golangorgxnetdnsdnsmessage使用用例

以下是一个简单的使用dnsmessage库的例子：

package main

import (
    "fmt"
    "net"
    "golang.org/x/net/dns/dnsmessage"
)

func main() {
    // 构造一个DNS请求消息
    q := dnsmessage.Question{
        Name:  dnsmessage.MustNewName("example.com."),
        Type:  dnsmessage.TypeA,
        Class: dnsmessage.ClassINET,
    }
    msg := dnsmessage.Message{
        Header: dnsmessage.Header{
            ID:               1234,
            Response:         false,
            Opcode:           dnsmessage.OpQuery,
            Authoritative:    false,
            Truncated:        false,
            RecursionDesired: true,
        },
        Questions: []dnsmessage.Question{q},
    }

    // 将DNS请求消息编码为二进制数据
    buf, err := msg.Pack()
    if err != nil {
        fmt.Printf("Failed to pack message: %v\n", err)
        return
    }

    // 向DNS服务器发送请求并接收响应
    conn, err := net.Dial("udp", "8.8.8.8:53")
    if err != nil {
        fmt.Printf("Failed to dial DNS server: %v\n", err)
        return
    }
    defer conn.Close()

    _, err = conn.Write(buf)
    if err != nil {
        fmt.Printf("Failed to send message: %v\n", err)
        return
    }

    responseBuf := make([]byte, 512)
    _, err = conn.Read(responseBuf)
    if err != nil {
        fmt.Printf("Failed to receive message: %v\n", err)
        return
    }

    // 将DNS响应消息解码为结构体
    var response dnsmessage.Message
    err = response.Unpack(responseBuf)
    if err != nil {
        fmt.Printf("Failed to unpack message: %v\n", err)
        return
    }

    // 打印响应信息
    fmt.Printf("ID: %d\n", response.Header.ID)
    fmt.Printf("Questions: %v\n", response.Questions)
    fmt.Printf("Answers: %v\n", response.Answers)
    fmt.Printf("Authorities: %v\n", response.Authorities)
    fmt.Printf("Additionals: %v\n", response.Additionals)
}

该程序构造了一个DNS请求消息并将其编码为二进制数据。然后，它向Google的公共DNS服务器发送请求并接收响应。最后，它将DNS响应消息解码为结构体并打印响应信息。