When receiving a measurement report including an A3 event, trigger
handover towards the indicated cell.
Note that currently, we are still limited to one Cell by DU, hence
looking up a cell comes down to looking up a DU, as is done here.
Co-authored-by: batuhanduyuler <batuhan.duyuler@firecell.io>
Co-authored-by: Luis Pereira <lpereira@allbesmart.pt>
Co-authored-by: Robert Schmidt <robert.schmidt@openairinterface.org>
This commit implements reestablishment during handover when occurring at
the source DU, either as a handover Failure or "normal" reestablishment
(something else went wrong). In this case, the CU will trigger HO
cancel, which in F1, means to cancel on the target DU. Also, undo any
previous ID changes. Retain the old CellGroupConfig (before handover)
for the case of reestablishment at source. If not needed, it is freed
after the reconfiguration complete.
Reestablishment on target cell during handover cannot be handled by the
gNB (yet). It is the same as with a normal reestablishment (not during
handover) on a different cell: that cell has no notion of the old UE, so
we cannot simply indicate the old UE to reestablish; at least, we would
need to cleanup the CellGroupConfig, and I am not sure this works out of
the box, either.
After handover, the last CellGroupConfig received is the one for
handover, containing a reconfigurationWithSync. Resending this
CellGroupConfig to the UE after reestablishment would trigger a
handover. Free the reconfigurationWithSync to have the UE complete
reestablishment at the current cell.
The CU implementation of reestablishment modifies the CellGroupConfig.
It should not do this, but does as of now. The specification (38.473 Sec
8.7) foresees an optional F1 UE context modification procedure (which
can be used to receive the CellGroupConfig). This should be done instead
to retrieve the correct CellGroupConfig.
Note that the F1 UE context setup procedure, similar to the UE context
modification procedure, would also allow to perform reestablishment on a
DU that is not the original one.
If we release a request from a DU during, handle as follows:
- from the source: Handover is still ongoing, so ignore it by
acknowledging the release, and marking handover as done. In this case,
we did not receive an acknowledgement from the target, but since the
source DU does not keep the UE context, we could not cancel the
handover anymore either. The UE might come back on any DU through
reestablishment (or simply be connected on the target)
- from the target: consider this to be a genuine release, and forward to
AMF.
Co-authored-by: batuhanduyuler <batuhan.duyuler@firecell.io>
Co-authored-by: rmagueta <rmagueta@allbesmart.pt>
The HO is completed (from a pure RAN perspective) when receiving
reconfiguration complete. In that case, remove the HO context, and
signal successful handover through the callback. For the F1 handover,
this means releasing the UE at the source DU.
Co-authored-by: batuhanduyuler <batuhan.duyuler@firecell.io>
Co-authored-by: rmagueta <rmagueta@allbesmart.pt>
We expect the UE's RRC Reconfiguration Complete to come through the
target DU, as the "new UE" at the target CU. Also, function
CU_handle_UL_RRC_MESSAGE_TRANSFER() checks that the UL RRC Message,
through which we will receive RRC Reconfiguration Complete, matches the
DU UE ID stored in RRC. Since the DU UE ID will be the one at the target
DU, while up to now, we stored the DU UE ID at the source DU.
Correspondingly, update the DU UE ID to the one at the target DU; also
update the corresponding assoc_id.
Co-authored-by: batuhanduyuler <batuhan.duyuler@firecell.io>
Co-authored-by: rmagueta <rmagueta@allbesmart.pt>
In this commit, handle the reception of a UE context setup response, in
the case of handover. In that case, store the gNB-DU UE ID and C-RNTI of
the UE at the target DU, and trigger a reconfiguration towards the UE at
the source DU via the callback.
To ensure that the CU-UP's PDCP is SN-aligned with the UE, use
cuup_notify_reestablishment() to reset the bearers with PDCP
reestablishment, which has already been implemented in the last commit.
Co-authored-by: batuhanduyuler <batuhan.duyuler@firecell.io>
Co-authored-by: rmagueta <rmagueta@allbesmart.pt>
This is preparatory work to handle the UE context setup response from
the target DU. There are two cases:
- "Initial" UE context setup response (during connection setup): we need
to inform the CU-UP via an E1 message of the new bearers (GTP tunnel
update)
- F1 handover: we need to inform the CU-UP via an E1 message that there
are DRBs to reestablish
There are two different functions, e1_send_bearer_updates() and
cuup_notify_reestablishment(), to do this. Harmonize the code, before
implementing the actual handover logic in the next commit.
Add a function to trigger an F1 handover, including the corresponding
telnet function implementation. The function looks up source&target DU,
creates a HO context, and reads PDU information to send a UE context
setup request to the target DU towards which to handover.
Co-authored-by: batuhanduyuler <batuhan.duyuler@firecell.io>
Co-authored-by: rmagueta <rmagueta@allbesmart.pt>
Functions get_qos_char_from_qos_flow_param() and
get_qos_characteristics() will be used in rrc_gNB_mobility.c to read PDU
information for handover. Move the definitions to a header to reuse
later.
HandoverPreparationInformation will be used in the follow-up commit to
trigger a handover.
Co-authored-by: batuhanduyuler <batuhan.duyuler@firecell.io>
Co-authored-by: rmagueta <rmagueta@allbesmart.pt>
This F1 message sends us the CellGroupConfig of the UE. Store it in case
we need it. For instance, at least in OAI, it is possible to make a
handover without a DRB (this might or might not be standard compliant).
However, in this case, we did never receive a UE context setup request,
which stores the CellGroupConfig. Hence, store the first CellGroupConfig
we receive, to be able to do e.g., handover.
RETURN_IF_INVALID_ASSOC_ID() checks if an assoc_id (of a DU) is valid.
It will be also used in the mobility RRC module later. Move it to the DU
header (where it logically belongs) to move it from there.
Implement the Transmission Action Indicator F1AP forwarding logic, and
add it to the F1 internal representation structure. After the
transmission interrupt timer (during which SRB1 can send messages), the
UE will be out-of-sync (we assume it's not there anymore).
Co-authored-by: batuhanduyuler <batuhan.duyuler@firecell.io>
Co-authored-by: rmagueta <rmagueta@allbesmart.pt>
Implement the HandoverPreparationInformation F1AP forwarding logic, and
add it to the F1 internal representation structure.
No logic is implemented in this commit.
Co-authored-by: batuhanduyuler <batuhan.duyuler@firecell.io>
Co-authored-by: rmagueta <rmagueta@allbesmart.pt>
- Fixes#853, #854, #858, #859, #862
- handle repeated NGAP Initial context setup requests, thereby fixing assert:
Assertion (!ue_p->as_security_active) failed!
In rrc_gNB_generate_SecurityModeCommand() /home/eurecom/raymond/openairinterface5g/openair2/RRC/NR/rrc_gNB.c:2590
logic error: security already activ
- A lot of cleanup: remove almost all use of protocol_ctxt_t in 5G RRC and use
existing pointers instead
A UE might send a ULInformationTransfer without the actual content present
(intentionally or not). Check this and handle appropriately to avoid
a segfault when reading the empty NAS message.
Closes: #862
Pass UE context pointer directly. In the switch, do not return to not
create memory leaks (after the switch, memory is freed). Move the
function up to make it appear before the use of the function.
Pass UE context, without protocol_ctxt_t, for cleanup. Remove the return
from within the switch, as this would lead to memory leaks; nothing is
executed after the switch statement (except for freeing memory).
A UE might send a MeasurementReport without the actual IEs present
(intentionally or not). Check this and handle appropriately to avoid
assertion
Assertion (measurementReport->criticalExtensions.present == NR_MeasurementReport__criticalExtensions_PR_measurementReport && measurementReport->criticalExtensions.choice.measurementReport != ((void*)0)) failed!
In rrc_gNB_process_MeasurementReport() ../../../openair2/RRC/NR/rrc_gNB.c
Closes: #859
A UE might send a UE Capability Information without unsolicitatedly
(intentionally or not). Check this and handle appropriately to avoid
assertion
Assertion (UE->xids[xid] == RRC_UECAPABILITY_ENQUIRY) failed!
In handle_ueCapabilityInformation() ../../../openair2/RRC/NR/rrc_gNB.c
Closes: #858
A UE might send a rrcReestablishmentComplete without the actual IEs
present (intentionally or not). Check this and handle appropriately to
avoid assertion
Assertion (reestablishment_complete->criticalExtensions.present == NR_RRCReestablishmentComplete__criticalExtensions_PR_rrcReestablishmentComplete) failed!
In handle_rrcReestablishmentComplete() ../../../openair2/RRC/NR/rrc_gNB.c:1364
Closes: #854
Prior to this commit, if we receive an Initial Context Setup Request for
a UE that has AS security set up, the gNB asserts with
Assertion (!ue_p->as_security_active) failed!
In rrc_gNB_generate_SecurityModeCommand() openairinterface5g/openair2/RRC/NR/rrc_gNB.c:2590
logic error: security already activ
However, TS 38.413 says:
> The AMF may initiate the Initial Context Setup procedure if a
> UE-associated logical NG-connection exists for the UE
(I interpret this as "it might happen anytime")
> store the received Security Key in the UE context and, if the NG-RAN
> node is required to activate security for the UE, take this security key
> into use.
(I interpret this as "do not set up AS security again")
In this commit, handle if we receive an Initial Context Setup Request
for an existing UE context. As said in the spec, we store the keys. If
security is not active, we trigger RRC Security Mode Command. If it is
active, we skip Security, and directly set up a PDU session. If there is
also no PDU session, we simply forward the NAS message, and acknowledge.
If there was no AS security, after security, the gNB would trigger the
setup of PDU sessions (if any), and then forward any NAS PDUs, which is
stated in the if block if AS security is already active.
Robert Schmidt