问从iphone设置获取DNS服务器IP

EN

open class Resolver {

    fileprivate var state = __res_9_state()

    public init() {
        res_9_ninit(&state)
    }

    deinit() {
        res_9_ndestroy(&state)
    }

    public final func getservers() -> [res_9_sockaddr_union] {

        let maxServers = 10
        var servers = [res_9_sockaddr_union](repeating: res_9_sockaddr_union(), count: maxServers)
        let found = Int(res_9_getservers(&state, &servers, Int32(maxServers)))

        // filter is to remove the erroneous empty entry when there's no real servers
       return Array(servers[0 ..< found]).filter() { $0.sin.sin_len > 0 }
    }
}

extension Resolver {
    public static func getnameinfo(_ s: res_9_sockaddr_union) -> String {
        var s = s
        var hostBuffer = [CChar](repeating: 0, count: Int(NI_MAXHOST))

        len sinlen = socklen_t(s.sin.sin_len)
        let _ = withUnsafePointer(to: &s) {
            $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
                Darwin.getnameinfo($0, sinlen,
                                   &hostBuffer, socklen_t(hostBuffer.count),
                                   nil, 0,
                                   NI_NUMERICHOST)
            }
        }

        return String(cString: hostBuffer)
    }
}

let servers = Resolver().getservers().map(Resolver.getnameinfo)