SoftDevice BLE chained advertisement not reassembled by Bluez Stack

RE: SoftDevice BLE chained advertisement not reassembled by Bluez Stack

tesc — Wed, 17 Jun 2026 15:27:45 GMT

Hi,

[quote user="rory0"]Unfortunately I do not have a sniffing device availabe, and running wireshark on my laptop gives more or less the same information as btmon.[/quote]

If you have an additional nRF device, either a DK or a Dongle, you can use that for the nRF Sniffer.

[quote user="rory0"]Are you able to tell from the btmon logs whether the packets in the HCI events look healthy?[/quote]

It would help significantly to know what data was being sent for those packets, and the total data length. To me it looks like a number of packets of different length, but without information about what is supposed to be sent it is hard to tell if anything is off or missing.

[quote user="rory0"]Also, in the meantime I learned that chained advertising is just an optional feature in the bluetooth 5.1 standard, so maybe my laptop doesn't even support chaining. What contradicts this in my understanding, however, is the fact that I see all packets in the HCI events. Do you have any thoughts on this?[/quote]

If you see all the packets, it may still be btmon listing all packets, but not necessarily having the ability to reassemble them. If btmon simply lists all HCI events between controller and host, and reassembly is done at a higher level (i.e. in the host), then I would not expect to see any reassembled packets from the btmon logs.

Regards,
Terje

RE: SoftDevice BLE chained advertisement not reassembled by Bluez Stack

rory0 — Fri, 12 Jun 2026 12:50:16 GMT

Hi!
Thank you for your answer and sorry for the late reply!

Unfortunately I do not have a sniffing device availabe, and running wireshark on my laptop gives more or less the same information as btmon. What I can say (and forgot to mention in my first post) is that nRF Connect app on my phone manages to reassemble the packets just fine. Is there any export from there that would be useful for you?

Are you able to tell from the btmon logs whether the packets in the HCI events look healthy?
For me, not knowing much about the BLE standards, the question was if there are maybe different timings for the chaining that in this case fail to work together? And I am also suprised that there are 3 packets rather than just 2 that would be sufficient for the size of data. Can you think of a reason for that?

Also, in the meantime I learned that chained advertising is just an optional feature in the bluetooth 5.1 standard, so maybe my laptop doesn't even support chaining. What contradicts this in my understanding, however, is the fact that I see all packets in the HCI events. Do you have any thoughts on this?

Many thanks and best regards!
-rory

RE: SoftDevice BLE chained advertisement not reassembled by Bluez Stack

tesc — Wed, 27 May 2026 20:57:03 GMT

Hi,

The output that you provided are from btmon, which is part of Bluez, which is where you experience the issue. This means there is no way to know if the issues with the output stems from the original packets sent over-the-air, or if it stems from Bluez. Would you be able to provide a sniffer trace, either using the nRF Sniffer or a different BLE sniffing tool which is not part of Bluez? That way, we could have a look at what has actually been sent over-the-air, in order to diagnose further if anything is off with the transmission.

Regards,
Terje

RE: SoftDevice BLE chained advertisement not reassembled by Bluez Stack

rory0 — Wed, 27 May 2026 09:58:30 GMT

I filed an issue with the Bluez developers as well: github.com/.../2156