TUN-3456: New protocol option auto to automatically select between http2 and h2mux

cmd/cloudflared/tunnel/configuration.go

@@ -11,6 +11,7 @@ import (
 	"github.com/cloudflare/cloudflared/cmd/cloudflared/config"
 	"github.com/cloudflare/cloudflared/cmd/cloudflared/ui"
 	"github.com/cloudflare/cloudflared/connection"
+	"github.com/cloudflare/cloudflared/edgediscovery"
 	"github.com/cloudflare/cloudflared/h2mux"
 	"github.com/cloudflare/cloudflared/ingress"
 	"github.com/cloudflare/cloudflared/logger"
@@ -231,7 +232,11 @@ func prepareTunnelConfig(
 		}
 	}
 
-	protocol := determineProtocol(namedTunnel)
+	protocol, err := determineProtocol(c, namedTunnel)
+	if err != nil {
+		return nil, err
+	}
+	logger.Infof("Using protocol %s", protocol)
 	toEdgeTLSConfig, err := tlsconfig.CreateTunnelConfig(c, protocol.ServerName())
 	if err != nil {
 		logger.Errorf("unable to create TLS config to connect with edge: %s", err)
@@ -293,9 +298,17 @@ func isRunningFromTerminal() bool {
 	return terminal.IsTerminal(int(os.Stdout.Fd()))
 }
 
-func determineProtocol(namedTunnel *connection.NamedTunnelConfig) connection.Protocol {
-	if namedTunnel != nil {
-		return namedTunnel.Protocol
+func determineProtocol(c *cli.Context, namedTunnel *connection.NamedTunnelConfig) (connection.Protocol, error) {
+	if namedTunnel == nil {
+		return connection.H2mux, nil
 	}
-	return connection.H2mux
+	http2Percentage, err := edgediscovery.HTTP2Percentage()
+	if err != nil {
+		return 0, err
+	}
+	protocol, ok := connection.SelectProtocol(c.String("protocol"), namedTunnel.Auth.AccountTag, http2Percentage)
+	if !ok {
+		return 0, fmt.Errorf("%s is not valid protocol. %s", c.String("protocol"), availableProtocol)
+	}
+	return protocol, nil
 }

cmd/cloudflared/tunnel/subcommand_context.go

@@ -260,16 +260,12 @@ func (sc *subcommandContext) run(tunnelID uuid.UUID) error {
 		return err
 	}
 
-	protocol, ok := connection.ParseProtocol(sc.c.String("protocol"))
-	if !ok {
-		return fmt.Errorf("%s is not valid protocol. %s", sc.c.String("protocol"), availableProtocol)
-	}
 	return StartServer(
 		sc.c,
 		version,
 		shutdownC,
 		graceShutdownC,
-		&connection.NamedTunnelConfig{Auth: *credentials, ID: tunnelID, Protocol: protocol},
+		&connection.NamedTunnelConfig{Auth: *credentials, ID: tunnelID},
 		sc.logger,
 		sc.isUIEnabled,
 	)

cmd/cloudflared/tunnel/subcommands.go

@@ -30,7 +30,7 @@ import (
 
 const (
 	credFileFlagAlias = "cred-file"
-	availableProtocol = "Available protocols: http2, Go's implementation and h2mux, Cloudflare's implementation of HTTP/2."
+	availableProtocol = "Available protocols: http2 - Go's implementation, h2mux - Cloudflare's implementation of HTTP/2, and auto - automatically select between http2 and h2mux"
 )
 
 var (
@@ -86,14 +86,14 @@ var (
 		Usage:   "Allows you to delete a tunnel, even if it has active connections.",
 		EnvVars: []string{"TUNNEL_RUN_FORCE_OVERWRITE"},
 	}
-	selectProtocolFlag = &cli.StringFlag{
+	selectProtocolFlag = altsrc.NewStringFlag(&cli.StringFlag{
 		Name:    "protocol",
 		Value:   "h2mux",
 		Aliases: []string{"p"},
 		Usage:   fmt.Sprintf("Protocol implementation to connect with Cloudflare's edge network. %s", availableProtocol),
 		EnvVars: []string{"TUNNEL_TRANSPORT_PROTOCOL"},
 		Hidden:  true,
-	}
+	})
 )
 
 func buildCreateCommand() *cli.Command {

connection/connection.go

@@ -1,6 +1,8 @@
 package connection
 
 import (
+	"fmt"
+	"hash/fnv"
 	"io"
 	"net/http"
 	"strconv"
@@ -25,10 +27,9 @@ type Config struct {
 }
 
 type NamedTunnelConfig struct {
-	Auth     pogs.TunnelAuth
-	ID       uuid.UUID
-	Client   pogs.ClientInfo
-	Protocol Protocol
+	Auth   pogs.TunnelAuth
+	ID     uuid.UUID
+	Client pogs.ClientInfo
 }
 
 type ClassicTunnelConfig struct {
@@ -49,17 +50,28 @@ const (
 	HTTP2
 )
 
-func ParseProtocol(s string) (Protocol, bool) {
+func SelectProtocol(s string, accountTag string, http2Percentage uint32) (Protocol, bool) {
 	switch s {
 	case "h2mux":
 		return H2mux, true
 	case "http2":
 		return HTTP2, true
+	case "auto":
+		if tryHTTP2(accountTag, http2Percentage) {
+			return HTTP2, true
+		}
+		return H2mux, true
 	default:
 		return 0, false
 	}
 }
 
+func tryHTTP2(accountTag string, http2Percentage uint32) bool {
+	h := fnv.New32a()
+	h.Write([]byte(accountTag))
+	return h.Sum32()%100 < http2Percentage
+}
+
 func (p Protocol) ServerName() string {
 	switch p {
 	case H2mux:
@@ -71,6 +83,17 @@ func (p Protocol) ServerName() string {
 	}
 }
 
+func (p Protocol) String() string {
+	switch p {
+	case H2mux:
+		return "h2mux"
+	case HTTP2:
+		return "http2"
+	default:
+		return fmt.Sprintf("unknown protocol")
+	}
+}
+
 type OriginClient interface {
 	Proxy(w ResponseWriter, req *http.Request, isWebsocket bool) error
 }

edgediscovery/protocol.go

@@ -0,0 +1,45 @@
+package edgediscovery
+
+import (
+	"fmt"
+	"net"
+	"strconv"
+	"strings"
+)
+
+const (
+	protocolRecord = "protocol.argotunnel.com"
+)
+
+var (
+	errNoProtocolRecord = fmt.Errorf("No TXT record found for %s to determine connection protocol", protocolRecord)
+)
+
+func HTTP2Percentage() (int32, error) {
+	records, err := net.LookupTXT(protocolRecord)
+	if err != nil {
+		return 0, err
+	}
+	if len(records) == 0 {
+		return 0, errNoProtocolRecord
+	}
+	return parseHTTP2Precentage(records[0])
+}
+
+// The record looks like http2=percentage
+func parseHTTP2Precentage(record string) (int32, error) {
+	const key = "http2"
+	slices := strings.Split(record, "=")
+	if len(slices) != 2 {
+		return 0, fmt.Errorf("Malformed TXT record %s, expect http2=percentage", record)
+	}
+	if slices[0] != key {
+		return 0, fmt.Errorf("Incorrect key %s, expect %s", slices[0], key)
+	}
+	percentage, err := strconv.ParseInt(slices[1], 10, 32)
+	if err != nil {
+		return 0, err
+	}
+	return int32(percentage), nil
+
+}

edgediscovery/protocol_test.go

@@ -0,0 +1,80 @@
+package edgediscovery
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestHTTP2Percentage(t *testing.T) {
+	_, err := HTTP2Percentage()
+	assert.NoError(t, err)
+}
+
+func TestParseHTTP2Precentage(t *testing.T) {
+	tests := []struct {
+		record     string
+		percentage int32
+		wantErr    bool
+	}{
+		{
+			record:     "http2=-1",
+			percentage: -1,
+			wantErr:    false,
+		},
+		{
+			record:     "http2=0",
+			percentage: 0,
+			wantErr:    false,
+		},
+		{
+			record:     "http2=50",
+			percentage: 50,
+			wantErr:    false,
+		},
+		{
+			record:     "http2=100",
+			percentage: 100,
+			wantErr:    false,
+		},
+		{
+			record:     "http2=1000",
+			percentage: 1000,
+			wantErr:    false,
+		},
+		{
+			record:  "http2=10.5",
+			wantErr: true,
+		},
+		{
+			record:  "http2=10 h2mux=90",
+			wantErr: true,
+		},
+		{
+			record:  "http2=ten",
+			wantErr: true,
+		},
+
+		{
+			record:  "h2mux=100",
+			wantErr: true,
+		},
+		{
+			record:  "http2",
+			wantErr: true,
+		},
+		{
+			record:  "http2=",
+			wantErr: true,
+		},
+	}
+
+	for _, test := range tests {
+		p, err := parseHTTP2Precentage(test.record)
+		if test.wantErr {
+			assert.Error(t, err)
+		} else {
+			assert.Equal(t, test.percentage, p)
+		}
+	}
+}

origin/tunnel.go

@@ -238,7 +238,7 @@ func ServeTunnel(
 		fuse:    fuse,
 		backoff: backoff,
 	}
-	if config.NamedTunnel != nil && config.NamedTunnel.Protocol == connection.HTTP2 {
+	if config.Protocol == connection.HTTP2 {
 		connOptions := config.ConnectionOptions(edgeConn.LocalAddr().String(), uint8(backoff.retries))
 		return ServeHTTP2(ctx, config, edgeConn, connOptions, connectionIndex, connectedFuse, reconnectCh)
 	}