CURLOPT_HAPROXY_CLIENT_IP(3) Introduction to Library Functions

NAME

CURLOPT_HAPROXY_CLIENT_IP - set HAProxy PROXY protocol client IP

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HAPROXY_CLIENT_IP,
char *client_ip);

DESCRIPTION

When this parameter is set to a valid IPv4 or IPv6 numerical address
in its printable ASCII string version, the library sends this as the
client address in the HAProxy PROXY protocol v1 header at beginning
of the connection.

The client address is reported upstream as the source and destination
address of the non-existing client connection (since 8.20.0).

This option is an alternative to CURLOPT_HAPROXYPROTOCOL(3) as that
one cannot use a specified address.

Using this option multiple times makes the last set string override
the previous ones. Set it to NULL to disable its use again.

The application does not have to keep the string around after setting
this option.

As with most libcurl options, the user of this option must make sure
that the correct data (address) is passed on. libcurl does little to
no verification.

Note that if you want to send a different HAProxy client IP in a
subsequent request, you need to make sure that it is done over a
fresh connection as libcurl does not send it again while reusing
connections.

DEFAULT

NULL, no HAProxy header is sent

PROTOCOLS

This functionality affects all supported protocols

EXAMPLE

int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode result;
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
curl_easy_setopt(curl, CURLOPT_HAPROXY_CLIENT_IP, "1.1.1.1");
result = curl_easy_perform(curl);
}
}

AVAILABILITY

Added in curl 8.2.0

RETURN VALUE

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error
occurred, see libcurl-errors(3).

SEE ALSO

CURLOPT_HAPROXYPROTOCOL(3), CURLOPT_PROXY(3)

libcurl 2026-04-29 CURLOPT_HAPROXY_CLIENT_IP(3)