Issue #7635 - implement maxBlockedStreams logic in QpackDecoder

Signed-off-by: Lachlan Roberts <lachlan@webtide.com>

jetty-http3/http3-qpack/src/main/java/org/eclipse/jetty/http3/qpack/QpackDecoder.java

@@ -16,7 +16,11 @@
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import org.eclipse.jetty.http.HttpField;
 import org.eclipse.jetty.http.MetaData;
@@ -50,6 +54,7 @@ public class QpackDecoder implements Dumpable
     private final List<EncodedFieldSection> _encodedFieldSections = new ArrayList<>();
     private final NBitIntegerParser _integerDecoder = new NBitIntegerParser();
     private final InstructionHandler _instructionHandler = new InstructionHandler();
+    private final Map<Long, AtomicInteger> _blockedStreams = new HashMap<>();
     private int _maxHeaderSize;
     private int _maxBlockedStreams;
 
@@ -100,7 +105,6 @@ public void setMaxHeaderSize(int maxHeaderSize)
 
     public int getMaxBlockedStreams()
     {
-        // TODO: implement logic about blocked streams by calling this method.
         return _maxBlockedStreams;
     }
 
@@ -172,6 +176,10 @@ public boolean decode(long streamId, ByteBuffer buffer, Handler handler) throws
             {
                 if (LOG.isDebugEnabled())
                     LOG.debug("Deferred Decoding: streamId={}, encodedFieldSection={}", streamId, encodedFieldSection);
+                AtomicInteger blockedFields = _blockedStreams.computeIfAbsent(streamId, id -> new AtomicInteger(0));
+                blockedFields.incrementAndGet();
+                if (_blockedStreams.size() > _maxBlockedStreams)
+                    throw new QpackException.SessionException(QPACK_DECOMPRESSION_FAILED, "exceeded max blocked streams");
                 _encodedFieldSections.add(encodedFieldSection);
             }
 
@@ -226,6 +234,7 @@ public void parseInstructions(ByteBuffer buffer) throws QpackException
     public void streamCancellation(long streamId)
     {
         _encodedFieldSections.removeIf(encodedFieldSection -> encodedFieldSection.getStreamId() == streamId);
+        _blockedStreams.remove(streamId);
         _metaDataNotifications.removeIf(notification -> notification._streamId == streamId);
         _instructions.add(new StreamCancellationInstruction(streamId));
         notifyInstructionHandler();
@@ -234,12 +243,17 @@ public void streamCancellation(long streamId)
     private void checkEncodedFieldSections() throws QpackException
     {
         int insertCount = _context.getDynamicTable().getInsertCount();
-        for (EncodedFieldSection encodedFieldSection : _encodedFieldSections)
+        Iterator<EncodedFieldSection> iterator = _encodedFieldSections.iterator();
+        while (iterator.hasNext())
         {
+            EncodedFieldSection encodedFieldSection = iterator.next();
             if (encodedFieldSection.getRequiredInsertCount() <= insertCount)
             {
+                iterator.remove();
                 long streamId = encodedFieldSection.getStreamId();
                 MetaData metaData = encodedFieldSection.decode(_context, _maxHeaderSize);
+                if (_blockedStreams.get(streamId).decrementAndGet() <= 0)
+                    _blockedStreams.remove(streamId);
                 if (LOG.isDebugEnabled())
                     LOG.debug("Decoded: streamId={}, metadata={}", streamId, metaData);