Weird behavior on UE connectivity (-e trace enables/disables internet connectivity)

[polhenarejos]

I updated to v2.2.8 and suddenly I lost the UE connectivity to internet. UE cannot ping PDN and CN cannot ping UE. Actually, when CN pings UE, the reply arrives to the CN via GTP, but it not processed by ogstun. See capture

I am scanning enp5s0f0, the physical interface connected to gNB and ogstun. As you can see, the replies arrive to CN, but not processed.

I followed the guidelines for iptables and so on and so forth, but without luck. But wait, the weird thing is that if I execute the "app" with "-e trace" parameter (lots of traces on screen), everything works properly. With "-e trace", CN can ping and get back the reply, UE can ping google and there is not any problem. I assume that enable the log trace should not affect on the UE connectivity, but it does, at least to me.

I cloned and compiled a new fresh v2.2.8 tag, and the behavior is still the same. So, at this point, my impression is not related to iptables or kernel stuff, but with Open5GS itself. Running the "app" program with "-e trace" is not a bad solution, at least if UEs have connectivity, but I guess it is not really what it should be expected.

I attach my configuration.

5gcn-nsa-local.yaml.txt

I also attach a capture where UE pings google

and CN pings UE

Of course I can provide any PCAP you may consider interesting.

Hope you can fix it!

[acetcom]

@polhenarejos

Please share with all conf/log files. And, please provide a PCAP by distinguishing between those that work and those that do not. It is important that PCAP captures any interface with all signaling packets.(NGAP, PFCP, HTTP2)

Thank you so much!
Sukchan

[polhenarejos]

Hi @acetcom

Please find attached your requirements:

• Config: 5gcn-nsa-local.yaml.txt

For each experiment, the following is performed in this order:

1. UE (10.45.0.2) pings CN (10.45.0.1)
2. UE (10.45.0.2) pings 8.8.8.8
3. CN (10.45.0.1) pings UE (10.45.0.2)

With "./build/tests/app/app -c 5gcn-nsa-local.yaml -l install/var/log/open5gs/app_info.log":
No internet / UE connectivity. UE attaches but it cannot ping CN (10.45.0.1) and CN cannot ping UE (10.45.0.2)

• Log: app_info.log
• PCAP (1.2 GB): https://cloud.cttc.es/index.php/s/dtEQXE2zfnzaTft
• PCAP filtered (6 KB): open5gs_app_info_filtered.pcapng.gz

With "./build/tests/app/app -e trace -c 5gcn-nsa-local.yaml -l install/var/log/open5gs/app_trace.log":
Everything works as expected and pings are replied back.

• Log: app_trace.log
• PCAP (1.2 GB): https://cloud.cttc.es/index.php/s/yePDTY2N4EiipQx
• PCAP filtered (7 KB): open5gs_app_trace_filtered.pcapng.gz

Filtered PCAPs are exported with the following filter: "ngap or pfcp or http2 or icmp"

Thanks!

[acetcom]

@polhenarejos

It seems to be a configuration issue in 5gcn-nsa-local.yaml, not a trace issue.

SGW-U and UPF GTP-U address is duplicated with 10.100.1.1. It seems that the execution order of NFs has changed according to the debug log level(info or trace).

You should not use the same address for GTP-U address. Please change SGW-U GTP-U address or use the ./tests/app/5gc program.

Good luck with you!
Sukchan

[polhenarejos]

Thank you, @acetcom. Using ./tests/app/5gc works correctly, as you mentioned. Probably enabling trace alters the execution order.

I did not know I could not use the same ip for SWG-U and UPF GTP-U. Both share the same physical interface. I'll try a secondary ip.

Thank you for you time and effort!

[acetcom]

Refer to #986