feat: add IPV4_DOMAIN config for dual-stack IP detection

.env.example

@@ -13,9 +13,17 @@ DB_UPDATE_INTERVAL_HOURS=24
 # Site domain name (used for display/metadata)
 SITE_DOMAIN=localhost
 
+# IPv4-only domain for dual-stack detection (e.g., noipv6.org)
+# Leave empty to disable IPv4 detection for IPv6 users
+IPV4_DOMAIN=
+
 # Enable development mode (uses 1.1.1.1 as fallback when CF-Connecting-IP is absent)
 DEV_MODE=false
 
-# Path to the TLS certificate directory for HAproxy
+# Path to the TLS certificate directory for HAProxy (main domain)
 # The directory must contain origin.pem (combined cert + key)
 CERT_PATH=./haproxy/certs
+
+# Path to the TLS certificate directory for the IPv4-only domain
+# The directory must contain origin.pem (combined cert + key)
+IPV4_CERT_PATH=./haproxy/certs-ipv4

docker-compose.yml

@@ -6,6 +6,7 @@ services:
     volumes:
       - ./haproxy/haproxy.cfg:/usr/local/etc/haproxy/haproxy.cfg:ro
       - ${CERT_PATH:-./haproxy/certs}:/etc/haproxy/certs:ro
+      - ${IPV4_CERT_PATH:-./haproxy/certs-ipv4}:/etc/haproxy/certs-ipv4:ro
     depends_on:
       app:
         condition: service_healthy
@@ -21,6 +22,7 @@ services:
       - DB_UPDATE_URL=${DB_UPDATE_URL:-https://github.com/NetworkCats/Merged-IP-Data/releases/latest/download/Merged-IP.mmdb}
       - DB_UPDATE_INTERVAL_HOURS=${DB_UPDATE_INTERVAL_HOURS:-24}
       - SITE_DOMAIN=${SITE_DOMAIN:-localhost}
+      - IPV4_DOMAIN=${IPV4_DOMAIN:-}
     volumes:
       - db_data:/data
     healthcheck:

src/config.rs

@@ -7,6 +7,7 @@ pub struct Config {
     pub db_update_url: String,
     pub db_update_interval_hours: u64,
     pub site_domain: String,
+    pub ipv4_domain: String,
     pub dev_mode: bool,
 }
 
@@ -31,6 +32,8 @@ impl Config {
 
         let site_domain = env::var("SITE_DOMAIN").unwrap_or_else(|_| "localhost".to_string());
 
+        let ipv4_domain = env::var("IPV4_DOMAIN").unwrap_or_default();
+
         let dev_mode = env::var("DEV_MODE")
             .unwrap_or_default()
             .eq_ignore_ascii_case("true");
@@ -41,6 +44,7 @@ impl Config {
             db_update_url,
             db_update_interval_hours,
             site_domain,
+            ipv4_domain,
             dev_mode,
         }
     }
@@ -67,6 +71,7 @@ mod tests {
         "DB_UPDATE_URL",
         "DB_UPDATE_INTERVAL_HOURS",
         "SITE_DOMAIN",
+        "IPV4_DOMAIN",
         "DEV_MODE",
     ];
 
@@ -98,6 +103,7 @@ mod tests {
         assert!(config.db_update_url.contains("Merged-IP.mmdb"));
         assert_eq!(config.db_update_interval_hours, 24);
         assert_eq!(config.site_domain, "localhost");
+        assert!(config.ipv4_domain.is_empty());
         assert!(!config.dev_mode);
     }
 
@@ -181,6 +187,22 @@ mod tests {
         unsafe { remove_var("SITE_DOMAIN") };
     }
 
+    #[test]
+    fn custom_ipv4_domain() {
+        let _guard = lock_env();
+        // SAFETY: ENV_LOCK is held.
+        unsafe {
+            clear_config_vars();
+            set_var("IPV4_DOMAIN", "noipv6.org");
+        }
+
+        let config = Config::from_env();
+        assert_eq!(config.ipv4_domain, "noipv6.org");
+
+        // SAFETY: ENV_LOCK is held.
+        unsafe { remove_var("IPV4_DOMAIN") };
+    }
+
     #[test]
     fn dev_mode_enabled() {
         let _guard = lock_env();

src/handlers.rs

@@ -25,6 +25,7 @@ const DEV_FALLBACK_IP: IpAddr = IpAddr::V4(std::net::Ipv4Addr::new(1, 1, 1, 1));
 pub struct AppState {
     pub db: SharedDb,
     pub site_domain: Arc<str>,
+    pub ipv4_domain: Arc<str>,
     pub dev_mode: bool,
     pub openapi_json: Arc<str>,
 }
@@ -36,6 +37,7 @@ struct IndexTemplate {
     query: String,
     is_query: bool,
     site_domain: Arc<str>,
+    ipv4_domain: Arc<str>,
     css_version: u64,
     js_version: u64,
     asn: String,
@@ -571,6 +573,7 @@ pub async fn root(
         query: query.ip.unwrap_or_default(),
         is_query,
         site_domain: state.site_domain.clone(),
+        ipv4_domain: state.ipv4_domain.clone(),
         css_version: static_assets::asset_version("style.css"),
         js_version: static_assets::asset_version("script.js"),
         asn: format_asn(&info),

src/main.rs

@@ -39,11 +39,13 @@ async fn main() {
     let cancel = CancellationToken::new();
 
     let site_domain: std::sync::Arc<str> = config.site_domain.into();
+    let ipv4_domain: std::sync::Arc<str> = config.ipv4_domain.into();
     let openapi_json = handlers::build_openapi_json(&site_domain);
 
     let state = handlers::AppState {
         db: shared_db.clone(),
         site_domain,
+        ipv4_domain,
         dev_mode: config.dev_mode,
         openapi_json,
     };

tests/integration.rs

@@ -26,9 +26,11 @@ fn build_test_app_with_dev_mode(dev_mode: bool) -> axum::Router {
     let shared_db = db::new_shared(reader);
     let site_domain: std::sync::Arc<str> = "test.example.com".into();
     let openapi_json = build_openapi_json(&site_domain);
+    let ipv4_domain: std::sync::Arc<str> = "noipv6.test.example.com".into();
     let state = AppState {
         db: shared_db,
         site_domain,
+        ipv4_domain,
         dev_mode,
         openapi_json,
     };