WEB: Resolve opt-in decoy hostnames during config preparation #929

Co-Authored-By: brekotis <93345790+brekotis@users.noreply.github.com>

src/config/hot_reload/watcher/preparation.rs

@@ -0,0 +1,85 @@
+use super::*;
+
+/// Restart-only differences must not enqueue another DNS preparation after activation.
+pub(super) fn source_matches_active(
+    active: &ProxyConfig,
+    source: &crate::config::ParsedConfigSource,
+) -> bool {
+    config_equal(active, &overlay_hot_fields(active, &source.config))
+}
+
+/// Reads only source state; watcher initialization and unchanged events never need DNS.
+pub(super) async fn read_source(path: &PathBuf) -> Option<crate::config::ParsedConfigSource> {
+    let path = path.clone();
+    match tokio::task::spawn_blocking(move || ProxyConfig::parse_source(path)).await {
+        Ok(Ok(source)) => Some(source),
+        Ok(Err(error)) => {
+            error!("config reload: failed to parse: {}", error);
+            None
+        }
+        Err(error) => {
+            error!("config reload: source reader failed: {}", error);
+            None
+        }
+    }
+}
+
+/// Prepares fresh evidence only for changed sources or an explicit reload request.
+pub(super) async fn reload(
+    path: &PathBuf,
+    config_tx: &watch::Sender<Arc<ProxyConfig>>,
+    log_tx: &watch::Sender<LogLevel>,
+    detected_ip_v4: Option<IpAddr>,
+    detected_ip_v6: Option<IpAddr>,
+    reload_state: &mut ReloadState,
+    dns_resolver: Option<Arc<crate::network::dns_overrides::GenerationDnsResolver>>,
+    force: bool,
+) -> Option<WatchManifest> {
+    let source = read_source(path).await?;
+    let manifest = WatchManifest::from_source_files(&source.source_files);
+    if !force && reload_state.is_applied(source.rendered_hash) {
+        return Some(manifest);
+    }
+    let loaded = match source.prepare().await {
+        Ok(loaded) => loaded,
+        Err(error) => {
+            error!(
+                "config reload: preparation failed: {}; keeping old config",
+                error
+            );
+            return Some(manifest);
+        }
+    };
+    let old = config_tx.borrow().clone();
+    // Static-site reconstruction after the listener overlay must not block Tokio workers.
+    // The worker only builds data: cancellation cannot leave a detached publisher behind.
+    let result = tokio::task::spawn_blocking(move || {
+        prepare_effective_config(&old, &loaded.config).map(|applied| (loaded, applied))
+    })
+    .await;
+    match result {
+        Ok(Ok(prepared)) => reload_config_with_resolver(
+            prepared,
+            config_tx,
+            log_tx,
+            detected_ip_v4,
+            detected_ip_v6,
+            reload_state,
+            dns_resolver.as_deref(),
+        ),
+        Ok(Err(error)) => {
+            error!(
+                "config reload: effective WEB validation failed: {}; keeping old config",
+                error
+            );
+            Some(manifest)
+        }
+        Err(error) => {
+            error!(
+                "config reload: runtime builder failed: {}; keeping old config",
+                error
+            );
+            Some(manifest)
+        }
+    }
+}