pfSense

signed 32bit int max**

That FreeBSD-net posting is 3 years old.

Current code looks better (function: read_bandwidth())
https://svnweb.freebsd.org/base/releng/11.1/sbin/ipfw/dummynet.c?revision=320486&view=markup#l829

Support was added in June for a 'G' suffix:
https://svnweb.freebsd.org/base?view=revision&revision=320268

So I don't know that it's a signed 32-bit int overflow.

# Function definition
# unsigned long int strtoul (const char* str, char** endptr, int base);
# Usage in dummynet code
# int bw;
# bw = strtoul(arg, &end, 0);

... Could be because bw isn't an unsigned long int and is just a regular (signed) int ?

#include <stdint.h>
#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>

int _substrcmp2(const char *str1, const char* str2, const char* str3)
{

        if (strncmp(str1, str2, strlen(str2)) != 0)
                return 1;

        if (strcmp(str1, str3) != 0)
                warnx("DEPRECATED: '%s' matched '%s'",
                    str1, str3);
        return 0;
}

static void read_bandwidth(char *arg)
{

        int bw;
        char *end = NULL;

        bw = strtoul(arg, &end, 0);
        if (*end == 'K' || *end == 'k') {
                end++;
                bw *= 1000;
        } else if (*end == 'M' || *end == 'm') {
                end++;
                bw *= 1000000;
        } else if (*end == 'G' || *end == 'g') {
                end++;
                bw *= 1000000000;
        }
        if ((*end == 'B' &&
                _substrcmp2(end, "Bi", "Bit/s") != 0) ||
                _substrcmp2(end, "by", "bytes") == 0)
                bw *= 8;

        if (bw < 0)
                errx(EX_DATAERR, "bandwidth too large");

        printf("%i\n",bw);
}

int main(void)
{
    char *stuff = "2GBit/s";
    char *stuff2 = "4GBit/s";
    read_bandwidth(stuff);
    read_bandwidth(stuff2);
}

If you print before the bandwidth too large message you get this.

2000000000
-294967296
a.out: bandwidth too large

I should note I am doing all this on a 64bit Ubuntu VM. No idea if there are differences in output on a *BSD box.

Tried 4096Mb/s looks fine

00001: 4.096 Gbit/s 0 ms burst 0
q131073 50 sl. 0 flows (1 buckets) sched 65537 weight 0 lmax 0 pri 0 droptail
sched 65537 type FIFO flags 0x1 256 buckets 1 active
mask: 0x00 0xffffffff/0x0000 -> 0x00000000/0x0000
BKT Prot ___Source IP/port____ ____Dest. IP/port____ Tot_pkt/bytes Pkt/Byte Drp
176 ip 192.168.128.12/0 0.0.0.0/0 15 5540 0 0 0