haproxy

The haproxy protocol, while still having proxy in its name, is different thanother proxy options and does not work with proxies in the same way the otherproxy options do.

This is a way for a client to pass its IP address to the server in spite ofhow the traffic reaches it: tunnels, TCP proxies, load balancers, transparentproxies and what not. Services that somehow change what source IP address thatis being used when the traffic ends up in the server, making it impossible forthe server to figure out the IP address of the client by itself.

The haproxy protocol is simple. It needs to be supported by the server,meaning a user cannot just decide to use it with an unwilling or uncooperativeserver. If itdoes support it, you can tell curl to use it to pass on itsown IP address to the server.

curl and haproxy

curl only supports the haproxy protocol v1.

To pass on the actual IP address of the connection that is being used rightnow, simply add the boolean flag like this:

curl --haproxy-protocol https://example.com/

If such a command line for some reason does not provide the IP address youthink it should pass on, you can specify the exact address yourself, usingeither an IPv4 or an IPv6 numerical address:

curl --haproxy-clientip 10.0.0.1 https://example.com/curl --haproxy-clientip fe80::fea3:8a22 https://example.com/