ULCL Not Working #168
Description
Dear Free5GC Team,
I believe there has been a regression in a recent version of the SMF where ULCL has stopped working. Specifically:
- with SMF v4.0.0, ULCL works correctly.
- with SMF v4.0.1 or latest, packets forwarded between two UPFs (over N9) fail.
Note that the version numbers above correspond to the versioning of the docker containers. I am not sure how this corresponds to the versions of the SMF?
The specifics of the failure are documented in this issue on the free5gc-compose repo (as that is how I was running the setup, and I initially believed it to be a bug in free5gc-compose). However, a summary (copy-pasted from that issue) is that when I ping 1.0.0.1 the traffic correctly exists early at the I-UPF, rather than continuing through to the PSA-UPF (as per the uerouting.yaml configuration). However, when I try to ping another public IP (e.g. 8.8.8.8 or 1.1.1.1), where the traffic should go through first the I-UPF and then the PSA-UPF, I get no response.
I've looked at the traffic flow inside the I-UPF using tshark, and observed the following (I've edited the tshark log slightly to include the names of the components rather than their IPs).
Source (GTP Src) | Destination (GTP Dest) | Info
-------------------------|---------------------------|---------------
UERANSIM (GTP 10.60.0.1) => I-UPF (GTP 1.1.1.1) GTP <ICMP> 144 Echo (ping) request id=0x001e, seq=1/256, ttl=64
I-UPF (GTP 10.60.0.1) => PSA-UPF (GTP 1.1.1.1) GTP <ICMP> 144 Echo (ping) request id=0x001e, seq=1/256, ttl=64
PSA-UPF (GTP 1.1.1.1) => I-UPF (GTP 10.60.0.1) GTP <ICMP> 144 Echo (ping) reply id=0x001e, seq=1/256, ttl=253
The ping to 1.1.1.1 is correctly sent through the I-UPF to the PSA-UPF, the PSA-UPF sends it to 1.1.1.1, and receives a reply, which is sent back to the I-UPF. However the I-UPF does not forward the packet back to the UE - there are no more GTP messages in the flow, only the three I've listed above. Additionally, I observe the following kernel message in the VM hosting the docker containers:
upfgtp:[gtp5g] gtp1u_udp_encap_recv: No PDR match this skb : teid[1]
When searching for similar issues I can across #141 , which seems like a very similar issue. But it's also marked as resolved, whereas I am having the same issue - even when I use the latest tag for the SMF docker image. So I believe this is a separate issue?
I am able to continue my work using the older SMF version for my work, so on my side this is not a showstopper issue. But I thought I would report it regardless!
Many thanks for your excellent work!