Prevent assertion in ngap_gNB_nas_uplink() due to uninitialized selected_plmn_identity:
the selected_plmn_identity field was not being set during N2 handover,
causing the assertion ((plmn->mnc_digit_length == 3) || (plmn->mnc_digit_length == 2))
to fail when processing subsequent NAS messages. The issue is that the Serving PLMN
is not stored by RRC. During N2 mobility, RRC can get this info from GUAMI.
When receiving the Handover Request the target gNB knows from GUAMI
which serving PLMN is the AMF belonging to. In current design, allowed PLMNs
are stored in rrc.configuration. The incoming PLMN needs to be validate
against the PLMNs in the list, then stored in the UE context as Serving PLMN.
This change adds PLMN validation when processing handover requests from the source gNB.
The validation is needed because:
- Target gNB must verify that the PLMN from the GUAMI in the handover request
is allowed by its configuration before accepting the handover to prevent handover
to unsupported PLMNs.
- When PLMN validation fails, the target gNB now properly sends NGAP_HANDOVER_FAILURE
- UE Context must store serving PLMN for later use
Guido Casati
5f261d4f4c