SYSTEMD-SOCKET-PROXYD(8)     systemd-socket-proxyd    SYSTEMD-SOCKET-PROXYD(8)

NAME
       systemd-socket-proxyd - Bidirectionally proxy local sockets to another
       (possibly remote) socket

SYNOPSIS
       systemd-socket-proxyd [OPTIONS...] HOST:PORT

       systemd-socket-proxyd [OPTIONS...] UNIX-DOMAIN-SOCKET-PATH

DESCRIPTION
       systemd-socket-proxyd 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.

       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.

       This utility's behavior is similar to socat(1). The main differences
       for systemd-socket-proxyd are support for socket activation with
       "Accept=no" and an event-driven design that scales better with the
       number of connections.

       Note that systemd-socket-proxyd will not forward socket side channel
       information, i.e. will not forward SCM_RIGHTS, SCM_CREDENTIALS,
       SCM_SECURITY, SO_PEERCRED, SO_PEERPIDFD, SO_PEERSEC, SO_PEERGROUPS and
       similar.

OPTIONS
       The following options are understood:

       -h, --help
	   Print a short help text and exit.

       --version
	   Print a short version string and exit.

       --connections-max=, -c
	   Sets the maximum number of simultaneous connections, defaults to
	   256. If the limit of concurrent connections is reached further
	   connections will be refused.

	   Added in version 233.

       --exit-idle-time=
	   Sets the time before exiting when there are no connections,
	   defaults to infinity. Takes a unit-less value in seconds, or a time
	   span value such as "5min 20s".

	   Added in version 246.

EXIT STATUS
       On success, 0 is returned, a non-zero failure code otherwise.

EXAMPLES
   Simple Example
       Use two services with a dependency and no namespace isolation.

       Example 1. proxy-to-nginx.socket

	   [Socket]
	   ListenStream=80

	   [Install]
	   WantedBy=sockets.target

       Example 2. proxy-to-nginx.service

	   [Unit]
	   Requires=nginx.service
	   After=nginx.service
	   Requires=proxy-to-nginx.socket
	   After=proxy-to-nginx.socket

	   [Service]
	   Type=notify
	   ExecStart=/usr/lib/systemd/systemd-socket-proxyd /run/nginx/socket
	   PrivateTmp=yes
	   PrivateNetwork=yes

       Example 3. nginx.conf

	   [...]
	   server {
	       listen	    unix:/run/nginx/socket;
	       [...]

       Example 4. Enabling the proxy

	   # systemctl enable --now proxy-to-nginx.socket
	   $ curl http://localhost:80/

       If nginx.service has StopWhenUnneeded= set, then passing
       --exit-idle-time= to systemd-socket-proxyd allows both services to stop
       during idle periods.

   Namespace Example
       Similar as above, but runs the socket proxy and the main service in the
       same private namespace, assuming that nginx.service has PrivateTmp= and
       PrivateNetwork= set, too.

       Example 5. proxy-to-nginx.socket

	   [Socket]
	   ListenStream=80

	   [Install]
	   WantedBy=sockets.target

       Example 6. proxy-to-nginx.service

	   [Unit]
	   Requires=nginx.service
	   After=nginx.service
	   Requires=proxy-to-nginx.socket
	   After=proxy-to-nginx.socket
	   JoinsNamespaceOf=nginx.service

	   [Service]
	   Type=notify
	   ExecStart=/usr/lib/systemd/systemd-socket-proxyd 127.0.0.1:8080
	   PrivateTmp=yes
	   PrivateNetwork=yes

       Example 7. nginx.conf

	   [...]
	   server {
	       listen	    8080;
	       [...]

       Example 8. Enabling the proxy

	   # systemctl enable --now proxy-to-nginx.socket
	   $ curl http://localhost:80/

SEE ALSO
       systemd(1), systemd.socket(5), systemd.service(5), systemctl(1),
       socat(1), nginx(1), curl(1)

systemd 258					      SYSTEMD-SOCKET-PROXYD(8)