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I am trying to create a BR/EDR header and verifying with the Wireshark using the Link-Header type (255) of PCAP dump.

As per the Bluetooth core specification: Bit ordering for BR/EDR packets is LSB first format. Refer: Bluetooth core specification v5.1 Vol 2, PART B, Section 6.2.

I tried to send following bits as BT packet header and generated a PCAP file:

ltAddr = [1; 1; 0];
packetType = [1; 1; 0; 0];
flow = 1;
arq = 0;
seq = 1;

btManualHeaderSpec = [ltAddr;packetType;flow;arq;seq;zeros(8,1)]; % As per the spec
btManualHeaderWireShark = [zeros(8,1);seq;arq;flow;packetType;ltAddr]; % Working in Wireshark

Note: Passed zeros as HEC

When i pass the btManualHeaderSpec pattern, Wireshark is unable to decode: Failed to decode as expected But when i passed the btManualHeaderWireShark, Wireshark successfully decoded: Successfully decoded I am confused. can somebody help me to understand this behavior? Is it the problem with Wireshark or my understanding of the spec?

Prasanth Kumar Arisetti
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  • A couple questions/comments: 1) What is the difference between actual and expected in words *not images*? Which PDU or field is not being decoded properly? 2) If you generated a pcap file that is relevant to the question, you should post a link to it. 3) What language is your code written in? Please add the language name to the code fences like \`\`\`java ... \`\`\` to your question. 4) In your question, can you link directly to the relevant spec for the benefit of future readers? You may want to look at Stack Overflow's [markdown guide](https://stackoverflow.com/editing-help). – Ross Jacobs Oct 31 '19 at 20:21
  • I am using MATLAB for creating a PCAP file. Here, i am trying to generate DM1 packet type and only focusing on BT packet header. In the first case, Wireshark shows it is a NULL type, in the second case it is successfully decoded as DM1. But, as of my understanding 1st case is as per the Bluetooth core specification V5.1. – Prasanth Kumar Arisetti Nov 01 '19 at 04:40

1 Answers1

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In the first packet, you are not specifying the packet Type like DM1, DM3 etc. Possibly that why WS is not able to decode it.

Manivannan Radhakannan
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