Fix - Http3FrameCodec decode fail during unknown settings

src/main/java/io/netty/incubator/codec/http3/Http3SettingIdentifier.java

@@ -90,11 +90,7 @@ public enum Http3SettingIdentifier {
     private final long id;
 
     private static final Map<Long, Http3SettingIdentifier> LOOKUP = Collections.unmodifiableMap(
-            Arrays.stream(values())
-                    .collect(Collectors.toMap(
-                            Http3SettingIdentifier::id,
-                            Function.identity()
-                    ))
+            Arrays.stream(values()).collect(Collectors.toMap(Http3SettingIdentifier::id, Function.identity()))
     );
 
     Http3SettingIdentifier(long id) {

src/main/java/io/netty/incubator/codec/http3/Http3Settings.java

@@ -119,7 +119,7 @@ public final class Http3Settings implements Iterable<Map.Entry<Long, Long>> {
      * Creates a new instance
      */
     public Http3Settings() {
-        this.settings = new LongObjectHashMap<>(4);
+        this.settings = new LongObjectHashMap<>(Http3SettingIdentifier.values().length);
     }
 
     /**
@@ -164,7 +164,7 @@ public Long put(long key, Long value) {
 
         // When Non-Standard/Unknown settings identifier identifier present - Ignore
         if (identifier == null) {
-            return value;
+            return null;
         }
 
         //Validation

src/test/java/io/netty/incubator/codec/http3/Http3SettingsTest.java

@@ -32,7 +32,6 @@
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertNotSame;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
-import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 
 /**
  * unit tests for {@link Http3Settings}.
@@ -264,4 +263,46 @@ void testCopyFromNullThrows() {
         Http3Settings settings = new Http3Settings();
         assertThrows(NullPointerException.class, () -> settings.putAll(null));
     }
+
+    @Test
+    void duplicateSettingsValuesInsideFrameTest() {
+        Http3SettingsFrame settingsFrame = new DefaultHttp3SettingsFrame();
+        assertNull(settingsFrame.put(Http3SettingIdentifier.HTTP3_SETTINGS_QPACK_MAX_TABLE_CAPACITY.id(), 100L));
+        assertNull(settingsFrame.put(Http3SettingIdentifier.HTTP3_SETTINGS_QPACK_BLOCKED_STREAMS.id(), 1L));
+        assertNull(settingsFrame.put(Http3SettingIdentifier.HTTP3_SETTINGS_MAX_FIELD_SECTION_SIZE.id(), 128L));
+        assertNull(settingsFrame.put(Http3SettingIdentifier.HTTP3_SETTINGS_ENABLE_CONNECT_PROTOCOL.id(), 0L));
+        assertNull(settingsFrame.put(Http3SettingIdentifier.HTTP3_SETTINGS_H3_DATAGRAM.id(), 1L));
+        //known headers should not contain duplicate so give non-null
+        // which is used in http3framecodec to throw error
+        assertNotNull(settingsFrame.put(Http3SettingIdentifier.HTTP3_SETTINGS_H3_DATAGRAM.id(), 1L));
+        // Ensure we can encode and decode all sizes correctly.
+        // unknown settings id/key will be ignored
+        assertNull(settingsFrame.put(63, 63L));
+        assertNull(settingsFrame.put(16383, 16383L));
+        assertNull(settingsFrame.put(1073741823, 1073741823L));
+        assertNull(settingsFrame.put(4611686018427387903L, 4611686018427387903L));
+        //even duplicates of unknown ignored as we ignore unknown
+        assertNull(settingsFrame.put(4611686018427387903L, 4611686018427387903L));
+    }
+
+    @Test
+    void duplicateSettingsValuesInsideHttp3SettingsTest() {
+        Http3Settings http3Settings = new Http3Settings();
+        assertNull(http3Settings.put(Http3SettingIdentifier.HTTP3_SETTINGS_QPACK_MAX_TABLE_CAPACITY.id(), 100L));
+        assertNull(http3Settings.put(Http3SettingIdentifier.HTTP3_SETTINGS_QPACK_BLOCKED_STREAMS.id(), 1L));
+        assertNull(http3Settings.put(Http3SettingIdentifier.HTTP3_SETTINGS_MAX_FIELD_SECTION_SIZE.id(), 128L));
+        assertNull(http3Settings.put(Http3SettingIdentifier.HTTP3_SETTINGS_ENABLE_CONNECT_PROTOCOL.id(), 0L));
+        assertNull(http3Settings.put(Http3SettingIdentifier.HTTP3_SETTINGS_H3_DATAGRAM.id(), 1L));
+        //known headers should not contain duplicate so give non-null
+        // which is used in http3framecodec to throw error
+        assertNotNull(http3Settings.put(Http3SettingIdentifier.HTTP3_SETTINGS_H3_DATAGRAM.id(), 1L));
+        // Ensure we can encode and decode all sizes correctly.
+        // unknown settings id/key will be ignored
+        assertNull(http3Settings.put(63, 63L));
+        assertNull(http3Settings.put(16383, 16383L));
+        assertNull(http3Settings.put(1073741823, 1073741823L));
+        assertNull(http3Settings.put(4611686018427387903L, 4611686018427387903L));
+        //even duplicates of unknown ignored as we ignore unknown
+        assertNull(http3Settings.put(4611686018427387903L, 4611686018427387903L));
+    }
 }