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asked 2025-09-09 10:31:23 +0000

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How to dissect 5G RRC L3 messsages from L1 packets Tx_Data.request (FAPI logs) in wireshark using a custom dissector DLL?

I am working at the PHY (L1) layer in a 5G NR stack implementation. At this layer, I receive Tx_Data.request messages from MAC (as per Small Cell Forum FAPI interface). These contain transport blocks that L1 needs to transmit.

My goal is to:

Export these Tx_Data.request payloads into a pcap.

Open the pcap in Wireshark.

Decode the actual RRC messages (e.g., RRCSetup, RRCReconfiguration) contained in SRB PDUs.

What I tried so far

I can already capture and dump the Tx_Data.request into a pcap file.

Wireshark correctly shows my custom protocol dissector for FAPI messages.

However, if I try to directly call the RRC dissector on the payload, it fails.

If I modify my custom Wireshark plugin DLL (generated using C, nmake), can I just strip headers and call the RRC dissector directly, or do I need to implement the whole MAC → RLC → PDCP chain first?

How to dissect 5G RRC L3 messsages from L1 packets Tx_Data.request (FAPI logs) in wireshark using a custom dissector DLL?

I am working at the PHY (L1) layer in a 5G NR stack implementation. At this layer, I receive Tx_Data.request messages from MAC (as per Small Cell Forum FAPI interface). These contain transport blocks that L1 needs to transmit.

My goal is to:

Export these Tx_Data.request payloads into a pcap.

Open the pcap in Wireshark.

Decode the actual RRC messages (e.g., RRCSetup, RRCReconfiguration) contained in SRB PDUs.

What I tried so far

I can already capture and dump the Tx_Data.request into a pcap file.

Wireshark correctly shows my custom protocol dissector for FAPI messages.

However, if I try to directly call the RRC dissector on the payload, it fails.

If I modify my custom Wireshark plugin DLL (generated using C, nmake), can I just strip headers and call the RRC dissector directly, or do I need to implement the whole MAC → RLC → PDCP chain first?

How to dissect 5G RRC L3 messsages from L1 packets Tx_Data.request (FAPI logs) in wireshark using a custom dissector DLL?

I am working at the PHY (L1) layer in a 5G NR stack implementation. At this layer, I receive Tx_Data.request messages from MAC (as per Small Cell Forum FAPI interface). These contain transport blocks that L1 needs to transmit.

My goal is to:

     
  • Export these Tx_Data.request payloads into a pcap.

pcap.   
    •  
  • Open the pcap in Wireshark.

Wireshark.    
    •  
  • Decode the actual RRC messages (e.g., RRCSetup, RRCReconfiguration) contained in SRB PDUs.
PDUs.

What I tried so far

far   
 
     
  • I can already capture and dump the Tx_Data.request into a pcap file.

file.    
    •  
  • Wireshark correctly shows my custom protocol dissector for FAPI messages.

messages.    
    •  
  • However, if I try to directly call the RRC dissector on the payload, it fails.
fails.

If I modify my custom Wireshark plugin DLL (generated using C, nmake), can I just strip headers and call the RRC dissector directly, or do I need to implement the whole MAC → RLC → PDCP chain first?

How to dissect 5G RRC L3 messsages from L1 packets Tx_Data.request (FAPI logs) in wireshark using a custom dissector DLL?

I am working at the PHY (L1) layer in a 5G NR stack implementation. At this layer, I receive Tx_Data.request messages from MAC (as per Small Cell Forum FAPI interface). These contain transport blocks that L1 needs to transmit.

My goal is to:

  • Export these Tx_Data.request payloads into a pcap.

  • Open the pcap in Wireshark.

  • Decode the actual RRC messages (e.g., RRCSetup, RRCReconfiguration) contained in SRB PDUs.

What I tried so far

  • I can already capture and dump the Tx_Data.request into a pcap file.

  • Wireshark correctly shows my custom protocol dissector for FAPI messages.

  • However, if I try to directly call the RRC dissector on the payload, it fails.

If I modify my custom Wireshark plugin DLL (generated using C, nmake), can I just strip headers and call the RRC dissector directly, or do I need to implement the whole MAC → RLC → PDCP chain first?

How to dissect 5G RRC L3 messsages from L1 packets Tx_Data.request (FAPI logs) in wireshark using a custom dissector DLL?

I am working at the PHY (L1) layer in a 5G NR stack implementation. At this layer, I receive Tx_Data.request messages from MAC (as per Small Cell Forum FAPI interface). These contain transport blocks that L1 needs to transmit.

My goal is to:

  • Export these Tx_Data.request payloads into a pcap.

  • Open the pcap in Wireshark.

  • Decode the actual RRC messages (e.g., RRCSetup, RRCReconfiguration) contained in SRB PDUs.

What I tried so far

  • I can already capture and dump the Tx_Data.request into a pcap file.

  • Wireshark correctly shows my custom protocol dissector for FAPI messages.

  • However, if I try to directly call the RRC dissector on the payload, it fails.

If I modify my custom Wireshark plugin DLL (generated using C, nmake), can I just strip headers and call the RRC dissector directly, or do I need to implement the whole MAC → RLC → PDCP chain first?