connection to a configured server for each client, and
                then bidirectionally forwards data between the
                two.</para>
                <para>This utility's behavior is similar to
                <citerefentry><refentrytitle>socat</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
                The main differences for <command>systemd-socket-proxyd</command>
                are support for socket activation with
                <literal>Accept=false</literal> and an event-driven
                design that scales better with the number of
                connections.</para>
        </refsect1>
        <refsect1>
                <title>Options</title>
                <para>The following options are understood:</para>
                <variablelist>
                        <xi:include href="standard-options.xml" xpointer="help" />
                        <xi:include href="standard-options.xml" xpointer="version" />
                </variablelist>
        </refsect1>
        <refsect1>
                <title>Exit status</title>
                <para>On success, 0 is returned, a non-zero failure
                code otherwise.</para>
        </refsect1>
        <refsect1>
                <title>Examples</title>
                <refsect2>
                        <title>Simple Example</title>
                        <para>Use two services with a dependency
                        and no namespace isolation.</para>
                        <example>
                                <title>proxy-to-nginx.socket</title>
                                <programlisting><![CDATA[[Socket]
ListenStream=80

[Install]
WantedBy=sockets.target]]></programlisting>
                        </example>
                        <example>
                                <title>proxy-to-nginx.service</title>
                                <programlisting><![CDATA[[Unit]
Requires=nginx.service
After=nginx.service

[Service]
ExecStart=/usr/lib/systemd/systemd-socket-proxyd /tmp/nginx.sock
PrivateTmp=yes
PrivateNetwork=yes]]></programlisting>
                        </example>
                        <example>
                                <title>nginx.conf</title>
                                <programlisting>
<![CDATA[[...]
server {
    listen       unix:/tmp/nginx.sock;
    [...]]]>
</programlisting>
                        </example>
                        <example>
                                <title>Enabling the proxy</title>
                                <programlisting><![CDATA[# systemctl enable proxy-to-nginx.socket
# systemctl start proxy-to-nginx.socket
$ curl http://localhost:80/]]></programlisting>
                        </example>
                </refsect2>
                <refsect2>
                        <title>Namespace Example</title>
                        <para>Similar as above, but runs the socket
                        proxy and the main service in the same private
                        namespace, assuming that
                        <filename>nginx.service</filename> has
                        <varname>PrivateTmp=</varname> and
                        <varname>PrivateNetwork=</varname> set,
                        too.</para>
                        <example>
                                <title>proxy-to-nginx.socket</title>
                                <programlisting><![CDATA[[Socket]
ListenStream=80

[Install]
WantedBy=sockets.target]]></programlisting>
                        </example>
                        <example>
                                <title>proxy-to-nginx.service</title>
                                <programlisting><![CDATA[[Unit]
Requires=nginx.service
After=nginx.service
JoinsNamespaceOf=nginx.service

[Service]
ExecStart=/usr/lib/systemd/systemd-socket-proxyd 127.0.0.1:8080
PrivateTmp=yes
PrivateNetwork=yes]]></programlisting>
                        </example>
                        <example>
                                <title>nginx.conf</title>
                                <programlisting><![CDATA[[...]
server {
    listen       8080;
    listen       unix:/tmp/nginx.sock;
    [...]]]></programlisting>
                        </example>
                        <example>
                                <title>Enabling the proxy</title>
                                <programlisting><![CDATA[# systemctl enable proxy-to-nginx.socket
# systemctl start proxy-to-nginx.socket
$ curl http://localhost:80/]]></programlisting>
                        </example>
                </refsect2>
        </refsect1>
        <refsect1>
                <title>See Also</title>
                <para>
                        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>socat</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>nginx</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>curl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
                </para>
        </refsect1>
</refentry>
