scratch/dns-server/server.go (view raw)
| 1 | package main |
| 2 | |
| 3 | import ( |
| 4 | "bytes" |
| 5 | "fmt" |
| 6 | "net" |
| 7 | ) |
| 8 | |
| 9 | func HandleQuery(conn *net.UDPConn) error { |
| 10 | buf := make([]byte, 512) |
| 11 | n, src, err := conn.ReadFromUDP(buf) |
| 12 | if err != nil { |
| 13 | return err |
| 14 | } |
| 15 | |
| 16 | request, err := ParsePacket(buf[:n]) |
| 17 | if err != nil { |
| 18 | return err |
| 19 | } |
| 20 | |
| 21 | response := Packet{ |
| 22 | Header: Header{ |
| 23 | ID: request.Header.ID, |
| 24 | RecursionDesired: true, |
| 25 | RecursionAvailable: true, |
| 26 | Response: true, |
| 27 | }, |
| 28 | } |
| 29 | |
| 30 | if len(request.Questions) == 0 { |
| 31 | response.Header.Rescode = FORMERR |
| 32 | } else { |
| 33 | q := request.Questions[0] |
| 34 | fmt.Printf("Received query: %+v\n", q) |
| 35 | |
| 36 | res, rerr := Lookup(q.Name, q.Type) |
| 37 | if rerr != nil { |
| 38 | response.Header.Rescode = SERVFAIL |
| 39 | } else { |
| 40 | response.Questions = append(response.Questions, q) |
| 41 | response.Header.Rescode = res.Header.Rescode |
| 42 | for _, rec := range res.Answers { |
| 43 | fmt.Printf("Answer: %+v\n", rec) |
| 44 | response.Answers = append(response.Answers, rec) |
| 45 | } |
| 46 | for _, rec := range res.Authorities { |
| 47 | fmt.Printf("Authority: %+v\n", rec) |
| 48 | response.Authorities = append(response.Authorities, rec) |
| 49 | } |
| 50 | for _, rec := range res.Resources { |
| 51 | fmt.Printf("Resource: %+v\n", rec) |
| 52 | response.Resources = append(response.Resources, rec) |
| 53 | } |
| 54 | } |
| 55 | } |
| 56 | |
| 57 | resBuf := &bytes.Buffer{} |
| 58 | if err = response.Write(resBuf); err != nil { |
| 59 | return err |
| 60 | } |
| 61 | |
| 62 | _, err = conn.WriteToUDP(resBuf.Bytes(), src) |
| 63 | return err |
| 64 | } |