package connection import ( "fmt" "hash/fnv" "sync" "time" "github.com/rs/zerolog" ) const ( AvailableProtocolFlagMessage = "Available protocols: http2 - Go's implementation, h2mux - Cloudflare's implementation of HTTP/2, and auto - automatically select between http2 and h2mux" // 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 edgeH2TLSServerName = "h2.cftunnel.com" // threshold to switch back to h2mux when the user intentionally pick --protocol http2 explicitHTTP2FallbackThreshold = -1 autoSelectFlag = "auto" ) var ( ProtocolList = []Protocol{H2mux, HTTP2} ) type Protocol int64 const ( H2mux Protocol = iota HTTP2 ) func (p Protocol) ServerName() string { switch p { case H2mux: return edgeH2muxTLSServerName case HTTP2: return edgeH2TLSServerName default: return "" } } // 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 default: return 0, false } } func (p Protocol) String() string { switch p { case H2mux: return "h2mux" case HTTP2: return "http2" default: return fmt.Sprintf("unknown protocol") } } type ProtocolSelector interface { Current() Protocol Fallback() (Protocol, bool) } type staticProtocolSelector struct { current Protocol } func (s *staticProtocolSelector) Current() Protocol { return s.current } func (s *staticProtocolSelector) Fallback() (Protocol, bool) { return 0, false } type autoProtocolSelector struct { lock sync.RWMutex current Protocol switchThrehold int32 fetchFunc PercentageFetcher refreshAfter time.Time ttl time.Duration log *zerolog.Logger } func newAutoProtocolSelector( current Protocol, switchThrehold int32, fetchFunc PercentageFetcher, ttl time.Duration, log *zerolog.Logger, ) *autoProtocolSelector { return &autoProtocolSelector{ current: current, switchThrehold: switchThrehold, fetchFunc: fetchFunc, refreshAfter: time.Now().Add(ttl), ttl: ttl, log: log, } } func (s *autoProtocolSelector) Current() Protocol { s.lock.Lock() defer s.lock.Unlock() if time.Now().Before(s.refreshAfter) { return s.current } percentage, err := s.fetchFunc() if err != nil { s.log.Err(err).Msg("Failed to refresh protocol") return s.current } if s.switchThrehold < percentage { s.current = HTTP2 } else { s.current = H2mux } s.refreshAfter = time.Now().Add(s.ttl) return s.current } func (s *autoProtocolSelector) Fallback() (Protocol, bool) { s.lock.RLock() defer s.lock.RUnlock() return s.current.fallback() } type PercentageFetcher func() (int32, error) func NewProtocolSelector( protocolFlag string, namedTunnel *NamedTunnelConfig, fetchFunc PercentageFetcher, ttl time.Duration, log *zerolog.Logger, ) (ProtocolSelector, error) { if namedTunnel == nil { return &staticProtocolSelector{ current: H2mux, }, nil } if protocolFlag == H2mux.String() { return &staticProtocolSelector{ current: H2mux, }, nil } http2Percentage, err := fetchFunc() if err != nil { return nil, err } if protocolFlag == HTTP2.String() { if http2Percentage < 0 { return newAutoProtocolSelector(H2mux, explicitHTTP2FallbackThreshold, fetchFunc, ttl, log), nil } return newAutoProtocolSelector(HTTP2, explicitHTTP2FallbackThreshold, fetchFunc, ttl, log), nil } if protocolFlag != autoSelectFlag { return nil, fmt.Errorf("Unknown protocol %s, %s", protocolFlag, AvailableProtocolFlagMessage) } threshold := switchThreshold(namedTunnel.Credentials.AccountTag) if threshold < http2Percentage { return newAutoProtocolSelector(HTTP2, threshold, fetchFunc, ttl, log), nil } return newAutoProtocolSelector(H2mux, threshold, fetchFunc, ttl, log), nil } func switchThreshold(accountTag string) int32 { h := fnv.New32a() _, _ = h.Write([]byte(accountTag)) return int32(h.Sum32() % 100) }