fix(embedded-nal): workaround for binding to any address

Workaround-For: smoltcp-rs/smoltcp#1037

Author: chrysn

src/ariel-os-coap/src/lib.rs

@@ -79,9 +79,7 @@ pub async fn coap_run(handler: impl coap_handler::Handler + coap_handler::Report
 
     info!("Starting up CoAP server");
 
-    // Can't that even bind to the Any address??
-    // let local_any = "0.0.0.0:5683".parse().unwrap(); // shame
-    let local_any = "10.42.0.61:5683".parse().unwrap(); // shame
+    let local_any = "0.0.0.0:5683".parse().unwrap(); // shame
     let mut unconnected = udp_nal::UnconnectedUdp::bind_multiple(socket, local_any)
         .await
         .unwrap();

src/ariel-os-coap/src/udp_nal/mod.rs

@@ -66,7 +66,15 @@ impl<'a> ConnectedUdp<'a> {
         local: SocketAddr,
         remote: SocketAddr,
     ) -> Result<Self, Error> {
-        socket.bind(sockaddr_nal2smol(local)?)?;
+        // Workaround for https://github.com/smoltcp-rs/smoltcp/issues/1037
+        let bind_to = sockaddr_nal2smol(local)?;
+        if bind_to.addr.is_unspecified() {
+            defmt::info!("Binding to port {}", bind_to.port);
+            socket.bind(bind_to.port)?;
+        } else {
+            defmt::info!("Binding to sockaddr {}", bind_to);
+            socket.bind(bind_to)?;
+        }
 
         Ok(ConnectedUdp {
             remote: sockaddr_nal2smol(remote)?,
@@ -111,7 +119,13 @@ impl<'a> UnconnectedUdp<'a> {
         mut socket: udp::UdpSocket<'a>,
         local: SocketAddr,
     ) -> Result<Self, Error> {
-        socket.bind(sockaddr_nal2smol(local)?)?;
+        // Workaround for https://github.com/smoltcp-rs/smoltcp/issues/1037
+        let bind_to = sockaddr_nal2smol(local)?;
+        if bind_to.addr.is_unspecified() {
+            socket.bind(bind_to.port)?;
+        } else {
+            socket.bind(bind_to)?;
+        }
 
         Ok(UnconnectedUdp { socket })
     }