Directed advertising to Android does not work

[pdunaj]

Describe the bug
I bond the device with various host and then use direct advertising to reconnect.
I am able to connect to Windows 7 with Intel drivers and Windows 10. I am also able to connect to Nordic dongle (pca10059) though Zephyr's option scan with identity must be enabled.

I am unable to connect (using the direct advertising) to an Android devices. I have tried Samsung Galaxy S8 (Android 9.0) and Moto G5 (Android 8.1.0).

Maybe the problem is how these device perform scanning?

To Reproduce
Steps to reproduce the behavior:
See description.

Expected behavior
Direct advertising should work.

Impact
showstopper

Screenshots or console output
N/A

Environment (please complete the following information):
ncs zephyr: e7a0e52 (19de7ec upstream)

Additional context
N/A

[jhedberg]

Could the issue be related to the central using privacy? Do you have CONFIG_BT_CTLR_PRIVACY enabled?

[pdunaj]

Hi @jhedberg , no - it is disabled.

[jhedberg]

Hi @jhedberg , no - it is disabled.

@pdunaj could you enable it and try again? I think it might be needed for doing directed advertising toward a privacy-enabled central.

[jhedberg]

@carlescufi @cvinayak any thoughts on this issue?

[pdunaj]

sure, will enable and retry

[pdunaj]

When I enable privacy I cannot create connection. Device either disconnects right after connection or does not even connect.

[rljordan-zz]

@jhedberg Please review priority.

[jhedberg]

@pdunaj did you already determine if the devices in question use privacy, i.e. that this is the differentiating factor between "works" and "doesn't work"? @carlescufi @cvinayak I'd really need your input here to understand if this is a controller issue or a host issue. @pdunaj just to get this straight, your test procedure is to pair with these devices and then request a connection to them using bt_conn_create_slave_le() and you're passing the remote identity address to this function, correct?

[jhedberg]

@pdunaj also, it'd be good if you could produce an HCI trace of what's going on. See https://docs.zephyrproject.org/latest/guides/bluetooth/bluetooth-dev.html#embedded-hci-tracing

[pdunaj]

Hi @jhedberg ,
we do as follows (case with no privacy):

• device starts with clear settings,
• no bond is established on selected identity - advertise undirectly (bt_le_adv_start),
• host (Android, Windows, nrf840_pca10059) sees device, connects and bonds,
• device reboots,
• bond is present, device starts direct advertising (bt_conn_create_slave_le) to address obtained from info->addr from callback to bt_foreach_bond
• when host is present and is Windows or nrf52840_pca10059 it connects instantly; when host is Android no connection is done
• when no connection is done we do low duty direct advertising but Android still does not connect

Note: for nrf52840_pca10059 we need to enable BT_SCAN_WITH_IDENTITY , as otherwise direct advertising does not work at all.

I have rechecked with privacy (BT_PRIVACY) enabled and the behavior is actually the same. I am able to connect to Windows but not to Android. Previously I was unable to connect at all but maybe I was doing something wrong or the last Zephyr upmerge helped.

[pdunaj]

@jhedberg I will capture traces and try to debug it on Monday.
BTW our app's advertising module is here:
https://github.com/NordicPlayground/fw-nrfconnect-nrf/blob/master/samples/nrf_desktop/src/modules/ble_adv.c