mdns: get_interface_addr_for_ip once per query (#275)

Author: melekes

mdns/src/conn/mod.rs

@@ -297,6 +297,7 @@ async fn run(
     dst_addr: SocketAddr,
     queries: &Arc<Mutex<Vec<Query>>>,
 ) {
+    let mut interface_addr = None;
     for _ in 0..=MAX_MESSAGE_RECORDS {
         let q = match p.question() {
             Ok(q) => q,
@@ -313,16 +314,22 @@ async fn run(
 
         for local_name in local_names {
             if *local_name == q.name.data {
-                let interface_addr = match get_interface_addr_for_ip(src).await {
-                    Ok(e) => e,
-                    Err(e) => {
-                        log::warn!(
-                            "Failed to get local interface to communicate with {}: {:?}",
-                            &src,
-                            e
-                        );
-                        continue;
-                    }
+                let interface_addr = match interface_addr {
+                    Some(addr) => addr,
+                    None => match get_interface_addr_for_ip(src).await {
+                        Ok(addr) => {
+                            interface_addr.replace(addr);
+                            addr
+                        }
+                        Err(e) => {
+                            log::warn!(
+                                "Failed to get local interface to communicate with {}: {:?}",
+                                &src,
+                                e
+                            );
+                            continue;
+                        }
+                    },
                 };
 
                 log::trace!(
@@ -332,7 +339,7 @@ async fn run(
                     interface_addr
                 );
                 if let Err(e) =
-                    send_answer(socket, interface_addr, &q.name.data, src.ip(), dst_addr).await
+                    send_answer(socket, &interface_addr, &q.name.data, src.ip(), dst_addr).await
                 {
                     log::error!("Error sending answer to client: {:?}", e);
                     continue;
@@ -374,7 +381,7 @@ async fn run(
 
 async fn send_answer(
     socket: &Arc<UdpSocket>,
-    interface_addr: SocketAddr,
+    interface_addr: &SocketAddr,
     name: &str,
     dst: IpAddr,
     dst_addr: SocketAddr,