TUN-6938: Force h2mux protocol to http2 for named tunnels

Going forward, the only protocols supported will be QUIC and HTTP2,
defaulting to QUIC for "auto". Selecting h2mux protocol will be forcibly
upgraded to http2 internally.

connection/protocol.go

@@ -1,7 +1,6 @@
 package connection
 
 import (
-	"errors"
 	"fmt"
 	"hash/fnv"
 	"sync"
@@ -13,7 +12,7 @@ import (
 )
 
 const (
-	AvailableProtocolFlagMessage = "Available protocols: 'auto' - automatically chooses the best protocol over time (the default; and also the recommended one); 'quic' - based on QUIC, relying on UDP egress to Cloudflare edge; 'http2' - using Go's HTTP2 library, relying on TCP egress to Cloudflare edge; 'h2mux' - Cloudflare's implementation of HTTP/2, deprecated"
+	AvailableProtocolFlagMessage = "Available protocols: 'auto' - automatically chooses the best protocol over time (the default; and also the recommended one); 'quic' - based on QUIC, relying on UDP egress to Cloudflare edge; 'http2' - using Go's HTTP2 library, relying on TCP egress to Cloudflare edge"
 	// edgeH2muxTLSServerName is the server name to establish h2mux connection with edge
 	edgeH2muxTLSServerName = "cftunnel.com"
 	// edgeH2TLSServerName is the server name to establish http2 connection with edge
@@ -21,43 +20,31 @@ const (
 	// edgeQUICServerName is the server name to establish quic connection with edge.
 	edgeQUICServerName = "quic.cftunnel.com"
 	AutoSelectFlag     = "auto"
+	// SRV and TXT record resolution TTL
+	ResolveTTL = time.Hour
 )
 
 var (
 	// ProtocolList represents a list of supported protocols for communication with the edge.
-	ProtocolList = []Protocol{H2mux, HTTP2, HTTP2Warp, QUIC, QUICWarp}
+	ProtocolList = []Protocol{HTTP2, QUIC}
 )
 
 type Protocol int64
 
 const (
-	// H2mux protocol can be used both with Classic and Named Tunnels. .
-	H2mux Protocol = iota
-	// HTTP2 is used only with named tunnels. It's more efficient than H2mux for L4 proxying.
-	HTTP2
-	// QUIC is used only with named tunnels.
+	// HTTP2 using golang HTTP2 library for edge connections.
+	HTTP2 Protocol = iota
+	// QUIC using quic-go for edge connections.
 	QUIC
-	// HTTP2Warp is used only with named tunnels. It's useful for warp-routing where we don't want to fallback to
-	// H2mux on HTTP2 failure to connect.
-	HTTP2Warp
-	//QUICWarp is used only with named tunnels. It's useful for warp-routing where we want to fallback to HTTP2 but
-	// don't want HTTP2 to fallback to H2mux
-	QUICWarp
 )
 
 // Fallback returns the fallback protocol and whether the protocol has a fallback
 func (p Protocol) fallback() (Protocol, bool) {
 	switch p {
-	case H2mux:
-		return 0, false
 	case HTTP2:
-		return H2mux, true
-	case HTTP2Warp:
 		return 0, false
 	case QUIC:
 		return HTTP2, true
-	case QUICWarp:
-		return HTTP2Warp, true
 	default:
 		return 0, false
 	}
@@ -65,11 +52,9 @@ func (p Protocol) fallback() (Protocol, bool) {
 
 func (p Protocol) String() string {
 	switch p {
-	case H2mux:
-		return "h2mux"
-	case HTTP2, HTTP2Warp:
+	case HTTP2:
 		return "http2"
-	case QUIC, QUICWarp:
+	case QUIC:
 		return "quic"
 	default:
 		return fmt.Sprintf("unknown protocol")
@@ -78,15 +63,11 @@ func (p Protocol) String() string {
 
 func (p Protocol) TLSSettings() *TLSSettings {
 	switch p {
-	case H2mux:
-		return &TLSSettings{
-			ServerName: edgeH2muxTLSServerName,
-		}
-	case HTTP2, HTTP2Warp:
+	case HTTP2:
 		return &TLSSettings{
 			ServerName: edgeH2TLSServerName,
 		}
-	case QUIC, QUICWarp:
+	case QUIC:
 		return &TLSSettings{
 			ServerName: edgeQUICServerName,
 			NextProtos: []string{"argotunnel"},
@@ -106,6 +87,7 @@ type ProtocolSelector interface {
 	Fallback() (Protocol, bool)
 }
 
+// staticProtocolSelector will not provide a different protocol for Fallback
 type staticProtocolSelector struct {
 	current Protocol
 }
@@ -115,10 +97,11 @@ func (s *staticProtocolSelector) Current() Protocol {
 }
 
 func (s *staticProtocolSelector) Fallback() (Protocol, bool) {
-	return 0, false
+	return s.current, false
 }
 
-type autoProtocolSelector struct {
+// remoteProtocolSelector will fetch a list of remote protocols to provide for edge discovery
+type remoteProtocolSelector struct {
 	lock sync.RWMutex
 
 	current Protocol
@@ -127,23 +110,21 @@ type autoProtocolSelector struct {
 	protocolPool []Protocol
 
 	switchThreshold int32
-	fetchFunc       PercentageFetcher
+	fetchFunc       edgediscovery.PercentageFetcher
 	refreshAfter    time.Time
 	ttl             time.Duration
 	log             *zerolog.Logger
-	needPQ          bool
 }
 
-func newAutoProtocolSelector(
+func newRemoteProtocolSelector(
 	current Protocol,
 	protocolPool []Protocol,
 	switchThreshold int32,
-	fetchFunc PercentageFetcher,
+	fetchFunc edgediscovery.PercentageFetcher,
 	ttl time.Duration,
 	log *zerolog.Logger,
-	needPQ bool,
-) *autoProtocolSelector {
-	return &autoProtocolSelector{
+) *remoteProtocolSelector {
+	return &remoteProtocolSelector{
 		current:         current,
 		protocolPool:    protocolPool,
 		switchThreshold: switchThreshold,
@@ -151,11 +132,10 @@ func newAutoProtocolSelector(
 		refreshAfter:    time.Now().Add(ttl),
 		ttl:             ttl,
 		log:             log,
-		needPQ:          needPQ,
 	}
 }
 
-func (s *autoProtocolSelector) Current() Protocol {
+func (s *remoteProtocolSelector) Current() Protocol {
 	s.lock.Lock()
 	defer s.lock.Unlock()
 	if time.Now().Before(s.refreshAfter) {
@@ -173,7 +153,13 @@ func (s *autoProtocolSelector) Current() Protocol {
 	return s.current
 }
 
-func getProtocol(protocolPool []Protocol, fetchFunc PercentageFetcher, switchThreshold int32) (Protocol, error) {
+func (s *remoteProtocolSelector) Fallback() (Protocol, bool) {
+	s.lock.RLock()
+	defer s.lock.RUnlock()
+	return s.current.fallback()
+}
+
+func getProtocol(protocolPool []Protocol, fetchFunc edgediscovery.PercentageFetcher, switchThreshold int32) (Protocol, error) {
 	protocolPercentages, err := fetchFunc()
 	if err != nil {
 		return 0, err
@@ -188,109 +174,74 @@ func getProtocol(protocolPool []Protocol, fetchFunc PercentageFetcher, switchThr
 	return protocolPool[len(protocolPool)-1], nil
 }
 
-func (s *autoProtocolSelector) Fallback() (Protocol, bool) {
+// defaultProtocolSelector will allow for a protocol to have a fallback
+type defaultProtocolSelector struct {
+	lock    sync.RWMutex
+	current Protocol
+}
+
+func newDefaultProtocolSelector(
+	current Protocol,
+) *defaultProtocolSelector {
+	return &defaultProtocolSelector{
+		current: current,
+	}
+}
+
+func (s *defaultProtocolSelector) Current() Protocol {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+	return s.current
+}
+
+func (s *defaultProtocolSelector) Fallback() (Protocol, bool) {
 	s.lock.RLock()
 	defer s.lock.RUnlock()
-	if s.needPQ {
-		return 0, false
-	}
 	return s.current.fallback()
 }
 
-type PercentageFetcher func() (edgediscovery.ProtocolPercents, error)
-
 func NewProtocolSelector(
 	protocolFlag string,
-	warpRoutingEnabled bool,
-	namedTunnel *NamedTunnelProperties,
-	fetchFunc PercentageFetcher,
-	ttl time.Duration,
-	log *zerolog.Logger,
+	accountTag string,
+	tunnelTokenProvided bool,
 	needPQ bool,
+	protocolFetcher edgediscovery.PercentageFetcher,
+	resolveTTL time.Duration,
+	log *zerolog.Logger,
 ) (ProtocolSelector, error) {
-	// Classic tunnel is only supported with h2mux
-	if namedTunnel == nil {
-		if needPQ {
-			return nil, errors.New("Classic tunnel does not support post-quantum")
-		}
-
+	// With --post-quantum, we force quic
+	if needPQ {
 		return &staticProtocolSelector{
-			current: H2mux,
+			current: QUIC,
 		}, nil
 	}
 
-	threshold := switchThreshold(namedTunnel.Credentials.AccountTag)
-	fetchedProtocol, err := getProtocol([]Protocol{QUIC, HTTP2}, fetchFunc, threshold)
-	if err != nil && protocolFlag == "auto" {
-		log.Err(err).Msg("Unable to lookup protocol. Defaulting to `http2`. If this fails, you can attempt `--protocol quic` instead.")
-		if needPQ {
-			return nil, errors.New("http2 does not support post-quantum")
-		}
-		return &staticProtocolSelector{
-			current: HTTP2,
-		}, nil
-	}
-	if warpRoutingEnabled {
-		if protocolFlag == H2mux.String() || fetchedProtocol == H2mux {
-			log.Warn().Msg("Warp routing is not supported in h2mux protocol. Upgrading to http2 to allow it.")
-			protocolFlag = HTTP2.String()
-			fetchedProtocol = HTTP2Warp
-		}
-		return selectWarpRoutingProtocols(protocolFlag, fetchFunc, ttl, log, threshold, fetchedProtocol, needPQ)
+	// When a --token is provided, we want to start with QUIC but have fallback to HTTP2
+	if tunnelTokenProvided {
+		return newDefaultProtocolSelector(QUIC), nil
 	}
 
-	return selectNamedTunnelProtocols(protocolFlag, fetchFunc, ttl, log, threshold, fetchedProtocol, needPQ)
-}
+	threshold := switchThreshold(accountTag)
+	fetchedProtocol, err := getProtocol(ProtocolList, protocolFetcher, threshold)
+	if err != nil {
+		log.Warn().Msg("Unable to lookup protocol percentage.")
+		// Falling through here since 'auto' is handled in the switch and failing
+		// to do the protocol lookup isn't a failure since it can be triggered again
+		// after the TTL.
+	}
 
-func selectNamedTunnelProtocols(
-	protocolFlag string,
-	fetchFunc PercentageFetcher,
-	ttl time.Duration,
-	log *zerolog.Logger,
-	threshold int32,
-	protocol Protocol,
-	needPQ bool,
-) (ProtocolSelector, error) {
 	// If the user picks a protocol, then we stick to it no matter what.
 	switch protocolFlag {
-	case H2mux.String():
-		return &staticProtocolSelector{current: H2mux}, nil
+	case "h2mux":
+		// Any users still requesting h2mux will be upgraded to http2 instead
+		log.Warn().Msg("h2mux is no longer a supported protocol: upgrading edge connection to http2. Please remove '--protocol h2mux' from runtime arguments to remove this warning.")
+		return &staticProtocolSelector{current: HTTP2}, nil
 	case QUIC.String():
 		return &staticProtocolSelector{current: QUIC}, nil
 	case HTTP2.String():
 		return &staticProtocolSelector{current: HTTP2}, nil
-	}
-
-	// If the user does not pick (hopefully the majority) then we use the one derived from the TXT DNS record and
-	// fallback on failures.
-	if protocolFlag == AutoSelectFlag {
-		return newAutoProtocolSelector(protocol, []Protocol{QUIC, HTTP2, H2mux}, threshold, fetchFunc, ttl, log, needPQ), nil
-	}
-
-	return nil, fmt.Errorf("Unknown protocol %s, %s", protocolFlag, AvailableProtocolFlagMessage)
-}
-
-func selectWarpRoutingProtocols(
-	protocolFlag string,
-	fetchFunc PercentageFetcher,
-	ttl time.Duration,
-	log *zerolog.Logger,
-	threshold int32,
-	protocol Protocol,
-	needPQ bool,
-) (ProtocolSelector, error) {
-	// If the user picks a protocol, then we stick to it no matter what.
-	switch protocolFlag {
-	case QUIC.String():
-		return &staticProtocolSelector{current: QUICWarp}, nil
-	case HTTP2.String():
-		return &staticProtocolSelector{current: HTTP2Warp}, nil
-	}
-
-	// If the user does not pick (hopefully the majority) then we use the one derived from the TXT DNS record and
-	// fallback on failures.
-	if protocolFlag == AutoSelectFlag {
-		return newAutoProtocolSelector(protocol, []Protocol{QUICWarp, HTTP2Warp}, threshold, fetchFunc, ttl, log, needPQ), nil
+	case AutoSelectFlag:
+		return newRemoteProtocolSelector(fetchedProtocol, ProtocolList, threshold, protocolFetcher, resolveTTL, log), nil
 	}
 
 	return nil, fmt.Errorf("Unknown protocol %s, %s", protocolFlag, AvailableProtocolFlagMessage)