systemd-socket-proxyd(8) — Chainguard OS Manuals

SYSTEMD-SOCKET-PROXYD(8)

systemd-socket-proxyd

SYSTEMD-SOCKET-PROXYD(8)

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

.SH "SYNOPSIS"

.HP 528u

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

.HP 528u

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

.SH "DESCRIPTION"

.PP 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.

.PP 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.

.PP 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.

.PP 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.

.SH "OPTIONS"

.PP The following options are understood:

.PP -h, --help

Print a short help text and exit.

.RE
.PP --version

Print a short version string and exit.

.RE
.PP --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.

.RE
.PP --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.

.RE
.PP --proxy-protocol=

Uses the PROXY protocol[1] to communicate with the server. This allows an appropriately configured server to know the real client IP address. Takes the version of the PROXY protocol[1] used, and only supports v1 for now. Default is not to use a PROXY protocol.

Added in version 261.

.RE

.SH "EXIT STATUS"

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

.SH "EXAMPLES"

.SS "Simple Example"

.PP Use two services with a dependency and no namespace isolation.

.PP Example 1. proxy-to-nginx.socket

[Socket]
ListenStream=80
[Install]
WantedBy=sockets.target

.PP 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

.PP Example 3. nginx.conf

[...]
server {


    listen       unix:/run/nginx/socket;


    [...]

.PP Example 4. Enabling the proxy

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

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

.SS "Namespace Example"

.PP 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.

.PP Example 5. proxy-to-nginx.socket

[Socket]
ListenStream=80
[Install]
WantedBy=sockets.target

.PP 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

.PP Example 7. nginx.conf

[...]
server {


    listen       8080;


    [...]

.PP Example 8. Enabling the proxy

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

.SS "PROXY protocol example with nginx"

.PP systemd-socket-proxyd and nginx using the PROXY protocol

.PP Example 9. proxy-to-nginx.socket

[Socket]
ListenStream=80
[Install]
WantedBy=sockets.target

.PP Example 10. 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 --proxy-protocol=v1 /run/nginx/socket
PrivateTmp=yes
PrivateNetwork=yes

.PP Example 11. nginx.conf

[...]
server {


    listen         unix:/run/nginx/socket proxy_protocol;


    real_ip_header proxy_protocol;


    [...]

.PP Example 12. Enabling the proxy

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

.SH "SEE ALSO"

.PP systemd(1), systemd.socket(5), systemd.service(5), systemctl(1), socat(1), nginx(1), curl(1), PROXY protocol specification[1], nginx: Accepting the PROXY Protocol[2]

NOTES

1.: PROXY protocol

https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt

2.: nginx: Accepting the PROXY Protocol

https://docs.nginx.com/nginx/admin-guide/load-balancer/using-proxy-protocol/

systemd 262.2