make mainline a separate config section

iroh-dns-server/config.dev.toml

@@ -17,4 +17,5 @@ origins = ["irohdns.example.", "."]
 rr_a = "127.0.0.1"
 rr_ns = "ns1.irohdns.example."
 
-dht_fallback = false
+[mainline]
+enabled = false

iroh-dns-server/config.prod.toml

@@ -12,4 +12,5 @@ origins = ["irohdns.example.org", "."]
 rr_a = "203.0.10.10"
 rr_ns = "ns1.irohdns.example.org."
 
-dht_fallback = false
+[mainline]
+enabled = false

iroh-dns-server/src/config.rs

@@ -41,8 +41,8 @@ pub struct Config {
     /// `Some(MetricsConfig::disabled())`.
     pub metrics: Option<MetricsConfig>,
 
-    /// Fall back to the dht for resolution.
-    pub dht_fallback: bool,
+    /// Config for the mainline lookup.
+    pub mainline: Option<MainlineConfig>,
 }
 
 /// The config for the metrics server.
@@ -64,6 +64,20 @@ impl MetricsConfig {
     }
 }
 
+/// The config for the metrics server.
+#[derive(Debug, Serialize, Deserialize)]
+pub struct MainlineConfig {
+    /// Set to true to enable the mainline lookup.
+    pub enabled: bool,
+}
+
+#[allow(clippy::derivable_impls)]
+impl Default for MainlineConfig {
+    fn default() -> Self {
+        Self { enabled: false }
+    }
+}
+
 impl Config {
     /// Load the config from a file.
     pub async fn load(path: impl AsRef<Path>) -> Result<Config> {
@@ -106,6 +120,10 @@ impl Config {
             },
         }
     }
+
+    pub(crate) fn mainline_enabled(&self) -> bool {
+        self.mainline.as_ref().map(|x| x.enabled).unwrap_or_default()
+    }
 }
 
 impl Default for Config {
@@ -137,7 +155,7 @@ impl Default for Config {
                 rr_ns: Some("ns1.irohdns.example.".to_string()),
             },
             metrics: None,
-            dht_fallback: true,
+            mainline: None,
         }
     }
 }

iroh-dns-server/src/server.rs

@@ -14,8 +14,8 @@ use crate::{
 /// Spawn the server and run until the `Ctrl-C` signal is received, then shutdown.
 pub async fn run_with_config_until_ctrl_c(config: Config) -> Result<()> {
     let mut store = ZoneStore::persistent(Config::signed_packet_store_path()?)?;
-    if config.dht_fallback {
-        store = store.with_pkarr(Some(Default::default()));
+    if config.mainline_enabled() {
+        store = store.with_pkarr(Default::default());
     };
     let server = Server::spawn(config, store).await?;
     tokio::signal::ctrl_c().await?;