golang 實現簡單DNS服務器

簡單的DNS服務器

提供一個簡單的可以查詢域名和反向查詢的DNS服務器。

dig命令主要用來從 DNS 域名服務器查詢主機地址信息。

查找www.baidu.com的ip （A記錄）：

命令：dig @127.0.0.1 www.baidu.com

根據ip查找對應域名 （PTR記錄）：

命令：dig @127.0.0.1 -x 220.181.38.150

源碼 ：

package main import ( "fmt" "net" "golang.org/x/net/dns/dnsmessage" ) func main() { conn, err := net.ListenUDP("udp", &net.UDPAddr{Port: 53}) if err != nil { panic(err) } defer conn.Close() fmt.Println("Listing ...") for { buf := make([]byte, 512) _, addr, _ := conn.ReadFromUDP(buf) var msg dnsmessage.Message if err := msg.Unpack(buf); err != nil { fmt.Println(err) continue } go ServerDNS(addr, conn, msg) } } // address books var ( addressBookOfA = map[string][4]byte{ "www.baidu.com.": [4]byte{220, 181, 38, 150}, } addressBookOfPTR = map[string]string{ "150.38.181.220.in-addr.arpa.": "www.baidu.com.", } ) // ServerDNS serve func ServerDNS(addr *net.UDPAddr, conn *net.UDPConn, msg dnsmessage.Message) { // query info if len(msg.Questions) < 1 { return } question := msg.Questions[0] var ( queryTypeStr = question.Type.String() queryNameStr = question.Name.String() queryType = question.Type queryName, _ = dnsmessage.NewName(queryNameStr) ) fmt.Printf("[%s] queryName: [%s]\n", queryTypeStr, queryNameStr) // find record var resource dnsmessage.Resource switch queryType { case dnsmessage.TypeA: if rst, ok := addressBookOfA[queryNameStr]; ok { resource = NewAResource(queryName, rst) } else { fmt.Printf("not fount A record queryName: [%s] \n", queryNameStr) Response(addr, conn, msg) return } case dnsmessage.TypePTR: if rst, ok := addressBookOfPTR[queryName.String()]; ok { resource = NewPTRResource(queryName, rst) } else { fmt.Printf("not fount PTR record queryName: [%s] \n", queryNameStr) Response(addr, conn, msg) return } default: fmt.Printf("not support dns queryType: [%s] \n", queryTypeStr) return } // send response msg.Response = true msg.Answers = append(msg.Answers, resource) Response(addr, conn, msg) } // Response return func Response(addr *net.UDPAddr, conn *net.UDPConn, msg dnsmessage.Message) { packed, err := msg.Pack() if err != nil { fmt.Println(err) return } if _, err := conn.WriteToUDP(packed, addr); err != nil { fmt.Println(err) } } // NewAResource A record func NewAResource(query dnsmessage.Name, a [4]byte) dnsmessage.Resource { return dnsmessage.Resource{ Header: dnsmessage.ResourceHeader{ Name: query, Class: dnsmessage.ClassINET, TTL: 600, }, Body: &dnsmessage.AResource{ A: a, }, } } // NewPTRResource PTR record func NewPTRResource(query dnsmessage.Name, ptr string) dnsmessage.Resource { name, _ := dnsmessage.NewName(ptr) return dnsmessage.Resource{ Header: dnsmessage.ResourceHeader{ Name: query, Class: dnsmessage.ClassINET, }, Body: &dnsmessage.PTRResource{ PTR: name, }, } } 

 轉載: https://blog.csdn.net/qq_27068845/article/details/104597845