It might be desirable to run the UE without superuser rights. More
concretely, it might run without NET_ADMIN. In this case, various
corresponding operations on the TUN socket fd might fail. In this
commit,

- improve error reports to make them more clear
- do not automatically exit(1), but return from the function to ensure
  continuity of the softmodem

Use common threadCreate() function to create P7 thread with high(er)
priority. Remove old calls to set_priority(), as this is already done
with threadCreate().

Use common threadCreate() function to create P7 thread with high(er)
priority. Remove old calls to set_priority(), as this is already done
with threadCreate().

Use common threadCreate() function to create P7 thread with high(er)
priority. Remove old calls to set_priority(), as this is already done
with threadCreate().

The main thread of nr-uesoftmodem (executing main()) is mostly working;
it is thus not necessary to set high priority. Instead, the threads
created with threadCreate() will receive higher priority, if possible
(as determined by the availability of SYS_NICE capability).

To inform if SYS_NICE is not present, print a warning in main().

SYS_NICE is a capability that allows a process to set thread affinity
and priority, among other things (see capabilities(7) for more info).

In this commit, add a function that allows to determine if the process
has this capability, and try to change the thread affinity and priority,
if requested. If the capability does not exist, the function will simply
not attempt to change the corresponding thread attributes.

To determine if the process has SYS_NICE, libcap can be used. However,
it might not be installed by default. To avoid requiring another
dependency, if we detect that libcap is not present, use a workaround by
try to set a real-time scheduling policy; if it's present, or can be
changed, we assume that the process has SYS_NICE (and clean up, if
relevant).

Simplify reading of capabilities

A later commit in this series adds performance tuning tips, which
includes the call made in RFsim until this commit.

set_latency_target() attempts to set keep "low latency" by
- writing a specific latency to /dev/cpu_dma_latency
- setting manually the minimum CPU processor frequency to be the maximum

There is no functionality to undo this after stopping the softmodem(s),
and most users are probably not even aware that OAI does this. It is
generally preferable to set this beforehand using a governor or by
disabling sleep states (as outlined in the tutorial, and in a follow-up
commit in the performance tuning docs).

The previous mlockall() call, to lock memory to RAM, is retained in a
new function. There were additional mlockall() calls, which have been
replaced with lock_memory_to_ram(), where necessary.

It's completely unclear what this is supposed to do.

Print a clear error if a config file does not exist (unclear previously,
when the user would get a confusing, unspecific, "file I/O error" on
line 0)

I tried to free the memory that had been allocated at that point, and
verified that using the address sanitizer. Nevertheless, the function
does too much, and is too complicated for refactoring.

Use correct baseTag for Unit Tests build in execution:
- if build_helper or othe files changed, which would trigger rebuild of
  ran-base, use the corresponding ci-temp tag
- use that tag consistently afterwards

Reviewed-By: Laurent THOMAS <laurent.thomas@open-cells.com>

Integration: `2024.w22` (Part 1)

See merge request oai/openairinterface5g!2773

* !2698 Handle division by 0 gracefully in average channel level calculation
* !2743 Demystifying 10log10(2^30) in signal energy calculations.
* !2767 NR UE imeisv fix
* !2768 Over-estimate short and long BSR for better latency and TCP throughput
* !2769 maxMIMOLayers parameter in configuration file

hotfix: current vlm_master (5fa129cf3161da9ff2d67341e6277e818c0f5d6a)
breaks F1, NG, so use the one before
(940dd5fa9f3917913fd487b13dfddfacd0ded06e)

38.321 6.1.3.1 says: "The size of the RLC headers and MAC subheaders are
not considered in the buffer size computation" [for BSR]. However, prior
to this commit, we take the size signaled of the BSR and schedule the UE
with that amount of data, making it impossible for the UE to transmit
all its data at once (because it is the size signaled + headers).

In this commit, over-estimate the buffer status size. As we cannot know
the exact number and size of headers, we simply use "BSR size + n", as
done in function overestim_bsr_index().

* nb_re_pdsch is directly linked to nb_rb_pdsch, if the latter is 0 the
  former is also 0
* compute average channel level only when number of RE for PDSCH is not 0
  the average channel level will be set to 0 otherwise
* Added a log message to handle this special case, which is consequence
  of other issues in the RX chain
* with this commit, the inconsistency in the RX chain will be handled
  in later in nr_ue_pdsch_procedures with a demodulation failure

other minor changes:

* Improved clarity by using NR_NB_SC_PER_RB instead of hard-coded value 12 in nb of RBs calculation
* cleaned up unused variable and outdated comments

antennas.

Integration: `2024.w21`

See merge request oai/openairinterface5g!2757

* !2733 Remove duplicated function to reverse N bits
* !2712 rfsimulator: add support to simulate a long propagation delay
* !2695 improve polar init and polar readability
* !2709 Fix cmdline configmodule in phy simulators
* !2756 remove some enb dependencies in NR files
* !2687 bug fix ue UL payload filling randomly done in retransmissions (pointer not set)
* !2543 power/PHR normalizations for deltaMCS power adaptation
* !2719 Refactor LC handling at MAC
* !2736 Fix debug for ongoing transactions
* !2747 Fix aerial memory leak
* !2761 Use timeout command to kill hanging iperf3
* !2752 fix-dci11-type0-bitmap-setting
* !2759 Fix invalid MSG2 HARQ feedback attempt and remove accumulated_delta_PUCCH field from UE FAPI IF
* !2740 bugfix/cleanup: remove uint8_t to encode size plus some cleanup
* !2760 fix 5G NR SA FDD configs for 24 and 25 PRBs
* !2520 Documentation on coding style, workflow, and review instructions