http_proxy.go

package proxy

import (
	"bytes"
	"context"
	"crypto/tls"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"net"
	"net/http"
	_ "net/http/pprof"
	"os"
	"regexp"
	"runtime"
	"strconv"
	"strings"
	"time"

	rclient "github.com/go-redis/redis/v8"

	"github.com/getlantern/cmux/v2"
	"github.com/getlantern/cmuxprivate"
	"github.com/getlantern/enhttp"
	"github.com/getlantern/errors"
	"github.com/getlantern/geo"
	"github.com/getlantern/golog"
	"github.com/getlantern/gonat"
	"github.com/getlantern/kcpwrapper"

	"github.com/getlantern/http-proxy-lantern/v2/broflake"
	"github.com/getlantern/http-proxy-lantern/v2/opsfilter"
	"github.com/getlantern/http-proxy-lantern/v2/otel"
	"github.com/getlantern/http-proxy-lantern/v2/shadowsocks"
	"github.com/getlantern/http-proxy-lantern/v2/starbridge"
	"github.com/getlantern/http-proxy-lantern/v2/v2ray/vmess"

	"github.com/xtaci/smux"

	"github.com/getlantern/multipath"
	packetforward "github.com/getlantern/packetforward/server"
	"github.com/getlantern/proxy/v3"
	"github.com/getlantern/proxy/v3/filters"
	"github.com/getlantern/psmux"
	"github.com/getlantern/quicwrapper"
	"github.com/getlantern/tinywss"
	"github.com/getlantern/tlsdefaults"

	"github.com/getlantern/http-proxy-lantern/v2/listeners"
	"github.com/getlantern/http-proxy-lantern/v2/proxyfilters"
	"github.com/getlantern/http-proxy-lantern/v2/server"

	"github.com/getlantern/http-proxy-lantern/v2/analytics"
	"github.com/getlantern/http-proxy-lantern/v2/blacklist"
	"github.com/getlantern/http-proxy-lantern/v2/cleanheadersfilter"
	"github.com/getlantern/http-proxy-lantern/v2/devicefilter"
	"github.com/getlantern/http-proxy-lantern/v2/diffserv"
	"github.com/getlantern/http-proxy-lantern/v2/domains"
	"github.com/getlantern/http-proxy-lantern/v2/googlefilter"
	"github.com/getlantern/http-proxy-lantern/v2/httpsupgrade"
	"github.com/getlantern/http-proxy-lantern/v2/instrument"
	"github.com/getlantern/http-proxy-lantern/v2/lampshade"
	"github.com/getlantern/http-proxy-lantern/v2/mimic"
	"github.com/getlantern/http-proxy-lantern/v2/obfs4listener"
	"github.com/getlantern/http-proxy-lantern/v2/ping"
	"github.com/getlantern/http-proxy-lantern/v2/redis"
	"github.com/getlantern/http-proxy-lantern/v2/throttle"
	"github.com/getlantern/http-proxy-lantern/v2/tlslistener"
	"github.com/getlantern/http-proxy-lantern/v2/tlsmasq"
	"github.com/getlantern/http-proxy-lantern/v2/tokenfilter"
	"github.com/getlantern/http-proxy-lantern/v2/wss"

	algeneva "github.com/getlantern/lantern-algeneva"
	waterDownloader "github.com/getlantern/lantern-water/downloader"
	waterListener "github.com/getlantern/lantern-water/listener"
)

const (
	timeoutToDialOriginSite = 10 * time.Second

	teleportHost = "telemetry.iantem.io:443"
)

var (
	log = golog.LoggerFor("lantern-proxy")

	proxyNameRegex = regexp.MustCompile(`(fp-([a-z0-9]+-)?([a-z0-9]+)-[0-9]{8}-[0-9]+)(-.+)?`)
)

// Proxy is an HTTP proxy.
type Proxy struct {
	TestingLocal                       bool
	HTTPAddr                           string
	HTTPMultiplexAddr                  string
	TracesSampleRate                   int
	TeleportSampleRate                 int
	ExternalIP                         string
	CertFile                           string
	CfgSvrAuthToken                    string
	CfgSvrCacheClear                   time.Duration
	ConnectOKWaitsForUpstream          bool
	ENHTTPAddr                         string
	ENHTTPServerURL                    string
	ENHTTPReapIdleTime                 time.Duration
	EnableMultipath                    bool
	HTTPS                              bool
	IdleTimeout                        time.Duration
	KeyFile                            string
	Track                              string
	Pro                                bool
	ProxiedSitesSamplePercentage       float64
	ProxiedSitesTrackingID             string
	ReportingRedisClient               *rclient.Client
	ThrottleRefreshInterval            time.Duration
	Token                              string
	TunnelPorts                        string
	Obfs4Addr                          string
	Obfs4MultiplexAddr                 string
	Obfs4Dir                           string
	Obfs4HandshakeConcurrency          int
	Obfs4MaxPendingHandshakesPerClient int
	Obfs4HandshakeTimeout              time.Duration
	KCPConf                            string
	Benchmark                          bool
	DiffServTOS                        int
	LampshadeAddr                      string
	LampshadeKeyCacheSize              int
	LampshadeMaxClientInitAge          time.Duration
	GoogleSearchRegex                  string
	GoogleCaptchaRegex                 string
	BlacklistMaxIdleTime               time.Duration
	BlacklistMaxConnectInterval        time.Duration
	BlacklistAllowedFailures           int
	BlacklistExpiration                time.Duration
	ProxyName                          string
	ProxyProtocol                      string
	Provider                           string
	DC                                 string
	FrontendProvider                   string
	FrontendDC                         string
	BuildType                          string
	BBRUpstreamProbeURL                string
	QUICIETFAddr                       string
	QUICUseBBR                         bool
	WSSAddr                            string
	PacketForwardAddr                  string
	ExternalIntf                       string
	SessionTicketKeys                  string
	SessionTicketKeyFile               string
	FirstSessionTicketKey              string
	RequireSessionTickets              bool
	MissingTicketReaction              tlslistener.HandshakeReaction
	TLSListenerAllowTLS13              bool
	TLSMasqAddr                        string
	TLSMasqOriginAddr                  string
	TLSMasqSecret                      string
	TLSMasqTLSMinVersion               uint16
	TLSMasqTLSCipherSuites             []uint16
	ShadowsocksWithTLS                 bool
	ShadowsocksAddr                    string
	ShadowsocksMultiplexAddr           string
	ShadowsocksSecret                  string
	ShadowsocksCipher                  string
	ShadowsocksReplayHistory           int
	StarbridgeAddr                     string
	StarbridgePrivateKey               string
	CountryLookup                      geo.CountryLookup
	ISPLookup                          geo.ISPLookup

	MultiplexProtocol             string
	SmuxVersion                   int
	SmuxMaxFrameSize              int
	SmuxMaxReceiveBuffer          int
	SmuxMaxStreamBuffer           int
	PsmuxVersion                  int
	PsmuxMaxFrameSize             int
	PsmuxMaxReceiveBuffer         int
	PsmuxMaxStreamBuffer          int
	PsmuxDisablePadding           bool
	PsmuxMaxPaddingRatio          float64
	PsmuxMaxPaddedSize            int
	PsmuxDisableAggressivePadding bool
	PsmuxAggressivePadding        int
	PsmuxAggressivePaddingRatio   float64

	BroflakeAddr string
	BroflakeCert string
	BroflakeKey  string

	AlgenevaAddr string

	// deprecated: use WaterWASMAvailableAt
	WaterWASM             string
	WaterWASMAvailableAt  string
	WaterTransport        string
	WaterAddr             string
	WaterMismatchProtocol string

	VMessAddr  string
	VMessUUIDs []string

	throttleConfig throttle.Config
	instrument     instrument.Instrument
}

type listenerBuilderFN func(addr string) (net.Listener, error)

// ListenAndServe listens, serves and blocks.
func (p *Proxy) ListenAndServe(ctx context.Context) error {
	if p.CountryLookup == nil {
		log.Debugf("Maxmind not configured, will not report country data with telemetry")
		p.CountryLookup = geo.NoLookup{}
	}
	if p.ISPLookup == nil {
		log.Debugf("Maxmind not configured, will not report ISP data with telemetry")
		p.ISPLookup = geo.NoLookup{}
	}

	var err error
	p.instrument, err = instrument.NewDefault(
		p.CountryLookup,
		p.ISPLookup,
		p.ProxyName,
	)
	if err != nil {
		return errors.New("Unable to configure instrumentation: %v", err)
	}

	var onServerError func(conn net.Conn, err error)
	if err := p.setupPacketForward(); err != nil {
		log.Errorf("Unable to set up packet forwarding, will continue to start up: %v", err)
	}
	p.setBenchmarkMode()
	p.loadThrottleConfig()

	if p.ENHTTPAddr != "" {
		return p.ListenAndServeENHTTP()
	}

	// Only allow connections from remote IPs that are not blacklisted
	blacklist := p.createBlacklist()
	filterChain, dial, err := p.createFilterChain(blacklist)
	if err != nil {
		return err
	}

	if p.WSSAddr != "" {
		filterChain = filterChain.Append(wss.NewMiddleware())
	}
	filterChain = filterChain.Prepend(opsfilter.New())

	instrumentedFilter, err := p.instrument.WrapFilter("proxy", filterChain)
	if err != nil {
		return errors.New("unable to instrument filter: %v", err)
	}
	instrumentedErrorHandler, err := p.instrument.WrapConnErrorHandler("proxy_serve", onServerError)
	if err != nil {
		return errors.New("unable to instrument error handler: %v", err)
	}
	srv := server.New(&server.Opts{
		IdleTimeout:              p.IdleTimeout,
		Dial:                     dial,
		Filter:                   instrumentedFilter,
		OKDoesNotWaitForUpstream: !p.ConnectOKWaitsForUpstream,
		OnError:                  instrumentedErrorHandler,
		OnActive: func(conn net.Conn) {
			clientIP := conn.RemoteAddr().(*net.TCPAddr).IP
			// count the connection only when a connection is established and becomes active
			p.instrument.Connection(ctx, clientIP)
		},
	})
	stopProxiedBytes := p.configureTeleportProxiedBytes()
	defer stopProxiedBytes()

	stopOriginBytes := p.configureTeleportOriginBytes()
	defer stopOriginBytes()

	stopMetrics, err := p.configureOTELMetrics()
	if err != nil {
		return errors.New("unable to initialize global meter provider: %v", err)
	}
	defer stopMetrics()

	bwReporting := p.configureBandwidthReporting()
	// Throttle connections when signaled
	srv.AddListenerWrappers(listeners.NewBitrateListener, bwReporting.wrapper)

	// Add listeners for all protocols
	allListeners := make([]net.Listener, 0)
	listenerProtocols := make([]string, 0)

	listenerArgs := getProtoListenersArgs(p)
	for _, args := range listenerArgs {
		if args.addr == "" {
			continue
		}

		l, err := args.fn(args.addr)
		if err != nil {
			return err
		}

		listenerProtocols = append(listenerProtocols, args.protocol)
		// Although we include blacklist functionality, it's currently only used to
		// track potential blacklisting ad doesn't actually blacklist anyone.
		allListeners = append(allListeners, listeners.NewAllowingListener(l, blacklist.OnConnect))
	}

	errCh := make(chan error, len(allListeners))
	if p.EnableMultipath {
		mpl := multipath.NewListener(allListeners, p.instrument.MultipathStats(listenerProtocols))
		log.Debug("Serving multipath at:")
		for i, l := range allListeners {
			log.Debugf("  %-20s:  %v", listenerProtocols[i], l.Addr())
		}
		go func() {
			errCh <- srv.Serve(mpl, nil)
		}()
	} else {
		for _, _l := range allListeners {
			l := _l
			go func() {
				log.Debugf("Serving at: %v", l.Addr())
				errCh <- srv.Serve(l, mimic.SetServerAddr)
			}()
		}
	}
	select {
	case err := <-errCh:
		return err
	case <-ctx.Done():
		// this is an expected path for closing, no error
		return err
	}
}

func (p *Proxy) ListenAndServeENHTTP() error {
	el, err := net.Listen("tcp", p.ENHTTPAddr)
	if err != nil {
		return errors.New("Unable to listen for encapsulated HTTP at %v: %v", p.ENHTTPAddr, err)
	}
	log.Debugf("Listening for encapsulated HTTP at %v", el.Addr())
	instrumentedPingFilter, err := p.instrument.WrapFilter("proxy_http_ping", ping.New(0))
	if err != nil {
		return errors.New("unable to instrument ping filter: %v", err)
	}
	filterChain := filters.Join(tokenfilter.New(p.Token, p.instrument), instrumentedPingFilter)
	enhttpHandler := enhttp.NewServerHandler(p.ENHTTPReapIdleTime, p.ENHTTPServerURL)
	instrumentedProxyFilter, err := p.instrument.WrapFilter("proxy", filterChain)
	if err != nil {
		return errors.New("unable to instrument proxy filter: %v", err)
	}
	server := &http.Server{
		Handler: filters.Intercept(enhttpHandler, instrumentedProxyFilter),
	}
	return server.Serve(el)
}

func (p *Proxy) wrapTLSIfNecessary(fn listenerBuilderFN) listenerBuilderFN {
	return func(addr string) (net.Listener, error) {
		l, err := fn(addr)
		if err != nil {
			return nil, err
		}

		if p.HTTPS {
			l, err = tlslistener.Wrap(
				l, p.KeyFile, p.CertFile, p.SessionTicketKeyFile, p.FirstSessionTicketKey, p.SessionTicketKeys,
				p.RequireSessionTickets, p.MissingTicketReaction, p.TLSListenerAllowTLS13,
				p.instrument)
			if err != nil {
				return nil, err
			}

			log.Debugf("Using TLS on %v", l.Addr())
		}

		return l, nil
	}
}

func (p *Proxy) wrapMultiplexing(fn listenerBuilderFN) listenerBuilderFN {
	return func(addr string) (net.Listener, error) {
		l, err := fn(addr)
		if err != nil {
			return nil, err
		}

		var proto cmux.Protocol
		// smux is the default, but can be explicitly specified also
		if p.MultiplexProtocol == "" || p.MultiplexProtocol == "smux" {
			proto, err = p.buildSmuxProtocol()
		} else if p.MultiplexProtocol == "psmux" {
			proto, err = p.buildPsmuxProtocol()
		} else {
			err = errors.New("unknown multiplex protocol: %v", p.MultiplexProtocol)
		}
		if err != nil {
			return nil, err
		}

		l = cmux.Listen(&cmux.ListenOpts{
			Listener: l,
			Protocol: proto,
		})

		log.Debugf("Multiplexing on %v", l.Addr())
		return l, nil
	}
}

func (p *Proxy) buildSmuxProtocol() (cmux.Protocol, error) {
	config := smux.DefaultConfig()
	if p.SmuxVersion > 0 {
		config.Version = p.SmuxVersion
	}
	if p.SmuxMaxFrameSize > 0 {
		config.MaxFrameSize = p.SmuxMaxFrameSize
	}
	if p.SmuxMaxReceiveBuffer > 0 {
		config.MaxReceiveBuffer = p.SmuxMaxReceiveBuffer
	}
	if p.SmuxMaxStreamBuffer > 0 {
		config.MaxStreamBuffer = p.SmuxMaxStreamBuffer
	}
	return cmux.NewSmuxProtocol(config), nil
}

func (p *Proxy) buildPsmuxProtocol() (cmux.Protocol, error) {
	config := psmux.DefaultConfig()
	if p.PsmuxVersion > 0 {
		config.Version = p.PsmuxVersion
	}
	if p.PsmuxMaxFrameSize > 0 {
		config.MaxFrameSize = p.PsmuxMaxFrameSize
	}
	if p.PsmuxMaxReceiveBuffer > 0 {
		config.MaxReceiveBuffer = p.PsmuxMaxReceiveBuffer
	}
	if p.PsmuxMaxStreamBuffer > 0 {
		config.MaxStreamBuffer = p.PsmuxMaxStreamBuffer
	}
	if p.PsmuxDisablePadding {
		config.MaxPaddingRatio = 0.0
		config.MaxPaddedSize = 0
		config.AggressivePadding = 0
		config.AggressivePaddingRatio = 0.0
	} else {
		if p.PsmuxMaxPaddingRatio > 0.0 {
			config.MaxPaddingRatio = p.PsmuxMaxPaddingRatio
		}
		if p.PsmuxMaxPaddedSize > 0 {
			config.MaxPaddedSize = p.PsmuxMaxPaddedSize
		}
		if p.PsmuxDisableAggressivePadding {
			config.AggressivePadding = 0
			config.AggressivePaddingRatio = 0.0
		} else {
			if p.PsmuxAggressivePadding > 0 {
				config.AggressivePadding = p.PsmuxAggressivePadding
			}
			if p.PsmuxAggressivePaddingRatio > 0.0 {
				config.AggressivePaddingRatio = p.PsmuxAggressivePaddingRatio
			}
		}
	}
	return cmuxprivate.NewPsmuxProtocol(config), nil
}

func proxyNameAndDC(name string) (proxyName string, dc string) {
	match := proxyNameRegex.FindStringSubmatch(name)
	if len(match) != 5 {
		return name, ""
	}
	return match[1], match[3]
}

func (p *Proxy) setBenchmarkMode() {
	if p.Benchmark {
		log.Debug("Putting proxy into benchmarking mode. Only a limited rate of requests to a specific set of domains will be allowed, no authentication token required.")
		p.HTTPS = true
		p.Token = "bench"
	}
}

func (p *Proxy) createBlacklist() *blacklist.Blacklist {
	return blacklist.New(blacklist.Options{
		MaxIdleTime:        p.BlacklistMaxIdleTime,        // 30 * time.Second,
		MaxConnectInterval: p.BlacklistMaxConnectInterval, // 5 * time.Second,
		AllowedFailures:    p.BlacklistAllowedFailures,    // 10,
		Expiration:         p.BlacklistExpiration,         // 6 * time.Hour,
	})
}

// createFilterChain creates a chain of filters that modify the default behavior
// of proxy.Proxy to implement Lantern-specific logic like authentication,
// Apache mimicry, bandwidth throttling, BBR metric reporting, etc. The actual
// work of proxying plain HTTP and CONNECT requests is handled by proxy.Proxy
// itself.
func (p *Proxy) createFilterChain(bl *blacklist.Blacklist) (filters.Chain, proxy.DialFunc, error) {
	filterChain := filters.Join()

	if p.Benchmark {
		filterChain = filterChain.Append(proxyfilters.RateLimit(5000, map[string]time.Duration{
			"www.google.com":      30 * time.Minute,
			"www.facebook.com":    30 * time.Minute,
			"67.media.tumblr.com": 30 * time.Minute,
			"i.ytimg.com":         30 * time.Minute,    // YouTube play button
			"149.154.167.91":      30 * time.Minute,    // Telegram
			"ping-chained-server": 1 * time.Nanosecond, // Internal ping-chained-server protocol
		}))
	} else {
		filterChain = filterChain.Append(proxy.OnFirstOnly(tokenfilter.New(p.Token, p.instrument)))
	}

	if p.ReportingRedisClient == nil {
		log.Debug("Not enabling bandwidth limiting")
	} else {
		filterChain = filterChain.Append(
			proxy.OnFirstOnly(devicefilter.NewPre(
				redis.NewDeviceFetcher(p.ReportingRedisClient), p.throttleConfig, !p.Pro, p.instrument)),
		)
	}

	filterChain = filterChain.Append(
		proxy.OnFirstOnly(googlefilter.New(p.GoogleSearchRegex, p.GoogleCaptchaRegex)),
	)
	if p.ProxiedSitesSamplePercentage > 0 && p.ProxiedSitesTrackingID != "" {
		log.Debugf("Tracking proxied sites in Google Analytics")
		filterChain = filterChain.Append(analytics.New(&analytics.Options{
			TrackingID:       p.ProxiedSitesTrackingID,
			SamplePercentage: p.ProxiedSitesSamplePercentage,
		}),
		)
	} else {
		log.Debugf("Not tracking proxied sites in Google Analytics")
	}
	filterChain = filterChain.Append(proxy.OnFirstOnly(devicefilter.NewPost(bl)))

	if !p.TestingLocal {
		allowedLocalAddrs := []string{"127.0.0.1:7300"}
		if p.PacketForwardAddr != "" {
			allowedLocalAddrs = append(allowedLocalAddrs, p.PacketForwardAddr)
		}
		filterChain = filterChain.Append(proxyfilters.BlockLocal(allowedLocalAddrs, &proxyfilters.Resolver{}))
	}
	instrumentedProxyPingFilter, err := p.instrument.WrapFilter("proxy_http_ping", ping.New(0))
	if err != nil {
		return nil, nil, errors.New("unable to instrument proxy ping filter: %v", err)
	}
	filterChain = filterChain.Append(instrumentedProxyPingFilter)

	dialer := func(ctx context.Context, network, addr string) (net.Conn, error) {
		// resolve separately so that we can track the DNS resolution time
		resolvedAddr, resolveErr := net.ResolveTCPAddr(network, addr)
		if resolveErr != nil {
			return nil, resolveErr
		}

		d := net.Dialer{
			Deadline: time.Now().Add(timeoutToDialOriginSite),
		}
		conn, dialErr := d.DialContext(ctx, network, resolvedAddr.String())
		if dialErr != nil {
			return nil, dialErr
		}

		return conn, nil
	}
	dialerForPforward := dialer

	filterChain = filterChain.Append(
		proxyfilters.DiscardInitialPersistentRequest,
		filters.FilterFunc(func(cs *filters.ConnectionState, req *http.Request, next filters.Next) (*http.Response, *filters.ConnectionState, error) {
			if domains.ConfigForRequest(req).AddForwardedFor {
				// Only add X-Forwarded-For for certain domains
				return proxyfilters.AddForwardedFor(cs, req, next)
			}
			return next(cs, req)
		}),
		httpsupgrade.NewHTTPSUpgrade(p.CfgSvrAuthToken),
		proxyfilters.RestrictConnectPorts(p.allowedTunnelPorts()),
		proxyfilters.RecordOp,
		cleanheadersfilter.New(), // IMPORTANT, this should be the last filter in the chain to avoid stripping any headers that other filters might need
	)

	return filterChain, func(ctx context.Context, isCONNECT bool, network, addr string) (net.Conn, error) {
		if isCONNECT {
			return dialer(ctx, network, addr)
		}
		return dialerForPforward(ctx, network, addr)
	}, nil
}

func (p *Proxy) configureTeleportProxiedBytes() func() {
	log.Debug("Configuring Teleport proxied bytes")
	tp, stop := otel.BuildTracerProvider(p.buildOTELOpts(teleportHost, true))
	if tp != nil {
		go p.instrument.ReportProxiedBytesPeriodically(1*time.Hour, tp)
		ogStop := stop
		stop = func() {
			p.instrument.ReportProxiedBytes(tp)
			ogStop()
		}
	}
	return stop
}

func (p *Proxy) configureTeleportOriginBytes() func() {
	log.Debug("Configuring Teleport origin bytes")
	// Note - we do not include the proxy name here to avoid associating origin site usage with devices on that proxy name
	tp, stop := otel.BuildTracerProvider(p.buildOTELOpts(teleportHost, false))
	if tp != nil {
		go p.instrument.ReportOriginBytesPeriodically(1*time.Hour, tp)
		ogStop := stop
		stop = func() {
			p.instrument.ReportOriginBytes(tp)
			ogStop()
		}
	}
	return stop
}

func (p *Proxy) configureOTELMetrics() (func(), error) {
	return otel.InitGlobalMeterProvider(
		p.buildOTELOpts(
			teleportHost,
			false, // don't include proxy name in order to reduce DataDog costs
		))
}

func (p *Proxy) buildOTELOpts(endpoint string, includeProxyName bool) *otel.Opts {
	proxyName, provider, dc := p.ProxyName, p.Provider, p.DC
	if dc == "" {
		// This proxy is running on the old infrastructure, parse the name to get the dc
		proxyName, dc = proxyNameAndDC(p.ProxyName)
	}
	opts := &otel.Opts{
		Endpoint:         endpoint,
		Track:            p.Track,
		Provider:         provider,
		DC:               dc,
		FrontendProvider: p.FrontendProvider,
		FrontendDC:       p.FrontendDC,
		ProxyProtocol:    p.ProxyProtocol,
		IsPro:            p.Pro,
		Legacy:           strings.HasPrefix(proxyName, "fp-"),
	}
	if p.ShadowsocksMultiplexAddr != "" {
		opts.Addr = p.ShadowsocksMultiplexAddr
	} else if p.ShadowsocksAddr != "" {
		opts.Addr = p.ShadowsocksAddr
	} else if p.QUICIETFAddr != "" {
		opts.Addr = p.QUICIETFAddr
	} else if p.LampshadeAddr != "" {
		opts.Addr = p.LampshadeAddr
	} else if p.Obfs4MultiplexAddr != "" {
		opts.Addr = p.Obfs4MultiplexAddr
	} else if p.Obfs4Addr != "" {
		opts.Addr = p.Obfs4Addr
	} else if p.StarbridgeAddr != "" {
		opts.Addr = p.StarbridgeAddr
	} else if p.TLSMasqAddr != "" {
		opts.Addr = p.TLSMasqAddr
	} else if p.HTTPMultiplexAddr != "" {
		opts.Addr = p.HTTPMultiplexAddr
	} else if p.HTTPAddr != "" {
		opts.Addr = p.HTTPAddr
	} else if p.BroflakeAddr != "" {
		opts.Addr = p.BroflakeAddr
	} else if p.AlgenevaAddr != "" {
		opts.Addr = p.AlgenevaAddr
	} else if p.WaterAddr != "" {
		opts.Addr = p.WaterAddr
	} else if p.VMessAddr != "" {
		opts.Addr = p.VMessAddr
	}
	if includeProxyName {
		opts.ProxyName = proxyName
	}
	return opts
}

func (p *Proxy) configureBandwidthReporting() *reportingConfig {
	return newReportingConfig(p.CountryLookup, p.ReportingRedisClient, p.instrument, p.throttleConfig)
}

func (p *Proxy) loadThrottleConfig() {
	if !p.Pro && p.ThrottleRefreshInterval > 0 && p.ReportingRedisClient != nil {
		p.throttleConfig = throttle.NewRedisConfig(p.ReportingRedisClient, p.ThrottleRefreshInterval)
	} else {
		log.Debug("Not loading throttle config")
		return
	}
}

func (p *Proxy) allowedTunnelPorts() []int {
	if p.TunnelPorts == "" {
		log.Debug("tunnelling all ports")
		return nil
	}
	ports, err := portsFromCSV(p.TunnelPorts)
	if err != nil {
		log.Fatal(err)
	}
	return ports
}

func (p *Proxy) listenHTTP(baseListen func(string) (net.Listener, error)) listenerBuilderFN {
	return func(addr string) (net.Listener, error) {
		l, err := baseListen(addr)
		if err != nil {
			return nil, errors.New("Unable to listen for HTTP: %v", err)
		}
		log.Debugf("Listening for HTTP(S) at %v", l.Addr())
		return l, nil
	}
}

func (p *Proxy) listenOBFS4(baseListen func(string) (net.Listener, error)) listenerBuilderFN {
	return func(addr string) (net.Listener, error) {
		l, err := baseListen(addr)
		if err != nil {
			return nil, errors.New("Unable to listen for OBFS4: %v", err)
		}
		wrapped, err := obfs4listener.Wrap(l, p.Obfs4Dir, p.Obfs4HandshakeConcurrency, p.Obfs4MaxPendingHandshakesPerClient, p.Obfs4HandshakeTimeout)
		if err != nil {
			l.Close()
			return nil, errors.New("Unable to wrap listener with OBFS4: %v", err)
		}
		log.Debugf("Listening for OBFS4 at %v", wrapped.Addr())
		return wrapped, nil
	}
}

func (p *Proxy) listenLampshade(onListenerError func(net.Conn, error), baseListen func(string) (net.Listener, error)) listenerBuilderFN {
	return func(addr string) (net.Listener, error) {
		l, err := baseListen(addr)
		if err != nil {
			return nil, err
		}
		wrapped, wrapErr := lampshade.Wrap(l, p.CertFile, p.KeyFile, p.LampshadeKeyCacheSize, p.LampshadeMaxClientInitAge, onListenerError)
		if wrapErr != nil {
			log.Fatalf("Unable to initialize lampshade with tcp: %v", wrapErr)
		}
		log.Debugf("Listening for lampshade at %v", wrapped.Addr())

		// Wrap lampshade streams with idletiming as well
		wrapped = listeners.NewIdleConnListener(wrapped, p.IdleTimeout)

		return wrapped, nil
	}
}

func (p *Proxy) listenTLSMasq(baseListen func(string) (net.Listener, error)) listenerBuilderFN {
	return func(addr string) (net.Listener, error) {
		l, err := baseListen(addr)
		if err != nil {
			return nil, err
		}

		nonFatalErrorsHandler := func(err error) {
			log.Debugf("non-fatal error from tlsmasq: %v", err)
		}

		wrapped, wrapErr := tlsmasq.Wrap(
			l, p.CertFile, p.KeyFile, p.TLSMasqOriginAddr, p.TLSMasqSecret,
			p.TLSMasqTLSMinVersion, p.TLSMasqTLSCipherSuites, nonFatalErrorsHandler)
		if wrapErr != nil {
			log.Fatalf("unable to wrap listener with tlsmasq: %v", wrapErr)
		}
		log.Debugf("listening for tlsmasq at %v", wrapped.Addr())

		return wrapped, nil
	}
}

func (p *Proxy) listenTCP(addr string) (net.Listener, error) {
	l, err := net.Listen("tcp", addr)
	if err != nil {
		return nil, err
	}
	if p.IdleTimeout > 0 {
		l = listeners.NewIdleConnListener(l, p.IdleTimeout)
	}
	if p.DiffServTOS > 0 {
		log.Debugf("Setting diffserv TOS to %d", p.DiffServTOS)
		// Note - this doesn't actually wrap the underlying connection, it'll still
		// be a net.TCPConn
		l = diffserv.Wrap(l, p.DiffServTOS)
	} else {
		log.Debugf("Not setting diffserv TOS")
	}
	return l, nil
}

func (p *Proxy) listenKCP(kcpConf string) (net.Listener, error) {
	cfg := &kcpwrapper.ListenerConfig{}
	file, err := os.Open(kcpConf) // For read access.
	if err != nil {
		return nil, errors.New("Unable to open KCPConf at %v: %v", p.KCPConf, err)
	}

	err = json.NewDecoder(file).Decode(cfg)
	file.Close()
	if err != nil {
		return nil, errors.New("Unable to decode KCPConf at %v: %v", p.KCPConf, err)
	}

	log.Debugf("Listening KCP at %v", cfg.Listen)
	return kcpwrapper.Listen(cfg, func(conn net.Conn) net.Conn {
		if p.IdleTimeout <= 0 {
			return conn
		}
		return listeners.WrapIdleConn(conn, p.IdleTimeout)
	})
}

func (p *Proxy) listenQUICIETF(addr string) (net.Listener, error) {
	tlsConf, err := tlsdefaults.BuildListenerConfig(addr, p.KeyFile, p.CertFile)
	if err != nil {
		return nil, err
	}

	config := &quicwrapper.Config{
		MaxIncomingStreams:      1000,
		DisablePathMTUDiscovery: true,
	}

	l, err := quicwrapper.ListenAddr(p.QUICIETFAddr, tlsConf, config)
	if err != nil {
		return nil, err
	}

	log.Debugf("Listening for quic at %v", l.Addr())
	return l, err
}

func (p *Proxy) listenShadowsocks(addr string) (net.Listener, error) {
	// This is not using p.ListenTCP on purpose to avoid additional wrapping with idle timing.
	// The idea here is to be as close to what outline shadowsocks does without any intervention,
	// especially with respect to draining connections and the timing of closures.

	configs := []shadowsocks.CipherConfig{
		{
			ID:     "default",
			Secret: p.ShadowsocksSecret,
			Cipher: p.ShadowsocksCipher,
		},
	}
	ciphers, err := shadowsocks.NewCipherListWithConfigs(configs)
	if err != nil {
		return nil, errors.New("Unable to create shadowsocks cipher: %v", err)
	}
	var tlsConfig *tls.Config
	if p.ShadowsocksWithTLS {
		var cert tls.Certificate
		cert, err = tls.LoadX509KeyPair(p.CertFile, p.KeyFile)
		if err != nil {
			return nil, errors.New("unable to load cert: %v", err)
		}

		tlsConfig = &tls.Config{Certificates: []tls.Certificate{cert}}
	}

	base, err := net.Listen("tcp", addr)
	if err != nil {
		return nil, err
	}

	l, err := shadowsocks.ListenLocalTCP(
		base, ciphers,
		p.ShadowsocksReplayHistory,
	)
	if err != nil {
		return nil, errors.New("Unable to listen for shadowsocks: %v", err)
	}

	if tlsConfig != nil {
		l = tls.NewListener(l, tlsConfig)
	}

	log.Debugf("Listening for shadowsocks at %v", l.Addr())
	return l, nil
}

func (p *Proxy) listenStarbridge(baseListen func(string) (net.Listener, error)) listenerBuilderFN {
	return func(addr string) (net.Listener, error) {
		if p.StarbridgePrivateKey == "" {
			return nil, errors.New("starbridge private key is required")
		}

		base, err := baseListen(addr)
		if err != nil {
			return nil, err
		}

		l, err := starbridge.Wrap(base, p.StarbridgePrivateKey)
		if err != nil {
			base.Close()
			return nil, fmt.Errorf("starbridge wrapping error: %w", err)
		}

		log.Debugf("Listening for starbridge at %v", l.Addr().String())
		return l, nil
	}
}

func (p *Proxy) listenWSS(addr string) (net.Listener, error) {
	l, err := p.listenTCP(addr)
	if err != nil {
		return nil, errors.New("Unable to listen for wss: %v", err)
	}

	if p.HTTPS {
		l, err = tlslistener.Wrap(
			l, p.KeyFile, p.CertFile, p.SessionTicketKeyFile, p.FirstSessionTicketKey, p.SessionTicketKeys,
			p.RequireSessionTickets, p.MissingTicketReaction, p.TLSListenerAllowTLS13, p.instrument)
		if err != nil {
			return nil, err
		}
		log.Debugf("Using TLS on %v", l.Addr())
	}
	opts := &tinywss.ListenOpts{
		Listener: l,
	}

	l, err = tinywss.ListenAddr(opts)
	if err != nil {
		return nil, err
	}

	log.Debugf("Listening for wss at %v", l.Addr())
	return l, err
}

func (p *Proxy) listenBroflake(baseListen func(string) (net.Listener, error)) listenerBuilderFN {
	return func(addr string) (net.Listener, error) {
		l, err := net.Listen("tcp", addr)
		if err != nil {
			return nil, err
		}

		certPEM, err := os.ReadFile(p.CertFile)
		if err != nil {
			log.Fatalf("Unable to read certificate file: %v", err)
		}

		keyPEM, err := os.ReadFile(p.KeyFile)
		if err != nil {
			log.Fatalf("Unable to read key file: %v", err)
		}

		wrapped, wrapErr := broflake.Wrap(l, string(certPEM), string(keyPEM))
		if wrapErr != nil {
			log.Fatalf("Unable to initialize broflake with tcp: %v", wrapErr)
		}
		log.Debugf("Listening for broflake at %v", wrapped.Addr())

		// Wrap broflake streams with idletiming as well
		wrapped = listeners.NewIdleConnListener(wrapped, p.IdleTimeout)

		return wrapped, nil
	}
}

// listenAlgeneva returns a listenerBuilderFN that wraps the listener returned by the provided
// baseListen function with a algeneva.Listener.
func (p *Proxy) listenAlgeneva(baseListen func(string) (net.Listener, error)) listenerBuilderFN {
	return func(addr string) (net.Listener, error) {
		var tlsConfig *tls.Config
		if p.KeyFile != "" && p.CertFile != "" {
			cert, err := tls.LoadX509KeyPair(p.CertFile, p.KeyFile)
			if err != nil {
				return nil, errors.New("Unable to load cert: %v", err)
			}

			tlsConfig = &tls.Config{Certificates: []tls.Certificate{cert}}
		}

		base, err := baseListen(addr)
		if err != nil {
			return nil, err
		}

		ll, connErrC := algeneva.WrapListener(base, tlsConfig)
		// create a goroutine to log any connection errors
		go func() {
			for err := range connErrC {
				log.Errorf("Error accepting algeneva connection: %v", err)
			}
		}()

		log.Debugf("Listening for algeneva at %v", ll.Addr())
		return ll, nil
	}
}

func (p *Proxy) listenVMess(baseListen func(string) (net.Listener, error)) listenerBuilderFN {
	return func(addr string) (net.Listener, error) {
		base, err := baseListen(addr)
		if err != nil {
			return nil, err
		}
		log.Debugf("Listening for vmess at %v", base.Addr())
		wrapper, err := vmess.NewVMessListener(base, p.VMessUUIDs)
		if err != nil {
			_ = base.Close()
			return nil, fmt.Errorf("vmess wrapping error: %w", err)
		}

		return wrapper, nil
	}
}

// listenWATER start a WATER listener and return it
// Currently water doesn't support customized TCP connections and we need to listen and receive requests directly from the WATER listener
func (p *Proxy) listenWATER(addr string) (net.Listener, error) {
	ctx := context.Background()
	var wasm []byte
	if p.WaterWASM != "" {
		var err error
		wasm, err = base64.StdEncoding.DecodeString(p.WaterWASM)
		if err != nil {
			log.Errorf("failed to decode WASM base64: %v", err)
			return nil, err
		}
	}

	if p.WaterWASMAvailableAt != "" {
		wasmBuffer := new(bytes.Buffer)
		d, err := waterDownloader.NewWASMDownloader(strings.Split(p.WaterWASMAvailableAt, ","), &http.Client{Timeout: 1 * time.Minute})
		if err != nil {
			return nil, log.Errorf("failed to create wasm downloader: %w", err)
		}

		err = d.DownloadWASM(ctx, wasmBuffer)
		if err != nil {
			return nil, log.Errorf("unable to download water wasm: %w", err)
		}
		wasm = wasmBuffer.Bytes()
	}

	switch p.WaterMismatchProtocol {
	case "PROTOCOL_UNSPECIFIED":
		listener, err := waterListener.NewWATERListener(ctx, waterListener.ListenerParams{
			Logger:    golog.LoggerFor("water"),
			Transport: p.WaterTransport,
			Address:   addr,
			WASM:      wasm,
		})
		if err != nil {
			return nil, log.Errorf("failed to start WATER listener: %w", err)
		}

		log.Debugf("Listening for water at %v", listener.Addr())
		return listener, nil
	case "PROTOCOL_UTLS":
		certPEM, err := os.ReadFile(p.CertFile)
		if err != nil {
			log.Fatalf("Unable to read certificate file: %v", err)
		}

		keyPEM, err := os.ReadFile(p.KeyFile)
		if err != nil {
			log.Fatalf("Unable to read key file: %v", err)
		}
		cert, err := tls.X509KeyPair([]byte(certPEM), []byte(keyPEM))
		if err != nil {
			return nil, log.Errorf("failed to load cert: %w", err)
		}

		return tls.Listen("tcp", addr, &tls.Config{Certificates: []tls.Certificate{cert}})
	default:
		return nil, log.Errorf("unsupported mismatch protocol provided: %s", p.WaterMismatchProtocol)
	}
}

func (p *Proxy) setupPacketForward() error {
	if runtime.GOOS != "linux" {
		log.Debugf("Ignoring packet forward on %v", runtime.GOOS)
		return nil
	}
	if p.PacketForwardAddr == "" {
		return nil
	}
	l, err := net.Listen("tcp", p.PacketForwardAddr)
	if err != nil {
		return errors.New("Unable to listen for packet forwarding at %v: %v", p.PacketForwardAddr, err)
	}
	s, err := packetforward.NewServer(&packetforward.Opts{
		Opts: gonat.Opts{
			StatsInterval: 15 * time.Second,
			IFName:        p.ExternalIntf,
			IdleTimeout:   90 * time.Second,
			BufferDepth:   1000,
		},
		BufferPoolSize: 50 * 1024 * 1024,
	})
	if err != nil {
		return errors.New("Error configuring packet forwarding: %v", err)
	}
	log.Debugf("Listening for packet forwarding at %v", l.Addr())

	go func() {
		if err := s.Serve(l); err != nil {
			log.Errorf("Error serving packet forwarding: %v", err)
		}
	}()
	return nil
}

func portsFromCSV(csv string) ([]int, error) {
	fields := strings.Split(csv, ",")
	ports := make([]int, len(fields))
	for i, f := range fields {
		p, err := strconv.Atoi(strings.TrimSpace(f))
		if err != nil {
			return nil, err
		}
		ports[i] = p
	}
	return ports, nil
}