PDU Session Release
This MR implements end-to-end PDU Session Release functionality
according to 3GPP TS 38.413 and TS 38.331 specifications.
Reason for Change Previous implementation had incomplete and wrongly
places tunnel cleanup during PDU session release. UP cleanup shall be
done at CUUP, RRCReconfiguration shall be sent after retrieval of
updated CellGroupConfig from the DU. This implies F1 and E1 exchanges
during PDU session release procedure.
Major Changes:
1. RRC PDU Session Release: DRBs and PDU session teardown in NGAP PDU
Session Release Response callback
- Helper Functions: Introduced rm_pduSession,
find_drb_by_pdusession_id and rm_drbs() helpers to locate and clean
up DRBs linked to a specific PDU session
- Targeted Cleanup: RRC PDU Session and per-session DRB removal in
rrc_gNB_send_NGAP_PDUSESSION_RELEASE_RESPONSE()
- Status Cleanup: Removed unused PDU_SESSION_STATUS_RELEASED status
2. RRC PDU Session Release: Refactor
rrc_gNB_process_NGAP_PDUSESSION_RELEASE_COMMAND
- Any PDU session in the pdusession_release_params list that is
present in the RRC list can be set to release, regardless of its
status
- Function Signature Update: Updated function signature and other
minor changes
- Response Handling: rrc_gNB_send_NGAP_PDUSESSION_RELEASE_RESPONSE is
sent upon completion of RRCReconfiguration
3. RRC PDU Session Release: add missing procedures E1AP Integration:
- Populates E1AP Bearer Modification for each to be released session
- PDCP Enhancement: Added nr_pdcp_release_drbs() to remove all DRBs
linked to a given PDU session in CUUP
- GTP-U Cleanup: GTP tunnel teardown handled in CUUP
e1_bearer_context_modif() using correct F1 or N3 GTP instance
4. NR PDCP/GTP:
- Enhanced Tunnel Deletion Logic: Separate handling for N3 tunnels (1
per PDU session) and F1-U tunnels (1 per DRB)
- New PDCP API Function: Added nr_pdcp_get_drb_ids_for_pdusession()
function to retrieve all DRB IDs associated with a specific PDU
session
5. RRC PDU Session Release: F1AP-based UE Context Modification:
- Replaced direct RRC message transfer with F1AP UE Context
Modification Request for proper retrieval from DU
- Cell Group Configuration: handling of updated CellGroupConfig from
DU ensures DRB release at CU
6. Docs and testing:
- Added PDU session add/remove test cases to 25 PRB RFSIM pipeline
- Documentation: Added PDU Session Release sequence diagram
- Telnet Commands: Added ci command to trigger NGAP PDU Session
Release and ciUE command to trigger establishment of a new PDU
Session
7. Additional fixes:
- UE RLC Management: ensure release of RLC entities
- Unify NG delay control before calling the RRC NGAP handler, for both
Setup and Release
8. Code Cleanup: Cleaned up unused GTP teardown functions.
Closes#867
This commit implements proper PDU Session Release handling across
RRC, PDCP, F1AP, E1AP to ensure clean resource cleanup when
a PDU session is terminated.
Key changes:
NGAP:
In `rrc_gNB_process_NGAP_PDUSESSION_RELEASE_COMMAND()`:
* Populates E1AP Bearer Modification for each released session
* If a CU-UP is connected, triggers `bearer_context_mod()` for PDU teardown
PDCP:
* Added `nr_pdcp_release_drbs()` to remove all DRBs linked to a given PDU session
* Called from `e1_bearer_context_modif()` for correct clean-up during session release
F1AP UE Context Modification:
Replace direct RRC message transfer with F1AP UE Context Modification Request
to properly handle PDU session release according to 3GPP TS 38.331.
3GPP TS 38.331 `5.3.5.6.4 DRB release` says: whether or not the RLC and MAC entities associated
with a PDCP entity are reset or released is determined by the CellGroupConfig. Thus,
updated CellGroupConfig needs to be received by the UE. This has to be retrieved by CUCP
from the DU. Therefore:
After receiving an NGAP_PDUSESSION_RELEASE_COMMAND, the CUCP shall:
1) forward (store for later) the NAS PDU to the UE, if present as per 3GPP TS 38.413, and
2) send a UE Context Modification to the DU with the list of DRBs to release
and the RRC container (RRCReconfiguration with NAS PDU)
After reception of UE Context Modification Response, the list of drbs to release
is prepared based on PDU session status PDU_SESSION_STATUS_TORELEASE
in rrc_gNB_generate_dedicatedRRCReconfiguration and then encoded
in drb_ToReleaseList for a new RRCReconfiguration with the new cellGroupConfig.
Key changes:
* rrc_gNB_generate_dedicatedRRCReconfiguration_release() now uses F1AP UE Context
Modification Request instead of direct RRC transfer
* Only DRBs to be released are now added to the list.
* The ASN.1 memory allocation is entirely done in build_RRCReconfiguration_IEs
* No longer needed to store ASN1 struct in UE context
GTP-U:
* Previous implementation had incomplete tunnel cleanup during PDU session release
- Missing distinction between N3 (PDU session level) and F1-U (DRB level) tunnels
- Lack of proper DRB identification for F1-U tunnel deletion
Major Changes:
* GTP tunnel teardown now handled in `e1_bearer_context_modif()` using the correct
F1 or N3 GTP instance (`newGtpuDeleteOneTunnel()`)
* Enhanced Tunnel Deletion Logic (cucp_cuup_handler.c):
- Separate handling for N3 tunnels (1 per PDU session) and F1-U tunnels (1 per DRB)
- Added proper DRB identification for F1-U tunnel cleanup
- Improved error handling with detailed logging for each tunnel deletion
- Enhanced logging to distinguish between N3 and F1-U tunnel operations
* New PDCP API Function (nr_pdcp_oai_api.c/h):
- Added nr_pdcp_get_drb_ids_for_pdusession() function
- Enables retrieval of all DRB IDs associated with a specific PDU session
- Supports proper F1-U tunnel cleanup by providing DRB identifiers in CUUP
* Enhanced GTP Interface (gtp_itf.cpp/h):
- Modified newGtpuDeleteOneTunnel() to accept tunnel_type parameter
- Improved logging to distinguish between PDU session and DRB tunnel types
- Better error messages for tunnel deletion failures
- Enhanced debugging information for remaining tunnels
Clean-up:
* Ensured xid tracking works consistently between PDU Session Establishment (with NAS PDU)
and dedicated RRCReconfiguration
* Add function to release GTP-U tunnel in Bearer Context Modification Request handler
* Do not send rrc_gNB_send_NGAP_PDUSESSION_RELEASE_RESPONSE when no PDU session are to
be released: it is sent upon completion of the RRCReconfiguration and needs to contain
released PDU Sessions (mandatory IE), therefore it is no necessary to send it in case
there is no PDU session to release.
Related to #867
Co-authored-by: rmagueta <rmagueta@allbesmart.pt>
!3519 refactored the SDAP to use the QFI from the header rather
than pass it to the rx function and got rid of the initialization
of QFI to -1.
However, entity roles are stored into the drb2qfi table, and the
indexing implies that the QFI is known. While in TX it is not an
issue since packets are forwarded based on the QFI, in RX the QFI
can only be parsed from the heaedr, therefore if headers are
disabled (--enable_sdap) the QFI is not there and it is wrong to
access the header (`buf[0]`) and looking for it.
This commit adds `enable_sdap` to `nr_sdap_entity_t` and initialize
it in `nr_sdap_add_entity()` from `sdap->role`
(disabled when `NO_SDAP_HEADER`). In `nr_sdap_rx_entity()`, only
parse `buf[0]` for QFI and derive `sdap_ul_rx`/`sdap_dl_rx` when
`enable_sdap` is true; otherwise, keep `offset=0` and forward
payload unchanged.
QFI 0 is a valid QFI: don't check for qfi <= 0, as uint8 cannot be
negative. Also, correctly use SDAP_MAP_RULE_EMPTY for a DRB ID (which
need to be larger than 0).
This commit refactors the SDAP entity QoS flow to DRB mapping functionality
to improve code organization and enhance maintainability.
Key changes:
- Split nr_sdap_qfi2drb_map_update into focused functions:
* nr_sdap_add_qos_flows_to_drb: handles QFI addition to DRB
* nr_sdap_rm_qos_flows_from_drb: handles QFI removal from DRB
* nr_sdap_ue_control_pdu_config: handles UE control PDU generation
- Consolidate add/modify logic into reusable nr_sdap_addmod_entity function
- Remove entity existence checking and updating from new_nr_sdap_entity:
this function should only add SDAP entities
- Improve function separation of concerns: do SDAP entity add or update
separately and improve modularity by splitting operations in self
contained functions
- At SDAP creation, do only add of QFI to DRB mapping
- rename new_nr_sdap_entity to nr_sdap_add_entity for function naming consinstency
- Remove rb_id parameter from nr_sdap_tx_entity() function signature
- Update tx_entity function pointer
- Remove rb_id parameter from sdap_data_req() function signature
- Remove unused rb_id variable from sdap_tun_read_thread
The rb_id parameter was redundant since SDAP determines DRB ID
from QFI mapping via entity->qfi2drb_map(entity, qfi). This
simplifies the interface.
Each QFI should always be mapped to a DRB. If that is not the case, we
have an undefined behavior. This should not occur. This commit prints
an error in tx_entity and returns.
The TX/RX entity should have different behavior according to
5.2.1, 5.2.2, 3GPP TS 37.324, depending on whether it is UL and DL.
The gNB can play a role both as UL RX entity and DL TX entity, while
the UE can play a role both as UL TX entity and DL RX entity.
The goal of this commit is to extend the information stored in the
SDAP entity as the current code is just marking the entity as TX/RX.
The commit introduces a bitmap to store the role of the
entity, which can be DL RX, DL TX, UL RX and UL TX. Based on this
the TX SDAP entity knows whether a DL/UL PDU should be build, and
the RX SDAP entity knows whether a DL/UL PDU should be processed.
See also Figure 4.2.2-1.
SDAP headers are present only if enable_sdap option is used.
nr_sdap_qfi2drb_map_update function pointer should
process QFIs to add and release from the entity mapping, therefore
a new function pointer for QFIs to add was introduced and
the function pointer to release the QFIs was called in the same function.
Now the nr_sdap_qfi2drb_map_update is:
(1) looping through the QFIs to add/update and store in the qfi2drb_table
(2) looping through the QFIs to release and delete from qfi2drb_table
Also:
* Update the function signature to use sdap_config_t and nr_sdap_entity_t
* log error when the update fails
* limit the scope of the function
* clang-formatted
* removed limit on table entries set by AVLBL_DRB, replaced with MAX_DRBS_PER_UE
The function nr_sdap_ue_qfi2drb_config should do UL QoS flow to DRB mapping configuration
for a SDAP entity has already been established according to TS 37.324, 5.3 QoS flow to
DRB Mapping, 5.3.1 Configuration Procedures. It should handle both mapping rules to add and to remove.
To this purpose:
* Simplify function signature by passing the sdap config.
* Improve readability of the function.
* Move handling of sdap.mappedQFIs2ReleaseCount (in nr_reconfigure_sdap_entity)
inside the function.
* Simplify end-marker control PDU mapping function by removing unused
DRB ID input parameter (the function is fetching the DRB ID based on the input
map type)
* use int instead of legacy rb_id_t
* limit scope of functions whenever necessary
The goal of this function is to return the DRB ID mapped to the input QFI, for both DL and UL.
The function looks up the DRB that is mapped to the QFI, if no mapping rule exists
returns the default DRB. Returns 0 If no mapping and no default DRB exists for that QFI
The function should not update the stored mapping rules, that is done when receiving
a new SDAP configuration. In this function it was removed.
See TS 37.324, 5.2.1 Uplink
> If there is no stored QoS flow to DRB mapping rule for the QoS flow as specified in the subclause 5.3,
> map the SDAP SDU to the default DRB else, map the SDAP SDU to the DRB according to the stored QoS flow to DRB mapping rule.
* change function signature: pass the sdap_config_t
* update qfi2drb mapping when receiving a configuration for an already existing SDAP entity
* always update mapping rules, not only for default DRB
The function was printing a "not found" error message even in the case
the return value was set to "true". Return directly true/false.
This is relevant in PDU Session Release procedures.
sdap_tun_read_thread needs to know if we are gNB/UE. Previously, we
passed this into the thread, but the next commit also needs to for
interface termination, where this info is not available. So, for noS1
mode, pass this in.
This commit refactors the TUN interface management by moving its creation
and configuration from the PDCP layer to the SDAP layer for UE.
Key changes include:
- Introduced `tun_generate_ue_ifname` and `tun_destroy` functions for better
TUN interface lifecycle management.
- Added support for creating and destroying UE-specific TUN interfaces in SDAP.
- Refactored `nr_pdcp_module_init` to remove TUN-related logic and moved it
to SDAP.
- Updated NAS and SDAP layers to handle PDU session-specific TUN interface
creation and configuration.
- Enhanced SDAP entity management to include TUN socket handling and thread
lifecycle.
- Updated NAS message handling to initialize default PDU session TUN
interfaces in NOS1 mode.
- Use a single SDAP thread function for gNB and UE
- Allow noS1 mode also in SA on gNB
These changes improve modularity by isolating TUN interface management within
the SDAP layer, aligning with the 3GPP architecture, and simplifying the PDCP
layer.
Co-Authored-By: Robert Schmidt <robert.schmidt@openairinterface.org>
Using ITTI calls for user plane implies (1) a memory allocation, (2)
mutexes, and (3) queueing messages for each user plane packet, which is
heavy. Use a direct API call instead to reduce overhead.
- triggered by RRC reconfiguration events according to clause 5.3.5.6.5 of TS 38.331
- This procedure does QoS flow to DRB mapping according to clause 5.3.1 of TS 37.324
- QoS flows to DRBs to be released are also handled
nr_pdcp_entity_recv_sdu() processes PDCP SDUs, and forwards the PDU at the
end of the function, while having the PDCP lock. This can lead to
deadlocks, e.g., when another thread goes through RLC and tries to
access the PDCP while the PDCP tries to lock the RLC.
This commit changes the logic: instead of having recv_sdu() forward the
PDU directly, it fills a buffer with the PDU (thus the name change to
process_sdu()), and returns. We then unlock the PDCP, before forwarding
the PDU, thus eliminating potential deadlocks.
Creates function that have nr_pdcp_ prepended to their name, and change
the signature of some functions for the 5G PDCP:
- nr_pdcp_layer_init()
- nr_pdcp_data_req()
- nr_pdcp_remove_UE()
- nr_pdcp_config_set_security()
- nr_pdcp_remove_UE()
- Make separate functions for nr_pdcp_data_req_srb/drb()
There was a problem testing accelleran cu + oai du + oai ue + rfsim
because accelleran cu configures sdap header for UL but not for DL
and our sdap implementation deals with either "no sdap header at all"
or "sdap headers for both UL and DL".
The code has been modified to deal with the other cases
("sdap header for UL but not DL" and "sdap header for DL but not UL").
has_sdapDLheader and has_sdapULheader have been removed, has_sdap
too, replaced by has_sdap_rx and has_sdap_tx, which makes the code
independant of ue or gnb and is, I think, clearer.
With this work, accelleran cu + oai du + oai ue + rfsim works. We
also have oai gnb + oai ue + rfsim functional for all cases of sdap
header configuration (this won't happen for users, the code of gnb has to
be modified to have sdap header for only ul or only dl). It also works
with a COTS UE for all cases of sdap configuration (again, this won't
happen for users, only "no sdap header" and "sdap headers for both
UL and DL" exist in oai gnb with the current code).
To have other cases, you can edit openair2/RRC/NR/rrc_gNB_radio_bearers.c
and search for NR_SDAP_Config__sdap_HeaderDL_present in there.
To enable sdap, run the gnb with the command line argument
--gNBs.[0].enable_sdap 1
OAI is riddled with boolean_t, FALSE, TRUE, etc. This makes no sense, as
there is a standard bool type, and could lead to nasty bugs if a
definition of a bool is non-standard (0 == false, true == !false). This
commit removes all non-standard bools in the whole project.
1. Removed SDAP struct from protocol context.
2. Added configuration for the SDAP.
3. SDAP doesn't use pdcp_entities, the values come from function arguements.
4. Make nr_pdcp_ue_manager accessible from SDAP.
5. Avoid using the PDCP locking mechanism in SDAP.
6. Removed nr_pdcp_find_entity_sdap function.
7. Rename dummy eNB function to make GTP compile (no SDAP).
8. Fix: Regression issues with LTE
9. Fix: Regression issues with NR CU/DU
Robert Schmidt