Merge pull request #1355 from weaveworks/1343-docker-bridge-in-resolv-conf

Pass docker bridge ip to dns server, and filter it out of upstream dns ips.

nameserver/dns.go

@@ -38,8 +38,18 @@ type DNSServer struct {
 	udpClient *dns.Client
 }
 
-func NewDNSServer(ns *Nameserver, domain string, address string, ttl uint32, clientTimeout time.Duration) (*DNSServer, error) {
+func filter(ss []string, s string) []string {
+	for i := 0; i < len(ss); {
+		if ss[i] == s {
+			ss = append(ss[:i], ss[i+1:]...)
+			continue
+		}
+		i++
+	}
+	return ss
+}
 
+func NewDNSServer(ns *Nameserver, domain, address, effectiveAddress string, ttl uint32, clientTimeout time.Duration) (*DNSServer, error) {
 	s := &DNSServer{
 		ns:        ns,
 		domain:    dns.Fqdn(domain),
@@ -52,6 +62,9 @@ func NewDNSServer(ns *Nameserver, domain string, address string, ttl uint32, cli
 	if s.upstream, err = dns.ClientConfigFromFile(etcResolvConf); err != nil {
 		return nil, err
 	}
+	if s.upstream != nil {
+		s.upstream.Servers = filter(s.upstream.Servers, effectiveAddress)
+	}
 
 	err = s.listen(address)
 	return s, err

nameserver/dns_test.go

@@ -19,7 +19,7 @@ func startServer(t *testing.T) (*DNSServer, *Nameserver, int, int) {
 	peername, err := router.PeerNameFromString("00:00:00:02:00:00")
 	require.Nil(t, err)
 	nameserver := New(peername, nil, nil, "")
-	dnsserver, err := NewDNSServer(nameserver, "weave.local.", "0.0.0.0:0", 30, 5*time.Second)
+	dnsserver, err := NewDNSServer(nameserver, "weave.local.", "0.0.0.0:0", "", 30, 5*time.Second)
 	require.Nil(t, err)
 	udpPort := dnsserver.servers[0].PacketConn.LocalAddr().(*net.UDPAddr).Port
 	tcpPort := dnsserver.servers[1].Listener.Addr().(*net.TCPAddr).Port

prog/weaver/main.go

@@ -55,11 +55,13 @@ func main() {
 		peerCount          int
 		apiPath            string
 		peers              []string
-		noDNS              bool
-		dnsDomain          string
-		dnsListenAddress   string
-		dnsTTL             int
-		dnsClientTimeout   time.Duration
+
+		noDNS                     bool
+		dnsDomain                 string
+		dnsListenAddress          string
+		dnsTTL                    int
+		dnsClientTimeout          time.Duration
+		dnsEffectiveListenAddress string
 	)
 
 	mflag.BoolVar(&justVersion, []string{"#version", "-version"}, false, "print version and exit")
@@ -86,6 +88,7 @@ func main() {
 	mflag.StringVar(&dnsListenAddress, []string{"-dns-listen-address"}, nameserver.DefaultListenAddress, "address to listen on for DNS requests")
 	mflag.IntVar(&dnsTTL, []string{"-dns-ttl"}, nameserver.DefaultTTL, "TTL for DNS request from our domain")
 	mflag.DurationVar(&dnsClientTimeout, []string{"-dns-fallback-timeout"}, nameserver.DefaultClientTimeout, "timeout for fallback DNS requests")
+	mflag.StringVar(&dnsEffectiveListenAddress, []string{"-dns-effective-listen-address"}, "", "address DNS will actually be listening, after Docker port mapping")
 
 	// crude way of detecting that we probably have been started in a
 	// container, with `weave launch` --> suppress misleading paths in
@@ -191,7 +194,8 @@ func main() {
 		}
 		ns.Start()
 		defer ns.Stop()
-		dnsserver, err = nameserver.NewDNSServer(ns, dnsDomain, dnsListenAddress, uint32(dnsTTL), dnsClientTimeout)
+		dnsserver, err = nameserver.NewDNSServer(ns, dnsDomain, dnsListenAddress,
+			dnsEffectiveListenAddress, uint32(dnsTTL), dnsClientTimeout)
 		if err != nil {
 			Log.Fatal("Unable to start dns server: ", err)
 		}

weave

@@ -1162,7 +1162,7 @@ launch_router() {
         -v /var/run/docker.sock:/var/run/docker.sock \
         -e WEAVE_PASSWORD \
         -e WEAVE_CIDR=none \
-        $WEAVE_DOCKER_ARGS $IMAGE $COVERAGE_ARGS --iface $CONTAINER_IFNAME --port $CONTAINER_PORT --name "$PEERNAME" --nickname "$(hostname)" --ipalloc-range "$IPRANGE" "$@")
+        $WEAVE_DOCKER_ARGS $IMAGE $COVERAGE_ARGS --iface $CONTAINER_IFNAME --port $CONTAINER_PORT --name "$PEERNAME" --nickname "$(hostname)" --ipalloc-range "$IPRANGE" --dns-effective-listen-address "$DOCKER_BRIDGE_IP" "$@")
     with_container_netns_or_die $ROUTER_CONTAINER launch
     wait_for_status $CONTAINER_NAME $HTTP_PORT
     if [ -n "$IPRANGE" ] ; then