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 255                                           SYSTEMD-SOCKET-PROXYD(8)