nimble/host: implement robust gatt caching (server side)

Add support for Robust GATT Caching.

Author: piotrnarajowski

nimble/host/include/host/ble_att.h

@@ -110,6 +110,9 @@ struct os_mbuf;
 /**Insufficient Resources to complete the request. */
 #define BLE_ATT_ERR_INSUFFICIENT_RES        0x11
 
+/**The server requests the client to rediscover the database. */
+#define BLE_ATT_ERR_DB_OUT_OF_SYNC          0x12
+
 /**Requested value is not allowed. */
 #define BLE_ATT_ERR_VALUE_NOT_ALLOWED       0x13
 

nimble/host/include/host/ble_gatt.h

@@ -1214,6 +1214,7 @@ int ble_gatts_start(void);
  */
 int ble_gatts_peer_cl_sup_feat_get(uint16_t conn_handle, uint8_t *out_supported_feat, uint8_t len);
 
+int ble_gatts_calculate_db_hash(void);
 #ifdef __cplusplus
 }
 #endif

nimble/host/include/host/ble_store.h

@@ -48,6 +48,9 @@ extern "C" {
 /** Object type: Client Characteristic Configuration Descriptor. */
 #define BLE_STORE_OBJ_TYPE_CCCD         3
 
+/** Object type: Peer last known database hash. */
+#define BLE_STORE_OBJ_TYPE_DB_HASH      4
+
 /** @} */
 
 /**
@@ -154,6 +157,36 @@ struct ble_store_value_cccd {
     unsigned value_changed:1;
 };
 
+/**
+ * Used as key for lookups of stored database hash.
+ * This struct corresponds to the BLE_STORE_OBJ_TYPE_DB_HASH store object
+ * type.
+ */
+struct ble_store_key_db_hash {
+    /**
+     * Key by peer identity address;
+     * peer_addr=BLE_ADDR_NONE means don't key off peer.
+     */
+    ble_addr_t peer_addr;
+
+    /** Number of results to skip; 0 means retrieve the first match. */
+    uint8_t idx;
+};
+
+/**
+ * Represents a stored database hash of a peer. This struct
+ * corresponds to the BLE_STORE_OBJ_TYPE_DB_HASH store object type.
+ */
+ struct ble_store_value_db_hash {
+     /** The peer address associated with the stored database hash.  */
+     ble_addr_t peer_addr;
+     /** Flag indicating whether the peer is supporting robust cacheing. */
+//     bool is_cache_supported;
+     /** Database hash; can be used to determine whether the peer
+      * is change aware/unaware. */
+     uint8_t *db_hash;
+ };
+
 /**
  * Used as a key for store lookups.  This union must be accompanied by an
  * object type code to indicate which field is valid.
@@ -163,6 +196,8 @@ union ble_store_key {
     struct ble_store_key_sec sec;
     /** Key for Client Characteristic Configuration Descriptor store lookups. */
     struct ble_store_key_cccd cccd;
+    /** Key for database hash store lookups */
+    struct ble_store_key_db_hash db_hash;
 };
 
 /**
@@ -174,6 +209,8 @@ union ble_store_value {
     struct ble_store_value_sec sec;
     /** Stored Client Characteristic Configuration Descriptor. */
     struct ble_store_value_cccd cccd;
+    /** Stored database hash. */
+    struct ble_store_value_db_hash db_hash;
 };
 
 /** Represents an event associated with the BLE Store. */
@@ -540,6 +577,28 @@ int ble_store_read_cccd(const struct ble_store_key_cccd *key,
  */
 int ble_store_write_cccd(const struct ble_store_value_cccd *value);
 
+/**
+ * @brief Writes a database hash to a storage.
+ *
+ * This function writes database hash value to a storage based on the
+ * provided value.
+ *
+ * @param value                 A pointer to a `ble_store_value_db_hash`
+ *                                  structure representing the database hash
+ *                                  to be written to a storage.
+ *
+ * @return                      0 if the database hash was successfully
+ *                                  written to a storage;
+ *                              Non-zero on error.
+ */
+int ble_store_write_db_hash(const struct ble_store_value_db_hash *value);
+int ble_store_read_db_hash(const struct ble_store_key_db_hash *key,
+                           struct ble_store_value_db_hash *out_value);
+int ble_store_delete_db_hash(const struct ble_store_value_db_hash *key);
+void ble_store_key_from_value_db_hash(struct ble_store_key_db_hash *out_key,
+                                       const struct ble_store_value_db_hash
+                                       *value);
+
 /**
  * @brief Deletes a Client Characteristic Configuration Descriptor (CCCD) from
  * a storage.

nimble/host/services/gatt/include/services/gatt/ble_svc_gatt.h

@@ -31,6 +31,7 @@ struct ble_hs_cfg;
 #define BLE_SVC_GATT_CHR_SERVICE_CHANGED_UUID16         0x2a05
 #define BLE_SVC_GATT_CHR_SERVER_SUPPORTED_FEAT_UUID16   0x2b3a
 #define BLE_SVC_GATT_CHR_CLIENT_SUPPORTED_FEAT_UUID16   0x2b29
+#define BLE_SVC_GATT_CHR_DATABASE_HASH_UUID16           0x2b2a
 
 uint8_t ble_svc_gatt_get_local_cl_supported_feat(void);
 void ble_svc_gatt_changed(uint16_t start_handle, uint16_t end_handle);

nimble/host/services/gatt/src/ble_svc_gatt.c

@@ -21,6 +21,7 @@
 
 #include "sysinit/sysinit.h"
 #include "host/ble_hs.h"
+#include "../src/ble_hs_priv.h"
 #include "services/gatt/ble_svc_gatt.h"
 #include "../src/ble_gatt_priv.h"
 
@@ -32,13 +33,12 @@ static uint16_t ble_svc_gatt_end_handle;
 #define BLE_SVC_GATT_SRV_SUP_FEAT_EATT_BIT      (0x00)
 
 /* Client supported features */
-#define BLE_SVC_GATT_CLI_SUP_FEAT_ROBUST_CATCHING_BIT   (0x00)
+#define BLE_SVC_GATT_CLI_SUP_FEAT_ROBUST_CACHING_BIT    (0x00)
 #define BLE_SVC_GATT_CLI_SUP_FEAT_EATT_BIT              (0x01)
 #define BLE_SVC_GATT_CLI_SUP_FEAT_MULT_NTF_BIT          (0x02)
 
 static uint8_t ble_svc_gatt_local_srv_sup_feat = 0;
 static uint8_t ble_svc_gatt_local_cl_sup_feat = 0;
-
 static int
 ble_svc_gatt_access(uint16_t conn_handle, uint16_t attr_handle,
                     struct ble_gatt_access_ctxt *ctxt, void *arg);
@@ -51,6 +51,10 @@ static int
 ble_svc_gatt_cl_sup_feat_access(uint16_t conn_handle, uint16_t attr_handle,
                                 struct ble_gatt_access_ctxt *ctxt, void *arg);
 
+static int
+ble_svc_gatt_db_hash_access(uint16_t conn_handle, uint16_t attr_handle,
+                            struct ble_gatt_access_ctxt *ctxt, void *arg);
+
 static const struct ble_gatt_svc_def ble_svc_gatt_defs[] = {
     {
         /*** Service: GATT */
@@ -73,6 +77,13 @@ static const struct ble_gatt_svc_def ble_svc_gatt_defs[] = {
                 .access_cb = ble_svc_gatt_cl_sup_feat_access,
                 .flags = BLE_GATT_CHR_F_READ | BLE_GATT_CHR_F_WRITE,
             },
+#if MYNEWT_VAL(BLE_ATT_SVR_ROBUST_CACHE)
+            {
+                .uuid = BLE_UUID16_DECLARE(BLE_SVC_GATT_CHR_DATABASE_HASH_UUID16),
+                .access_cb = ble_svc_gatt_db_hash_access,
+                .flags = BLE_GATT_CHR_F_READ,
+            },
+#endif
             {
                 0, /* No more characteristics in this service. */
             }
@@ -113,14 +124,49 @@ ble_svc_gatt_cl_sup_feat_access(uint16_t conn_handle, uint16_t attr_handle,
         return 0;
     }
     if (ctxt->op == BLE_GATT_ACCESS_OP_WRITE_CHR) {
-        if (ble_gatts_peer_cl_sup_feat_update(conn_handle, ctxt->om)) {
-            return BLE_ATT_ERR_UNLIKELY;
+        rc = ble_gatts_peer_cl_sup_feat_update(conn_handle, ctxt->om);
+        if (rc != 0) {
+            return rc;
         }
     }
 
     return 0;
 }
 
+static int
+ble_svc_gatt_db_hash_access(uint16_t conn_handle, uint16_t attr_handle,
+                            struct ble_gatt_access_ctxt *ctxt, void *arg)
+{
+    int rc;
+    struct ble_gap_sec_state sec_state;
+    const uint8_t *hash;
+    uint8_t local_hash[16];
+
+    if (ctxt->op != BLE_GATT_ACCESS_OP_READ_CHR) {
+        return BLE_ATT_ERR_WRITE_NOT_PERMITTED;
+    }
+
+    hash = ble_gatts_get_db_hash();
+
+    for (int i = 0; i < 16; i++) {
+        local_hash[i] = hash[i];
+    }
+
+    rc = os_mbuf_append(ctxt->om, local_hash, sizeof(local_hash));
+
+    if (rc == 0) {
+        /* Peer will become change aware after first att request after
+         * reading hash*/
+        set_change_aware(conn_handle, BLE_GATTS_HASH_READ_PENDING);
+        ble_att_svr_get_sec_state(conn_handle, &sec_state);
+        if (sec_state.bonded) {
+            db_hash_store(conn_handle, local_hash);
+        }
+    }
+
+    return rc == 0 ? 0 : BLE_ATT_ERR_INSUFFICIENT_RES;
+}
+
 static int
 ble_svc_gatt_access(uint16_t conn_handle, uint16_t attr_handle,
                     struct ble_gatt_access_ctxt *ctxt, void *arg)
@@ -163,9 +209,15 @@ ble_svc_gatt_get_local_cl_supported_feat(void)
 void
 ble_svc_gatt_changed(uint16_t start_handle, uint16_t end_handle)
 {
+    int rc;
     ble_svc_gatt_start_handle = start_handle;
     ble_svc_gatt_end_handle = end_handle;
+    rc = ble_gatts_calculate_db_hash();
+    if (rc != 0) {
+        return;
+    }
     ble_gatts_chr_updated(ble_svc_gatt_changed_val_handle);
+    set_all_change_aware_action(set_change_unaware, NULL);
 }
 
 void
@@ -193,4 +245,8 @@ ble_svc_gatt_init(void)
     if (MYNEWT_VAL(BLE_ATT_SVR_NOTIFY_MULTI) > 0) {
         ble_svc_gatt_local_cl_sup_feat |= (1 << BLE_SVC_GATT_CLI_SUP_FEAT_MULT_NTF_BIT);
     }
+
+    if (MYNEWT_VAL(BLE_ATT_SVR_ROBUST_CACHE) > 0) {
+        ble_svc_gatt_local_cl_sup_feat |= (1 << BLE_SVC_GATT_CLI_SUP_FEAT_ROBUST_CACHING_BIT);
+    }
 }

nimble/host/src/ble_att_priv.h

@@ -47,6 +47,7 @@ struct ble_att_prep_write_cmd;
 struct ble_att_exec_write_req;
 struct ble_att_notify_req;
 struct ble_att_indicate_req;
+struct ble_gap_sec_state;
 
 STATS_SECT_START(ble_att_stats)
     STATS_SECT_ENTRY(error_rsp_rx)
@@ -173,6 +174,9 @@ uint16_t ble_att_mtu_by_cid(uint16_t conn_handle, uint16_t cid);
 int ble_att_init(void);
 
 /*** @svr */
+/** Type definition for ATT svr entry interation callback. */
+typedef int (*ble_gatts_entry_foreach)(struct ble_att_svr_entry *entry,
+                                       void *arg);
 
 int ble_att_svr_start(void);
 
@@ -217,6 +221,7 @@ void ble_att_svr_prep_clear(struct ble_att_prep_entry_list *prep_list);
 int ble_att_svr_read_handle(uint16_t conn_handle, uint16_t attr_handle,
                             uint16_t offset, struct os_mbuf *om,
                             uint8_t *out_att_err);
+void ble_att_svr_foreach(ble_gatts_entry_foreach cb, void *arg);
 void ble_att_svr_reset(void);
 int ble_att_svr_init(void);
 
@@ -226,6 +231,8 @@ void ble_att_svr_restore_range(uint16_t start_handle, uint16_t end_handle);
 int ble_att_svr_tx_error_rsp(uint16_t conn_handle, uint16_t cid, struct os_mbuf *txom,
                              uint8_t req_op, uint16_t handle,
                              uint8_t error_code);
+void ble_att_svr_get_sec_state(uint16_t conn_handle,
+                               struct ble_gap_sec_state *out_sec_state);
 /*** $clt */
 
 /** An information-data entry in a find information response. */