Exchange proxy mode via signal (#727)

Before defining if we will use direct or proxy connection we will exchange a 
message with the other peer if the modes match we keep the decision 
from the shouldUseProxy function otherwise we skip using direct connection.

Added a feature support message to the signal protocol

client/internal/engine.go

@@ -353,6 +353,10 @@ func signalCandidate(candidate ice.Candidate, myKey wgtypes.Key, remoteKey wgtyp
 	return nil
 }
 
+func sendSignal(message *sProto.Message, s signal.Client) error {
+	return s.Send(message)
+}
+
 // SignalOfferAnswer signals either an offer or an answer to remote peer
 func SignalOfferAnswer(offerAnswer peer.OfferAnswer, myKey wgtypes.Key, remoteKey wgtypes.Key, s signal.Client, isAnswer bool) error {
 	var t sProto.Body_Type
@@ -369,6 +373,10 @@ func SignalOfferAnswer(offerAnswer peer.OfferAnswer, myKey wgtypes.Key, remoteKe
 	if err != nil {
 		return err
 	}
+
+	// indicates message support in gRPC
+	msg.Body.FeaturesSupported = []uint32{signal.DirectCheck}
+
 	err = s.Send(msg)
 	if err != nil {
 		return err
@@ -827,6 +835,9 @@ func (e Engine) createPeerConn(pubKey string, allowedIPs string) (*peer.Conn, er
 	peerConn.SetSignalCandidate(signalCandidate)
 	peerConn.SetSignalOffer(signalOffer)
 	peerConn.SetSignalAnswer(signalAnswer)
+	peerConn.SetSendSignalMessage(func(message *sProto.Message) error {
+		return sendSignal(message, e.signal)
+	})
 
 	return peerConn, nil
 }
@@ -850,6 +861,9 @@ func (e *Engine) receiveSignalEvents() {
 				if err != nil {
 					return err
 				}
+
+				conn.RegisterProtoSupportMeta(msg.Body.GetFeaturesSupported())
+
 				conn.OnRemoteOffer(peer.OfferAnswer{
 					IceCredentials: peer.IceCredentials{
 						UFrag: remoteCred.UFrag,
@@ -863,6 +877,9 @@ func (e *Engine) receiveSignalEvents() {
 				if err != nil {
 					return err
 				}
+
+				conn.RegisterProtoSupportMeta(msg.Body.GetFeaturesSupported())
+
 				conn.OnRemoteAnswer(peer.OfferAnswer{
 					IceCredentials: peer.IceCredentials{
 						UFrag: remoteCred.UFrag,
@@ -878,6 +895,19 @@ func (e *Engine) receiveSignalEvents() {
 					return err
 				}
 				conn.OnRemoteCandidate(candidate)
+			case sProto.Body_MODE:
+				protoMode := msg.GetBody().GetMode()
+				if protoMode == nil {
+					return fmt.Errorf("received an empty mode message")
+				}
+
+				err := conn.OnModeMessage(peer.ModeMessage{
+					Direct: protoMode.GetDirect(),
+				})
+				if err != nil {
+					log.Errorf("failed processing a mode message -> %s", err)
+					return err
+				}
 			}
 
 			return nil

client/internal/peer/conn.go

@@ -2,6 +2,7 @@ package peer
 
 import (
 	"context"
+	"fmt"
 	"net"
 	"strings"
 	"sync"
@@ -14,6 +15,8 @@ import (
 	"github.com/netbirdio/netbird/client/internal/proxy"
 	"github.com/netbirdio/netbird/iface"
 	"github.com/netbirdio/netbird/version"
+	signal "github.com/netbirdio/netbird/signal/client"
+	sProto "github.com/netbirdio/netbird/signal/proto"
 )
 
 // ConnConfig is a peer Connection configuration
@@ -71,6 +74,7 @@ type Conn struct {
 	// signalOffer is a handler function to signal remote peer our connection offer (credentials)
 	signalOffer       func(OfferAnswer) error
 	signalAnswer      func(OfferAnswer) error
+	sendSignalMessage func(message *sProto.Message) error
 
 	// remoteOffersCh is a channel used to wait for remote credentials to proceed with the connection
 	remoteOffersCh chan OfferAnswer
@@ -86,6 +90,19 @@ type Conn struct {
 	statusRecorder *Status
 
 	proxy        proxy.Proxy
+	remoteModeCh chan ModeMessage
+	meta         meta
+}
+
+// meta holds meta information about a connection
+type meta struct {
+	protoSupport signal.FeaturesSupport
+}
+
+// ModeMessage represents a connection mode chosen by the peer
+type ModeMessage struct {
+	// Direct indicates that it decided to use a direct connection
+	Direct bool
 }
 
 // GetConf returns the connection config
@@ -109,6 +126,7 @@ func NewConn(config ConnConfig, statusRecorder *Status) (*Conn, error) {
 		remoteOffersCh: make(chan OfferAnswer),
 		remoteAnswerCh: make(chan OfferAnswer),
 		statusRecorder: statusRecorder,
+		remoteModeCh:   make(chan ModeMessage, 1),
 	}, nil
 }
 
@@ -366,15 +384,7 @@ func (conn *Conn) startProxy(remoteConn net.Conn, remoteWgPort int) error {
 	}
 
 	peerState := State{PubKey: conn.config.Key}
-	useProxy := shouldUseProxy(pair)
+	p := conn.getProxyWithMessageExchange(pair, remoteWgPort)
-	var p proxy.Proxy
-	if useProxy {
-		p = proxy.NewWireguardProxy(conn.config.ProxyConfig)
-		peerState.Direct = false
-	} else {
-		p = proxy.NewNoProxy(conn.config.ProxyConfig, remoteWgPort)
-		peerState.Direct = true
-	}
 	conn.proxy = p
 	err = p.Start(remoteConn)
 	if err != nil {
@@ -390,6 +400,7 @@ func (conn *Conn) startProxy(remoteConn net.Conn, remoteWgPort int) error {
 	if pair.Local.Type() == ice.CandidateTypeRelay || pair.Remote.Type() == ice.CandidateTypeRelay {
 		peerState.Relayed = true
 	}
+	peerState.Direct = p.Type() == proxy.TypeNoProxy
 
 	err = conn.statusRecorder.UpdatePeerState(peerState)
 	if err != nil {
@@ -399,6 +410,63 @@ func (conn *Conn) startProxy(remoteConn net.Conn, remoteWgPort int) error {
 	return nil
 }
 
+func (conn *Conn) getProxyWithMessageExchange(pair *ice.CandidatePair, remoteWgPort int) proxy.Proxy {
+
+	useProxy := shouldUseProxy(pair)
+	localDirectMode := !useProxy
+	remoteDirectMode := localDirectMode
+
+	if conn.meta.protoSupport.DirectCheck {
+		go conn.sendLocalDirectMode(localDirectMode)
+		// will block until message received or timeout
+		remoteDirectMode = conn.receiveRemoteDirectMode()
+	}
+
+	if localDirectMode && remoteDirectMode {
+		log.Debugf("using WireGuard direct mode with peer %s", conn.config.Key)
+		return proxy.NewNoProxy(conn.config.ProxyConfig, remoteWgPort)
+	}
+
+	log.Debugf("falling back to local proxy mode with peer %s", conn.config.Key)
+	return proxy.NewWireguardProxy(conn.config.ProxyConfig)
+}
+
+func (conn *Conn) sendLocalDirectMode(localMode bool) {
+	// todo what happens when we couldn't deliver this message?
+	// we could retry, etc but there is no guarantee
+
+	err := conn.sendSignalMessage(&sProto.Message{
+		Key:       conn.config.LocalKey,
+		RemoteKey: conn.config.Key,
+		Body: &sProto.Body{
+			Type: sProto.Body_MODE,
+			Mode: &sProto.Mode{
+				Direct: &localMode,
+			},
+			NetBirdVersion: version.NetbirdVersion(),
+		},
+	})
+	if err != nil {
+		log.Errorf("failed to send local proxy mode to remote peer %s, error: %s", conn.config.Key, err)
+	}
+}
+
+func (conn *Conn) receiveRemoteDirectMode() bool {
+	timeout := time.Second
+	timer := time.NewTimer(timeout)
+	defer timer.Stop()
+
+	select {
+	case receivedMSG := <-conn.remoteModeCh:
+		return receivedMSG.Direct
+	case <-timer.C:
+		// we didn't receive a message from remote so we assume that it supports the direct mode to keep the old behaviour
+		log.Debugf("timeout after %s while waiting for remote direct mode message from remote peer %s",
+			timeout, conn.config.Key)
+		return true
+	}
+}
+
 // cleanup closes all open resources and sets status to StatusDisconnected
 func (conn *Conn) cleanup() error {
 	log.Debugf("trying to cleanup %s", conn.config.Key)
@@ -459,6 +527,11 @@ func (conn *Conn) SetSignalCandidate(handler func(candidate ice.Candidate) error
 	conn.signalCandidate = handler
 }
 
+// SetSendSignalMessage sets a handler function to be triggered by Conn when there is new message to send via signal
+func (conn *Conn) SetSendSignalMessage(handler func(message *sProto.Message) error) {
+	conn.sendSignalMessage = handler
+}
+
 // onICECandidate is a callback attached to an ICE Agent to receive new local connection candidates
 // and then signals them to the remote peer
 func (conn *Conn) onICECandidate(candidate ice.Candidate) {
@@ -613,3 +686,19 @@ func (conn *Conn) OnRemoteCandidate(candidate ice.Candidate) {
 func (conn *Conn) GetKey() string {
 	return conn.config.Key
 }
+
+// OnModeMessage unmarshall the payload message and send it to the mode message channel
+func (conn *Conn) OnModeMessage(message ModeMessage) error {
+	select {
+	case conn.remoteModeCh <- message:
+		return nil
+	default:
+		return fmt.Errorf("unable to process mode message: channel busy")
+	}
+}
+
+// RegisterProtoSupportMeta register supported proto message in the connection metadata
+func (conn *Conn) RegisterProtoSupportMeta(support []uint32) {
+	protoSupport := signal.ParseFeaturesSupported(support)
+	conn.meta.protoSupport = protoSupport
+}

client/internal/peer/conn_test.go

@@ -7,9 +7,11 @@ import (
 
 	"github.com/magiconair/properties/assert"
 	"github.com/pion/ice/v2"
+	"golang.org/x/sync/errgroup"
 
 	"github.com/netbirdio/netbird/client/internal/proxy"
 	"github.com/netbirdio/netbird/iface"
+	sproto "github.com/netbirdio/netbird/signal/proto"
 )
 
 var connConf = ConnConfig{
@@ -329,3 +331,110 @@ func TestConn_ShouldUseProxy(t *testing.T) {
 		})
 	}
 }
+
+func TestGetProxyWithMessageExchange(t *testing.T) {
+	publicHostCandidate := &mockICECandidate{
+		AddressFunc: func() string {
+			return "8.8.8.8"
+		},
+		TypeFunc: func() ice.CandidateType {
+			return ice.CandidateTypeHost
+		},
+	}
+	relayCandidate := &mockICECandidate{
+		AddressFunc: func() string {
+			return "1.1.1.1"
+		},
+		TypeFunc: func() ice.CandidateType {
+			return ice.CandidateTypeRelay
+		},
+	}
+
+	testCases := []struct {
+		name                   string
+		candatePair            *ice.CandidatePair
+		inputDirectModeSupport bool
+		inputRemoteModeMessage bool
+		expected               proxy.Type
+	}{
+		{
+			name: "Should Result In Using Wireguard Proxy When Local Eval Is Use Proxy",
+			candatePair: &ice.CandidatePair{
+				Local:  relayCandidate,
+				Remote: publicHostCandidate,
+			},
+			inputDirectModeSupport: true,
+			inputRemoteModeMessage: true,
+			expected:               proxy.TypeWireguard,
+		},
+		{
+			name: "Should Result In Using Wireguard Proxy When Remote Eval Is Use Proxy",
+			candatePair: &ice.CandidatePair{
+				Local:  publicHostCandidate,
+				Remote: publicHostCandidate,
+			},
+			inputDirectModeSupport: true,
+			inputRemoteModeMessage: false,
+			expected:               proxy.TypeWireguard,
+		},
+		{
+			name: "Should Result In Using Wireguard Proxy When Remote Direct Mode Support Is False And Local Eval Is Use Proxy",
+			candatePair: &ice.CandidatePair{
+				Local:  relayCandidate,
+				Remote: publicHostCandidate,
+			},
+			inputDirectModeSupport: false,
+			inputRemoteModeMessage: false,
+			expected:               proxy.TypeWireguard,
+		},
+		{
+			name: "Should Result In Using Direct When Remote Direct Mode Support Is False And Local Eval Is No Use Proxy",
+			candatePair: &ice.CandidatePair{
+				Local:  publicHostCandidate,
+				Remote: publicHostCandidate,
+			},
+			inputDirectModeSupport: false,
+			inputRemoteModeMessage: false,
+			expected:               proxy.TypeNoProxy,
+		},
+		{
+			name: "Should Result In Using Direct When Local And Remote Eval Is No Proxy",
+			candatePair: &ice.CandidatePair{
+				Local:  publicHostCandidate,
+				Remote: publicHostCandidate,
+			},
+			inputDirectModeSupport: true,
+			inputRemoteModeMessage: true,
+			expected:               proxy.TypeNoProxy,
+		},
+	}
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			g := errgroup.Group{}
+			conn, err := NewConn(connConf, nil)
+			if err != nil {
+				t.Fatal(err)
+			}
+			conn.meta.protoSupport.DirectCheck = testCase.inputDirectModeSupport
+			conn.SetSendSignalMessage(func(message *sproto.Message) error {
+				return nil
+			})
+
+			g.Go(func() error {
+				return conn.OnModeMessage(ModeMessage{
+					Direct: testCase.inputRemoteModeMessage,
+				})
+			})
+
+			resultProxy := conn.getProxyWithMessageExchange(testCase.candatePair, 1000)
+
+			err = g.Wait()
+			if err != nil {
+				t.Error(err)
+			}
+			if resultProxy.Type() != testCase.expected {
+				t.Errorf("result didn't match expected value: Expected: %s, Got: %s", testCase.expected, resultProxy.Type())
+			}
+		})
+	}
+}

go.mod

@@ -55,6 +55,7 @@ require (
 	go.opentelemetry.io/otel/metric v0.33.0
 	go.opentelemetry.io/otel/sdk/metric v0.33.0
 	golang.org/x/net v0.8.0
+	golang.org/x/sync v0.1.0
 	golang.org/x/term v0.6.0
 	gopkg.in/yaml.v3 v3.0.1
 )
@@ -128,7 +129,6 @@ require (
 	golang.org/x/exp v0.0.0-20220518171630-0b5c67f07fdf // indirect
 	golang.org/x/image v0.0.0-20200430140353-33d19683fad8 // indirect
 	golang.org/x/mod v0.8.0 // indirect
-	golang.org/x/sync v0.1.0 // indirect
 	golang.org/x/text v0.8.0 // indirect
 	golang.org/x/tools v0.6.0 // indirect
 	golang.zx2c4.com/go118/netip v0.0.0-20211111135330-a4a02eeacf9d // indirect

signal/client/client.go

@@ -19,6 +19,16 @@ type Status string
 const StreamConnected Status = "Connected"
 const StreamDisconnected Status = "Disconnected"
 
+const (
+	// DirectCheck indicates support to direct mode checks
+	DirectCheck uint32 = 1
+)
+
+// FeaturesSupport register protocol supported features
+type FeaturesSupport struct {
+	DirectCheck bool
+}
+
 type Client interface {
 	io.Closer
 	StreamConnected() bool
@@ -62,3 +72,15 @@ type Credential struct {
 	UFrag string
 	Pwd   string
 }
+
+// ParseFeaturesSupported parses a slice of supported features into FeaturesSupport
+func ParseFeaturesSupported(featuresMessage []uint32) FeaturesSupport {
+	var protoSupport FeaturesSupport
+	for _, feature := range featuresMessage {
+		if feature == DirectCheck {
+			protoSupport.DirectCheck = true
+			return protoSupport
+		}
+	}
+	return protoSupport
+}

signal/client/client_test.go

@@ -2,8 +2,11 @@ package client
 
 import (
 	"context"
-	sigProto "github.com/netbirdio/netbird/signal/proto"
+	"net"
-	"github.com/netbirdio/netbird/signal/server"
+	"sync"
+	"testing"
+	"time"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 	log "github.com/sirupsen/logrus"
@@ -12,9 +15,9 @@ import (
 	"google.golang.org/grpc/credentials/insecure"
 	"google.golang.org/grpc/keepalive"
 	"google.golang.org/grpc/metadata"
-	"net"
+
-	"sync"
+	sigProto "github.com/netbirdio/netbird/signal/proto"
-	"time"
+	"github.com/netbirdio/netbird/signal/server"
 )
 
 var _ = Describe("GrpcClient", func() {
@@ -43,15 +46,18 @@ var _ = Describe("GrpcClient", func() {
 				var msgReceived sync.WaitGroup
 				msgReceived.Add(2)
 
-				var receivedOnA string
+				var payloadReceivedOnA string
-				var receivedOnB string
+				var payloadReceivedOnB string
+				var featuresSupportedReceivedOnA []uint32
+				var featuresSupportedReceivedOnB []uint32
 
 				// connect PeerA to Signal
 				keyA, _ := wgtypes.GenerateKey()
 				clientA := createSignalClient(addr, keyA)
 				go func() {
 					err := clientA.Receive(func(msg *sigProto.Message) error {
-						receivedOnA = msg.GetBody().GetPayload()
+						payloadReceivedOnA = msg.GetBody().GetPayload()
+						featuresSupportedReceivedOnA = msg.GetBody().GetFeaturesSupported()
 						msgReceived.Done()
 						return nil
 					})
@@ -67,7 +73,8 @@ var _ = Describe("GrpcClient", func() {
 
 				go func() {
 					err := clientB.Receive(func(msg *sigProto.Message) error {
-						receivedOnB = msg.GetBody().GetPayload()
+						payloadReceivedOnB = msg.GetBody().GetPayload()
+						featuresSupportedReceivedOnB = msg.GetBody().GetFeaturesSupported()
 						err := clientB.Send(&sigProto.Message{
 							Key:       keyB.PublicKey().String(),
 							RemoteKey: keyA.PublicKey().String(),
@@ -90,7 +97,7 @@ var _ = Describe("GrpcClient", func() {
 				err := clientA.Send(&sigProto.Message{
 					Key:       keyA.PublicKey().String(),
 					RemoteKey: keyB.PublicKey().String(),
-					Body:      &sigProto.Body{Payload: "ping"},
+					Body:      &sigProto.Body{Payload: "ping", FeaturesSupported: []uint32{DirectCheck}},
 				})
 				if err != nil {
 					Fail("failed sending a message to PeerB")
@@ -100,9 +107,10 @@ var _ = Describe("GrpcClient", func() {
 					Fail("test timed out on waiting for peers to exchange messages")
 				}
 
-				Expect(receivedOnA).To(BeEquivalentTo("pong"))
+				Expect(payloadReceivedOnA).To(BeEquivalentTo("pong"))
-				Expect(receivedOnB).To(BeEquivalentTo("ping"))
+				Expect(payloadReceivedOnB).To(BeEquivalentTo("ping"))
-
+				Expect(featuresSupportedReceivedOnA).To(BeNil())
+				Expect(featuresSupportedReceivedOnB).To(ContainElements([]uint32{DirectCheck}))
 			})
 		})
 	})
@@ -160,6 +168,41 @@ var _ = Describe("GrpcClient", func() {
 
 })
 
+func TestParseFeaturesSupported(t *testing.T) {
+	expectedOnEmptyOrUnsupported := FeaturesSupport{DirectCheck: false}
+	expectedWithDirectCheck := FeaturesSupport{DirectCheck: true}
+	testCases := []struct {
+		name     string
+		input    []uint32
+		expected FeaturesSupport
+	}{
+		{
+			name:     "Should Return DirectCheck Supported",
+			input:    []uint32{DirectCheck},
+			expected: expectedWithDirectCheck,
+		},
+		{
+			name:     "Should Return DirectCheck Unsupported When Nil",
+			input:    nil,
+			expected: expectedOnEmptyOrUnsupported,
+		},
+		{
+			name:     "Should Return DirectCheck Unsupported When Not Known Feature",
+			input:    []uint32{9999},
+			expected: expectedOnEmptyOrUnsupported,
+		},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.name, func(t *testing.T) {
+			result := ParseFeaturesSupported(testCase.input)
+			if result.DirectCheck != testCase.expected.DirectCheck {
+				t.Errorf("Direct check feature should match: Expected: %t, Got: %t", testCase.expected.DirectCheck, result.DirectCheck)
+			}
+		})
+	}
+}
+
 func createSignalClient(addr string, key wgtypes.Key) *GrpcClient {
 	var sigTLSEnabled = false
 	client, err := NewClient(context.Background(), addr, key, sigTLSEnabled)

signal/proto/generate.sh

@@ -1,4 +1,17 @@
 #!/bin/bash
+set -e
+
+if ! which realpath > /dev/null 2>&1
+then
+  echo realpath is not installed
+  echo run: brew install coreutils
+  exit 1
+fi
+
+old_pwd=$(pwd)
+script_path=$(dirname $(realpath "$0"))
+cd "$script_path"
 go install google.golang.org/protobuf/cmd/protoc-gen-go@v1.26
 go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@v1.1
-protoc -I proto/ proto/signalexchange.proto --go_out=. --go-grpc_out=.
+protoc -I ./ ./signalexchange.proto --go_out=../ --go-grpc_out=../
+cd "$old_pwd"

signal/proto/signalexchange.pb.go

@@ -1,15 +1,15 @@
 // Code generated by protoc-gen-go. DO NOT EDIT.
 // versions:
 // 	protoc-gen-go v1.26.0
-// 	protoc        v3.12.4
+// 	protoc        v3.21.9
 // source: signalexchange.proto
 
 package proto
 
 import (
-	_ "github.com/golang/protobuf/protoc-gen-go/descriptor"
 	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
 	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
+	_ "google.golang.org/protobuf/types/descriptorpb"
 	reflect "reflect"
 	sync "sync"
 )
@@ -28,6 +28,7 @@ const (
 	Body_OFFER     Body_Type = 0
 	Body_ANSWER    Body_Type = 1
 	Body_CANDIDATE Body_Type = 2
+	Body_MODE      Body_Type = 4
 )
 
 // Enum value maps for Body_Type.
@@ -36,11 +37,13 @@ var (
 		0: "OFFER",
 		1: "ANSWER",
 		2: "CANDIDATE",
+		4: "MODE",
 	}
 	Body_Type_value = map[string]int32{
 		"OFFER":     0,
 		"ANSWER":    1,
 		"CANDIDATE": 2,
+		"MODE":      4,
 	}
 )
 
@@ -217,6 +220,9 @@ type Body struct {
 	// wgListenPort is an actual WireGuard listen port
 	WgListenPort   uint32 `protobuf:"varint,3,opt,name=wgListenPort,proto3" json:"wgListenPort,omitempty"`
 	NetBirdVersion string `protobuf:"bytes,4,opt,name=netBirdVersion,proto3" json:"netBirdVersion,omitempty"`
+	Mode           *Mode  `protobuf:"bytes,5,opt,name=mode,proto3" json:"mode,omitempty"`
+	// featuresSupported list of supported features by the client of this protocol
+	FeaturesSupported []uint32 `protobuf:"varint,6,rep,packed,name=featuresSupported,proto3" json:"featuresSupported,omitempty"`
 }
 
 func (x *Body) Reset() {
@@ -279,6 +285,68 @@ func (x *Body) GetNetBirdVersion() string {
 	return ""
 }
 
+func (x *Body) GetMode() *Mode {
+	if x != nil {
+		return x.Mode
+	}
+	return nil
+}
+
+func (x *Body) GetFeaturesSupported() []uint32 {
+	if x != nil {
+		return x.FeaturesSupported
+	}
+	return nil
+}
+
+// Mode indicates a connection mode
+type Mode struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	Direct *bool `protobuf:"varint,1,opt,name=direct,proto3,oneof" json:"direct,omitempty"`
+}
+
+func (x *Mode) Reset() {
+	*x = Mode{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_signalexchange_proto_msgTypes[3]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *Mode) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*Mode) ProtoMessage() {}
+
+func (x *Mode) ProtoReflect() protoreflect.Message {
+	mi := &file_signalexchange_proto_msgTypes[3]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use Mode.ProtoReflect.Descriptor instead.
+func (*Mode) Descriptor() ([]byte, []int) {
+	return file_signalexchange_proto_rawDescGZIP(), []int{3}
+}
+
+func (x *Mode) GetDirect() bool {
+	if x != nil && x.Direct != nil {
+		return *x.Direct
+	}
+	return false
+}
+
 var File_signalexchange_proto protoreflect.FileDescriptor
 
 var file_signalexchange_proto_rawDesc = []byte{
@@ -298,7 +366,7 @@ var file_signalexchange_proto_rawDesc = []byte{
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@@ -308,22 +376,32 @@ var file_signalexchange_proto_rawDesc = []byte{
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+	0x33,
 }
 
 var (
@@ -339,25 +417,27 @@ func file_signalexchange_proto_rawDescGZIP() []byte {
 }
 
 var file_signalexchange_proto_enumTypes = make([]protoimpl.EnumInfo, 1)
-var file_signalexchange_proto_msgTypes = make([]protoimpl.MessageInfo, 3)
+var file_signalexchange_proto_msgTypes = make([]protoimpl.MessageInfo, 4)
 var file_signalexchange_proto_goTypes = []interface{}{
 	(Body_Type)(0),           // 0: signalexchange.Body.Type
 	(*EncryptedMessage)(nil), // 1: signalexchange.EncryptedMessage
 	(*Message)(nil),          // 2: signalexchange.Message
 	(*Body)(nil),             // 3: signalexchange.Body
+	(*Mode)(nil),             // 4: signalexchange.Mode
 }
 var file_signalexchange_proto_depIdxs = []int32{
 	3, // 0: signalexchange.Message.body:type_name -> signalexchange.Body
 	0, // 1: signalexchange.Body.type:type_name -> signalexchange.Body.Type
-	1, // 2: signalexchange.SignalExchange.Send:input_type -> signalexchange.EncryptedMessage
+	4, // 2: signalexchange.Body.mode:type_name -> signalexchange.Mode
-	1, // 3: signalexchange.SignalExchange.ConnectStream:input_type -> signalexchange.EncryptedMessage
+	1, // 3: signalexchange.SignalExchange.Send:input_type -> signalexchange.EncryptedMessage
-	1, // 4: signalexchange.SignalExchange.Send:output_type -> signalexchange.EncryptedMessage
+	1, // 4: signalexchange.SignalExchange.ConnectStream:input_type -> signalexchange.EncryptedMessage
-	1, // 5: signalexchange.SignalExchange.ConnectStream:output_type -> signalexchange.EncryptedMessage
+	1, // 5: signalexchange.SignalExchange.Send:output_type -> signalexchange.EncryptedMessage
-	4, // [4:6] is the sub-list for method output_type
+	1, // 6: signalexchange.SignalExchange.ConnectStream:output_type -> signalexchange.EncryptedMessage
-	2, // [2:4] is the sub-list for method input_type
+	5, // [5:7] is the sub-list for method output_type
-	2, // [2:2] is the sub-list for extension type_name
+	3, // [3:5] is the sub-list for method input_type
-	2, // [2:2] is the sub-list for extension extendee
+	3, // [3:3] is the sub-list for extension type_name
-	0, // [0:2] is the sub-list for field type_name
+	3, // [3:3] is the sub-list for extension extendee
+	0, // [0:3] is the sub-list for field type_name
 }
 
 func init() { file_signalexchange_proto_init() }
@@ -402,14 +482,27 @@ func file_signalexchange_proto_init() {
 				return nil
 			}
 		}
+		file_signalexchange_proto_msgTypes[3].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*Mode); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
 			}
+		}
+	}
+	file_signalexchange_proto_msgTypes[3].OneofWrappers = []interface{}{}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
 		File: protoimpl.DescBuilder{
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: file_signalexchange_proto_rawDesc,
 			NumEnums:      1,
-			NumMessages:   3,
+			NumMessages:   4,
 			NumExtensions: 0,
 			NumServices:   1,
 		},

signal/proto/signalexchange.proto

@@ -46,10 +46,20 @@ message Body {
     OFFER = 0;
     ANSWER = 1;
     CANDIDATE = 2;
+    MODE = 4;
   }
   Type type = 1;
   string payload = 2;
   // wgListenPort is an actual WireGuard listen port
   uint32 wgListenPort = 3;
   string netBirdVersion = 4;
+  Mode mode = 5;
+
+  // featuresSupported list of supported features by the client of this protocol
+  repeated uint32 featuresSupported = 6;
+}
+
+// Mode indicates a connection mode
+message Mode {
+  optional bool direct = 1;
 }