nimble/ll: Fix channel map update instant calculation

The instant for channel map update was calculated at the time PDU was
enqueued in connsm. This caused new map to be always applied at instant
regardless if PDU was even dequeued for tx, e.g. in case there
encryption procedure pending. This could result in connection being
dropped.

Currently we calculate instant when PDU is dequeued to make sure this is
the next PDU to be sent and thus instant is valid.

nimble/host/include/host/ble_gatt.h

@@ -1076,26 +1076,6 @@ int ble_gatts_reset(void);
  */
 int ble_gatts_start(void);
 
-/**
- * Saves Client Supported Features for specified connection.
- *
- * @param conn_handle           Connection handle identifying connection for
- *                              which Client Supported Features should be saved
- * @param om                    The mbuf chain to set value from.
- *
- * @return                      0 on success;
- *                              BLE_HS_ENOTCONN if no matching connection
- *                              was found
- *                              BLE_HS_EINVAL if supplied buffer is empty or
- *                              if any Client Supported Feature was
- *                              attempted to be disabled.
- *                              A BLE host core return code on unexpected
- *                              error.
- *
- */
-int ble_gatts_peer_cl_sup_feat_update(uint16_t conn_handle,
-                                      struct os_mbuf *om);
-
 /**
  * Gets Client Supported Features for specified connection.
  *

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

@@ -22,6 +22,7 @@
 #include "sysinit/sysinit.h"
 #include "host/ble_hs.h"
 #include "services/gatt/ble_svc_gatt.h"
+#include "../src/ble_gatt_priv.h"
 
 static uint16_t ble_svc_gatt_changed_val_handle;
 static uint16_t ble_svc_gatt_start_handle;
@@ -112,7 +113,9 @@ 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) {
-        return ble_gatts_peer_cl_sup_feat_update(conn_handle, ctxt->om);
+        if (ble_gatts_peer_cl_sup_feat_update(conn_handle, ctxt->om)) {
+            return BLE_ATT_ERR_UNLIKELY;
+        }
     }
 
     return 0;

nimble/host/src/ble_gatt_priv.h

@@ -201,6 +201,8 @@ int ble_gatts_clt_cfg_access(uint16_t conn_handle, uint16_t attr_handle,
                              uint8_t op, uint16_t offset, struct os_mbuf **om,
                              void *arg);
 
+int ble_gatts_peer_cl_sup_feat_update(uint16_t conn_handle,
+                                      struct os_mbuf *om);
 /*** @misc. */
 int ble_gatts_conn_can_alloc(void);
 int ble_gatts_conn_init(struct ble_gatts_conn *gatts_conn);