This commit repairs the reestablishment after the introduction of the CU
UE ID in the CU, different from the DU UE ID. Now, the CU uses an
identifier different from the RNTI, used in the MAC, to refer to UEs.
To repair the reestablishment, a number of changes needed to be
introduced:
- Handle old_gNB_DU_UE_id in MAC
The MAC handles the old_gNB_DU_UE_id field in the DL RRC Message. The
commit adds encoding/decoding of the field. The MAC will drop the old
UE, but retain the CellGroup of the corresponding UE(!). Because a UE
releases the spCellGroup on reestablishment, the MAC does the same; it
needs to reapply the old configuration after a reconfiguration. For the
latter, introduce new variables to keep a "future" CellGroupConfig to be
applied (reconfigCellGroup) and a flag (expect_reconfiguration) that
applies the CellGroupConfig if a DL RRC Message transfer on DCCH, which
is assumed to be the reconfiguration.
- Add RNTI change in RLC
The RLC needs to reuse the old UE context. Hence, we simply change the
RNTI in the old context, and delete the new one.
- No PDCP UE ID change
The previous implementation of the PDCP used the RNTI; hence, the ID
needed to be switch (as above for the RLC). Since the PDCP now also uses
the CU UE ID, no identifier change is needed, and we remove all
corresponding code.
- No MAC modifications/update from CU
As foreseen by the spec, the CU does not modify or change the
cellGroupConfig in the RRC during reestablishment. This change will be
generalized in the future to all of the RRC. Also, the
nr_rrc_mac_remove_ue() function has been removed: the MAC handles any UE
changes autonomeously, without being triggered from the RRC explicitly.
- Remove reestablish_rnti_map
The RRC does not use RNTIs for UE identification. Hence, a
reestablish_rnti_map to link two UEs to each other is not necessary
anymore.
The UE had a list of known UEs. With the introduction of a separate
module for F1 UE ID handling that is also used in monolithic (to
separate CU UE ID from DU UE ID), this functionality is not needed, and
deleted in this commit.
Previously, the F1AP handler called various functions directly, instead
of sending an ITTI message to the RRC thread. This has two drawbacks:
- it can lead to data races if the RRC task uses functionality that is
being accessed by the F1 task through this function
- no homogeneity: all other handlers send an ITTI message, so this one
should too
- The CU/DU UE ID is used in DL RRC Message Transfer
- Note: The CU UE ID currently is still the RNTI
- on every DL RRC Message, the DU verifies that the UE exists
- Refactor RRC: common function to forward protected SRB PDUs
The RRC uses gNB_ue_ngap_id as its primary ID; the following commits
will introduce the usage of the (F1) gNB CU UE ID. This commits renames
the gNB_ue_ngap_id to rrc_ue_id to better reflect its usage as the RRC's
primary UE ID.
It will be used as the NGAP and F1 (CU) UE IDs.
ENB_MODE is a cmake option to swap the order of include directories.
This has historical reasons; before OAI used cmake, it was very
sensitive to the order of includes. Nowadays, the order does not matter.
Remove this option, and fix the compilation issues that arise while
doing so.
CMake now takes the option ASN1C_EXEC to select an asn1c to use for
compilation. For instance, run with
cmake .. -GNinja -DASN1C_EXEC=/opt/asn1c/bin/asn1c
or
./build_oai --cmake-opt -DASN1C_EXEC=/opt/asn1c/bin/asn1c
to select the alternative asn1c. For instance, this is important for the
CI to allow to build multiple versions of OAI in parallel that might use
different commits of OAI.
Further, this patch introduces functionality to check for the support of
asn1c options that we require, and alerts the user if they are missing,
alongside a message of how to resolve the problem.
We don't work much on asn1c. The version we use has several bugs.
There is an active community out there that fixes bugs and improves
asn1c. Let's use their version.
Previously, in f1ap_decoder.c, we asserted if we did not know a message.
Apart form decoding, we did not do anything in that file.
Additionally, in f1ap_handlers.c, we were also checking for an unknown
message, and printing a warning if a handler is not known.
This commit moves the F1AP message decoding to f1ap_handlers.c, and
deletes f1ap_decoder.c. In summary, we don't assert on an unknown
message, and compile less files. The rest is unchanged.
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()
The simulators have been changed: due to linker errors that would arise
otherwise, a lot of functions are defined in them to avoid such errors.
Some functions are also defined in header files; in this commit, we
define most functoins in nr_dummy_functions.c, which is compiled in, not
by including the C file, but by adding it to the target in
CMakeLists.txt
- nr_dlsim+nr_ulsim need NR_IF_Module_init(), so it cannot be in
nr_dummy_functions, but the others need it
- Link correcr NR_IF_Module_init() into these simulators, and reduce
overall link list
- Correctly link remaining simulators
Laurent THOMAS