CODEWITHSUNDEEP
bluetoothbluetooth-lowenergybluezhci
Daniel
Daniel

Reputation: 2592

Bluetooth LE: scanning with whitelist?

I'm checking this source for scanning BT LE advertisement messages with BlueZ:

https://github.com/edrosten/libblepp/blob/master/src/lescan.cc

Mainly it does this (pseudo):

hci_fd=hci_open_dev(dev)
hci_le_set_scan_parameters(hci_fd, static_cast<int>(scan_type), interval, window,
                            own_type, filter_policy, 10000);

struct hci_filter nf;
hci_filter_clear(&nf);
hci_filter_set_ptype(HCI_EVENT_PKT, &nf);
hci_filter_set_event(EVT_LE_META_EVENT, &nf);
setsockopt(hci_fd, SOL_HCI, HCI_FILTER, &nf, sizeof(nf)
hci_le_set_scan_enable(hci_fd, 0x01, filter_dup, 10000);

In case I set hardware filter (by setting filter_dup to 1, I'm not getting my desired messages immediately. They come only at a low-frequency (1/min). That's fine, as the hardware filtering disables the duplicates, and I guess there is a timeout after which it let's them in again. (This seems to be exactly 1 minute in my case).

Turning off the filtering causes a huge traffic arriving in, from which I would only need all messages from a specific mac-addressed device. Can I somehow add a whitelist to the scanning command?

Then it can give me all the packets from my desired device, and leave out all the rest.

How can I do this with BlueZ over HCI?

Upvotes: 0

Views: 1216

Answers (1)

Tim Tisdall
Tim Tisdall

Reputation: 10382

I think your best option is to filter the messages within your code. I don't know of anything in the API to have it filter messages on the hardware level like you describe.

There is a "whitelist" function in BLE, but that's related to specifying a list of addresses that you want to connect to and then you let the hardware automatically connect to just those addresses. (sounds like you actually want just the ad packets and not actually connect, though)

EDIT: I think I was wrong... Look at the filter_policy to hci_le_set_scan_parameters. If it's 0x1 then I think it filters based on the whitelist. I don't know how to set the whitelist, though.

I found it very useful looking at the source code for hcitool and gatttool when trying to understand the bluez library C calls. https://github.com/bluez/bluez/blob/master/tools/hcitool.c has reference to an "acceptlist" which seems to be what you want.

Upvotes: 1

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