Add a cache to data link layer for control frames with hash

components/dataLink/include/DataLinkManager.h

@@ -46,6 +46,7 @@ static const uint16_t crc16_table[256] = {
 #define ASYNC_QUEUE_WAIT_TICKS 100
 #define SEQUENCE_NUM_MAP_MUTEX_MAX_WAIT_MS 50
 #define MAX_RX_QUEUE_SIZE 100
+#define CONTROL_FRAME_LUT_SIZE 5  // Maximum number of control frames cached in the receiver-side LFU LUT
 
 /**
  * @brief Class to represent the Data Link Layer
@@ -203,6 +204,27 @@ class DataLinkManager{
 
         SemaphoreHandle_t send_ack_queue_mutex[MAX_CHANNELS];
         std::queue<SendAckMetaData> send_ack_queue[MAX_CHANNELS];
+
+        // ==== Control Frame Hash / LFU LUT (receiver side) ====
+
+        /**
+         * @brief Compute a 32-bit FNV-1a hash over a byte buffer
+         */
+        static uint32_t compute_fnv1a_hash(const uint8_t* data, size_t len);
+
+        /**
+         * @brief Look up a hash in the control-frame LUT.
+         *        Returns true and populates @p out_message / @p out_header on a hit.
+         */
+        bool lut_lookup(uint32_t hash, std::vector<uint8_t>& out_message, FrameHeader& out_header);
+
+        /**
+         * @brief Insert (or update) an entry in the control-frame LUT using LFU eviction.
+         */
+        void lut_insert(uint32_t hash, const uint8_t* message, size_t message_len, const FrameHeader& header);
+
+        ControlFrameLutEntry control_frame_lut[CONTROL_FRAME_LUT_SIZE];
+        SemaphoreHandle_t control_frame_lut_mutex;
 };
 
 struct frame_scheduler_args {