Failed to allocate DL GTP-TEID.

[brightcheng]

Hi

We run srsRAN 25.10 for several days and saw "Failed to allocate DL [GTP-TEID." message in DU log.
Please see attached log.

gnb_25_11_28_00_11_37.zip

[robertfalkenberg]

Please describe some details on your setup and UE behavior. E.g. how many UEs are involved, are there UEs present that constantly fail registration or quickly attaching-detaching, etc.

I see the gNB was active for quite some days, and the first warnings on that topic are:

2025-11-19T22:43:21.239178 [GNB     ] [I] Built in Release mode using commit d2f4b70 on branch HEAD
...
2025-11-27T09:07:53.303790 [DU-MNG  ] [W] ue=15: Failed to allocate DL GTP-TEID.
2025-11-27T09:07:53.303793 [DU-MNG  ] [W] ue=15 rnti=0xe12d proc="UE Configuration": Failed to create DRB1. Cause: Failed to allocate DU UE resources..
2025-11-27T09:07:53.318208 [CU-CP   ] [W] Couldn't setup 1 DRBs at DU
2025-11-27T09:07:53.318209 [CU-CP   ] [W] ue=29714: "PDU Session Resource Setup Routine" failed to modify UE context at DU
2025-11-27T09:07:53.318223 [NGAP    ] [W] ue=29714 ran_ue=29714 amf_ue=825: Some or all PDUSessionResourceSetupItems failed to setup

The UE ID ue=29714 is suspiciously close to the maximum number of TEIDs:

du_ue_manager::du_ue_manager(du_manager_params& cfg_, du_ran_resource_manager& cell_res_alloc_):
...
  f1u_teid_pool(create_gtpu_allocator({MAX_NOF_DU_UES * MAX_NOF_DRBS}))

which is 1024*29 = 29696.

[brightcheng]

We use UE simulators to do ping/throughput test.
Total 64 UEs are running. After ping/throughput test completed each UE will terminate the pdu session/deregitser and repeat to register/active pdu session again.
No registration/pdu session activation failed before this allocation failure.

[robertfalkenberg]

Thanks for the response,

can you please switch on and share the following pcaps while running your experiment for a certain amount of time?

pcap:
  mac_enable: true                 # Set to true to enable MAC-layer PCAPs.
  mac_filename: /tmp/gnb_mac.pcap   # Path where the MAC PCAP is stored.
  mac_type: dlt
  ngap_enable: true                # Set to true to enable NGAP PCAPs.
  ngap_filename: /tmp/gnb_ngap.pcap # Path where the NGAP PCAP is stored.
  f1ap_enable: true
  f1ap_filename: /tmp/gnb_f1ap.pcap
  e1ap_enable: true
  e1ap_filename: /tmp/gnb_e1ap.pcap

If MAC pcaps grow big too quickly, you can do a short run with that pcap enabled; and a longer run without it.

[brightcheng]

I have a quick check of the code it looks release_teid() is not called at DU.
This maybe the cause of the failure.

[robertfalkenberg]

Thank you for the excellent analysis! I think your hypothesis is right. We will fix soon.