feat: Allow configuring the desired client IP source

src/core/config/mod.rs

@@ -370,6 +370,28 @@ pub struct Config {
 	#[serde(default = "default_ip_lookup_strategy")]
 	pub ip_lookup_strategy: u8,
 
+	/// The source to use for discovering the real connecting client IP.
+	///
+	/// Takes the number of any of the following options:
+	///
+	/// 0 - Use the IP address of the TCP connection
+	/// 1 - `Cf-Connecting-Ip` header
+	/// 2 - `CloudFront-Viewer-Address` header
+	/// 3 - `Fly-Client-IP` header
+	/// 4 - rightmost value of the `X-Forwarded-For` header
+	/// 5 - `True-Client-Ip` header
+	/// 6 - `X-Envoy-External-Address` header
+	/// 7 - `X-Real-Ip` header
+	///
+	/// Only change this from `0` if you are certain only your reverse proxy
+	/// will send the expected header. There is no "is the connecting IP allowed
+	/// to set this header" check; if the header selected is present, it is
+	/// used.
+	///
+	/// default: 0
+	#[serde(default)]
+	pub request_ip_source: u8,
+
 	/// Max request size for file uploads in bytes. Defaults to 20MB.
 	/// Also limits incoming federated media.
 	///