基于Go语言实现应用IP防火墙

// ParseCIDR parses s as a CIDR notation IP address and prefix length,
// like "192.0.2.0/24" or "2001:db8::/32", as defined in
// RFC 4632 and RFC 4291.
//
// It returns the IP address and the network implied by the IP and
// prefix length.
// For example, ParseCIDR("192.0.2.1/24") returns the IP address
// 192.0.2.1 and the network 192.0.2.0/24.
func ParseCIDR(s string) (IP, *IPNet, error)

package main

import (
	"fmt"
	"net"
	"strings"
)

func main() {
	ipWall := NewFireWall()
	// 设置可以访问应用的ip段
	ipWall.ParseNode("127.0.0.1")
	ipWall.ParseNode("192.0.2.1/24")
	ipWall.ParseNode("2001:db8::/32") // 可以支持ipv6

	// 测试
	fmt.Println("127.0.0.1", ipWall.Check("127.0.0.1"))
	fmt.Println("192.0.2.10", ipWall.Check("192.0.2.10"))
	fmt.Println("192.0.3.10", ipWall.Check("192.0.3.10"))
	fmt.Println("2001:db8::1", ipWall.Check("2001:db8::1"))
	fmt.Println("2001:db9::1", ipWall.Check("2001:db9::1"))

}

// 定义防火墙，保存规则nodes

type FireWall struct {
	nodes []net.IPNet
}

func NewFireWall() *FireWall {
	return &FireWall{
		nodes: make([]net.IPNet, 0),
	}
}

// 添加规则

func (b *FireWall) ParseNode(line string) {
	if !strings.Contains(line, "/") {
		parsedIP := net.ParseIP(line)

		if ipv4 := parsedIP.To4(); ipv4 != nil {
			// return ip in a 4-byte representation
			parsedIP = ipv4
		}
		if parsedIP != nil {
			switch len(parsedIP) {
			case net.IPv4len:
				line += "/32"
			case net.IPv6len:
				line += "/128"
			}
		}
	}
	_, cidrNet, err := net.ParseCIDR(line)
	if err == nil {
		b.nodes = append(b.nodes, *cidrNet)
	}
}

// 检查某个ip在不在设置的规则里

func (b *FireWall) Check(ip string) bool {
	for _, cidr := range b.nodes {
		remoteIP := net.ParseIP(ip)
		if cidr.Contains(remoteIP) {
			return true
		}
	}
	return false
}