When are peer managers connection handles invalidated?

RE: When are peer managers connection handles invalidated?

user84602 — Thu, 09 Jun 2022 07:32:19 GMT

Unfortunately I can't mark Sigurds answer ("it's a documentation error") as verified. But report is "fixed" with that.

RE: When are peer managers connection handles invalidated?

user15146 — Fri, 21 May 2021 10:24:31 GMT

Hi,

I agree. I have reported this to the SDK team as a documentation bug.

RE: When are peer managers connection handles invalidated?

user84602 — Wed, 12 May 2021 07:51:46 GMT

I found a reason why it was implemented like this.

im_peer_free() uses im_conn_handle_get() and this does not work for disconnected peers with my fix.

But then the docs of pm_peer_handle_get() are wrong:

 * @param[out] p_conn_handle  Connection handle, or @ref BLE_CONN_HANDLE_INVALID if the peer
 *                            is not connected.

On the other hand the docs for im_conn_handle_get() states that the conn_handle can refer to a recently disconnceted connection.

 * @return The corresponding connection handle, or @ref BLE_CONN_HANDLE_INVALID if none could be
 *         resolved. The conn_handle can refer to a recently disconnected connection.

RE: When are peer managers connection handles invalidated?

user84602 — Mon, 03 May 2021 15:36:56 GMT

Yes that would be possible too.

Though this looks like a bug in the SDK to me. It would be nice if you could report back when you know why it's implemented like this.

RE: When are peer managers connection handles invalidated?

user15146 — Mon, 03 May 2021 15:22:58 GMT

[quote user="mgux"]ble_conn_state_status() checks the valid_flags and connected_flags. This fixes my problem.[/quote]

Yeah, I see now that disconnected links are first invalidated when a device connects again (record_purge_disconnected() called on BLE_GAP_EVT_CONNECTED in ble_conn_state.c). I haven't looked into why it's implemented like this yet, but an alternative to your patch, could be to call ble_conn_state_status(connHandle) in your application code, and based on the return value of this, then do a disconnect and delete the bond info. With this approach, you don't need to modify the id_manager.c file

RE: When are peer managers connection handles invalidated?

user84602 — Mon, 03 May 2021 12:27:05 GMT

Please find the patch attached.

test-devzone.nordicsemi.com/.../0001_2D00_Fix_2D00_im_5F00_conn_5F00_handle_5F00_get_2D00_for_2D00_disconnected_2D00_peers.patch

RE: When are peer managers connection handles invalidated?

user84602 — Mon, 03 May 2021 12:15:57 GMT

Sorry, that was a copy&paste error.

I use connHandle everywhere.

I tried to change im__conn_handle_get to the following:

uint16_t im_conn_handle_get(pm_peer_id_t peer_id)
{
    if (peer_id == PM_PEER_ID_INVALID)
    {
        return BLE_CONN_HANDLE_INVALID;
    }

    for (uint16_t conn_handle = 0; conn_handle < IM_MAX_CONN_HANDLES; conn_handle++)
    {
        if ((m_connections[conn_handle].peer_id == peer_id) && ble_conn_state_status(conn_handle) == BLE_CONN_STATUS_CONNECTED)
        {
            return conn_handle;
        }
    }
    return BLE_CONN_HANDLE_INVALID;
}

ble_conn_state_status() checks the valid_flags and connected_flags. This fixes my problem.

RE: When are peer managers connection handles invalidated?

user15146 — Mon, 03 May 2021 12:10:30 GMT

[quote user="mgux"]I use this snippet to disconnect[/quote]

Seems like you are using both connectionHandle and connHandle?

Try this instead:

// disconnect and remove peer
uint16_t connHandle = BLE_CONN_HANDLE_INVALID;
auto ret = pm_conn_handle_get(peerId, &connHandle);
APP_ERROR_CHECK(ret);

if(connHandle == BLE_CONN_HANDLE_INVALID)
{
    return;
}
ret = sd_ble_gap_disconnect(connHandle, BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);

APP_ERROR_CHECK(ret);
// The peer got removed from the list of bonds.
ret = pm_peer_delete(peerId);
APP_ERROR_CHECK(ret);

RE: When are peer managers connection handles invalidated?

user84602 — Mon, 03 May 2021 12:09:24 GMT

I found some more:

in ble_conn_state.c:

typedef struct
{
    nrf_atflags_t valid_flags;                                 /**< Flags indicating which connection handles are valid. */
    nrf_atflags_t connected_flags;                             /**< Flags indicating which connections are connected, since disconnected connection handles will not immediately be invalidated. */
    nrf_atflags_t central_flags;                               /**< Flags indicating in which connections the local device is the central. */
    nrf_atflags_t encrypted_flags;                             /**< Flags indicating which connections are encrypted. */
    nrf_atflags_t mitm_protected_flags;                        /**< Flags indicating which connections have encryption with protection from man-in-the-middle attacks. */
    nrf_atflags_t lesc_flags;                                  /**< Flags indicating which connections have bonded using LE Secure Connections (LESC). */
    nrf_atflags_t user_flags[BLE_CONN_STATE_USER_FLAG_COUNT];  /**< Flags that can be reserved by the user. The flags will be cleared when a connection is invalidated, otherwise, the user is wholly responsible for the flag states. */
} ble_conn_state_flag_collections_t;

static void record_set_disconnected(uint16_t conn_handle)
{
    nrf_atflags_clear(&m_bcs.flags.connected_flags, conn_handle);
}

bool ble_conn_state_valid(uint16_t conn_handle)
{
    if (conn_handle >= BLE_CONN_STATE_MAX_CONNECTIONS)
    {
        return false;
    }
    return nrf_atflags_get(&m_bcs.flags.valid_flags, conn_handle);
}

ble_conn_state_valid() is used in pm_conn_handle_get() and checks the valid_flags.. But record_set_disconnected() clears the connected flag not the valid_flags.

Also the comment for connected_flags says that connection handles will no immediately be invalidated.

So maybe one should check the connected flag in pm_conn_handle_get()?

RE: When are peer managers connection handles invalidated?

user84602 — Mon, 03 May 2021 12:03:16 GMT

I can confirm that

record_set_disconnected(conn_handle);

is called in ble_conn_state.c.

RE: When are peer managers connection handles invalidated?

user84602 — Mon, 03 May 2021 11:54:52 GMT

[quote userid="15146" url="~/f/nordic-q-a/74638/when-are-peer-managers-connection-handles-invalidated/307896#307896"] 1)So you are in a active connection to another device when you try to delete the bond from the previously connected device?[/quote]

Sorry I was wrong. The command is sent via USB CDC. But it is possible to be connected to another peer while I delete the bond to another one.

I use this snippet to disconnect (if still connected) and remove the bond:

// disconnect and remove peer
uint16_t connHandle = BLE_CONN_HANDLE_INVALID;
auto ret = pm_conn_handle_get(peerId, &connHandle);
APP_ERROR_CHECK(ret);

if(connectionHandle == BLE_CONN_HANDLE_INVALID)
{
    return;
}
ret = sd_ble_gap_disconnect(connectionHandle, BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);

APP_ERROR_CHECK(ret);
// The peer got removed from the list of bonds.
ret = pm_peer_delete(peerId);
APP_ERROR_CHECK(ret);

RE: When are peer managers connection handles invalidated?

user15146 — Mon, 03 May 2021 11:47:09 GMT

[quote user="mgux"]After disconnect I send an command via BLE nus service to the central to remove the bonds.[/quote]

1)So you are in a active connection to another device when you try to delete the bond from the previously connected device?

2) Can you post the code you use to delete the bond ?

RE: When are peer managers connection handles invalidated?

user84602 — Mon, 03 May 2021 11:16:01 GMT

Hi,

I am using SDK version 17.0.2. I don't call pm_conn_handle_get() on BLE_GAP_EVT_DISCONNECTED.

After disconnect I send an command via BLE nus service to the central to remove the bonds.

I can verify that this code exists on my side. I guess it is called via

NRF_SDH_BLE_OBSERVER(m_ble_evt_observer, BLE_CONN_STATE_BLE_OBSERVER_PRIO, ble_evt_handler, NULL);

RE: When are peer managers connection handles invalidated?

user15146 — Mon, 03 May 2021 11:08:49 GMT

Hi,

The Peer Manager uses the Connection state module to check this. Snippet from ble_conn_state.c where connection handles are invalidated:

        case BLE_GAP_EVT_DISCONNECTED:
            record_set_disconnected(conn_handle);
            break;

What SDK version are you using?

When do you call pm_conn_handle_get() ? On BLE_GAP_EVT_DISCONNECTED or some other events?