[ffx][mdns] reduce log spam on parse failure

Cast devices are sending out some more interesting packets these days
that neither we nor several other mnds parsers know how to parse. For
now suppressing the log noise is a reasonable choice, though this is
another case where we want more control over subsystem log levels when
debugging.

Change-Id: I4f75770a91bbee0d7ea92516b306ed4cf6365689
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/559552
Commit-Queue: Auto-Submit <auto-submit@fuchsia-infra.iam.gserviceaccount.com>
Fuchsia-Auto-Submit: James Tucker <raggi@google.com>
Reviewed-by: Andrew Davies <awdavies@google.com>
diff --git a/src/developer/ffx/daemon/services/mdns/src/mdns.rs b/src/developer/ffx/daemon/services/mdns/src/mdns.rs
index e6ea5aa..811cc70 100644
--- a/src/developer/ffx/daemon/services/mdns/src/mdns.rs
+++ b/src/developer/ffx/daemon/services/mdns/src/mdns.rs
@@ -267,10 +267,15 @@
             }
         };
 
+        // Note: important, otherwise non-local responders could add themselves.
+        if !addr.ip().is_local_addr() {
+            continue;
+        }
+
         let msg = match buf.parse::<dns::Message<_>>() {
             Ok(msg) => msg,
             Err(e) => {
-                log::warn!(
+                log::trace!(
                     "unable to parse message received on {} from {}: {:?}",
                     sock.local_addr()
                         .map(|s| format!("{}", s))
@@ -282,11 +287,6 @@
             }
         };
 
-        // Note: important, otherwise non-local responders could add themselves.
-        if !addr.ip().is_local_addr() {
-            continue;
-        }
-
         if !is_fuchsia_response(&msg) && !is_fastboot_response(&msg) {
             continue;
         }