feat: Add TURN proxying to enable offline deployments (#1000)

* Add turnconn

* Add option for passing ICE servers

* Log TURN remote address

* Add TURN server to coder start

coderd/turnconn/turnconn_test.go

@@ -0,0 +1,106 @@
+package turnconn_test
+
+import (
+	"net"
+	"sync"
+	"testing"
+
+	"github.com/pion/webrtc/v3"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/goleak"
+
+	"cdr.dev/slog"
+	"cdr.dev/slog/sloggers/slogtest"
+	"github.com/coder/coder/coderd/turnconn"
+	"github.com/coder/coder/peer"
+)
+
+func TestMain(m *testing.M) {
+	goleak.VerifyTestMain(m)
+}
+
+func TestTURNConn(t *testing.T) {
+	t.Parallel()
+	turnServer, err := turnconn.New(nil)
+	require.NoError(t, err)
+	defer turnServer.Close()
+
+	logger := slogtest.Make(t, nil).Leveled(slog.LevelDebug)
+
+	clientDialer, clientTURN := net.Pipe()
+	turnServer.Accept(clientTURN, &net.TCPAddr{
+		IP:   net.IPv4(127, 0, 0, 1),
+		Port: 16000,
+	}, nil)
+	require.NoError(t, err)
+	clientSettings := webrtc.SettingEngine{}
+	clientSettings.SetNetworkTypes([]webrtc.NetworkType{webrtc.NetworkTypeTCP4, webrtc.NetworkTypeTCP6})
+	clientSettings.SetRelayAcceptanceMinWait(0)
+	clientSettings.SetICEProxyDialer(turnconn.ProxyDialer(func() (net.Conn, error) {
+		return clientDialer, nil
+	}))
+	client, err := peer.Client([]webrtc.ICEServer{turnconn.Proxy}, &peer.ConnOptions{
+		SettingEngine: clientSettings,
+		Logger:        logger.Named("client"),
+	})
+	require.NoError(t, err)
+
+	serverDialer, serverTURN := net.Pipe()
+	turnServer.Accept(serverTURN, &net.TCPAddr{
+		IP:   net.IPv4(127, 0, 0, 1),
+		Port: 16001,
+	}, nil)
+	require.NoError(t, err)
+	serverSettings := webrtc.SettingEngine{}
+	serverSettings.SetNetworkTypes([]webrtc.NetworkType{webrtc.NetworkTypeTCP4, webrtc.NetworkTypeTCP6})
+	serverSettings.SetRelayAcceptanceMinWait(0)
+	serverSettings.SetICEProxyDialer(turnconn.ProxyDialer(func() (net.Conn, error) {
+		return serverDialer, nil
+	}))
+	server, err := peer.Server([]webrtc.ICEServer{turnconn.Proxy}, &peer.ConnOptions{
+		SettingEngine: serverSettings,
+		Logger:        logger.Named("server"),
+	})
+	require.NoError(t, err)
+	exchange(t, client, server)
+
+	_, err = client.Ping()
+	require.NoError(t, err)
+}
+
+func exchange(t *testing.T, client, server *peer.Conn) {
+	var wg sync.WaitGroup
+	wg.Add(2)
+	t.Cleanup(func() {
+		_ = client.Close()
+		_ = server.Close()
+
+		wg.Wait()
+	})
+	go func() {
+		defer wg.Done()
+		for {
+			select {
+			case c := <-server.LocalCandidate():
+				client.AddRemoteCandidate(c)
+			case c := <-server.LocalSessionDescription():
+				client.SetRemoteSessionDescription(c)
+			case <-server.Closed():
+				return
+			}
+		}
+	}()
+	go func() {
+		defer wg.Done()
+		for {
+			select {
+			case c := <-client.LocalCandidate():
+				server.AddRemoteCandidate(c)
+			case c := <-client.LocalSessionDescription():
+				server.SetRemoteSessionDescription(c)
+			case <-client.Closed():
+				return
+			}
+		}
+	}()
+}