Refactor queue limit (#4098)

Author: nibanks

src/core/connection.c

@@ -3149,6 +3149,14 @@ QuicConnQueueRecvPackets(
         PacketsTail = (QUIC_RX_PACKET**)&((*PacketsTail)->Next);
     }
 
+    //
+    // Base the limit of queued packets on the connection-wide flow control, but
+    // allow at least a few packets even if the app configured an extremely
+    // tiny FC window.
+    //
+    const uint32_t QueueLimit =
+        CXPLAT_MAX(10, Connection->Settings.ConnFlowControlWindow >> 10);
+
     QuicTraceLogConnVerbose(
         QueueDatagrams,
         Connection,
@@ -3157,7 +3165,7 @@ QuicConnQueueRecvPackets(
 
     BOOLEAN QueueOperation;
     CxPlatDispatchLockAcquire(&Connection->ReceiveQueueLock);
-    if (Connection->ReceiveQueueCount >= QUIC_MAX_RECEIVE_QUEUE_COUNT) {
+    if (Connection->ReceiveQueueCount >= QueueLimit) {
         QueueOperation = FALSE;
     } else {
         *Connection->ReceiveQueueTail = Packets;

src/core/quicdef.h

@@ -194,16 +194,6 @@ typedef struct QUIC_RX_PACKET QUIC_RX_PACKET;
 //
 #define QUIC_MAX_CRYPTO_BATCH_COUNT             8
 
-//
-// The maximum number of received packets that may be queued on a single
-// connection. When this limit is reached, any additional packets are dropped.
-//
-#ifdef _KERNEL_MODE
-#define QUIC_MAX_RECEIVE_QUEUE_COUNT            1024
-#else
-#define QUIC_MAX_RECEIVE_QUEUE_COUNT            8192
-#endif
-
 //
 // The maximum number of received packets that may be processed in a single
 // flush operation.