Adding ability to set multicast query interface

client.go

@@ -1,6 +1,8 @@
 package mdns
 
 import (
+	"code.google.com/p/go.net/ipv4"
+	"code.google.com/p/go.net/ipv6"
 	"fmt"
 	"github.com/miekg/dns"
 	"log"
@@ -26,11 +28,30 @@ func (s *ServiceEntry) complete() bool {
 	return s.Addr != nil && s.Port != 0 && s.hasTXT
 }
 
-// LookupDomain looks up a given service, in a domain, waiting at most
+// QueryParam is used to customize how a Lookup is performed
+type QueryParam struct {
+	Service   string               // Service to lookup
+	Domain    string               // Lookup domain, default "local"
+	Timeout   time.Duration        // Lookup timeout, default 1 second
+	Interface *net.Interface       // Multicast interface to use
+	Entries   chan<- *ServiceEntry // Entries Channel
+}
+
+// DefaultParams is used to return a default set of QueryParam's
+func DefaultParams(service string) *QueryParam {
+	return &QueryParam{
+		Service: service,
+		Domain:  "local",
+		Timeout: time.Second,
+		Entries: make(chan *ServiceEntry),
+	}
+}
+
+// Query looks up a given service, in a domain, waiting at most
 // for a timeout before finishing the query. The results are streamed
 // to a channel. Sends will not block, so clients should make sure to
 // either read or buffer.
-func LookupDomain(service, domain string, timeout time.Duration, entries chan<- *ServiceEntry) error {
+func Query(params *QueryParam) error {
 	// Create a new client
 	client, err := newClient()
 	if err != nil {
@@ -38,17 +59,27 @@ func LookupDomain(service, domain string, timeout time.Duration, entries chan<-
 	}
 	defer client.Close()
 
-	// Create the query name
+	// Set the multicast interface
-	serviceAddr := fmt.Sprintf("%s.%s.", trimDot(service), trimDot(domain))
+	if params.Interface != nil {
-
+		if err := client.setInterface(params.Interface); err != nil {
-	// Run the query
+			return err
-	return client.query(serviceAddr, timeout, entries)
+		}
 	}
 
-// Lookup is the same as LookupDomain, however it only searches in the "local"
+	// Ensure a timeout
-// domain, and uses a one second lookup timeout.
+	if params.Timeout == 0 {
+		params.Timeout = time.Second
+	}
+
+	// Run the query
+	return client.query(params)
+}
+
+// Lookup is the same as Query, however it uses all the default parameters
 func Lookup(service string, entries chan<- *ServiceEntry) error {
-	return LookupDomain(service, "local", time.Second, entries)
+	params := DefaultParams(service)
+	params.Entries = entries
+	return Query(params)
 }
 
 // Client provides a query interface that can be used to
@@ -107,8 +138,25 @@ func (c *client) Close() error {
 	return nil
 }
 
+// setInterface is used to set the query interface, uses sytem
+// default if not provided
+func (c *client) setInterface(iface *net.Interface) error {
+	p := ipv4.NewPacketConn(c.ipv4List)
+	if err := p.SetMulticastInterface(iface); err != nil {
+		return err
+	}
+	p2 := ipv6.NewPacketConn(c.ipv6List)
+	if err := p2.SetMulticastInterface(iface); err != nil {
+		return err
+	}
+	return nil
+}
+
 // query is used to perform a lookup and stream results
-func (c *client) query(service string, timeout time.Duration, entries chan<- *ServiceEntry) error {
+func (c *client) query(params *QueryParam) error {
+	// Create the service name
+	serviceAddr := fmt.Sprintf("%s.%s.", trimDot(params.Service), trimDot(params.Domain))
+
 	// Start listening for response packets
 	msgCh := make(chan *dns.Msg, 32)
 	go c.recv(c.ipv4List, msgCh)
@@ -116,7 +164,7 @@ func (c *client) query(service string, timeout time.Duration, entries chan<- *Se
 
 	// Send the query
 	m := new(dns.Msg)
-	m.SetQuestion(service, dns.TypeANY)
+	m.SetQuestion(serviceAddr, dns.TypeANY)
 	if err := c.sendQuery(m); err != nil {
 		return nil
 	}
@@ -125,7 +173,7 @@ func (c *client) query(service string, timeout time.Duration, entries chan<- *Se
 	inprogress := make(map[string]*ServiceEntry)
 
 	// Listen until we reach the timeout
-	finish := time.After(timeout)
+	finish := time.After(params.Timeout)
 	for {
 		select {
 		case resp := <-msgCh:
@@ -163,7 +211,7 @@ func (c *client) query(service string, timeout time.Duration, entries chan<- *Se
 			if inp.complete() && !inp.sent {
 				inp.sent = true
 				select {
-				case entries <- inp:
+				case params.Entries <- inp:
 				default:
 				}
 			} else {

server_test.go

@@ -8,7 +8,7 @@ import (
 
 func TestServer_StartStop(t *testing.T) {
 	s := makeService(t)
-	serv, err := NewServer(&Config{s})
+	serv, err := NewServer(&Config{Zone: s})
 	if err != nil {
 		t.Fatalf("err: %v", err)
 	}
@@ -19,7 +19,7 @@ func TestServer_Lookup(t *testing.T) {
 	s := makeService(t)
 	s.Service = "_foobar._tcp"
 	s.Init()
-	serv, err := NewServer(&Config{s})
+	serv, err := NewServer(&Config{Zone: s})
 	if err != nil {
 		t.Fatalf("err: %v", err)
 	}
@@ -49,7 +49,13 @@ func TestServer_Lookup(t *testing.T) {
 		}
 	}()
 
-	err = LookupDomain("_foobar._tcp", "local", 50*time.Millisecond, entries)
+	params := &QueryParam{
+		Service: "_foobar._tcp",
+		Domain:  "local",
+		Timeout: 50 * time.Millisecond,
+		Entries: entries,
+	}
+	err = Query(params)
 	if err != nil {
 		t.Fatalf("err: %v", err)
 	}