systemd-socket-proxyd — Bidirectionally proxy local sockets to another (possibly remote) socket
systemd-socket-proxyd
[OPTIONS
...] HOST
:PORT
systemd-socket-proxyd
[OPTIONS
...] UNIX-DOMAIN-SOCKET-PATH
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.
The following options are understood:
-h
, --help
¶--version
¶--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.
--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
".
Use two services with a dependency and no namespace isolation.
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 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.
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 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 8. Enabling the proxy
# systemctl enable --now proxy-to-nginx.socket $ curl http://localhost:80/