Resend Close Frames

src/core/connection.c

@@ -4411,6 +4411,18 @@ QuicConnRecvFrames(
     uint16_t PayloadLength = Packet->PayloadLength;
     uint64_t RecvTime = CxPlatTimeUs64();
 
+    //
+    // RFC 9000 Section 10.2.1: 
+    // In closing state, respond to any packet with CONNECTION_CLOSE, rate-limited
+    // to once every 5ms.
+    //
+    if (Closed && !Connection->State.ShutdownComplete) {
+        if (RecvTime - Connection->LastCloseResponseTimeUs >= QUIC_CLOSING_RESPONSE_MIN_INTERVAL_US) {
+            QuicSendSetSendFlag(&Connection->Send, QUIC_CONN_SEND_FLAG_CONNECTION_CLOSE);
+            Connection->LastCloseResponseTimeUs = RecvTime;
+        }
+    }
+
     if (QuicConnIsClient(Connection) &&
         !Connection->State.GotFirstServerResponse) {
         Connection->State.GotFirstServerResponse = TRUE;

src/core/connection.h

@@ -682,6 +682,9 @@ typedef struct QUIC_CONNECTION {
         QUIC_FLOW_BLOCKED_TIMING_TRACKER FlowControl;
     } BlockedTimings;
 
+    // Timestamp (us) of last CONNECTION_CLOSE sent in closing state (for rate limiting)
+    uint64_t LastCloseResponseTimeUs;
+
 } QUIC_CONNECTION;
 
 typedef struct QUIC_SERIALIZED_RESUMPTION_STATE {

src/core/quicdef.h

@@ -318,6 +318,12 @@ CXPLAT_STATIC_ASSERT(
 //
 #define QUIC_DEFAULT_HANDSHAKE_IDLE_TIMEOUT     10000
 
+//
+// Minimum interval (in microseconds) between CONNECTION_CLOSE responses in
+// closing state.
+//
+#define QUIC_CLOSING_RESPONSE_MIN_INTERVAL_US   5000
+
 //
 // The default value for keep alives being enabled or not.
 //