ranges and negations12 Mar 2007 I've been playing with ugly algorithms the last couple days. I already had an infrastructure to add separate subnets to the tree and query for them. But I had no solution for negations ( ! 10.0.36.0/24) or ranges (1023-65535). That last item already reveals my plan. The tree I'm building is meant for 32-bit IP addresses, but it can be used for 16-bit port-numbers as well. While IP-ranges are not addressed in netfilter as far as I know, port ranges are. That's why I need such a thing.
I now have the capability to specify ranges and negations in my tree. Well actually, a range just spawns a lot of other subnets (for 32-bit, the theoretical maximum would be 64 subnets) that are added to the tree. The negations are similar. Combined, they can lead to a lot of extra nodes...
But anyway. In order to implement these, I introduced the Subnet and SubnetList structures in ALL of my code. In 1 go. Without testing. You probably know where this is leading... After I had replaced all unsigned long int code (for IP-addresses) with Subnet structures, the code broke. It took me a while to track down the bug, but I squashed it now. Things like this make me appreciate my coding-style, where I code and test incrementally.
As a testcase, I negate a subnetlist with 1 subnet in it, and then negate that too. The last result should be the same as the first subnet.
(deepstar/tachyon) ~/projects/hppc$ ./a.out 18.104.22.168 24
Negated subnetlist: 0.0.0.0/8 22.214.171.124/15 126.96.36.199/23 188.8.131.52/24
184.108.40.206/22 220.127.116.11/21 18.104.22.168/20 22.214.171.124/19 126.96.36.199/18
188.8.131.52/17 184.108.40.206/16 220.127.116.11/14 18.104.22.168/13 22.214.171.124/12
126.96.36.199/11 188.8.131.52/10 184.108.40.206/9 220.127.116.11/7 18.104.22.168/6
22.214.171.124/5 126.96.36.199/4 188.8.131.52/3 184.108.40.206/2 220.127.116.11/1
Negated negated subnetlist: 18.104.22.168/24
It works! :)