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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">
<!--
  This file is part of systemd.

  Copyright 2013 David Strauss

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="systemd-socket-proxyd">
        <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>1</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>
                        <varlistentry>
                                <term><option>-h</option></term>
                                <term><option>--help</option></term>
                                <listitem>
                                        <para>Prints a short help
                                        text and exits.</para>
                                </listitem>
                        </varlistentry>
                        <varlistentry>
                                <term><option>--version</option></term>
                                <listitem>
                                        <para>Prints a version
                                        string and exits.</para>
                                </listitem>
                        </varlistentry>
                </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>Direct-Use Example</title>
                        <para>Use two services with a dependency
                        and no namespace isolation.</para>
                        <example label="proxy socket unit">
                                <title>/etc/systemd/system/proxy-to-nginx.socket</title>
                                <programlisting>
<![CDATA[[Socket]
ListenStream=80

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

[Service]
ExecStart=/usr/bin/systemd-socket-proxyd /tmp/nginx.sock
PrivateTmp=true
PrivateNetwork=true]]>
</programlisting>
                        </example>
                        <example label="nginx configuration">
                                <title>/etc/nginx/nginx.conf</title>
                                <programlisting>
<![CDATA[[...]
server {
    listen       unix:/tmp/nginx.sock;
    [...]]]>
</programlisting>
                        </example>
                        <example label="commands">
                                <programlisting>
<![CDATA[# systemctl --system daemon-reload
# systemctl start proxy-to-nginx.socket
# systemctl enable proxy-to-nginx.socket
$ curl http://localhost:80/]]>
</programlisting>
                        </example>
                </refsect2>
                <refsect2>
                        <title>Indirect-Use Example</title>
                        <para>Use a shell script to isolate the
                        service and proxy into the same namespace.
                        This is particularly useful for running
                        TCP-only daemons without the daemon
                        affecting ports on regular
                        interfaces.</para>
                        <example label="combined proxy and nginx socket unit">

                                <title>
                                /etc/systemd/system/proxy-with-nginx.socket</title>
                                <programlisting>
<![CDATA[[Socket]
ListenStream=80

[Install]
WantedBy=sockets.target]]>
</programlisting>
                        </example>
                        <example label="combined proxy and nginx service unit">

                                <title>
                                /etc/systemd/system/proxy-with-nginx.service</title>
                                <programlisting>
<![CDATA[[Unit]
After=syslog.target remote-fs.target nss-lookup.target

[Service]
ExecStartPre=/usr/sbin/nginx -t
ExecStart=/usr/bin/socket-proxyd-nginx.sh
PrivateTmp=true
PrivateNetwork=true]]>
</programlisting>
                        </example>
                        <example label="shell script">
                                <title>
                                /usr/bin/socket-proxyd-nginx.sh</title>
                                <programlisting>
<![CDATA[#!/bin/sh
/usr/sbin/nginx
while [ ! -f /tmp/nginx.pid ]
  do
     /usr/bin/inotifywait /tmp/nginx.pid
  done
exec /usr/bin/systemd-socket-proxyd localhost 8080]]>
</programlisting>
                        </example>
                        <example label="nginx configuration">
                                <title>
                                /etc/nginx/nginx.conf</title>
                                <programlisting>
<![CDATA[[...]
server {
    listen       8080;
    listen       unix:/tmp/nginx.sock;
    [...]]]>
</programlisting>
                        </example>
                        <example label="commands">
                                <programlisting>
<![CDATA[# systemctl --system daemon-reload
# systemctl start proxy-with-nginx.socket
# systemctl enable proxy-with-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>
                </para>
        </refsect1>
</refentry>