Support 1:1 NAT option

Resolves #835

ice_go.go

@@ -23,6 +23,8 @@ func (api *API) NewICEGatherer(opts ICEGatherOptions) (*ICEGatherer, error) {
 		api.settingEngine.candidates.ICELite,
 		api.settingEngine.candidates.ICENetworkTypes,
 		api.settingEngine.candidates.InterfaceFilter,
+		api.settingEngine.candidates.NAT1To1IPs,
+		api.settingEngine.candidates.NAT1To1IPCandidate,
 		opts,
 	)
 }

icegatherer.go

@@ -38,6 +38,8 @@ type ICEGatherer struct {
 	log                       logging.LeveledLogger
 	networkTypes              []NetworkType
 	interfaceFilter           func(string) bool
+	nat1To1IPs                []string
+	nat1To1IPCandidateType    ice.CandidateType
 
 	onLocalCandidateHdlr func(candidate *ICECandidate)
 	onStateChangeHdlr    func(state ICEGathererState)
@@ -59,6 +61,8 @@ func NewICEGatherer(
 	lite bool,
 	networkTypes []NetworkType,
 	interfaceFilter func(string) bool,
+	nat1To1IPs []string,
+	nat1To1IPCandidate string,
 	opts ICEGatherOptions,
 ) (*ICEGatherer, error) {
 	var validatedServers []*ice.URL
@@ -79,6 +83,16 @@ func NewICEGatherer(
 		candidateTypes = append(candidateTypes, ice.CandidateTypeRelay)
 	}
 
+	var nat1To1IPCandidateType ice.CandidateType
+	switch nat1To1IPCandidate {
+	case "host":
+		nat1To1IPCandidateType = ice.CandidateTypeHost
+	case "srflx":
+		nat1To1IPCandidateType = ice.CandidateTypeServerReflexive
+	default:
+		nat1To1IPCandidateType = ice.CandidateTypeUnspecified
+	}
+
 	return &ICEGatherer{
 		state:                     ICEGathererStateNew,
 		validatedServers:          validatedServers,
@@ -98,6 +112,8 @@ func NewICEGatherer(
 		prflxAcceptanceMinWait:    prflxAcceptanceMinWait,
 		relayAcceptanceMinWait:    relayAcceptanceMinWait,
 		interfaceFilter:           interfaceFilter,
+		nat1To1IPs:                nat1To1IPs,
+		nat1To1IPCandidateType:    nat1To1IPCandidateType,
 	}, nil
 }
 

icegatherer_test.go

@@ -22,7 +22,7 @@ func TestNewICEGatherer_Success(t *testing.T) {
 		ICEServers: []ICEServer{{URLs: []string{"stun:stun.l.google.com:19302"}}},
 	}
 
-	gatherer, err := NewICEGatherer(0, 0, nil, nil, nil, nil, nil, nil, nil, logging.NewDefaultLoggerFactory(), false, false, nil, func(string) bool { return true }, opts)
+	gatherer, err := NewICEGatherer(0, 0, nil, nil, nil, nil, nil, nil, nil, logging.NewDefaultLoggerFactory(), false, false, nil, func(string) bool { return true }, nil, "", opts)
 	if err != nil {
 		t.Error(err)
 	}
@@ -71,7 +71,7 @@ func TestICEGather_LocalCandidateOrder(t *testing.T) {
 	}
 
 	to := time.Second
-	gatherer, err := NewICEGatherer(10000, 10010, &to, &to, &to, &to, &to, &to, &to, logging.NewDefaultLoggerFactory(), false, false, []NetworkType{NetworkTypeUDP4}, func(string) bool { return true }, opts)
+	gatherer, err := NewICEGatherer(10000, 10010, &to, &to, &to, &to, &to, &to, &to, logging.NewDefaultLoggerFactory(), false, false, []NetworkType{NetworkTypeUDP4}, func(string) bool { return true }, nil, "", opts)
 	if err != nil {
 		t.Error(err)
 	}

settingengine.go

@@ -34,6 +34,8 @@ type SettingEngine struct {
 		ICETrickle         bool
 		ICENetworkTypes    []NetworkType
 		InterfaceFilter    func(string) bool
+		NAT1To1IPs         []string
+		NAT1To1IPCandidate string
 	}
 	LoggerFactory logging.LoggerFactory
 }
@@ -114,3 +116,28 @@ func (e *SettingEngine) SetNetworkTypes(candidateTypes []NetworkType) {
 func (e *SettingEngine) SetInterfaceFilter(filter func(string) bool) {
 	e.candidates.InterfaceFilter = filter
 }
+
+// SetNAT1To1IPs has a list of external IP addresses of 1:1 (D)NAT.
+// This is useful when you are host a server using Pion on an AWS EC2 instance
+// which has a private address, behind a 1:1 DNAT with a public IP (e.g.
+// Elastic IP). In this case, you can give the public IP address so that
+// Pion will use the public IP address in its candidate instead of the private IP
+// address.
+func (e *SettingEngine) SetNAT1To1IPs(ips []string) {
+	e.candidates.NAT1To1IPs = ips
+}
+
+// SetNAT1To1IPCandidate is used along with SetNAT1To1IPs, to tell Pion which
+// type of candidate should use the given public IP address.
+// Two types of candidates are supported:
+// - "host": The public IP address will be used for the host candidate in the SDP.
+// - "srflx": A server reflexive candidate with the given public IP address will be added
+// to the SDP. If you choose "host", then the private IP address won't be advertised with
+// the peer. Also, this option cannot be used along with mDNS.
+// If you choose "srflx", it simply adds a server reflexive candidate with the public IP.
+// The host candidate is still available along with mDNS capabilities unaffected.
+// Please note that you cannot give STUN server URL at the same time. It will result in
+// an error otherwise.
+func (e *SettingEngine) SetNAT1To1IPCandidate(candidate string) {
+	e.candidates.NAT1To1IPCandidate = candidate
+}