MR978 : 
We have incorporated 5G NR nFAPI into the develop branch
P5 and P7 interfaces for NR have been implemented. 
With this MR, downlink transmission through nFAPI will be possible. 
We have also made sure that 4G nFAPI can be used from within the develop branch.

go figure...

Dirty!

Dirty.

Dirty...

- a new section in the configuration file to select security algorithms,
  with new code to deal with it
- cleanup CG-ConfigInfo: specs seem to indicate that we must not
  add mcg_RB_Config; the gNB has to deal with that
- as a consequence, modify fill_default_rbconfig() that is called in
  every cases and needs security and bearer parameters

The new section in the configuration file looks like:

    security = {
      # preferred ciphering algorithms
      # the first one of the list that an UE supports in chosen
      # valid values: nea0, nea1, nea2, nea3
      ciphering_algorithms = ( "nea0", "nea2" );

      # preferred integrity algorithms
      # the first one of the list that an UE supports in chosen
      # valid values: nia0, nia1, nia2, nia3
      integrity_algorithms = ( "nia0" );
    };

The code is forced to use nea2, no matter what the UE supports.

After 2^18 PDCP packets, it will fail to work (we don't use HFN yet).

These limitations will be fixed in later commits.

The existing security function was not reused, because it does too
much memory allocation and initializes the security context at each
ciphering. So here comes nr_pdcp_security_nea2_cipher(). And also
the ciphering is done inplace. To be changed if necessary.

- compute correct kgNB
- propagate properly NR security capabilities of an UE
  (involves: rrc, s1ap, x2ap)

This MR adds a multi-UE scheduler (proportional fair) for multiple UEs. Tested for two UEs, but should work for more. Additionally, it enables 12 DL slots and 2 UL slots (still fixed, will be read from the configuration file in a clean-up/follow-up MR).

* MR 1019: NASMESH: support for kernel version >= 5.6.0
he syntax for ndo_tx_timeout in Linux Kernel has changed since 5.6.0 i.e it has changed

* MR 1033: ue fixes
1. Write tx data to radio unit only on tx slots.
2. Fixed a bug in DL HARQ.
3. Disabled UE and some gNB side logs which were enabled (maybe by mistake) in previous MRs.
4. In UE, check if NDI toggled before reading SDU for PUSCH.

This reverts commit 71e297de.

As the precedent commit, this commit deals with the realtime problems
that we currently have on the CI bench.

For DL HARQ feedback, nFAPI does not give us the HARQ process ID.
Instead, we have to figure this out "from timing", i.e., if we trigger
PUCCH reception, we will get a message with HARQ if we instructed the
PHY to do so. If we have real-time problems, it seems (I cannot verify:
don't have real time problems) that we do not get the nFAPI message with
HARQ feedback. Thus, we need to skip the HARQ processes that should have
been processed in the past, which happens in this commit.