fix: Disable mDNS when responder startup fails

Fixes INTIFACE-CENTRAL-10K

Author: qdot

crates/intiface_engine/src/engine.rs

@@ -117,7 +117,7 @@ impl IntifaceEngine {
       // TODO Unregister whenever we have a live connection
 
       // TODO Support different services for engine versus repeater
-      Some(IntifaceMdns::new())
+      IntifaceMdns::new()
     } else {
       None
     };

crates/intiface_engine/src/mdns.rs

@@ -6,28 +6,63 @@
 // for full license information.
 
 use rand::distr::{Alphanumeric, SampleString};
+use std::{future::Future, io};
 
 pub struct IntifaceMdns {
   _responder: libmdns::Responder,
   _svc: libmdns::Service,
 }
 
 impl IntifaceMdns {
-  pub fn new() -> Self {
+  pub fn new() -> Option<Self> {
     let random_suffix = Alphanumeric.sample_string(&mut rand::rng(), 6);
     let instance_name = format!("Intiface {}", random_suffix);
     info!(
       "Bringing up mDNS Advertisment using instance name {}",
       instance_name
     );
 
-    let (_responder, task) = libmdns::Responder::with_default_handle().unwrap();
+    Self::from_responder_result(&instance_name, libmdns::Responder::with_default_handle())
+  }
+
+  fn from_responder_result<T>(
+    instance_name: &str,
+    responder_result: io::Result<(libmdns::Responder, T)>,
+  ) -> Option<Self>
+  where
+    T: Future<Output = ()> + Send + 'static,
+  {
+    let (_responder, task) = match responder_result {
+      Ok(result) => result,
+      Err(err) => {
+        warn!("Unable to bring up mDNS advertisement: {}", err);
+        return None;
+      }
+    };
     let _svc = _responder.register("_intiface_engine._tcp", &instance_name, 12345, &["path=/"]);
     tokio::spawn(async move {
       info!("Entering up mDNS task");
       task.await;
       info!("Exiting mDNS task");
     });
-    Self { _responder, _svc }
+    Some(Self { _responder, _svc })
+  }
+}
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  #[test]
+  fn mdns_startup_error_disables_advertisement() {
+    let result = IntifaceMdns::from_responder_result::<std::future::Pending<()>>(
+      "Intiface Test",
+      Err(io::Error::new(
+        io::ErrorKind::AddrInUse,
+        "Address already in use",
+      )),
+    );
+
+    assert!(result.is_none());
   }
 }