More error handling around interface iteration

If we can't iterate host interfaces give a warning to the user.
Also don't bail early if a single interface fails, other interfaces
might still be in a good condition.

Resolves pion/ice#75

gather.go

@@ -15,10 +15,11 @@ const (
 	stunGatherTimeout = time.Second * 5
 )
 
-func (a *Agent) localInterfaces(networkTypes []NetworkType) (ips []net.IP) {
+func (a *Agent) localInterfaces(networkTypes []NetworkType) ([]net.IP, error) {
+	ips := []net.IP{}
 	ifaces, err := a.net.Interfaces()
 	if err != nil {
-		return ips
+		return ips, err
 	}
 
 	var IPv4Requested, IPv6Requested bool
@@ -42,7 +43,7 @@ func (a *Agent) localInterfaces(networkTypes []NetworkType) (ips []net.IP) {
 
 		addrs, err := iface.Addrs()
 		if err != nil {
-			return ips
+			continue
 		}
 
 		for _, addr := range addrs {
@@ -71,7 +72,7 @@ func (a *Agent) localInterfaces(networkTypes []NetworkType) (ips []net.IP) {
 			ips = append(ips, ip)
 		}
 	}
-	return ips
+	return ips, nil
 }
 
 func (a *Agent) listenUDP(portMax, portMin int, network string, laddr *net.UDPAddr) (vnet.UDPPacketConn, error) {
@@ -167,7 +168,12 @@ func (a *Agent) gatherCandidatesLocal(networkTypes []NetworkType) {
 	var wg sync.WaitGroup
 	defer wg.Wait()
 
-	localIPs := a.localInterfaces(networkTypes)
+	localIPs, err := a.localInterfaces(networkTypes)
+	if err != nil {
+		a.log.Warnf("failed to iterate local interfaces, host candidates will not be gathered %s", err)
+		return
+	}
+
 	wg.Add(len(localIPs) * len(supportedNetworks))
 	for _, ip := range localIPs {
 		for _, network := range supportedNetworks {

gather_test.go

@@ -11,9 +11,11 @@ func TestListenUDP(t *testing.T) {
 		t.Fatalf("Failed to create agent: %s", err)
 	}
 
-	localIPs := a.localInterfaces([]NetworkType{NetworkTypeUDP4})
+	localIPs, err := a.localInterfaces([]NetworkType{NetworkTypeUDP4})
 	if len(localIPs) == 0 {
 		t.Fatal("localInterfaces found no interfaces, unable to test")
+	} else if err != nil {
+		t.Fatal(err)
 	}
 
 	ip := localIPs[0]

gather_vnet_test.go

@@ -20,9 +20,11 @@ func TestVNetGather(t *testing.T) {
 			t.Fatalf("Failed to create agent: %s", err)
 		}
 
-		localIPs := a.localInterfaces([]NetworkType{NetworkTypeUDP4})
+		localIPs, err := a.localInterfaces([]NetworkType{NetworkTypeUDP4})
 		if len(localIPs) > 0 {
 			t.Fatal("should return no local IP")
+		} else if err != nil {
+			t.Fatal(err)
 		}
 	})
 
@@ -58,9 +60,11 @@ func TestVNetGather(t *testing.T) {
 			t.Fatalf("Failed to create agent: %s", err)
 		}
 
-		localIPs := a.localInterfaces([]NetworkType{NetworkTypeUDP4})
+		localIPs, err := a.localInterfaces([]NetworkType{NetworkTypeUDP4})
 		if len(localIPs) == 0 {
 			t.Fatal("should have one local IP")
+		} else if err != nil {
+			t.Fatal(err)
 		}
 
 		for _, ip := range localIPs {
@@ -97,9 +101,11 @@ func TestVNetGather(t *testing.T) {
 			t.Fatalf("Failed to create agent: %s", err)
 		}
 
-		localIPs := a.localInterfaces([]NetworkType{NetworkTypeUDP4})
+		localIPs, err := a.localInterfaces([]NetworkType{NetworkTypeUDP4})
 		if len(localIPs) == 0 {
 			t.Fatal("localInterfaces found no interfaces, unable to test")
+		} else if err != nil {
+			t.Fatal(err)
 		}
 
 		ip := localIPs[0]

go.mod

@@ -4,7 +4,7 @@ go 1.12
 
 require (
 	github.com/pion/logging v0.2.2
-	github.com/pion/mdns v0.0.2
+	github.com/pion/mdns v0.0.3
 	github.com/pion/stun v0.3.1
 	github.com/pion/transport v0.8.6
 	github.com/pion/turn v1.3.2

go.sum

@@ -8,8 +8,8 @@ github.com/pion/logging v0.2.1 h1:LwASkBKZ+2ysGJ+jLv1E/9H1ge0k1nTfi1X+5zirkDk=
 github.com/pion/logging v0.2.1/go.mod h1:k0/tDVsRCX2Mb2ZEmTqNa7CWsQPc+YYCB7Q+5pahoms=
 github.com/pion/logging v0.2.2 h1:M9+AIj/+pxNsDfAT64+MAVgJO0rsyLnoJKCqf//DoeY=
 github.com/pion/logging v0.2.2/go.mod h1:k0/tDVsRCX2Mb2ZEmTqNa7CWsQPc+YYCB7Q+5pahoms=
-github.com/pion/mdns v0.0.2 h1:T22Gg4dSuYVYsZ21oRFh9z7twzAm27+5PEKiABbjCvM=
-github.com/pion/mdns v0.0.2/go.mod h1:VrN3wefVgtfL8QgpEblPUC46ag1reLIfpqekCnKunLE=
+github.com/pion/mdns v0.0.3 h1:DxdOYd0pgwLKiDlIIxfU0qdG5iWh1Xn6CsS9vc6cMAY=
+github.com/pion/mdns v0.0.3/go.mod h1:VrN3wefVgtfL8QgpEblPUC46ag1reLIfpqekCnKunLE=
 github.com/pion/stun v0.3.1 h1:d09JJzOmOS8ZzIp8NppCMgrxGZpJ4Ix8qirfNYyI3BA=
 github.com/pion/stun v0.3.1/go.mod h1:xrCld6XM+6GWDZdvjPlLMsTU21rNxnO6UO8XsAvHr/M=
 github.com/pion/transport v0.8.6 h1:xHQq2mxAjB+UrFs90aUBaXwlmIACfQAZnOiVAX3uqMw=