Issue #6728 - QUIC and HTTP/3

Made QuicConnection's fillable callback of type EITHER.
This is necessary when there are no threads available,
because we still want to read from the network and feed
Quiche so that it can progress with respect to packet
acknowledgments and flow control updates.

Signed-off-by: Simone Bordet <simone.bordet@gmail.com>

jetty-quic/quic-common/src/main/java/org/eclipse/jetty/quic/common/QuicConnection.java

@@ -62,6 +62,7 @@ public abstract class QuicConnection extends AbstractConnection
     private final ByteBufferPool byteBufferPool;
     private final AdaptiveExecutionStrategy strategy;
     private final Flusher flusher = new Flusher();
+    private final Callback fillableCallback = new FillableCallback();
     private int outputBufferSize = 2048;
     private boolean useInputDirectByteBuffers = true;
     private boolean useOutputDirectByteBuffers = true;
@@ -163,6 +164,12 @@ public abstract class QuicConnection extends AbstractConnection
         strategy.produce();
     }
 
+    @Override
+    public void fillInterested()
+    {
+        getEndPoint().fillInterested(fillableCallback);
+    }
+
     @Override
     public abstract boolean onIdleExpired();
 
@@ -409,4 +416,25 @@ public abstract class QuicConnection extends AbstractConnection
             }
         }
     }
+
+    private class FillableCallback implements Callback
+    {
+        @Override
+        public void succeeded()
+        {
+            onFillable();
+        }
+
+        @Override
+        public void failed(Throwable x)
+        {
+            onFillInterestedFailed(x);
+        }
+
+        @Override
+        public InvocationType getInvocationType()
+        {
+            return InvocationType.EITHER;
+        }
+    }
 }