Separated dockerising from code

main/main.go

@@ -0,0 +1,100 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"github.com/miekg/dns"
+	"github.com/zettio/weavedns"
+	"log"
+	"net"
+)
+
+var zone = new(weavedns.ZoneDb)
+
+func makeDNSReply(r *dns.Msg, name string, addr net.IP) *dns.Msg {
+	m := new(dns.Msg)
+	m.SetReply(r)
+	hdr := dns.RR_Header{Name: name, Rrtype: dns.TypeA,
+		Class: dns.ClassINET, Ttl: 3600}
+	a := &dns.A{hdr, addr}
+	m.Answer = append(m.Answer, a)
+	return m
+}
+
+var mdnsClient *weavedns.MDNSClient
+
+func handleMDNS(w dns.ResponseWriter, r *dns.Msg) {
+	// Here we have to handle both requests incoming, responses to queries
+	// we sent out, and responses to queries that other nodes sent
+	if len(r.Answer) > 0 {
+		mdnsClient.HandleResponse(r)
+	} else if len(r.Question) > 0 {
+		q := r.Question[0]
+		ip, err := zone.MatchLocal(q.Name)
+		if err == nil {
+			m := makeDNSReply(r, q.Name, net.ParseIP(ip))
+			mdnsClient.SendResponse(m)
+		} else if mdnsClient.IsInflightQuery(r) {
+			// ignore this - it's our own query received via multicast
+		} else {
+			log.Printf("Failed MDNS lookup for %s", q.Name)
+		}
+	}
+}
+
+func handleLocal(w dns.ResponseWriter, r *dns.Msg) {
+	log.Printf("Received message: %s", r)
+	q := r.Question[0]
+	ip, err := zone.MatchLocal(q.Name)
+	if err == nil {
+		m := makeDNSReply(r, q.Name, net.ParseIP(ip))
+		w.WriteMsg(m)
+	} else {
+		log.Printf("Failed lookup for %s", q.Name)
+		// We don't know the answer; see if someone else does
+		channel := make(chan *weavedns.ResponseA, 4)
+		go func() {
+			for resp := range channel {
+				log.Printf("Got address response %s to query %s addr %s", resp.Name, q.Name, resp.Addr)
+				m := makeDNSReply(r, resp.Name, resp.Addr)
+				w.WriteMsg(m)
+			}
+			// FIXME: need to add a time-out either here or in mdnsClient
+		}()
+		mdnsClient.SendQuery(q.Name, dns.TypeA, channel)
+	}
+	return
+}
+
+func main() {
+	var (
+		dnsPort int
+	)
+
+	flag.IntVar(&dnsPort, "dnsport", 53, "port to listen to dns requests (defaults to 53)")
+	flag.Parse()
+
+	LocalServeMux := dns.NewServeMux()
+	LocalServeMux.HandleFunc("local", handleLocal)
+	go weavedns.ListenHttp(zone)
+
+	MDNSServeMux := dns.NewServeMux()
+	MDNSServeMux.HandleFunc("local", handleMDNS)
+
+	conn, err := weavedns.LinkLocalMulticastListener()
+	if err != nil {
+		log.Fatal(err)
+	}
+	mdnsClient, err = weavedns.NewMDNSClient()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	go dns.ActivateAndServe(nil, conn, MDNSServeMux)
+
+	address := fmt.Sprintf(":%d", dnsPort)
+	err = dns.ListenAndServe(address, "udp", LocalServeMux)
+	if err != nil {
+		log.Fatal(err)
+	}
+}