[BUG] Unable to populate HandoverRequired with HO Type = 5GS to 4G

[saurabh-ghadage]

Describe the bug
Adding support for setting the target eNodeB ID, similar to the SetTargetGnodeB function, in the handover-required.go file for testing 5g to 4g handover.

To Reproduce
Execute the following command:

 ./packetrusher multi-ue --tr 2000 --ngh 7000 -n 1

Expected behavior
The function should support assigning the TargeteNB-ID structure as specified below:

TargeteNB-ID ::= SEQUENCE { 
    globalENB-ID         GlobalNgENB-ID, 
    selected-EPS-TAI     EPS-TAI, 
    iE-Extensions        ProtocolExtensionContainer {{TargeteNB-ID-ExtIEs}} OPTIONAL 
}

However, implementation attempts have been unsuccessful. The goal is to test 5G to 4G handover functionality.

Screenshots
Currently, the function supports the following structure:

Expected structure:

Request for Assistance
Could someone help test this functionality or provide guidance on implementing the desired changes? Any suggestions for achieving the required behavior would be greatly appreciated.

[linouxis9]

Hi @saurabh-ghadage!
Thank you for your interest in PacketRusher. PacketRusher does not support S1AP and NAS-EPS, these protocols supports must first be supported added for EPC support in PacketRusher for 5G -> 4G HO.
Just being able to assign a TargeteNB-ID won't be enough and I guess that's why you have been having troubles.
If you are looking to support NAS-EPS/S1AP in PacketRusher, I would gladly accept the changes!
Thanks,
Valentin

[saurabh-ghadage]

Hello @linouxis9, thank you for your response.

My query pertains to NGAP and specifically involves encoding the TargetID within the HandoverRequired command. Currently, the implementation supports only TargetRAT = N2. My objective is to enable 5GS to 4G handover, which requires encoding the TargetID as eNB-ID instead of GNB-ID, in alignment with the 3GPP specification 38.413.