[Udpcast] Regression in Udpcast 20211207

Howdy!  I found a strange bug in the new version of Udpcast.  When sending packets at speeds over around 80m, the program locks up.  I traced the problem to the doRateLimit function in rate-limit.c (I've added some printfs):

sleepTime = rateLimit->queueSize * 8 * MILLION / rateLimit->bitrate;

printf("sleepTime1 %lu\n",sleepTime);         printf("rateLimit->queueSize %lu\n",rateLimit->queueSize);

if(sleepTime > 40000 || rateLimit->queueSize >= 100000) {             printf("sleepTime2 %lu\n",sleepTime);

sleepTime -= 10000;

printf("sleepTime3 %lu\n",sleepTime);             printf("sleepTime3 % 10000 %u\n",sleepTime % 10000);

sleepTime -= sleepTime % 10000;             printf("sleepTime4 %lu\n",sleepTime);             usleep((useconds_t)sleepTime);         }

What is happening is that sometimes rateLimit->queueSize >= 100000 but sleepTime is small, so subtracting 10000 from it wraps around to near maxint.  The strange thing is that when the program then does sleepTime -= sleepTime % 10000 the result is *different* from the 20200328 version because of the change to long unsigned integers.  In the old version sleepTime would become zero, but now it stays huge, leading to an extremely long usleep.

Here is the old behavior:

sleepTime1 1338 rateLimit->queueSize 100350 sleepTime2 1338 sleepTime3 4294958634 sleepTime3 % 10000 4294958634 sleepTime4 0

Here is the new behavior (which hangs):

sleepTime1 1344 rateLimit->queueSize 100800 sleepTime2 1344 sleepTime3 18446744073709542960 sleepTime3 % 10000 2960 sleepTime4 18446744073709540000

It looks to me like the older version actually had offsetting bugs: sleepTime % 10000 *should* return a value less than 10000 but in the old code for some reason it just returned sleepTime, which then subtracted from itself gave zero.  In the new version the wraparound error from the sleepTime -= 10000 has been exposed, causing the hang.

Anyway, hopefully this isn't too hard to fix:  your program is super-useful for us, and the old version merrily blasts udp packets at gigabit speeds!

Thanks,

Robert II