AF crashes on POST M5 Network Assistance if policyTemplateId or requestedQoS is missing

[ErikGaida]

Summary

This bug was found while reviewing the Insomnia setup see PR #97

AF Crashes:

1. Start AF
2. POST {{ _.m5_url }}/3gpp-m5/v2/network-assistance
   body for step 2:

{
  "serviceDataFlowDescriptions": [
    {
      "flowDescription": {
        "direction": "DOWNLINK",
        "dstIp": "10.45.0.5"
      }
    }
  ],
  "provisioningSessionId": "{{ provisioning_session_id }}",
  "mediaType": "VIDEO"
}

03/27 14:40:31.009: [app] INFO: Configuration: '/usr/local/etc/open5gs/msaf.yaml' (../subprojects/open5gs/lib/app/ogs-init.c:126)
03/27 14:40:31.016: [sbi] INFO: mhd_server() [127.0.0.23]:7777 (../subprojects/open5gs/lib/sbi/mhd-server.c:274)
03/27 14:40:31.016: [sbi] INFO: mhd_server() [0.0.0.0]:7778 (../subprojects/open5gs/lib/sbi/mhd-server.c:274)
03/27 14:40:31.016: [sbi] INFO: mhd_server() [127.0.0.25]:7777 (../subprojects/open5gs/lib/sbi/mhd-server.c:274)
03/27 14:40:31.016: [sbi] INFO: nghttp2_server() [http://127.0.0.22]:7777 (../subprojects/open5gs/lib/sbi/nghttp2-server.c:391)
03/27 14:40:31.017: [sbi] INFO: nghttp2_server() [http://127.0.0.99]:7779 (../subprojects/open5gs/lib/sbi/nghttp2-server.c:391)
[New Thread 0x7ffff451d6c0 (LWP 56324)]
03/27 14:40:31.018: [app] INFO: 5GMSAF initialize...done (../src/5gmsaf/app.c:24)
03/27 14:40:31.036: [msaf] INFO: [85d95538-29e2-41f1-a46f-075a99b1d485] MSAF M1 Running (../src/5gmsaf/msaf-m1-sm.c:144)
03/27 14:40:31.036: [msaf] INFO: [85d95538-29e2-41f1-a46f-075a99b1d485] MSAF M5 Running (../src/5gmsaf/msaf-m5-sm.c:113)
03/27 14:40:31.036: [msaf] INFO: [85d95538-29e2-41f1-a46f-075a99b1d485] MSAF Management Interface Running (../src/5gmsaf/msaf-mgmt-sm.c:60)
03/27 14:40:31.036: [msaf] INFO: [85d95538-29e2-41f1-a46f-075a99b1d485] MSAF Running (../src/5gmsaf/msaf-sm.c:73)
03/27 14:40:31.039: [sbi] INFO: [85d95538-29e2-41f1-a46f-075a99b1d485] NF registered [Heartbeat:10s] (../subprojects/open5gs/lib/sbi/nf-sm.c:214)
03/27 14:41:05.110: [msaf] INFO: 10.45.0.5: dst_ip (../src/5gmsaf/network-assistance-session.c:319)

Thread 2 "open5gs-msafd" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff451d6c0 (LWP 56324)]
0x00005555555aa2c1 in populate_media_component (policy_template_id=0x0, flow_description=0x7fffec004bb0, requested_qos=0x0, 
    media_type=msaf_api_media_type_VAL_VIDEO) at ../src/5gmsaf/network-assistance-session.c:467
467	in ../src/5gmsaf/network-assistance-session.c
(gdb) 

[rjb1000]

The semantics of creating a Network Assistance Session are very poorly specified in clause 4.7.6 of TS 26.512 V17.9.1, but there is more helpful detail in clause 11.6.4.1, including the following:

If neither a policyTemplateId nor a requestedQoS are supplied when creating a Network Assistance session, operations
invoked on the 5GMS AF within the scope of the Network Assistance session are constrained only by the policies of the
PCF.

So, rather than segfaulting, it would be more reasonable for the 5GMS AF to do something more graceful if both properties are omitted. We will need to debate what the behaviour should be with SA4 experts. I'm not sure how to interpret the above specification.