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IPInSubnet - Fast Binary Tree IP Subnet Matching

Overview

IPInSubnet is a Lua library for efficient IPv4 and IPv6 subnet searches using a binary tree. It is designed for scenarios involving a large number of subnets, enabling quick lookups to determine whether an IP address belongs to a specific subnet.

Features

  • Supports both IPv4 and IPv6 addresses.
  • Efficient binary tree implementation for quick lookups.
  • Handles CIDR notation for subnet masks.
  • Ideal for firewalls, access control, and Nginx/OpenResty use cases.

Requirements

lua-bitop - for bitwise operations, for Nginx, Openrestry is preinstalled
    apt install lua-bitop

luaunit - for unit testing
    apt install lua-unit

Usage Example

Below is a complete example in Nginx

nginx.conf

...
init_by_lua_file "/{YOUR_PATH}/init.lua";
...
server {
    ...
    access_by_lua_file "/{YOUR_PATH}/access.lua";
    ...
}
...

init.lua

-- Load module dynamically
local info = debug.getinfo(1, "S")  
local path = info.source:sub(2):match("(.*/)")  
package.path = path.."../lib/?.lua;" .. package.path
-- or append to package.path where the lib is saved
-- package.path = package.path .. ";/usr/local/share/lua/IPInSubnet/lib/?.lua"

-- Require the module
IPInSubnet = require("IPInSubnet")

-- Create subnet lists
blockedIPs = IPInSubnet:new()
allowedIPs = IPInSubnet:new()

-- Define allowed and blocked subnets
allowedIPs:addSubnet("192.168.1.0/24")
allowedIPs:addSubnet("192.168.4.0/24")
allowedIPs:addSubnet("192.1.4.0/24")
allowedIPs:addSubnet("192.1.1.0/24")


blockedIPs:addSubnet("192.168.2.0/24")
blockedIPs:addSubnet("11:0db8::/32")

access.lua

ngx.header.content_type = "text/plain"

ngx.say("IP: ", ngx.var.remote_addr)
ngx.say("Is allowed: ", allowedIPs:isInSubnets(ngx.var.remote_addr))
ngx.say("Is blocked: ", blockedIPs:isInSubnets(ngx.var.remote_addr))

response

alt text

Show IPv4 tree for allowedIP

--if you add the subnets
allowedIPs:addSubnet("192.1.1.0/24")
allowedIPs:addSubnet("192.1.4.0/24")
allowedIPs:addSubnet("192.168.1.0/24")
allowedIPs:addSubnet("192.168.4.0/24")

--the tree will have the values from the image. 
-- where *8bits delimiter is a separator for visual efects
ngx.say("Allowed IPs Tree IPv4")
allowedIPs.treeIPv4.printTree(allowedIPs.treeIPv4.root)

192.1.1.0/24   => 11000000 00000001 00000001 /24
192.1.4.0/24   => 11000000 00000001 00000100 /24
192.168.1.0/24 => 11000000 10101000 00000001 /24
192.168.4.0/24 => 11000000 10101000 00000100 /24

alt text