improvements

- better performance
- fix memory leak due to mcnlog misusage (closes #3)
- add systemd example to the readme

README.md

@@ -111,9 +111,15 @@ Finally, the service can be enabled :
 
 Here again, it will depend on your Linux distribution.
 We'll take as example [Systemd](https://freedesktop.org/wiki/Software/systemd/),
-which is nowadays the default init system in Ubuntu/Debian.
+which is nowadays the default init system in most distributions.
 
 Create the following file at `/etc/systemd/system/dockness.service`:
 
-    TODO
+    [Unit]
+    Description=Dockness
 
+    [Service]
+    ExecStart=/path/to/dockness -port 10053
+
+    [Install]
+    WantedBy=multi-user.target

dockness.go

@@ -1,12 +1,14 @@
 package main
 
 import (
+	"encoding/json"
 	"flag"
+	"fmt"
 	"github.com/docker/machine/commands/mcndirs"
 	"github.com/docker/machine/libmachine"
-	mcnhost "github.com/docker/machine/libmachine/host"
-	mcnlog "github.com/docker/machine/libmachine/log"
+	"github.com/docker/machine/libmachine/drivers"
 	"github.com/miekg/dns"
+	//"github.com/pkg/profile"
 	"log"
 	"net"
 	"os"
@@ -16,68 +18,71 @@ import (
 
 var api *libmachine.Client
 var ttl uint
-var machines = make(map[string]*mcnhost.Host)
+
+func findIp(machineName string) (string, error) {
+	machine, err := api.Filestore.Load(machineName)
+	if err != nil {
+		return "", fmt.Errorf("couldn't load machine : %s", err)
+	}
+
+	var baseDriver drivers.BaseDriver
+	err = json.Unmarshal(machine.RawDriver, &baseDriver)
+	if err != nil {
+		return "", fmt.Errorf("couldn't load driver %s", machine.DriverName)
+	}
+
+	return baseDriver.IPAddress, nil
+}
 
 func lookup(w dns.ResponseWriter, r *dns.Msg) {
 	m := new(dns.Msg)
-
 	m.SetReply(r)
+	if m.Question[0].Qtype != dns.TypeA {
+		return
+	}
+
+	domLevels := strings.Split(m.Question[0].Name, ".")
+	domLevelsLen := len(domLevels)
+	if domLevelsLen < 3 {
+		log.Printf("Couldn't parse the DNS question '%s'", m.Question[0].Name)
+		return
+	}
 
-	var rr dns.RR
-	for _, q := range m.Question {
-		if q.Qtype != dns.TypeA {
-			continue
-		}
-
-		domLevels := strings.Split(q.Name, ".")
-		domLevelsLen := len(domLevels)
-		if domLevelsLen < 3 {
-			mcnlog.Debugf("Couldn't parse the DNS question '%s'", q.Name)
-			continue
-		}
-		machineName := domLevels[len(domLevels)-3]
-
-		if machines[machineName] == nil {
-			machine, err := api.Load(machineName)
-			if err != nil {
-				mcnlog.Debugf("Couldn't load machine '%s' : %s", machineName, err)
-				continue
-			}
-			machines[machineName] = machine
-		}
-
-		ip, err := machines[machineName].Driver.GetIP()
-		if err != nil {
-			mcnlog.Debugf("Couldn't find IP for machine '%s' : %s", machineName, err)
-			continue
-		}
-
-		mcnlog.Debugf("Found IP %s for machine '%s'", ip, machineName)
-
-		rr = &dns.A{
-			Hdr: dns.RR_Header{
-				Name:   q.Name,
-				Rrtype: dns.TypeA,
-				Class:  dns.ClassINET,
-				Ttl:    uint32(ttl),
-			},
-			A: net.ParseIP(ip).To4(),
-		}
-
-		m.Answer = append(m.Answer, rr)
+	machineName := domLevels[len(domLevels)-3]
+	ip, err := findIp(machineName)
+	if err != nil {
+		log.Printf("Couldn't find IP for machine '%s' : %s", machineName, err)
+	} // else {
+	//log.Printf("Found IP %s for machine '%s'", ip, machineName)
+	//}
+
+	rr := &dns.A{
+		Hdr: dns.RR_Header{
+			Name:   m.Question[0].Name,
+			Rrtype: dns.TypeA,
+			Class:  dns.ClassINET,
+			Ttl:    uint32(ttl),
+		},
+		A: net.ParseIP(ip).To4(),
 	}
 
+	m.Answer = append(m.Answer, rr)
+
 	w.WriteMsg(m)
 }
 
 func main() {
 	tld := flag.String("tld", "docker", "Top-level domain to use")
 	flag.UintVar(&ttl, "ttl", 0, "Time to Live for DNS records")
 	port := flag.String("port", "53", "Port to listen on")
-	debug := flag.Bool("debug", false, "Enable debugging")
+	_ = flag.Bool("debug", false, "Enable debugging")
 	flag.Parse()
 
-	mcnlog.SetDebug(*debug)
+	//if *debug {
+	//	p := profile.Start(profile.MemProfile, profile.ProfilePath("."))
+	//	defer p.Stop()
+	//}
+
 	api = libmachine.NewClient(mcndirs.GetBaseDir(), mcndirs.GetMachineCertDir())
 	defer api.Close()