This feature requires an un-official version of asn1c :

https://github.com/velichkov/asn1c/tree/s1ap

When doing TCP downlink traffic with iperf for several
hours, the memory consumption of lte-softmodem does not
stop to grow.

After analysis, this commit seems to be the only fix needed.
To be checked somehow.

This is hack-level development.

With this commit you can do UDP DL traffic of say 100Mb/s over
a 5MHz link with one connected UE and the eNB should not crash
because of memory exhaustion. Of course on the receiver side
you won't get 100Mb/s and many many lost packets. But the system
should not crash. 1Gb/s does not work. So in any case try to
remain within some reasonable limits. There is no reason to
push more than twice the maximum achievable throughput of
the link.

This work is based on a patch proposed by Francesco Gringoli.

S1AP specs say:

    initialUEMessage S1AP-ELEMENTARY-PROCEDURE ::= {
        INITIATING MESSAGE      InitialUEMessage
        PROCEDURE CODE          id-initialUEMessage
        CRITICALITY             ignore
    }

So let's use "ignore", not "reject".

The online decoder http://asn1-playground.oss.com/ did
not decode a message encoded by the eNB because of this.

Only the S1AP messages captured while doing a simple connection
of one UE have been tested with the online decoder.

So, not all the S1AP messages have been checked, maybe some
instances of this problem are still there.

It does not seem to harm the actual UE<->eNB<->EPC communication
(because we don't check the integrity of messages or because
asn1c does not do it), so it's not a big deal.

Fix #582, RTAI, RTAI_ENABLED, ENABLE_RTAI_CLOCK, RTAI_ISNT_POSIX, _RTAI_MATH_H, CELLULAR, TIMER_ONESHOT_MODE, EMOS, EMOS_CHANNEL, OAI_EMU, OPENAIR_EMU, PHY_ABSTRACTION, PHY_ABSTRACTION_UL removed

It has been chosen to not include the full history of commits
from David. He included a binary version of wireshark, probably
a modified one that understands NFAPI. Wireshark is released under
the GPL license, we cannot include it in the repository. We could
have done a next commit to remove this binary. But then it would
still be present in the history of commits, which may not be allowed.
And it would take space on disk. We could edit the history to remove
wireshark entirely. But this operation is too complicated.

There was also a pcap capture file, which has nothing to do in
the history of commits and would take space on disk. There again,
it's too difficult to edit the history to remove it.

There was a file .gitignore that was also removed.

The original history can be found on David's repository:
https://gitlab.eurecom.fr/daveprice/openairinterface5g/
The branch is: nfapi-ru-rau-split.

A copy of that branch has been included in the internal OAI
repository, for those who have access to it.
The branch is the same. The last commit ID is
9106438239e0bc626ff1fa1d97d911caadd0fbb9.

You can compare the current commit with the commit 9106...
to see what differs.

The current commit has to be considered non-working.
The commit following the current commit will fix problems with
the work in the current commit.

If you use git bisect, don't spend time analyzing the current
commit.

merge the implemention of Paging, RRCConnectionRelease, RRCConnectionReestablishment, E-RAB Modify, E-RAB Release

phy_init_lte_ue_signal was renamed init_lte_ue_signal in openair1/PHY/INIT/defs.h
maybe it's the opposite that should have been done?

Functions used in one file and defined in another may have been
declared in the wrong header file.

changes:
- ue mcc/mnc 208.93
- use correct key/opc for user
- change addresses in conf file for them to be easier to understand
  (maybe)

With those changes, running:
   sudo ./run_enb_ue_virt_s1
in cmake_targets/tools should work out of the box

The user still has to configure correct IP addresses in
targets/PROJECTS/GENERIC-LTE-EPC/CONF/enb.band7.generic.oaisim.local_mme.conf

We supposed oaisim (enb+ue) machine to be on IP address 10.0.1.1
and EPC (hss, mme, spgw) machine to be on IP address 10.0.1.2.

- print current working directory
- print git version (if available)
- print security keys
  this last one is a security breach, but as of today
  it's not a problem

see https://gitlab.eurecom.fr/oai/openairinterface5g/issues/227

When the UE connects to the eNodeB and receives its IP address from the
network, it calls system() to set it in the linux kernel world. This call
is not done in a realtime thread, but in the NAS, which uses its own thread,
independent of the realtime processing.

In some situations this totally disrupts realtime processing.

It is difficult to know precisely why that happens, but it seems that calling
fork(), as system() does, in a multi-threaded program is not a good idea. (So
say several people on the internet.) It is not clear why the softmodem is
impacted, but it seems that fork() is really what triggers the disruption.
Several tests lead to that conclusion.

To fix the problem, we create a child background process very early in main()
(before anything else basically). Then instead of calling system(), the main
process sends the string to the background process. The background process
gets the string, passes it to system() and reports the success/failure back
to the main process.

This solution involves a lot of system calls, but calling system() in the
first place is not cheap either. As long as no realtime thread uses this
mechanism, things should be fine. Time will tell.

Keys/IDs have been inadvertently changed.

We'll need to to do it in a separate thread/process.
To be done. In the meantime, put it back. It impacts
oaisim.

The compilation line was:
    ./build_oai --eNB -w USRP

The file openairinterface5g/cmake_targets/log/lte-softmodem.Rel10.txt
has been checked and all LOG_X (and 'msg') warnings have been fixed.

This reverts commit d31634c3.

Laurent Thomas had a problem on one machine with the build_oai
way of checking for nettle.

The problem with the alternative solution of including nettle/bignum.h
is that it is very unclear.

The problem with nettle is that the file nettle/config.h does not
exist for version 2. It was introduced in version 3.

We want to support both versions, but there is an API incompatibility.
So we need an #if #else mechanism.

The file nettle/bignum.h is present in both versions 2 and 3 and it
includes nettle/version.h in the version 3.

So by including this file, we can check for the existence of
NETTLE_VERSION_MAJOR (that comes from nettle/config.h) in the
code.

But as you can see, the reasoning is way too complex.

So it's better to keep the check in cmake_targets/CMakeLists.txt.

As long as we support version 2 this will be the way to go.

It is possible to force a given version in specific non-generic
customized environments.

Those functions modify a global char array (a string).

Let's pass a buffer to those functions, so that it's
thread safe. The caller has been modified, with hopefully
a buffer big enough (still bigger than what was there before,
so should not break more than it did).

- fix OPc key
- clear EHPLMN_LIST, UE does not start the RA procedure when set
  to be fixed

Guess what happens when we return from the function...

The case instance == INSTANCE_DEFAULT should normally not happen,
but let's be a bit verbose if it does.

oaisim is not functional with several UEs.
This fixes one issue. (It's still not functional for other reasons.)

It was not setting emm_data->eplmn.plmn[X], only emm_data->eplmn.n_plmns,
leading to the UE to dig for PLMN 00000.

(It's not the end of the story, seems like the PLMN selection
does not work, the UE only tries one from what I've seen, but
I didn't dig much, may be wrong.)

Adapt calling sites too.

When data comes from the user, it is good to check that
what we read is correct and warn the user if it's not.