Introduce env var OAI_RNGSEED

can be used to set a random number generator (RNG) seed uniformly from
command line

doc/environment-variables.md

@@ -8,6 +8,7 @@ OAI uses/supports a number of environment variables, documented in the following
 - `NVRAM_DIR`: directory to read/write NVRAM data in (5G) `nvram` tool; if not defined, will use `PWD` (working directory)
 - `OAI_CONFIGMODULE`: can be used to pass the configuration file instead of `-O`
 - `OAI_GDBSTACKS`: if defined when hitting an assertion (`DevAssert()`, `AssertFatal()`, ...), OAI will load `gdb` and provide a backtrace for every thread
+- `OAI_RNGSEED`: overwrites any seed for random number generators (RNG) in simulators
 - `OAI_THREADPOOLMEASUREMENTS`: path to a file to store thread pool debugging information, see the [thread pool documentation](..common/utils/threadPool/thread-pool.md)
 - `OPENAIR_DIR`: should point to the root directory of OpenAirInterface; some code relies on this to get a filename, e.g., BLER curves for L2sim channel emulation
 - `RFSIMULATOR`: the RFsimulator's work mode, can be either `server` (for server mode) or a valid IP address (for client mode)

openair1/SIMULATION/TOOLS/rangen_double.c

@@ -55,6 +55,8 @@ void randominit(unsigned long seed_init)
   unsigned long seed = seed_init;
   if (seed_init == 0)
     fill_random(&seed, sizeof(seed));
+  if (getenv("OAI_RNGSEED"))
+    seed = atoi(getenv("OAI_RNGSEED"));
   printf("Initializing random number generator, seed %lu\n", seed);
 
   // initialize uniformrandom RNG