Running TCP DL traffic with one connected UE showed a lot of
fluctuations in throughput. After analysis it was found that
sometimes the RLC UM PDU was not correct. It contained one byte
more than it should. On the receiver side, the TCP packet
contained in the RLC packet seems to be rejected by the TCP
stack of the UE (it has one byte more than it should),
leading to a brutal reduction of the throughput, probably due
to some congestion detection in the TCP implementation.
Or something.

This hotfix seems to solve the problem. Using iperf in downlink
with a 5MHz eNB, we see no more fluctuations, the traffic is
very steady at 16.8Mb/s, as reported by the iperf server running
on the phone. (17.5 in the PHY plot of the T tracer.)

A rewrite of both the MAC and RLC UM packet generation is needed.
The code is way too complex for what it does and may contain
several similar problems that only trigger in specific rare
conditions.

has been introduced in commit 365ca71a

Summary of changes:
- fix dlsim/ulsim
- fix centOS compilation
- Move the accounting phase of the DL pre-processor in a separate procedure
  and fix some issues
- additional Mac stats and Improvements
- minor fix in test setup v2

Merge remote-tracking branch 'origin/fix-centos-network-device-compilation' into develop_integration_2018_w08

added compilation directives for nasmesh and ue_ip kernel modules to allow for building on RHEL systems.

Without this revert, the following does not compile:

    ./build_oai --oaisim

- remove spaces at the end of lines
- remove useless dead code
  use: git show -p <this commit> -w
  to see it clearly

With value 4 when connecting one UE and doing some downlink
iperf TCP there is a crash. Probably due to the multiple wrong
RA detected leading to uplink failure of fake UE that never
sends Msg3 (because, well, there is no other UE).

This is another problem that will be fixed at some point.

Anyway, this value 4 fails. Let's put back 3.

Merge remote-tracking branch 'origin/fix-centos-compilation-2018-w08' into develop_integration_2018_w08

The following was not working properly:

    ./build_oai -I -w USRP

After this commit it works.

And so does:

  ./build_oai --eNB -w USRP

Conflicts:
	openair1/PHY/INIT/lte_init.c

Summary of changes:
- a lot of work on flexran
- several compilation bugfixes
- some bugfixes for some bad conflict resolutions
- various bugs fixed

Some more fixes for some bad conflict resolutions.

I ran:

    git diff 2018.w04 2018.w05

And saw some problems with config_sib2.

There was also something strange in openair2/LAYER2/openair2_proc.c
in the function dump_eNB_l2_stats. Maybe the fix is wrong for
this one. To be checked.

Doing an iperf UDP uplink test, we could reach only 6Mb/s
with very good radio conditions instead of around 8Mb/s.

It turns out the MCS was limited to 16.

With this commit, we are back to a bit more than 8Mb/s
as it used to be.

(This is with a 5MHz bandwidth.)

The following compilation failed before this commit:

    ./build_oai --eNB -w USRP -c --T-tracer

The following compilation did not work anymore:

    ./build_oai --eNB -c -w USRP --noS1

Neither did:

    ./build_oai --UE --noS1

Doing airplane mode off to connect a cots UE followed by airplane mode on
to disconnect it gives very bad results (bad disconnection with lots of
UL failures followed by lots of logs in the eNB). It used to work properly
after the work done by Xu Bo.

It turns out that in 2018.w04 things were still working okay. But
in 2018.w05 no.

So I ran:

    git diff 2018.w04 2018.w05

And I checked all the modifications that I thought were relevant
(everything related to the UE, oaisim, if4 and fapi has not been checked).

This commits takes back the version of 2018.w04.

The modifications in openair2/RRC/LITE/rrc_eNB.c are necessary, I think.

The other modifications may not be necessary or even wrong. To be checked
at some point.

the functions are meant to restart the lte-softmodem (lower layers) and are not
supported in oaisim. They are provided to make oaisim compile.