c# - 如何判断IPv6地址是否私有(private)？

Question

我试图确定给定的 IPv6 地址在 C# 中是否私有(private)，我很想简单地使用 IPAddress 类上的“IsIPv6SiteLocal”属性。但是，如本 comment 中所述，此属性中实现的逻辑已弃用。我运行了以下单元测试:

[TestMethod]
public void IsPrivate_ipv6_True()
{
    // This sample private IPv6 address was generated using: http://unique-local-ipv6.com/
    var ip = IPAddress.Parse("fd44:fda4:e1ba::1");
    Assert.IsTrue(ip.IsIPv6SiteLocal);
}

单元测试中的断言失败，确认 IsIPv6SiteLocal 未正确确定地址是否为本地地址。所以我需要一个替代方案。

我编写了以下扩展方法，我想知道是否有人能想到无法正确确定地址是私有(private)/公共(public)地址的场景。

public static bool IsPrivateIPv6(this IPAddress address)
{
    var addressAsString = address.ToString();
    var firstWord = addressAsString.Split(new[] { ':' }, StringSplitOptions.RemoveEmptyEntries)[0];

    // Make sure we are dealing with an IPv6 address
    if (address.AddressFamily != AddressFamily.InterNetworkV6) return false;

    // The original IPv6 Site Local addresses (fec0::/10) are deprecated. Unfortunately IsIPv6SiteLocal only checks for the original deprecated version:
    else if (address.IsIPv6SiteLocal) return true;

    // These days Unique Local Addresses (ULA) are used in place of Site Local. 
    // ULA has two variants: 
    //      fc00::/8 is not defined yet, but might be used in the future for internal-use addresses that are registered in a central place (ULA Central). 
    //      fd00::/8 is in use and does not have to registered anywhere.
    else if (firstWord.Substring(0, 2) == "fc" && firstWord.Length >= 4) return true;
    else if (firstWord.Substring(0, 2) == "fd" && firstWord.Length >= 4) return true;

    // Link local addresses (prefixed with fe80) are not routable
    else if (firstWord == "fe80") return true;

    // Discard Prefix
    else if (firstWord == "100") return true;

    // Any other IP address is not Unique Local Address (ULA)
    else return false;
}

2016 年 2 月 13 日编辑:

• 确保第一个单词至少有 4 个字符，如@RonMaupin 所建议的
• 按照@RonMaupin 的建议改进了“else return false”上面的注释
• 按照@KevinBurdett 的建议检查“fe80”前缀
• 按照@KevinBurdett 的建议检查“丢弃”前缀

Answer 1

通过为 ::1 添加一个特例并避免他的解决方案中的 ArgumentException(这将在 Substring() 调用中发生)改进了@​​desautelsj 的回答:

public static bool IsPrivateIPv6(IPAddress address)
{
    // Make sure we are dealing with an IPv6 address
    if (address.AddressFamily != AddressFamily.InterNetworkV6)
        throw new ArgumentException("IP address is not V6", "address");

    var addressAsString = address.ToString();
    var firstWord = addressAsString.Split(new[] { ':' }, StringSplitOptions.RemoveEmptyEntries)[0];

    // equivalent of 127.0.0.1 in IPv6
    if (addressAsString == "::1")
        return true;

    // The original IPv6 Site Local addresses (fec0::/10) are deprecated. Unfortunately IsIPv6SiteLocal only checks for the original deprecated version:
    else if (address.IsIPv6SiteLocal)
        return true;

    // These days Unique Local Addresses (ULA) are used in place of Site Local. 
    // ULA has two variants: 
    //      fc00::/8 is not defined yet, but might be used in the future for internal-use addresses that are registered in a central place (ULA Central). 
    //      fd00::/8 is in use and does not have to registered anywhere.
    else if (firstWord.Length >= 4 && firstWord.Substring(0, 2) == "fc")
        return true;
    else if (firstWord.Length >= 4 && firstWord.Substring(0, 2) == "fd")
        return true;

    // Link local addresses (prefixed with fe80) are not routable
    else if (firstWord == "fe80")
        return true;

    // Discard Prefix
    else if (firstWord == "100")
        return true;

    // Any other IP address is not Unique Local Address (ULA)
    return false;
}

在 F# 中:

let private IsIpv6AddressPrivate (address: IPAddress) =
    if address.AddressFamily = AddressFamily.InterNetwork then
        invalidArg "address" "address must be IPv6"

    // The original IPv6 Site Local addresses (fec0::/10) are deprecated. Unfortunately IsIPv6SiteLocal only checks for the original deprecated version:
    elif address.IsIPv6SiteLocal then
        true
    else
        let addressAsString = address.ToString()

        // equivalent of 127.0.0.1 in IPv6
        if addressAsString = "::1" then
            true
        else
            let firstWord = addressAsString.Split([|':'|], StringSplitOptions.RemoveEmptyEntries).[0]
            // These days Unique Local Addresses (ULA) are used in place of Site Local. 
            // ULA has two variants: 
            //      fc00::/8 is not defined yet, but might be used in the future for internal-use addresses that are registered in a central place (ULA Central). 
            //      fd00::/8 is in use and does not have to registered anywhere.
            if (firstWord.Length >= 4 && firstWord.Substring(0, 2) = "fc") ||
               (firstWord.Length >= 4 && firstWord.Substring(0, 2) = "fd") ||
               // Link local addresses (prefixed with fe80) are not routable
               (firstWord = "fe80") ||
               // Discard Prefix
               (firstWord = "100") then
                true
            else
                false