如何在 Swift 中从 DNS 查询中获取真实的 IP 地址？

Question

我想从 Swift 中的 DNS 查询中获取 IP 地址（如 192.168.0.1 或 87.12.56.50）。我用 100 种不同的方法尝试了 100 次……没有任何帮助，所以我不得不寻求帮助。 这是我到目前为止的代码：

let host = CFHostCreateWithName(nil,"subdomain.of.stackoverflow.com").takeUnretainedValue();
CFHostStartInfoResolution(host, .Addresses, nil);
var success: Boolean = 0;
let addresses = CFHostGetAddressing(host, &success).takeUnretainedValue() as NSArray;
if(addresses.count > 0){
   let theAddress = addresses[0] as NSData;
   println(theAddress);
}

好的...这些是我尝试实现但没有成功的代码的链接： https://gist.github.com/mikeash/bca3a341db74221625f5
如何在iOS上进行DNS查询
在 Swift 中从 NSData 对象创建数组
CFHostGetAddressing() 支持 ipv6 DNS 条目吗？
在 Swift 中进行简单的 DNS 查找

Answer 1

您的代码以“套接字地址”结构的形式检索地址。

getnameinfo()

可用于将地址转换为数字 IP 字符串 （代码从https://stackoverflow.com/a/25627545/1187415回收， 现已更新至 Swift 2):

let host = CFHostCreateWithName(nil,"www.google.com").takeRetainedValue()
CFHostStartInfoResolution(host, .Addresses, nil)
var success: DarwinBoolean = false
if let addresses = CFHostGetAddressing(host, &success)?.takeUnretainedValue() as NSArray?,
    let theAddress = addresses.firstObject as? NSData {
    var hostname = [CChar](count: Int(NI_MAXHOST), repeatedValue: 0)
    if getnameinfo(UnsafePointer(theAddress.bytes), socklen_t(theAddress.length),
        &hostname, socklen_t(hostname.count), nil, 0, NI_NUMERICHOST) == 0 {
            if let numAddress = String.fromCString(hostname) {
                print(numAddress)
            }
    }
}

输出（示例）：

173.194.112.147

另请注意第一行中

takeRetainedValue()

的用法，因为

CFHostCreateWithName()

名称中包含“Create”，因此返回保留的 (+1) 对象。

---

Swift 3/Xcode 8 更新：

let host = CFHostCreateWithName(nil,"www.google.com" as CFString).takeRetainedValue()
CFHostStartInfoResolution(host, .addresses, nil)
var success: DarwinBoolean = false
if let addresses = CFHostGetAddressing(host, &success)?.takeUnretainedValue() as NSArray?,
    let theAddress = addresses.firstObject as? NSData {
    var hostname = [CChar](repeating: 0, count: Int(NI_MAXHOST))
    if getnameinfo(theAddress.bytes.assumingMemoryBound(to: sockaddr.self), socklen_t(theAddress.length),
                   &hostname, socklen_t(hostname.count), nil, 0, NI_NUMERICHOST) == 0 {
        let numAddress = String(cString: hostname)
        print(numAddress)
    }
}

或者，获取主机的所有 IP 地址：

let host = CFHostCreateWithName(nil,"www.google.com" as CFString).takeRetainedValue()
CFHostStartInfoResolution(host, .addresses, nil)
var success: DarwinBoolean = false
if let addresses = CFHostGetAddressing(host, &success)?.takeUnretainedValue() as NSArray? {
    for case let theAddress as NSData in addresses {
        var hostname = [CChar](repeating: 0, count: Int(NI_MAXHOST))
        if getnameinfo(theAddress.bytes.assumingMemoryBound(to: sockaddr.self), socklen_t(theAddress.length),
                       &hostname, socklen_t(hostname.count), nil, 0, NI_NUMERICHOST) == 0 {
            let numAddress = String(cString: hostname)
            print(numAddress)
        }
    }
}

Answer 2

参考以下 Swift 代码获取网站的 DNS 解析。一种方法使用

CFHostStartInfoResolution

，而另一种方法使用

gethostbyname

。

这两个 API 都支持所有/多个 IP 地址解析。

private func urlToIP_cfHostResolution(_ url: String) -> [String] {

    var ipList: [String] = []

    let host = CFHostCreateWithName(nil,url as CFString).takeRetainedValue()

    CFHostStartInfoResolution(host, .addresses, nil)

    var success: DarwinBoolean = false

    if let addresses = CFHostGetAddressing(host, &success)?.takeUnretainedValue() as NSArray? {

        for case let theAddress as NSData in addresses {

            var hostname = [CChar](repeating: 0, count: Int(NI_MAXHOST))

            if getnameinfo(theAddress.bytes.assumingMemoryBound(to: sockaddr.self), socklen_t(theAddress.length),
                       &hostname, socklen_t(hostname.count), nil, 0, NI_NUMERICHOST) == 0 {

                ipList.append(String(cString: hostname))
            }    
        }
    }

    return ipList
}

此方法返回

["151.101.129.69", "151.101.1.69", "151.101.193.69", "151.101.65.69"]

表示

www.stackoverflow.com

private func urlToIP_gethostbyname(_ url: URL) -> [String] {

    var ipList: [String] = []

    guard let hostname = url.host else {

        return ipList
    }

    guard let host = hostname.withCString({gethostbyname($0)}) else {

        return ipList
    }

    guard host.pointee.h_length > 0 else {

        return ipList
    }

    var index = 0

    while host.pointee.h_addr_list[index] != nil {

        var addr: in_addr = in_addr()

        memcpy(&addr.s_addr, host.pointee.h_addr_list[index], Int(host.pointee.h_length))

        guard let remoteIPAsC = inet_ntoa(addr) else {

            return ipList
        }

        ipList.append(String.init(cString: remoteIPAsC))

        index += 1
    }

    return ipList
}

此方法还为

["151.101.129.69", "151.101.1.69", "151.101.193.69", "151.101.65.69"]

 返回 

www.stackoverflow.com

希望这有帮助。

Answer 3

许多答案正在使用已弃用的

bytes

来检索

sockaddr

以提供给

getnameinfo

。我们现在使用

address.withUnsafeBytes

。例如，在 Swift 5 中：

/// Returns the string representation of the supplied address.
///
/// - parameter address: Contains a `(struct sockaddr)` with the address to render.
///
/// - returns: A string representation of that address.

func stringRepresentation(forAddress address: Data) -> String? {
    address.withUnsafeBytes { pointer in
        var hostStr = [Int8](repeating: 0, count: Int(NI_MAXHOST))

        let result = getnameinfo(
            pointer.baseAddress?.assumingMemoryBound(to: sockaddr.self),
            socklen_t(address.count),
            &hostStr,
            socklen_t(hostStr.count),
            nil,
            0,
            NI_NUMERICHOST
        )
        guard result == 0 else { return nil }
        return String(cString: hostStr)
    }
}

Answer 4

现在有一个来自 Apple 的异步包。

https://github.com/apple/swift-async-dns-resolver