In my day job I'm a network engineer. Nothing smaller than a /24 gets routed on the internet. I would just do a quick and dirty approach: Ignore the last octet. So cache based on /24. If you want to go more complicated you can loose the length. An ipv4 address is 32 bit. A /24 says: Network is 24 bits and the host part is 8 bits. So for a /23 it's 23 bits of network and 9 bits of host. It's always on the bit boundary so a /24 is alway from 0 (network) to 255 (broadcast). Just Google a bit to find posts like https://learningnetwork.cisco.com/blogs/vip-perspectives/2014/05/15/network-binary-math-explained . So comparison is very easy and very efficient.
How are you going to deal with providers that announce large
chunks of ip space (like a /13) that are used for all sorts of
things? I assume you want to use INET objects and not ROUTE
objects? Be aware that mass harvesting of databases like RIPE
isn't allowed. Also the quality of these objects differ greatly
depending on the LIR/country/RIR.
I am working on a bot that fetches a list of anonymous editors on fawiki, uses WHOIS to retrieve more info about that IP, and uses a number of online APIs to check if the IP is a proxy or not.
I would like to improve the code by implementing a CIDR cache, so that if I run whois on 126.96.36.199 and determine that its ASN range is 188.8.131.52/24 and then I encounter 184.108.40.206 in the next iteration of my for loop, I would quickly determine this IP also belongs to the same range and skip the WHOIS part for it.
The search space would consist of IP ranges like "220.127.116.11 - 18.104.22.168" (these are the beginning and end IP addresses of the 22.214.171.124/24 range). Obviously, we can convert these IPs to Hex to make comparisons easier. Given an IP like 126.96.36.199, we need the object to efficiently determine if it already has an IP range that encompasses this given IP and if so, return the previously cached details for that IP pair. If not, we will store that in cache.
The part that I am not fully clear about is the following: how can I avoid having to loop through every range in the cache? Is there a way to create a hash function that checks two inequality comparisons efficiently?
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