tcpdump mailing list archives
Re: DLT for Bluetooth Low Energy
From: Mike Ryan <mikeryan () lacklustre net>
Date: Thu, 13 Jun 2013 20:08:11 -0700
So do LINKTYPE_BLUETOOTH_LE_LL/DLT_BLUETOOTH_LE_LL packets include the preamble octet and the CRC?They include the 3 octet CRC, they do not include the preamble.OK, I'll update the description on the "link-layer header types" page to note that. So the packet in the file has: 4 bytes of Access Address; 2-39 bytes of packet data; 3 bytes of CRC; in sequential order, with nothing separating them, right?
Correct.
To validate the CRC you must know a per-connection CrcInit. This value will be stored in the PPI with each packet."Stored in the PPI"? Does that mean "stored in per-packet information kept by the program reading the capture file", or does it mean "per-packet information stored *in* the capture file"? If the latter, that presumably means there's some form of pseudo-header preceding the Access Address.
I prepend a PPI packet header to the packet, which includes the DLT (thank you for assigning!) and some metadata about the packet and the state of the Ubertooth during capture. I've attached a screenshot: you can see the old version of the PPI header (lacks CrcInit), the USER0 DLT, and the 18 bytes of data captured from the air. 18 = 4 byte AA + 2 byte header + 9 byte data + 3 byte CRC
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Current thread:
- DLT for Bluetooth Low Energy dragorn (May 16)
- Re: DLT for Bluetooth Low Energy Michal.Labedzki (Jun 11)
- Re: DLT for Bluetooth Low Energy Guy Harris (Jun 13)
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- Re: DLT for Bluetooth Low Energy Guy Harris (Jun 13)
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- Re: DLT for Bluetooth Low Energy Guy Harris (Jun 13)
- Re: DLT for Bluetooth Low Energy Mike Ryan (Jun 13)
- Re: DLT for Bluetooth Low Energy Guy Harris (Jun 13)
- Re: DLT for Bluetooth Low Energy Mike Ryan (Jun 13)
- Re: DLT for Bluetooth Low Energy Mike Ryan (Jun 13)
- Re: DLT for Bluetooth Low Energy Guy Harris (Jun 14)
- Re: DLT for Bluetooth Low Energy Mike Ryan (Jun 14)
- Re: DLT for Bluetooth Low Energy Guy Harris (Jun 14)
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