Change mdns broadcast to allow treatement as success if sends (#7555)

* Change mdns broadcast to allow treatement as success if anything succeeds

* Fix typo

* Add progress log for mdns broadcast success

src/lib/mdns/minimal/Server.cpp

@@ -263,6 +263,17 @@ CHIP_ERROR ServerBase::BroadcastSend(chip::System::PacketBufferHandle && data, u
 
 CHIP_ERROR ServerBase::BroadcastSend(chip::System::PacketBufferHandle && data, uint16_t port)
 {
+    // Broadcast requires sending data multiple times, each of which may error
+    // out, yet broadcast only has a single error code.
+    //
+    // The general logic of error handling is:
+    //   - if no send done at all, return error
+    //   - if at least one broadcast succeeds, assume success overall
+    //   + some internal consistency validations for state error.
+
+    bool hadSuccesfulSend = false;
+    CHIP_ERROR lastError  = CHIP_ERROR_NO_ENDPOINT;
+
     for (size_t i = 0; i < mEndpointCount; i++)
     {
         EndpointInfo * info = &mEndpoints[i];
@@ -291,22 +302,28 @@ CHIP_ERROR ServerBase::BroadcastSend(chip::System::PacketBufferHandle && data, u
 #endif
         else
         {
+            // This is a general error of internal consistency: every address has a known type
+            // Fail completely otherwise.
             return CHIP_ERROR_INCORRECT_STATE;
         }
 
-        if (err == chip::System::MapErrorPOSIX(ENETUNREACH))
+        if (err == CHIP_NO_ERROR)
         {
-            // Send attempted to an unreachable network. Generally should not happen if
-            // interfaces are configured properly, however such a failure to broadcast
-            // may not be critical either.
-            ChipLogError(Discovery, "Attempt to mDNS broadcast to an unreachable destination.");
+            hadSuccesfulSend = true;
+            ChipLogProgress(Discovery, "mDNS broadcast success");
         }
-        else if (err != CHIP_NO_ERROR)
+        else
         {
-            return err;
+            ChipLogError(Discovery, "Attempt to mDNS broadcast failed:  %s", chip::ErrorStr(err));
+            lastError = err;
         }
     }
 
+    if (!hadSuccesfulSend)
+    {
+        return lastError;
+    }
+
     return CHIP_NO_ERROR;
 }