Go tool for merging CIDR ranges.

cidraggr.go

package main

import (
	"bufio"
	"fmt"
	"log"
	"net/http"
	"net/netip"
	"os"

	"go4.org/netipx"
)

// readCIDRsFromURL reads CIDR ranges from a URL.
func readCIDRsFromURL(url string) ([]netip.Prefix, error) {
	log.Println("Reading CIDRs from URL: ", url)
	resp, err := http.Get(url)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	var cidrs []netip.Prefix
	scanner := bufio.NewScanner(resp.Body)
	for scanner.Scan() {
		line := scanner.Text()
		cidr, err := netip.ParsePrefix(line)
		if err != nil {
			return nil, err
		}
		cidrs = append(cidrs, cidr)
	}
	return cidrs, scanner.Err()
}

// readCIDRsFromFile reads CIDR ranges from a file.
func readCIDRsFromFile(filename string) ([]netip.Prefix, error) {
	log.Println("Reading CIDRs from file: ", filename)
	file, err := os.Open(filename)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	var cidrs []netip.Prefix
	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		line := scanner.Text()
		cidr, err := netip.ParsePrefix(line)
		if err != nil {
			return nil, err
		}
		cidrs = append(cidrs, cidr)
	}
	return cidrs, scanner.Err()
}

// writeCIDRsToFile writes CIDR ranges to a file.
func writeCIDRsToFile(filename string, cidrs []netip.Prefix) error {
	log.Println("Writing CIDRs to file: ", filename)
	file, err := os.Create(filename)
	if err != nil {
		return err
	}
	defer file.Close()

	writer := bufio.NewWriter(file)
	for _, cidr := range cidrs {
		_, err := writer.WriteString(cidr.String() + "\n")
		if err != nil {
			return err
		}
	}
	return writer.Flush()
}

// mergeCIDRs merges and returns the unified list of CIDR ranges.
func mergeCIDRs(cidrs []netip.Prefix) []netip.Prefix {
	var b netipx.IPSetBuilder
	for _, cidr := range cidrs {
		b.AddPrefix(cidr)
	}
	// ignore errors on purpose to avoid errors in single cidr causing fail output,
	// see comment for IPSetBuilder.IPSet()
	ipset, _ := b.IPSet()

	return ipset.Prefixes()
}

func main() {
	// Define your sources here.
	urlSources := []string{
		"https://www.ipdeny.com/ipblocks/data/aggregated/cn-aggregated.zone",
		"https://raw.githubusercontent.com/17mon/china_ip_list/master/china_ip_list.txt",
	}
	fileSources := []string{
		//"ip1.txt",
		//"ip2.txt",
	}
	fileSources = os.Args[1:]

	var allCIDRs []netip.Prefix

	// Read CIDRs from URL sources.
	for _, url := range urlSources {
		cidrs, err := readCIDRsFromURL(url)
		if err != nil {
			fmt.Printf("Error reading CIDRs from URL %s: %v\n", url, err)
			continue
		}
		allCIDRs = append(allCIDRs, cidrs...)
	}

	// Read CIDRs from file sources.
	for _, file := range fileSources {
		cidrs, err := readCIDRsFromFile(file)
		if err != nil {
			fmt.Printf("Error reading CIDRs from file %s: %v\n", file, err)
			continue
		}
		allCIDRs = append(allCIDRs, cidrs...)
	}

	// Merge CIDRs.
	log.Println("Merging CIDRs...")
	mergedCIDRs := mergeCIDRs(allCIDRs)

	// Output the merged CIDRs.
	//fmt.Println("Merged CIDRs:")
	//for _, cidr := range mergedCIDRs {
	//	fmt.Println(cidr)
	//}

	// Write the merged CIDRs to a file.
	err := writeCIDRsToFile("merged_cidrs.txt", mergedCIDRs)
	if err != nil {
		fmt.Printf("Error writing CIDRs to file: %v\n", err)
		return
	}
}