How to SD assign connection handle after reconnect ?

[Vyacheslav Lebets]

Hi!
We develop multilink central FW for nRF 52840 having NRF_SDH_BLE_CENTRAL_LINK_COUNT = 6.
For enumerating connections and get info about concret connection, we use array with size of NRF_SDH_BLE_CENTRAL_LINK_COUNT (6).
If to see an example "ble_app_multilink_central" we see that to assign a connection handle, a current conn_handle is used as index of array of m_lbs_c and m_db_disc. 
But, I thought about this: For example: we have the maximum number of connections (6), and we have last active connection handle = 5.
After which there is one disconnection (for exaple conn_handle was 3), and then reconnection to the same device what will the connection handle be? 6 or 3 ? 
Because if the handle number increment by SD and in that situation next handle may be set to array, it exceeds the size of the array, there will be an exception.

My question is: Is it safe to use the connection handle as an index of array, or still need to implement own control algorithm?

[haakonsh]

My question is: Is it safe to use the connection handle as an index of array, or still need to implement own control algorithm?

 Not really, precisely because of the issues you've raised. You need to handle the state when a disconnected link is re-established. You can have an array of structs: 

typedef struct{
    /** Flag used to indicate available slot.*/
    bool taken;
    
    /** Connection handle.*/
    uint16_t conn_handle;
}conn_handles_t;

conn_handles_t conn_handles[NRF_SDH_BLE_CENTRAL_LINK_COUNT];

memset(conn_handles[0], '0', sizeof(conn_handles));

on_connect()
{
    for(i = 0; i < NRF_SDH_BLE_CENTRAL_LINK_COUNT; i++)
    {
        // Assing the connection handle to first available slot
        if(!conn_handles[i].taken)
        {
            conn_handles[i].taken = true;
            conn_handles[i].conn_handle = current_handle;
            
            //TODO: Save the index before exiting
            
            break;
        }
    }
}

on_disconnect()
{
    conn_handles[current_handle].taken = false;
    conn_handles[current_handle].conn_handle = BLE_CONN_HANDLE_INVALID;
}

Or you can find other ways to keep track of your handles. 

[Vyacheslav Lebets]

Ok, thanks.
You have confirmed my reasoning.
I was going to do so, just wanted to clarify. Maybe SD thinks instead of me. :).

[yuval]

Haakonsh,

I'm not sure i understand your solution. If "current_handle" in the example can get "6" from the SD then in the "on_disconnect"  function the "conn_handles" array will be out of bounds... Can you clarify this?

Another thing, Do we have the same issue in "multi peripheral" systems?

Thank in advance,

Yuval.