When processing a UE-requested PDU Session Modification Request, the
SMF treated every Requested QoS flow description as a QoS parameter
modification regardless of its operation code.
If the UE deletes a dedicated QoS flow by sending both:
- Delete existing QoS rule
- Delete existing QoS flow description
for the same QFI, the QoS rules handler sets OGS_PFCP_MODIFY_REMOVE,
but the QoS flow descriptions handler also set
OGS_PFCP_MODIFY_QOS_MODIFY. This produced an invalid
REMOVE|QOS_MODIFY combination and tripped the invariant in
gsm_handle_pdu_session_modification_request(), aborting smfd during
VoNR call teardown.
A "Delete existing QoS flow description" carries no QoS parameters, so
skip the QoS-parameter update path for that operation and let the QoS
rule deletion drive the actual PFCP removal.
Also update the test GSM message builder to encode QoS rule deletion
without packet filters, and add a VoNR regression test for the
UE-initiated dedicated QoS flow deletion case.
Issues #4672
72913dc927