├── .gitignore ├── Dockerfile ├── LICENSE ├── README.md └── microdns.go /.gitignore: -------------------------------------------------------------------------------- 1 | # Compiled Object files, Static and Dynamic libs (Shared Objects) 2 | *.o 3 | *.a 4 | *.so 5 | 6 | # Folders 7 | _obj 8 | _test 9 | 10 | # Architecture specific extensions/prefixes 11 | *.[568vq] 12 | [568vq].out 13 | 14 | *.cgo1.go 15 | *.cgo2.c 16 | _cgo_defun.c 17 | _cgo_gotypes.go 18 | _cgo_export.* 19 | 20 | _testmain.go 21 | 22 | *.exe 23 | *.test 24 | *.prof 25 | -------------------------------------------------------------------------------- /Dockerfile: -------------------------------------------------------------------------------- 1 | FROM golang:alpine AS builder 2 | WORKDIR /app 3 | COPY . . 4 | RUN CGO_ENABLED=0 go build -ldflags="-w -s" . 5 | 6 | FROM scratch 7 | COPY --from=builder /app/microdns /usr/local/bin 8 | EXPOSE 53 9 | ENTRYPOINT ["microdns"] 10 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | {one line to give the program's name and a brief idea of what it does.} 635 | Copyright (C) {year} {name of author} 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | {project} Copyright (C) {year} {fullname} 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # MicroDNS 2 | A tiny dockerized DNS server in Go that (almost) always returns the same IP for any query sent to it. 3 | 4 | [![](http://dockeri.co/image/fffaraz/microdns)](https://hub.docker.com/r/fffaraz/microdns/) 5 | [![](https://images.microbadger.com/badges/image/fffaraz/microdns.svg)](https://microbadger.com/images/fffaraz/microdns) 6 | 7 | ## Quick Start (TL;DR) 8 | 9 | ``` 10 | docker run -it --rm -p 53:53 -p 53:53/udp fffaraz/microdns:latest -log \ 11 | -ipv4 $(dig +short myip.opendns.com @resolver1.opendns.com) \ 12 | -ipv6 $(dig +short myip.opendns.com @2620:0:ccc::2 aaaa) 13 | ``` 14 | 15 | ## Arguments & Options 16 | 17 | ``` 18 | -ipv4 Default IPv4 to return (default: 127.0.0.1) 19 | -ipv6 Default IPv6 to return (default: ::1) 20 | -ttl Time to live value (default: 86400) 21 | -log Log requests to stdout (default: false) 22 | -conf Config file (default: /home/dns.conf) 23 | ``` 24 | 25 | ## Config file format 26 | 27 | ``` 28 | domain1.com. 127.0.0.1 ::1 29 | domain2.com. 127.0.0.1 ::1 30 | www.domain1.com. 127.0.0.1 ::1 31 | ftp.domain2.com. 127.0.0.1 ::1 32 | ``` 33 | 34 | ## How to Run 35 | 36 | ``` 37 | docker run -d --restart=always -p 53:53 -p 53:53/udp --name microdns \ 38 | -v /home/microdns:/home \ 39 | fffaraz/microdns:latest \ 40 | -ipv4 127.0.0.1 \ 41 | -ipv6 ::1 \ 42 | -ttl 86400 \ 43 | -log \ 44 | -conf /home/dns.conf 45 | ``` 46 | 47 | ## Request Stats 48 | 49 | ``` 50 | IP Adresses: cat log.out | cut -f2 | sort | uniq -cd | sort -nr 51 | Domains: cat log.out | cut -f3 | sort | uniq -cd | sort -nr 52 | ``` 53 | 54 | ## Metadata API 55 | 56 | ``` 57 | curl http://169.254.169.254/metadata/v1/interfaces/public/0/ipv4/address 58 | curl http://169.254.169.254/metadata/v1/interfaces/public/0/ipv6/address 59 | ``` 60 | -------------------------------------------------------------------------------- /microdns.go: -------------------------------------------------------------------------------- 1 | // go build -ldflags "-extldflags '-lm -lstdc++ -static'" . 2 | 3 | package main 4 | 5 | import ( 6 | "bufio" 7 | "flag" 8 | "fmt" 9 | "log" 10 | "net" 11 | "os" 12 | "os/signal" 13 | "strings" 14 | "syscall" 15 | "time" 16 | "github.com/miekg/dns" 17 | ) 18 | 19 | var ipv4, ipv6, conf string 20 | var ttl int 21 | var logflag bool 22 | var mapv4 map[string]string 23 | var mapv6 map[string]string 24 | 25 | func main() { 26 | flag.StringVar(&ipv4, "ipv4", "127.0.0.1", "IPv4 Address") 27 | flag.StringVar(&ipv6, "ipv6", "::1", "IPv6 Address") 28 | flag.IntVar(&ttl, "ttl", 86400, "Time to live") 29 | flag.BoolVar(&logflag, "log", false, "Log requests to stdout") 30 | flag.StringVar(&conf, "conf", "/home/dns.conf", "Config File") 31 | flag.Parse() 32 | fmt.Printf("ipv4: %s\n", ipv4) 33 | fmt.Printf("ipv6: %s\n", ipv6) 34 | fmt.Printf("ttl : %d\n", ttl) 35 | fmt.Printf("log : %t\n", logflag) 36 | fmt.Printf("conf: %s\n", conf) 37 | fmt.Println("") 38 | if _, err := os.Stat(conf); err == nil { 39 | file, err := os.Open(conf) 40 | if err != nil { 41 | fmt.Printf("err : %s\n", err) 42 | } else { 43 | defer file.Close() 44 | mapv4 = make(map[string]string) 45 | mapv6 = make(map[string]string) 46 | scanner := bufio.NewScanner(file) 47 | for scanner.Scan() { 48 | line := scanner.Text() 49 | if ! strings.HasPrefix(line, "#") { 50 | fields := strings.Fields(line) 51 | fmt.Printf("line: %q\n", fields) 52 | if len(fields) == 3 { 53 | mapv4[fields[0]] = fields[1] 54 | mapv6[fields[0]] = fields[2] 55 | } 56 | } 57 | } 58 | } 59 | fmt.Println("") 60 | } 61 | dns.HandleFunc(".", handleRequest) 62 | go func() { 63 | srv := &dns.Server{Addr: ":53", Net: "udp"} 64 | err := srv.ListenAndServe() 65 | if err != nil { 66 | log.Fatal("Failed to set udp listener %s\n", err.Error()) 67 | } 68 | }() 69 | go func() { 70 | srv := &dns.Server{Addr: ":53", Net: "tcp"} 71 | err := srv.ListenAndServe() 72 | if err != nil { 73 | log.Fatal("Failed to set tcp listener %s\n", err.Error()) 74 | } 75 | }() 76 | sig := make(chan os.Signal) 77 | signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM) 78 | for { 79 | select { 80 | case s := <-sig: 81 | log.Fatalf("Signal (%d) received, stopping\n", s) 82 | } 83 | } 84 | } 85 | 86 | func handleRequest(w dns.ResponseWriter, r *dns.Msg) { 87 | domain := r.Question[0].Name 88 | if logflag { 89 | t := time.Now() 90 | ip, _, _ := net.SplitHostPort(w.RemoteAddr().String()) 91 | fmt.Printf("%d-%02d-%02d_%02d:%02d:%02d\t%s\t%s\n", t.Year(), t.Month(), t.Day(), t.Hour(), t.Minute(), t.Second(), ip, domain) 92 | // TODO: log to file 93 | } 94 | m := new(dns.Msg) 95 | m.SetReply(r) 96 | m.Authoritative = true 97 | rr1 := new(dns.A) 98 | rr1.Hdr = dns.RR_Header{Name: domain, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: uint32(ttl)} 99 | rr2 := new(dns.AAAA) 100 | rr2.Hdr = dns.RR_Header{Name: domain, Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: uint32(ttl)} 101 | if val, ok := mapv4[domain]; ok { 102 | rr1.A = net.ParseIP(val) 103 | rr2.AAAA = net.ParseIP(mapv6[domain]) 104 | } else { 105 | rr1.A = net.ParseIP(ipv4) 106 | rr2.AAAA = net.ParseIP(ipv6) 107 | } 108 | m.Answer = []dns.RR{rr1, rr2} 109 | w.WriteMsg(m) 110 | } 111 | --------------------------------------------------------------------------------