Hi Luiz, Thanks for the prompt reply. On 03/05/18 18:58, Luiz Augusto von Dentz wrote: > Hi David, > > On Thu, May 3, 2018 at 7:42 PM David Llewellyn-Jones <david@xxxxxxxxxxxx> > wrote: > >> Hi, > >> I've been using bluez on a combination of an Ubuntu laptop running bluez >> 5.49 compiled from source and a Sailfish OS phone running the default >> install bluez 5.47. On the laptop I'm using DBUS to interact with bluez; >> on the phone I'm going via the QTBluetoothDiscoveryAgent interface, >> running QT 5.6. > >> The difficulty I've been experiencing is that BLE advertisements sent >> from the laptop in peripheral mode aren't being discovered by the phone. > >> I can see the advertisements being picked up by btmon on the phone, but >> it doesn't filter up to the QT wrapper. Looking through the bluez source >> code, it appears that the reason is because in the case of unfiltered >> discovery, bluez ignores adverts that don't have either EIR_LIM_DISC or >> EIR_GEN_DISC flags set, as in the following code: > > > https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/src/adapter.c?h=5.47#n5658 > >> However, as far as I can tell (I could easily be wrong), bluez never >> adds these flags into the advertising data. I was expecting to see them >> added in the following bit of code: > > > https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/src/shared/ad.c#n423 > >> As a result, I can't figure out a way to produce advertisements from my >> laptop that can be picked up by my phone. > >> Adding the flags by calling the following function within >> bt_ad_generate() with a value of 0x06 fixed the issue (i.e. allowed my >> phone to discover my laptop). > >> static void serialize_flags(uint8_t value, uint8_t *buf, uint8_t *pos) >> { >> if (value == 0) >> return; > >> buf[(*pos)++] = sizeof(value) + 1; >> buf[(*pos)++] = EIR_FLAGS; >> buf[(*pos)++] = value; >> } > >> My question is therefore whether there's a way for bluez to produce BLE >> advertisements (on my laptop) that can be picked up by a non-filtered >> scan using bluez (on my phone). I searched the Web and the list archives >> but didn't find anything that seemed to help answer. > > It is actually added if you have marked the adapter as Discoverable: > > https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/src/advertising.c#n740 >From what I can make out, the flag is registered, but never actually added to the advert payload data. At least, this is what I could make out from the 5.49 code, and running experiments matched this behaviour (i.e. marking the adapter discoverable and running the scan still yielded no results). I also noticed that making the adapter discoverable turns on visibility for Bluetooth Classic, which I was hoping to avoid. There would be definite value for me in separating the two (e.g. being able to explicitly set the flags in the advert). > There has been some debate if we should have this per instance but that > would probably require some changes in the way we deal with whitelist > devices since currently we only allow unknown devices to connect when > discoverable. I'm afraid I don't understand the issue as I'm not sure what you mean by whitelist devices, and I must have missed this discussing when searching the archives. I'll dig a bit further to try to understand better. David -- Website: http://www.flypig.co.uk -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
