c# - 如何在 C# 中比较 IP 地址范围？

Question

如果我有一个 IP 地址范围（CIDR 表示法）并且我需要知道某个任意 IP 地址是否在该范围内——两者都以字符串形式显示——用 C# 执行此操作的最简单方法是什么？

例子：

• IPv4 范围：192.168.168.100/24，要检查的 IP：192.168.168.200
• IPv6 范围：fe80::202:b3ff:fe1e:8329/24，要检查的 IP：2001:db8::

Answer 1

这是一个简单的类：

public class IPSubnet
{
    private readonly byte[] _address;
    private readonly int _prefixLength;

    public IPSubnet(string value)
    {
        if (value == null)
            throw new ArgumentNullException("value");

        string[] parts = value.Split('/');
        if (parts.Length != 2)
            throw new ArgumentException("Invalid CIDR notation.", "value");

        _address = IPAddress.Parse(parts[0]).GetAddressBytes();
        _prefixLength = Convert.ToInt32(parts[1], 10);
    }

    public bool Contains(string address)
    {
        return this.Contains(IPAddress.Parse(address).GetAddressBytes());
    }

    public bool Contains(byte[] address)
    {
        if (address == null)
            throw new ArgumentNullException("address");

        if (address.Length != _address.Length)
            return false; // IPv4/IPv6 mismatch

        int index = 0;
        int bits = _prefixLength;

        for (; bits >= 8; bits -= 8)
        {
            if (address[index] != _address[index])
                return false;
            ++index;
        }

        if (bits > 0)
        {
            int mask = (byte)~(255 >> bits);
            if ((address[index] & mask) != (_address[index] & mask))
                return false;
        }

        return true;
    }
}

示例用法：

Console.WriteLine(new IPSubnet("192.168.168.100/24").Contains("192.168.168.200")); // True
Console.WriteLine(new IPSubnet("fe80::202:b3ff:fe1e:8329/24").Contains("2001:db8::")); // False

此类将所有 IPv4 地址与所有 IPv6 地址区别对待，不尝试在 IPv4 和 IPv6 之间进行转换。

Answer 2

我不会为你写代码，但是：

• http://msdn.microsoft.com/en-us/library/system.net.ipaddress.aspx
• http://blogs.msdn.com/b/knom/archive/2008/12/31/ip-address-calculations-with-c-subnetmasks-networks.aspx
• IP 地址是否与本地计算机位于同一子网上（支持 IPv6）
• 计算子网内的所有地址...对于 IPv6

应该足以让你开始。

祝你好运

Answer 3

我建议使用 IPNetwork 库https://github.com/lduchosal/ipnetwork。从版本 2 开始，它也支持 IPv4 和 IPv6。

IPv6

  IPNetwork ipnetwork = IPNetwork.Parse("fe80::202:b3ff:fe1e:8329/24");

  IPAddress ipaddress = IPAddress.Parse("2001:db8::");
  IPAddress ipaddress2 = IPAddress.Parse("fe80::202:b3ff:fe1e:1");

  bool contains1 = IPNetwork.Contains(ipnetwork, ipaddress);
  bool contains2 = IPNetwork.Contains(ipnetwork, ipaddress2);

  Console.WriteLine("{0} contains {1} : {2}", ipnetwork, ipaddress,     contains1);
  Console.WriteLine("{0} contains {1} : {2}", ipnetwork, ipaddress2,     contains2);

输出

   fe80::/24 contains 2001:db8:: : False
   fe80::/24 contains fe80::202:b3ff:fe1e:1 : True

IPv4

  IPNetwork ipnetwork = IPNetwork.Parse("192.168.168.100/24");

  IPAddress ipaddress = IPAddress.Parse("192.168.168.200");
  IPAddress ipaddress2 = IPAddress.Parse("192.168.0.200");

  bool contains1 = IPNetwork.Contains(ipnetwork, ipaddress);
  bool contains2 = IPNetwork.Contains(ipnetwork, ipaddress2);

  Console.WriteLine("{0} contains {1} : {2}", ipnetwork, ipaddress, contains1);
  Console.WriteLine("{0} contains {1} : {2}", ipnetwork, ipaddress2, contains2);

输出

  192.168.168.0/24 contains 192.168.168.200 : True
  192.168.168.0/24 contains 192.168.0.200 : False

玩得开心 ！