Robert Gordon wrote:
>
> I think this:
>
> 1460 } else {
> 1461 if ((addr & 0x00ffffff) == 0)
> 1462 mask = 0xff000000;
> 1463 else if ((addr & 0x0000ffff) == 0)
> 1464 mask = 0xffff0000;
> 1465 else if ((addr & 0x000000ff) == 0)
> 1466 mask = 0xffffff00;
> 1467 else
> 1468 mask = 0xffffffff;
> 1469 }
>
> reads better as:
>
> if (IN_CLASSA(addr))
> mask = IN_CLASSA_NET;
> else if (IN_CLASSB(addr))
> mask = IN_CLASSB_NET;
> else if (IN_CLASSC(addr))
> mask = IN_CLASSC_NET;
> else
> mask = IP_HOST_MASK;
Might read better, but appears not to work correctly:
You can see the difference with the first test:
addr & 0x00ffffff == 0
versus
addr & 0x80000000U == 0
The first says disallow any addr which have any bits set in the lower
3 octets.
The second says only allow addr which have 0x80 set in the upper
octect and ignore anything in the lower 3.
I think you could say this:
if ((addr & IN_CLASSA_HOST) == 0) {
mask = IN_CLASSA_NET;
} else if ((addr & IN_CLASSB_HOST) == 0) {
mask = IN_CLASSB_NET;
} else if ((addr & IN_CLASSC_HOST) == 0) {
mask = IN_CLASSC_NET;
} else {
mask = IN_CLASSE_NET;
}
And that pans out via the attached test case...
Some test outout before the 3rd try:
============
[th199096 at warlock ~/src]> ./a.out 192.168.2.1
192.168.2.1 yields 3232236033 and that reverse maps to 192.168.2.1
old way::
16777215 that reverse maps to 0.255.255.255
65535 that reverse maps to 0.0.255.255
255 that reverse maps to 0.0.0.255
Is single IP!
We would apply the following netmask (4294967295): 255.255.255.255
new way::
2147483648 that reverse maps to 128.0.0.0
3221225472 that reverse maps to 192.0.0.0
3758096384 that reverse maps to 224.0.0.0
Is class C!
We would apply the following netmask (4294967040): 255.255.255.0
[th199096 at warlock ~/src]> ./a.out 192.168.2.0
192.168.2.0 yields 3232236032 and that reverse maps to 192.168.2.0
old way::
16777215 that reverse maps to 0.255.255.255
65535 that reverse maps to 0.0.255.255
255 that reverse maps to 0.0.0.255
Is class C!
We would apply the following netmask (4294967040): 255.255.255.0
new way::
2147483648 that reverse maps to 128.0.0.0
3221225472 that reverse maps to 192.0.0.0
3758096384 that reverse maps to 224.0.0.0
Is class C!
We would apply the following netmask (4294967040): 255.255.255.0
[th199096 at warlock ~/src]> ./a.out 192.168.0.0
192.168.0.0 yields 3232235520 and that reverse maps to 192.168.0.0
old way::
16777215 that reverse maps to 0.255.255.255
65535 that reverse maps to 0.0.255.255
255 that reverse maps to 0.0.0.255
Is class B!
We would apply the following netmask (4294901760): 255.255.0.0
new way::
2147483648 that reverse maps to 128.0.0.0
3221225472 that reverse maps to 192.0.0.0
3758096384 that reverse maps to 224.0.0.0
Is class C!
We would apply the following netmask (4294967040): 255.255.255.0
[th199096 at warlock ~/src]> ./a.out 192.0.0.0
192.0.0.0 yields 3221225472 and that reverse maps to 192.0.0.0
old way::
16777215 that reverse maps to 0.255.255.255
65535 that reverse maps to 0.0.255.255
255 that reverse maps to 0.0.0.255
Is class A!
We would apply the following netmask (4278190080): 255.0.0.0
new way::
2147483648 that reverse maps to 128.0.0.0
3221225472 that reverse maps to 192.0.0.0
3758096384 that reverse maps to 224.0.0.0
Is class C!
We would apply the following netmask (4294967040): 255.255.255.0
