[tcpdump-workers] Proposed update to DLT_BLUETOOTH_LE_LL_WITH_PHDR

Sultan Khan sultanqasim at gmail.com
Fri Jul 10 19:04:44 EDT 2020


The reason the extra auxiliary PDU type field is needed is that the
four-bit auxiliary PDU type is ambiguous and context-dependent for
auxiliary PDUs. See Volume 6, Part B, Section 2.3, Table 2.3. The four
least significant bits of the advertising PDU header will be 0b0111 for
AUX_ADV_IND, AUX_CHAIN_IND, AUX_SYNC_IND, and AUX_SCAN_RSP, so you need
extra information to distinguish those. The ADV_EXT_IND PDU can be
distinguished from those despite also being 0b0111 because it's not on a
secondary advertising channel (ie. not an auxiliary advertisement).

Sultan

On Fri, Jul 10, 2020 at 6:30 PM Guy Harris <gharris at sonic.net> wrote:

> For an advertising physical channel PDU, it appears that the PDU type is
> in the least-significant 4 bits of the PDU header.
>
> Is that not present in an auxiliary advertising packet?


More information about the tcpdump-workers mailing list