Sometimes when the user does ctrl+c to quit, it may not quit
if nothing comes on the socket. Closing the socket in the
signal handler fixes this.

Do not link the X stuff for tracers not needing it.

Later on, use this file with gtkwave.
To be used to check realtime behaviour of the system.

This tracer extracts output subframes generated by the eNodeB,
so they can be analyzed with some external tools.

This tracer extracts the content of a buffer field of an event
that was previously saved using the tracer 'record'.

For example, to extract the channel estimation done in
frame 924 and subframe 2 as saved in the file input_record.raw
and to store it in the file output.raw, do:

./extract -d ../T_messages.txt -o output.raw input_record.raw ENB_PHY_UL_CHANNEL_ESTIMATE chest_t -f frame 924 -f subframe 2

- UE_id 0 is for rnti 65535 (sib)
- UE_id 1 is for rnti 65534 (this is a hack)
- UE_id 2 is for rnti 2     (RA RNTI as of today's code/config)
- we start enb by displaying UE_id 3
- there was a bug: we need to lock when resetting UE ids (reset_ue_ids)

removal of LOG_I put for debugging.

remove getopt call in configuration module, it changes the argv order. Fix configuration module bugs (command line arguments sometimes not properly processed

not finished, UE may not work, many things bad/to fix properly

Improve configuration module error management at init time, Fix command line help option processing, remove shotopt field from parameter structure

Fix configuration module shared library improperly build and not loadable when libconfig version is below 1.5

lte-softmodem -O <config file> will trigger legacy config mode
ltesoftmodem  -O libconfig:<config file> will trigger configuration module usage.

- ENB_PHY_OUTPUT_SIGNAL to trace output signal
- ENB_MAC_SCHEDULING_REQUEST to trace scheduling requests

This program extracts a given subframe from a recorded trace.

Note: this commit is work in progress. Contains initial integration of NFAPI data structures which are tested for TX path. RX path to follow.

see oai/openairinterface5g#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.