commit 530888899a9d8b800769c66b0af4ffae43018f68
Author: Pim van Pelt <pim@ipng.nl>
Date:   Fri Dec 22 16:42:32 2017 +0100

    Initial checkin

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..e1f9f16
--- /dev/null
+++ b/README.md
@@ -0,0 +1,42 @@
+# Source
+http://mkaczanowski.com/golang-build-dynamic-dns-service-go/
+
+# Compiling
+
+```
+go get github.com/miekg/dns/...
+go get github.com/boltdb/bolt/...
+go build dyndns-server.go 
+ls -la dyndns-server
+```
+
+# Deploying
+
+MACH=dyn.paphosting.net
+scp dyndns-server root@$MACH:/usr/local/sbin
+scp systemd/dyndns-server.service root@$MACH:/etc/systemd/system/
+
+# Running
+
+ssh root@$MACH
+adduser dyndns
+mkdir /var/dyndns
+chown dyndns /var/dyndns
+service dyndns-server start
+
+# Testing
+
+cat << EOL > update.txt
+server $MACH 53
+debug yes
+key key bWFyaWVsbGU=
+zone dyn.ipng.nl.
+update delete test.dyn.ipng.nl. A
+update delete test.dyn.ipng.nl. AAAA
+update add test.dyn.ipng.nl. 120 A 192.0.2.1
+update add test.dyn.ipng.nl. 120 AAAA 2001:db8::1
+show
+send
+EOL
+
+nsupdate update.txt
diff --git a/dyndns-server.go b/dyndns-server.go
new file mode 100644
index 0000000..7e01195
--- /dev/null
+++ b/dyndns-server.go
@@ -0,0 +1,322 @@
+package main
+
+import (
+    "errors"
+    "flag"
+    "github.com/boltdb/bolt"
+    "github.com/miekg/dns"
+    "log"
+    "math"
+    "net"
+    "os"
+    "os/signal"
+    "strconv"
+    "strings"
+    "syscall"
+    "time"
+)
+
+var (
+    tsig     *string
+    db_path  *string
+    ip       *string
+    port     *int
+    bdb      *bolt.DB
+    logfile  *string
+    pid_file *string
+)
+
+const rr_bucket = "rr"
+
+func getKey(domain string, rtype uint16) (r string, e error) {
+    if n, ok := dns.IsDomainName(domain); ok {
+        labels := dns.SplitDomainName(domain)
+
+        // Reverse domain, starting from top-level domain
+        // eg. ".com.mkaczanowski.test"
+        var tmp string
+        for i := 0; i  < int(math.Floor(float64(n/2))); i++ {
+            tmp = labels[i]
+            labels[i] = labels[n-1]
+            labels[n-1] = tmp
+        }
+
+        reverse_domain := strings.Join(labels, ".")
+        r = strings.Join([]string{reverse_domain, strconv.Itoa(int(rtype))}, "_")
+    } else {
+        e = errors.New("Invailid domain: " + domain)
+        log.Println(e.Error())
+    }
+
+    return r, e
+}
+
+func createBucket(bucket string) (err error) {
+    err = bdb.Update(func(tx *bolt.Tx) error {
+        _, err := tx.CreateBucketIfNotExists([]byte(bucket))
+        if err != nil {
+            e := errors.New("Create bucket: " + bucket)
+            log.Println(e.Error())
+
+            return e
+        }
+
+        return nil
+    })
+
+    return err
+}
+
+func deleteRecord(domain string, rtype uint16) (err error) {
+    key, _ := getKey(domain, rtype)
+    err = bdb.Update(func(tx *bolt.Tx) error {
+        b := tx.Bucket([]byte(rr_bucket))
+        err := b.Delete([]byte(key))
+
+        if err != nil {
+            e := errors.New("Delete record failed for domain: " + domain)
+            log.Println(e.Error())
+
+            return e
+        }
+
+        return nil
+    })
+
+    return err
+}
+
+func storeRecord(rr dns.RR) (err error) {
+    key, _ := getKey(rr.Header().Name, rr.Header().Rrtype)
+    err = bdb.Update(func(tx *bolt.Tx) error {
+        b := tx.Bucket([]byte(rr_bucket))
+        err := b.Put([]byte(key), []byte(rr.String()))
+
+        if err != nil {
+            e := errors.New("Store record failed: " + rr.String())
+            log.Println(e.Error())
+
+            return e
+        }
+
+        return nil
+    })
+
+    return err
+}
+
+func getRecord(domain string, rtype uint16) (rr dns.RR, err error) {
+    key, _ := getKey(domain, rtype)
+    var v []byte
+
+    err = bdb.View(func(tx *bolt.Tx) error {
+        b := tx.Bucket([]byte(rr_bucket))
+        v = b.Get([]byte(key))
+
+        if string(v) == "" {
+            e := errors.New("Record not found, key: " + key)
+            log.Println(e.Error())
+
+            return e
+        }
+
+        return nil
+    })
+
+    if err == nil {
+        rr, err = dns.NewRR(string(v))
+    }
+
+    return rr, err
+}
+
+func updateRecord(r dns.RR, q *dns.Question) {
+    var (
+        rr    dns.RR
+        name  string
+        rtype uint16
+        ttl   uint32
+        ip    net.IP
+    )
+
+    header := r.Header()
+    name = header.Name
+    rtype = header.Rrtype
+    ttl = header.Ttl
+
+    if _, ok := dns.IsDomainName(name); ok {
+        if header.Class == dns.ClassANY && header.Rdlength == 0 { // Delete record
+            deleteRecord(name, rtype)
+        } else { // Add record
+            rheader := dns.RR_Header{
+                Name:   name,
+                Rrtype: rtype,
+                Class:  dns.ClassINET,
+                Ttl:    ttl,
+            }
+
+            if a, ok := r.(*dns.A); ok {
+                rrr, err := getRecord(name, rtype)
+                if err == nil {
+                    rr = rrr.(*dns.A)
+                } else {
+                    rr = new(dns.A)
+                }
+
+                ip = a.A
+                rr.(*dns.A).Hdr = rheader
+                rr.(*dns.A).A = ip
+            } else if a, ok := r.(*dns.AAAA); ok {
+                rrr, err := getRecord(name, rtype)
+                if err == nil {
+                    rr = rrr.(*dns.AAAA)
+                } else {
+                    rr = new(dns.AAAA)
+                }
+
+                ip = a.AAAA
+                rr.(*dns.AAAA).Hdr = rheader
+                rr.(*dns.AAAA).AAAA = ip
+            }
+
+            storeRecord(rr)
+        }
+    }
+}
+
+func parseQuery(m *dns.Msg) {
+    var rr dns.RR
+
+    for _, q := range m.Question {
+        if read_rr, e := getRecord(q.Name, q.Qtype); e == nil {
+            rr = read_rr.(dns.RR)
+            if rr.Header().Name == q.Name {
+                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)
+
+    case dns.OpcodeUpdate:
+        for _, question := range r.Question {
+            for _, rr := range r.Ns {
+                updateRecord(rr, &question)
+            }
+        }
+    }
+
+    if r.IsTsig() != nil {
+        if w.TsigStatus() == nil {
+            m.SetTsig(r.Extra[len(r.Extra)-1].(*dns.TSIG).Hdr.Name,
+                dns.HmacMD5, 300, time.Now().Unix())
+        } else {
+            log.Println("Status", w.TsigStatus().Error())
+        }
+    }
+
+    w.WriteMsg(m)
+}
+
+func serve(name, secret string, ip string, port int) {
+    server := &dns.Server{Addr: "[" +ip + "]:" + strconv.Itoa(port), Net: "udp"}
+
+    if name != "" {
+        server.TsigSecret = map[string]string{name: secret}
+    }
+
+    err := server.ListenAndServe()
+    defer server.Shutdown()
+
+    if err != nil {
+        log.Fatalf("Failed to setup the udp server: %sn", err.Error())
+    }
+}
+
+func main() {
+    var (
+        name   string   // tsig keyname
+        secret string   // tsig base64
+        fh     *os.File // logfile handle
+    )
+
+    // Parse flags
+    logfile = flag.String("logfile", "", "path to log file")
+    port = flag.Int("port", 53, "server port")
+    ip = flag.String("ip", "::", "ip to listen on")
+    tsig = flag.String("tsig", "", "use MD5 hmac tsig: keyname:base64")
+    db_path = flag.String("db_path", "/var/dyndns/dyndns.db", "location where db will be stored")
+    pid_file = flag.String("pid", "/var/dyndns/go-dyndns.pid", "pid file location")
+
+    flag.Parse()
+
+    // Open db
+    db, err := bolt.Open(*db_path, 0600,
+        &bolt.Options{Timeout: 10 * time.Second})
+
+    if err != nil {
+        log.Fatal(err)
+    }
+    defer db.Close()
+    bdb = db
+
+    // Create dns bucket if doesn't exist
+    createBucket(rr_bucket)
+
+    // Attach request handler func
+    dns.HandleFunc(".", handleDnsRequest)
+
+    // Tsig extract
+    if *tsig != "" {
+        a := strings.SplitN(*tsig, ":", 2)
+        name, secret = dns.Fqdn(a[0]), a[1]
+    }
+
+    // Logger setup
+    if *logfile != "" {
+        if _, err := os.Stat(*logfile); os.IsNotExist(err) {
+            if file, err := os.Create(*logfile); err != nil {
+                if err != nil {
+                    log.Panic("Couldn't create log file: ", err)
+                }
+
+                fh = file
+            }
+        } else {
+            fh, _ = os.OpenFile(*logfile, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
+        }
+        defer fh.Close()
+        log.SetOutput(fh)
+    }
+
+    // Pidfile
+    file, err := os.OpenFile(*pid_file, os.O_RDWR|os.O_CREATE, 0666)
+    if err != nil {
+        log.Panic("Couldn't create pid file: ", err)
+    } else {
+        file.Write([]byte(strconv.Itoa(syscall.Getpid())))
+        defer file.Close()
+    }
+
+    // Start server
+    go serve(name, secret, *ip, *port)
+
+    sig := make(chan os.Signal)
+    signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
+endless:
+    for {
+        select {
+        case s :=  <-sig:
+            log.Printf("Signal (%d) received, stopping", s)
+            break endless
+        }
+    }
+}
diff --git a/systemd/dyndns-server.service b/systemd/dyndns-server.service
new file mode 100644
index 0000000..ec8f2b5
--- /dev/null
+++ b/systemd/dyndns-server.service
@@ -0,0 +1,16 @@
+[Unit]
+Description=DynDNS server in Go
+# Documentation=See git@git.ipng.nl:pim/dyndns-go.git
+
+[Service]
+User=dyndns
+Group=nogroup
+ExecStart=/usr/local/sbin/dyndns-server -port=53 -ip=:: -tsig=key:bWFyaWVsbGU=
+Restart=always
+ProtectSystem=full
+ProtectHome=true
+CapabilityBoundingSet=CAP_NET_BIND_SERVICE
+AmbientCapabilities=CAP_NET_BIND_SERVICE
+
+[Install]
+WantedBy=multi-user.target
diff --git a/update-dyndns.sh b/update-dyndns.sh
new file mode 100755
index 0000000..20ced04
--- /dev/null
+++ b/update-dyndns.sh
@@ -0,0 +1,30 @@
+#!/bin/sh
+
+SERVER="dyn.paphosting.net"
+PORT="53"
+TSIG="bWFyaWVsbGU="
+INTERFACE_A="eth0"
+INTERFACE_AAAA="eth0"
+
+# Generated variables follow:
+UPDATE_FILE="/tmp/go-dyndns-nsupdate.$$"
+A_RECORD=$(ip addr show $INTERFACE_A | awk '/inet .*scope global/ { ip=$2; gsub("/.*","", ip); } END { print ip}')
+AAAA_RECORD=$(ip addr show $INTERFACE_AAAA | awk '/inet6 .*scope global/ { ip=$2; gsub("/.*","", ip); } END { print ip}')
+HOSTNAME_SHORT=$(hostname -s)
+
+cat << EOL > $UPDATE_FILE
+server $SERVER $PORT
+key key bWFyaWVsbGU=
+; debug
+zone dyn.ipng.nl.
+; update delete ${HOSTNAME_SHORT}.dyn.ipng.nl. A
+; update delete ${HOSTNAME_SHORT}.dyn.ipng.nl. AAAA
+update add ${HOSTNAME_SHORT}.dyn.ipng.nl. 120 A ${A_RECORD}
+update add ${HOSTNAME_SHORT}.dyn.ipng.nl. 120 AAAA ${AAAA_RECORD}
+show
+send
+EOL
+
+nsupdate ${UPDATE_FILE}
+rm -f ${UPDATE_FILE}
+
diff --git a/update.txt b/update.txt
new file mode 100644
index 0000000..4a03e44
--- /dev/null
+++ b/update.txt
@@ -0,0 +1,10 @@
+server 194.1.163.24 53
+debug yes
+key key bWFyaWVsbGU=
+zone dyn.ipng.nl.
+update delete test.dyn.ipng.nl. A
+update delete test.dyn.ipng.nl. AAAA
+update add test.dyn.ipng.nl. 120 A 192.0.2.1
+update add test.dyn.ipng.nl. 120 AAAA 2001:db8::1
+show
+send