Write A Simple DNS Server With Golang
The following DNS knows how to answer A queries and it only knows IP address of domain. First we need to get the package:
go get github.com/miekg/dns
Then we have this code:
package main import ( "fmt" "log" "strconv" "github.com/miekg/dns"
) var records = map[string]string{ "nguyenxuanquang.service": "192.168.1.15",
} func parseQuery(m *dns.Msg) { for _, q := range m.Question { switch q.Qtype { case dns.TypeA: log.Printf("Query for %s\n", q.Name) ip := records[q.Name] if ip != "" { rr, err := dns.NewRR(fmt.Sprintf("%s A %s", q.Name, ip)) if err == nil { m.Answer = append(m.Answer, rr) } } } }
}
func handleDnsRequest(w dns.ResponseWriter, r *dns.Msg) { m := new(dns.Msg) m.SetReply(r) m.Compress = false switch r.Opcode { case dns.OpcodeQuery: parseQuery(m) } w.WriteMsg(m)
} func main() { dns.HandleFunc("service.", handleDnsRequest) //start server port := 8080 server := &dns.Server{ Addr: ":" + strconv.Itoa(port), Net: "udp", } log.Printf("Starting at %d\n", port) err := server.ListenAndServe() defer server.Shutdown() if err != nil { log.Fatalf("Failed to start server: %s\n", err.Error()) }
}
Use dig(linux) to query the server. If you are the windows user, use this https://help.dyn.com/how-to-use-binds-dig-tool/
Now the result:
So easy right? Hope you guys feel this topic useful. Thank you for read my topic, have a nice day
.
Ref:
Simple Golang Server: https://gist.github.com/walm/0d67b4fb2d5daf3edd4fad3e13b162cb