When the UE sends a Tracking Area Update (TAU) Request with active_flag=0,
the MME previously sent TAU Accept without verifying the EPS Bearer Context
Status (EBCS). This caused stale bearer sessions to remain in the MME even
if the UE had already released them.
According to 3GPP TS 24.301 §5.5.3.2, the MME should release any bearer
not reported in the UE’s EBCS when active_flag=0. This patch introduces
mme_send_delete_session_or_tau_accept(), which compares the UE’s EBCS bitmask
with the MME session list and deletes any missing default bearer session
before sending TAU Accept.
If no mismatch is found, TAU Accept is sent immediately. The Delete Session
response triggers TAU Accept when deletions are required. This ensures that
the TAU Accept message reflects the UE’s current bearer context accurately.
Also includes:
- Added OGS_GTP_DELETE_SEND_TAU_ACCEPT handling in mme-s11-handler.c
- Simplified EBCS structure (uint16_t value) for bitmask comparison
- Updated TAU-related tests with realistic EBI bitmasks (0x20, 0x60)
This change aligns TAU handling with 3GPP 24.301 and prevents bearer
mismatch issues between UE and EPC during TAU.
o Generate the private key as below.
$ openssl genpkey -algorithm X25519 -out /etc/open5gs/hnet/curve25519-1.key
$ openssl ecparam -name prime256v1 -genkey -conv_form compressed -out /etc/open5gs/hnet/secp256r1-2.key
o The private and public keys can be viewed with the command.
The public key is used when creating the SIM.
$ openssl pkey -in /etc/open5gs/hnet/curve25519-1.key -text
$ openssl ec -in /etc/open5gs/hnet/secp256r1-2.key -conv_form compressed -text
In ausf/udm.yaml
hnet:
o Home network public key identifier(PKI) value : 1
Protection scheme identifier : ECIES scheme profile A
- id: 1
scheme: 1
key: /etc/open5gs/hnet/curve25519-1.key
o Home network public key identifier(PKI) value : 2
Protection scheme identifier : ECIES scheme profile B
- id: 2
scheme: 2
key: /etc/open5gs/hnet/secp256r1-2.key
o Home network public key identifier(PKI) value : 3
Protection scheme identifier : ECIES scheme profile A
- id: 3
scheme: 1
key: /etc/open5gs/hnet/curve25519-1.key
o Home network public key identifier(PKI) value : 4
Protection scheme identifier : ECIES scheme profile B
- id: 4
scheme: 2
key: /etc/open5gs/hnet/secp256r1-2.key
Related to #1779
When a UE that requests slices tries to connect and there are no slices configured, the reject message is:
5GMM cause = 0x7 (5GS Services not allowed)
however it should be:
5GMM cause = 0x3e (No network slices available)
All 5GMM cause value in reject message is reviewed in this commit
If both Delete-Session-Request/Response and
UEContextReleaseCommand/UEContextReleaseComplete are failed at the same time,
UE cannot attach to the EPC infinitely.
So, I've add the protection code
if timer expires when MME does not receive Delete-Session-Response.
