F1AP IDs: Add update, fix concurrency bug
I suspect a concurrency bug: For instance, during reestablishment, the
CU needs to update the DU UE ID under which the UE is identified in the
DU. Previously, the CU would remove, then add the DU UE ID info. At the
same time, the PDCP thread might look up the information. This can lead
to asserts. Modify the code to do the update under (one) lock.
Also, refactor some code.
Introduce function cu_update_f1_ue_data() which does remove+add under
one lock. This fixes a concurrency bug. For instance, during
reestablishment, the CU needs to update the DU UE ID under which the UE
is identified in the DU. Previously, the CU would remove, then add the
DU UE ID info. At the same time, the PDCP thread might look up the
information. This can lead to asserts. Use the above addmod
functionality to do the remove-add under a mutex.
Modify test to verify this works as expected.
- Refactor SCTP Association Response Handling
- Unified function for both CU-CP and CU-UP handling
- CU-CP: Notifies RRC of E1 connection loss with CU-UP
- CU-UP: Initiates a new SCTP association request to regain E1 connection
- this fix will prevent issue #878 from happening
- Send list of PDU Session Resources to Failed Setup in the (PDU Session
Resource/Initial Context) Setup Response
- depending on different failure scenarios
- e.g. (#878) when No CU-UP is associated and still the CU-CP receives a PDU
Session Setup Request
- add relevant functions to handle NGAP Setup Response messages with failed
list of items
- this is an extra failure handling to make #878 is handled if it ever happens
again
- NGAP Cause Refactoring
- Refactor struct for NGAP cause group and value
- Add extended radio network cause enumeration values
- Refactor redundant code into a new NGAP cause encoding function
- Minor logging, function descriptions improvements
Closes#878
Modify xu_add_f1_ue_data() to be xu_addmod_f1_ue_data(), i.e., "addmod"
behavior in which it is possible to also update f1_ue_data. I do it this
way since an xu_updade_f1_ue_data() function would be almost the same as
the add function (only deleting existing data, whereas the original
add() was asserting in that case).
Modify tests to test for this behavior.
This fixes a concurrency bug. For instance, during reestablishment, the
CU needs to update the DU UE ID under which the UE is identified in the
DU. Previously, the CU would remove, then add the DU UE ID info.
At the same time, the PDCP thread might look up the information. This
can lead to asserts. Use the above addmod functionality to do the
remove-add under a mutex.
* this function is used by both CU-CP and CU-UP
* it behaves differently depending on the type of E1 instance:
CU-CP: inform RRC of E1 connection loss with CU-UP
CU-UP: trigger a new SCTP association request by sending an ITTI to the CU-UP task
* after receiving the E1AP register request, the CU-UP will send a new association request to
SCTP until new E1 connection is achieved by sending a TIMER_HAS_EXPIRED message to the CU-UP
task. The function e1apHandleTimer() is basically triggering a new E1 association request
until new E1 connection is achieved
* print SCTP association state in e1ap.c whenever needed
Related to #878
Need to proper forward declaration, as we otherwise need to make
telnet_o1 module dependent on F1. Make functions publicly accessible,
as the F1 functions are used in an upcoming commit to start the L1.
Split out these functions, to be reused in a follow-up commit to
correctly have gNB-DU configuration update message working.
Change the return type copy_f1ap_served_cell_info(), to return the copy,
which IMO is more intuitive then passing target and source in
parentheses.
Add F1 Handover procedures
- Clean up at RRC and MAC
- Add DU handover procedures, completely handle CellGroupConfig at DU
- Add CU handover procedures
- Maintain reestablishment working between/after handover
- Changes at UE to resync on different frequency DUs
Instructions: see doc/handover-tutorial.md
Things not implemented/open/missing: see #855
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>
Currently, sD has not been allocated, so the octet string is empty. Fix the
allocation to correctly write&read NSSAIs in UE context setup/modification
request messages.
The existing check for the initialization of GTP is wrong; GTP returns
-1 if it could not initialize. Correct this, such that the DU will stop
if GTP cannot be initialize.
If we continue, the DU is requested to set up a GTP tunnel; because GTP
is not initialized, it assumes it is in monolithic/no F1, and does not
set up a tunnel. The F1 UE Context setup response encoder then fails
with this assertion:
Assertion (tnl->teid > 0) failed!
In DU_send_UE_CONTEXT_SETUP_RESPONSE() ../../../openair2/F1AP/f1ap_du_ue_context_management.c:415
Exiting execution
../../../openair2/F1AP/f1ap_du_ue_context_management.c:415 DU_send_UE_CONTEXT_SETUP_RESPONSE() Exiting OAI softmodem: _Assert_Exit_
Aborted
Closes: #853
Robert Schmidt