.net core get RemoteIpAddress.MapToIPv4() that is behind cloudflare proxy - asp.net-core

Question

I need to extract the user IP address (v4).
I have the following code to do so:
HttpContext.Connection.RemoteIpAddress.MapToIPv4().ToString();
The problem is that in this case I am getting cloud flare ip address.
How can I get the forwarded v4 IP address?
Thanks

Answer 1

Cloudflare passes all HTTP request headers to your origin web server and adds additional headers.
The header:
CF-Connecting-IP
provides the client IP address connecting to Cloudflare to the origin
web server.
You can also use the header:
X-Forwarded-For
which maintains proxy server and original visitor IP addresses.
For more information about the CloudFlare headers you can refer to the documentation
Actually, you can created a method that tries to check all these headers and return the client IP address value.
private string getRemoteIpAddress(HttpContext accessor) {
// try reading the CloudFlare client IP address header
if (!string.IsNullOrEmpty(accessor.Request.Headers["CF-CONNECTING-IP"]))
return accessor.Request.Headers["CF-CONNECTING-IP"];
// try reading the proxy server and original visitor IP addresses header
var ipAddress = accessor.GetServerVariable("HTTP_X_FORWARDED_FOR");
if (!string.IsNullOrEmpty(ipAddress)) {
var addresses = ipAddress.Split(',');
if (addresses.Length != 0) return addresses.Last();
}
// try reading the remote IpAddress without a proxy
return accessor.Connection.RemoteIpAddress.ToString();
}