prototype for reverse proxy

app/reverse/bridge.go

@@ -0,0 +1,172 @@
+package reverse
+
+import (
+	"context"
+	"time"
+
+	"github.com/golang/protobuf/proto"
+	"v2ray.com/core/common/mux"
+	"v2ray.com/core/common/net"
+	"v2ray.com/core/common/session"
+	"v2ray.com/core/common/task"
+	"v2ray.com/core/common/vio"
+	"v2ray.com/core/features/routing"
+	"v2ray.com/core/transport/pipe"
+)
+
+type Bridge struct {
+	dispatcher  routing.Dispatcher
+	tag         string
+	domain      string
+	workers     []*BridgeWorker
+	monitorTask *task.Periodic
+}
+
+func NewBridge(config *BridgeConfig, dispatcher routing.Dispatcher) (*Bridge, error) {
+	if len(config.Tag) == 0 {
+		return nil, newError("bridge tag is empty")
+	}
+	if len(config.Domain) == 0 {
+		return nil, newError("bridge domain is empty")
+	}
+
+	b := &Bridge{
+		dispatcher: dispatcher,
+	}
+	b.monitorTask = &task.Periodic{
+		Execute:  b.monitor,
+		Interval: time.Second * 2,
+	}
+	return b, nil
+}
+
+func (b *Bridge) monitor() error {
+	var numConnections uint32
+	var numWorker uint32
+
+	for _, w := range b.workers {
+		if w.IsActive() {
+			numConnections += w.Connections()
+			numWorker++
+		}
+	}
+
+	if numWorker == 0 || numConnections/numWorker > 16 {
+		worker, err := NewBridgeWorker(b.domain, b.tag, b.dispatcher)
+		if err != nil {
+			newError("failed to create bridge worker").Base(err).AtWarning().WriteToLog()
+			return nil
+		}
+		b.workers = append(b.workers, worker)
+	}
+
+	return nil
+}
+
+func (b *Bridge) Start() error {
+	return b.monitorTask.Start()
+}
+
+func (b *Bridge) Close() error {
+	return b.monitorTask.Close()
+}
+
+type BridgeWorker struct {
+	tag        string
+	worker     *mux.ServerWorker
+	dispatcher routing.Dispatcher
+	state      Control_State
+}
+
+func NewBridgeWorker(domain string, tag string, d routing.Dispatcher) (*BridgeWorker, error) {
+	ctx := context.Background()
+	ctx = session.ContextWithInbound(ctx, &session.Inbound{
+		Tag: tag,
+	})
+	link, err := d.Dispatch(ctx, net.Destination{
+		Network: net.Network_TCP,
+		Address: net.DomainAddress(domain),
+		Port:    0,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	w := &BridgeWorker{
+		dispatcher: d,
+		tag:        tag,
+	}
+
+	worker, err := mux.NewServerWorker(context.Background(), w, link)
+	if err != nil {
+		return nil, err
+	}
+	w.worker = worker
+
+	return w, nil
+}
+
+func (w *BridgeWorker) Type() interface{} {
+	return routing.DispatcherType()
+}
+
+func (w *BridgeWorker) Start() error {
+	return nil
+}
+
+func (w *BridgeWorker) Close() error {
+	return nil
+}
+
+func (w *BridgeWorker) IsActive() bool {
+	return w.state == Control_ACTIVE
+}
+
+func (w *BridgeWorker) Connections() uint32 {
+	return w.worker.ActiveConnections()
+}
+
+func (w *BridgeWorker) handleInternalConn(link vio.Link) {
+	go func() {
+		reader := link.Reader
+		for {
+			mb, err := reader.ReadMultiBuffer()
+			if err != nil {
+				break
+			}
+			for _, b := range mb {
+				var ctl Control
+				if err := proto.Unmarshal(b.Bytes(), &ctl); err != nil {
+					newError("failed to parse proto message").Base(err).WriteToLog()
+					break
+				}
+				if ctl.State != w.state {
+					w.state = ctl.State
+				}
+			}
+		}
+	}()
+}
+
+func (w *BridgeWorker) Dispatch(ctx context.Context, dest net.Destination) (*vio.Link, error) {
+	if !isInternalDomain(dest) {
+		ctx = session.ContextWithInbound(ctx, &session.Inbound{
+			Tag: w.tag,
+		})
+		return w.dispatcher.Dispatch(ctx, dest)
+	}
+
+	opt := []pipe.Option{pipe.WithSizeLimit(16 * 1024)}
+	uplinkReader, uplinkWriter := pipe.New(opt...)
+	downlinkReader, downlinkWriter := pipe.New(opt...)
+
+	w.handleInternalConn(vio.Link{
+		Reader: downlinkReader,
+		Writer: uplinkWriter,
+	})
+
+	return &vio.Link{
+		Reader: uplinkReader,
+		Writer: downlinkWriter,
+	}, nil
+}

app/reverse/config.go

@@ -0,0 +1,14 @@
+package reverse
+
+import (
+	"crypto/rand"
+	"io"
+
+	"v2ray.com/core/common/dice"
+)
+
+func (c *Control) FillInRandom() {
+	randomLength := dice.Roll(64)
+	c.Random = make([]byte, randomLength)
+	io.ReadFull(rand.Reader, c.Random)
+}

app/reverse/config.pb.go

@@ -0,0 +1,267 @@
+package reverse
+
+import (
+	fmt "fmt"
+	proto "github.com/golang/protobuf/proto"
+	math "math"
+)
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+// A compilation error at this line likely means your copy of the
+// proto package needs to be updated.
+const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package
+
+type Control_State int32
+
+const (
+	Control_ACTIVE Control_State = 0
+	Control_DRAIN  Control_State = 1
+)
+
+var Control_State_name = map[int32]string{
+	0: "ACTIVE",
+	1: "DRAIN",
+}
+
+var Control_State_value = map[string]int32{
+	"ACTIVE": 0,
+	"DRAIN":  1,
+}
+
+func (x Control_State) String() string {
+	return proto.EnumName(Control_State_name, int32(x))
+}
+
+func (Control_State) EnumDescriptor() ([]byte, []int) {
+	return fileDescriptor_829a0eeb60380cbc, []int{0, 0}
+}
+
+type Control struct {
+	State                Control_State `protobuf:"varint,1,opt,name=state,proto3,enum=v2ray.core.app.reverse.Control_State" json:"state,omitempty"`
+	Random               []byte        `protobuf:"bytes,99,opt,name=random,proto3" json:"random,omitempty"`
+	XXX_NoUnkeyedLiteral struct{}      `json:"-"`
+	XXX_unrecognized     []byte        `json:"-"`
+	XXX_sizecache        int32         `json:"-"`
+}
+
+func (m *Control) Reset()         { *m = Control{} }
+func (m *Control) String() string { return proto.CompactTextString(m) }
+func (*Control) ProtoMessage()    {}
+func (*Control) Descriptor() ([]byte, []int) {
+	return fileDescriptor_829a0eeb60380cbc, []int{0}
+}
+
+func (m *Control) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Control.Unmarshal(m, b)
+}
+func (m *Control) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Control.Marshal(b, m, deterministic)
+}
+func (m *Control) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Control.Merge(m, src)
+}
+func (m *Control) XXX_Size() int {
+	return xxx_messageInfo_Control.Size(m)
+}
+func (m *Control) XXX_DiscardUnknown() {
+	xxx_messageInfo_Control.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_Control proto.InternalMessageInfo
+
+func (m *Control) GetState() Control_State {
+	if m != nil {
+		return m.State
+	}
+	return Control_ACTIVE
+}
+
+func (m *Control) GetRandom() []byte {
+	if m != nil {
+		return m.Random
+	}
+	return nil
+}
+
+type BridgeConfig struct {
+	Tag                  string   `protobuf:"bytes,1,opt,name=tag,proto3" json:"tag,omitempty"`
+	Domain               string   `protobuf:"bytes,2,opt,name=domain,proto3" json:"domain,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *BridgeConfig) Reset()         { *m = BridgeConfig{} }
+func (m *BridgeConfig) String() string { return proto.CompactTextString(m) }
+func (*BridgeConfig) ProtoMessage()    {}
+func (*BridgeConfig) Descriptor() ([]byte, []int) {
+	return fileDescriptor_829a0eeb60380cbc, []int{1}
+}
+
+func (m *BridgeConfig) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_BridgeConfig.Unmarshal(m, b)
+}
+func (m *BridgeConfig) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_BridgeConfig.Marshal(b, m, deterministic)
+}
+func (m *BridgeConfig) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_BridgeConfig.Merge(m, src)
+}
+func (m *BridgeConfig) XXX_Size() int {
+	return xxx_messageInfo_BridgeConfig.Size(m)
+}
+func (m *BridgeConfig) XXX_DiscardUnknown() {
+	xxx_messageInfo_BridgeConfig.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_BridgeConfig proto.InternalMessageInfo
+
+func (m *BridgeConfig) GetTag() string {
+	if m != nil {
+		return m.Tag
+	}
+	return ""
+}
+
+func (m *BridgeConfig) GetDomain() string {
+	if m != nil {
+		return m.Domain
+	}
+	return ""
+}
+
+type PortalConfig struct {
+	Tag                  string   `protobuf:"bytes,1,opt,name=tag,proto3" json:"tag,omitempty"`
+	Domain               string   `protobuf:"bytes,2,opt,name=domain,proto3" json:"domain,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *PortalConfig) Reset()         { *m = PortalConfig{} }
+func (m *PortalConfig) String() string { return proto.CompactTextString(m) }
+func (*PortalConfig) ProtoMessage()    {}
+func (*PortalConfig) Descriptor() ([]byte, []int) {
+	return fileDescriptor_829a0eeb60380cbc, []int{2}
+}
+
+func (m *PortalConfig) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_PortalConfig.Unmarshal(m, b)
+}
+func (m *PortalConfig) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_PortalConfig.Marshal(b, m, deterministic)
+}
+func (m *PortalConfig) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_PortalConfig.Merge(m, src)
+}
+func (m *PortalConfig) XXX_Size() int {
+	return xxx_messageInfo_PortalConfig.Size(m)
+}
+func (m *PortalConfig) XXX_DiscardUnknown() {
+	xxx_messageInfo_PortalConfig.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_PortalConfig proto.InternalMessageInfo
+
+func (m *PortalConfig) GetTag() string {
+	if m != nil {
+		return m.Tag
+	}
+	return ""
+}
+
+func (m *PortalConfig) GetDomain() string {
+	if m != nil {
+		return m.Domain
+	}
+	return ""
+}
+
+type Config struct {
+	BridgeConfig         []*BridgeConfig `protobuf:"bytes,1,rep,name=bridge_config,json=bridgeConfig,proto3" json:"bridge_config,omitempty"`
+	PortalConfig         []*PortalConfig `protobuf:"bytes,2,rep,name=portal_config,json=portalConfig,proto3" json:"portal_config,omitempty"`
+	XXX_NoUnkeyedLiteral struct{}        `json:"-"`
+	XXX_unrecognized     []byte          `json:"-"`
+	XXX_sizecache        int32           `json:"-"`
+}
+
+func (m *Config) Reset()         { *m = Config{} }
+func (m *Config) String() string { return proto.CompactTextString(m) }
+func (*Config) ProtoMessage()    {}
+func (*Config) Descriptor() ([]byte, []int) {
+	return fileDescriptor_829a0eeb60380cbc, []int{3}
+}
+
+func (m *Config) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Config.Unmarshal(m, b)
+}
+func (m *Config) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Config.Marshal(b, m, deterministic)
+}
+func (m *Config) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Config.Merge(m, src)
+}
+func (m *Config) XXX_Size() int {
+	return xxx_messageInfo_Config.Size(m)
+}
+func (m *Config) XXX_DiscardUnknown() {
+	xxx_messageInfo_Config.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_Config proto.InternalMessageInfo
+
+func (m *Config) GetBridgeConfig() []*BridgeConfig {
+	if m != nil {
+		return m.BridgeConfig
+	}
+	return nil
+}
+
+func (m *Config) GetPortalConfig() []*PortalConfig {
+	if m != nil {
+		return m.PortalConfig
+	}
+	return nil
+}
+
+func init() {
+	proto.RegisterEnum("v2ray.core.app.reverse.Control_State", Control_State_name, Control_State_value)
+	proto.RegisterType((*Control)(nil), "v2ray.core.app.reverse.Control")
+	proto.RegisterType((*BridgeConfig)(nil), "v2ray.core.app.reverse.BridgeConfig")
+	proto.RegisterType((*PortalConfig)(nil), "v2ray.core.app.reverse.PortalConfig")
+	proto.RegisterType((*Config)(nil), "v2ray.core.app.reverse.Config")
+}
+
+func init() {
+	proto.RegisterFile("v2ray.com/core/app/reverse/config.proto", fileDescriptor_829a0eeb60380cbc)
+}
+
+var fileDescriptor_829a0eeb60380cbc = []byte{
+	// 310 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x94, 0x91, 0xc1, 0x4b, 0xfb, 0x30,
+	0x14, 0xc7, 0x7f, 0xd9, 0x58, 0xc7, 0xde, 0xaf, 0x93, 0x91, 0xc3, 0xe8, 0x41, 0x64, 0x0c, 0xc5,
+	0x9d, 0x52, 0xa8, 0x17, 0xc1, 0xd3, 0xd6, 0x79, 0xe8, 0x45, 0x46, 0x94, 0x1d, 0xbc, 0x48, 0xd6,
+	0xc5, 0x52, 0x58, 0xfb, 0x42, 0x16, 0x86, 0xbd, 0xf8, 0xa7, 0xf8, 0x07, 0xf8, 0x57, 0x4a, 0xd3,
+	0x14, 0x7a, 0x50, 0xc1, 0xdb, 0x7b, 0xc9, 0xe7, 0xf3, 0xf2, 0x4d, 0x02, 0xd7, 0xa7, 0x48, 0x8b,
+	0x8a, 0xa5, 0x58, 0x84, 0x29, 0x6a, 0x19, 0x0a, 0xa5, 0x42, 0x2d, 0x4f, 0x52, 0x1f, 0x65, 0x98,
+	0x62, 0xf9, 0x9a, 0x67, 0x4c, 0x69, 0x34, 0x48, 0xa7, 0x2d, 0xa8, 0x25, 0x13, 0x4a, 0x31, 0x07,
+	0xcd, 0xdf, 0x61, 0x18, 0x63, 0x69, 0x34, 0x1e, 0xe8, 0x1d, 0x0c, 0x8e, 0x46, 0x18, 0x19, 0x90,
+	0x19, 0x59, 0x9c, 0x45, 0x57, 0xec, 0x7b, 0x85, 0x39, 0x9e, 0x3d, 0xd6, 0x30, 0x6f, 0x1c, 0x3a,
+	0x05, 0x4f, 0x8b, 0x72, 0x8f, 0x45, 0x90, 0xce, 0xc8, 0xc2, 0xe7, 0xae, 0x9b, 0x5f, 0xc0, 0xc0,
+	0x72, 0x14, 0xc0, 0x5b, 0xc6, 0x4f, 0xc9, 0xf6, 0x7e, 0xf2, 0x8f, 0x8e, 0x60, 0xb0, 0xe6, 0xcb,
+	0xe4, 0x61, 0x42, 0xe6, 0xb7, 0xe0, 0xaf, 0x74, 0xbe, 0xcf, 0x64, 0x6c, 0xd3, 0xd2, 0x09, 0xf4,
+	0x8d, 0xc8, 0x6c, 0x84, 0x11, 0xaf, 0xcb, 0x7a, 0xf2, 0x1e, 0x0b, 0x91, 0x97, 0x41, 0xcf, 0x2e,
+	0xba, 0xae, 0x36, 0x37, 0xa8, 0x8d, 0x38, 0xfc, 0xd9, 0xfc, 0x20, 0xe0, 0x39, 0x29, 0x81, 0xf1,
+	0xce, 0x1e, 0xff, 0xd2, 0xbc, 0x56, 0x40, 0x66, 0xfd, 0xc5, 0xff, 0xe8, 0xf2, 0xa7, 0xbb, 0x77,
+	0xb3, 0x72, 0x7f, 0xd7, 0x4d, 0x9e, 0xc0, 0x58, 0xd9, 0x3c, 0xed, 0xa8, 0xde, 0xef, 0xa3, 0xba,
+	0xe1, 0xb9, 0xaf, 0x3a, 0xdd, 0x6a, 0x0d, 0xe7, 0x29, 0x16, 0x5d, 0x51, 0x69, 0x7c, 0xab, 0x5a,
+	0x75, 0x43, 0x9e, 0x87, 0xae, 0xfc, 0xec, 0x05, 0xdb, 0x88, 0x8b, 0x8a, 0xc5, 0x35, 0xb5, 0xb1,
+	0x14, 0x6f, 0xb6, 0x76, 0x9e, 0xfd, 0xf9, 0x9b, 0xaf, 0x00, 0x00, 0x00, 0xff, 0xff, 0xb7, 0x83,
+	0x30, 0xdb, 0x24, 0x02, 0x00, 0x00,
+}

app/reverse/config.proto

@@ -0,0 +1,33 @@
+syntax = "proto3";
+
+package v2ray.core.app.reverse;
+option csharp_namespace = "V2Ray.Core.Proxy.Reverse";
+option go_package = "reverse";
+option java_package = "com.v2ray.core.proxy.reverse";
+option java_multiple_files = true;
+
+message Control {
+  enum State {
+    ACTIVE = 0;
+    DRAIN = 1;
+  }
+
+  State state = 1;
+  bytes random = 99;
+}
+
+message BridgeConfig {
+  string tag = 1;
+  string domain = 2;
+
+}
+
+message PortalConfig {
+  string tag = 1;
+  string domain = 2;
+}
+
+message Config {
+  repeated BridgeConfig bridge_config = 1;
+  repeated PortalConfig portal_config = 2;
+}

app/reverse/errors.generated.go

@@ -0,0 +1,9 @@
+package reverse
+
+import "v2ray.com/core/common/errors"
+
+type errPathObjHolder struct{}
+
+func newError(values ...interface{}) *errors.Error {
+	return errors.New(values...).WithPathObj(errPathObjHolder{})
+}

app/reverse/portal.go

@@ -0,0 +1,242 @@
+package reverse
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"github.com/golang/protobuf/proto"
+	"v2ray.com/core/common"
+	"v2ray.com/core/common/buf"
+	"v2ray.com/core/common/dice"
+	"v2ray.com/core/common/mux"
+	"v2ray.com/core/common/session"
+	"v2ray.com/core/common/task"
+	"v2ray.com/core/common/vio"
+	"v2ray.com/core/features/outbound"
+	"v2ray.com/core/transport/pipe"
+)
+
+type Portal struct {
+	ohm    outbound.Manager
+	tag    string
+	domain string
+	picker *StaticMuxPicker
+	client *mux.ClientManager
+}
+
+func NewPortal(config *PortalConfig, ohm outbound.Manager) (*Portal, error) {
+	if len(config.Tag) == 0 {
+		return nil, newError("portal tag is empty")
+	}
+
+	if len(config.Domain) == 0 {
+		return nil, newError("portal domain is empty")
+	}
+
+	picker, err := NewStaticMuxPicker()
+	if err != nil {
+		return nil, err
+	}
+
+	return &Portal{
+		ohm:    ohm,
+		tag:    config.Tag,
+		domain: config.Domain,
+		picker: picker,
+		client: &mux.ClientManager{
+			Picker: picker,
+		},
+	}, nil
+}
+
+func (p *Portal) Start() error {
+	return p.ohm.AddHandler(context.Background(), &Outbound{
+		portal: p,
+	})
+}
+
+func (p *Portal) Close() error {
+	return p.ohm.RemoveHandler(context.Background(), p.tag)
+}
+
+func (s *Portal) HandleConnection(ctx context.Context, link *vio.Link) error {
+	outboundMeta := session.OutboundFromContext(ctx)
+	if outboundMeta == nil {
+		return newError("outbound metadata not found").AtError()
+	}
+
+	if isInternalDomain(outboundMeta.Target) {
+		muxClient, err := mux.NewClientWorker(*link, mux.ClientStrategy{
+			MaxConcurrency: 0,
+			MaxConnection:  256,
+		})
+		if err != nil {
+			return newError("failed to create mux client worker").Base(err).AtWarning()
+		}
+
+		worker, err := NewPortalWorker(muxClient)
+		if err != nil {
+			return newError("failed to create portal worker").Base(err)
+		}
+
+		s.picker.AddWorker(worker)
+		return nil
+	}
+
+	return s.client.Dispatch(ctx, link)
+}
+
+type Outbound struct {
+	portal *Portal
+	tag    string
+}
+
+func (o *Outbound) Tag() string {
+	return o.tag
+}
+
+func (o *Outbound) Dispatch(ctx context.Context, link *vio.Link) {
+	if err := o.portal.HandleConnection(ctx, link); err != nil {
+		newError("failed to process reverse connection").Base(err).WriteToLog(session.ExportIDToError(ctx))
+		pipe.CloseError(link.Writer)
+	}
+}
+
+func (o *Outbound) Start() error {
+	return nil
+}
+
+func (o *Outbound) Close() error {
+	return nil
+}
+
+type StaticMuxPicker struct {
+	access  sync.Mutex
+	workers []*PortalWorker
+	cTask   *task.Periodic
+}
+
+func NewStaticMuxPicker() (*StaticMuxPicker, error) {
+	p := &StaticMuxPicker{}
+	p.cTask = &task.Periodic{
+		Execute:  p.cleanup,
+		Interval: time.Second * 30,
+	}
+	p.cTask.Start()
+	return p, nil
+}
+
+func (p *StaticMuxPicker) cleanup() error {
+	p.access.Lock()
+	defer p.access.Unlock()
+
+	var activeWorkers []*PortalWorker
+	for _, w := range p.workers {
+		if !w.Closed() {
+			activeWorkers = append(activeWorkers, w)
+		}
+	}
+
+	if len(activeWorkers) != len(p.workers) {
+		p.workers = activeWorkers
+	}
+
+	return nil
+}
+
+func (p *StaticMuxPicker) PickAvailable() (*mux.ClientWorker, error) {
+	p.access.Lock()
+	defer p.access.Unlock()
+
+	n := len(p.workers)
+	if n == 0 {
+		return nil, newError("empty worker list")
+	}
+
+	idx := dice.Roll(n)
+	for i := 0; i < n; i++ {
+		w := p.workers[(i+idx)%n]
+		if !w.IsFull() {
+			return w.client, nil
+		}
+	}
+
+	return nil, newError("no mux client worker available")
+}
+
+func (p *StaticMuxPicker) AddWorker(worker *PortalWorker) {
+	p.access.Lock()
+	defer p.access.Unlock()
+
+	p.workers = append(p.workers, worker)
+}
+
+type PortalWorker struct {
+	client  *mux.ClientWorker
+	control *task.Periodic
+	writer  buf.Writer
+	reader  buf.Reader
+}
+
+func NewPortalWorker(client *mux.ClientWorker) (*PortalWorker, error) {
+	opt := []pipe.Option{pipe.WithSizeLimit(16 * 1024)}
+	uplinkReader, uplinkWriter := pipe.New(opt...)
+	downlinkReader, downlinkWriter := pipe.New(opt...)
+
+	f := client.Dispatch(context.Background(), &vio.Link{
+		Reader: uplinkReader,
+		Writer: downlinkWriter,
+	})
+	if !f {
+		return nil, newError("unable to dispatch control connection")
+	}
+	w := &PortalWorker{
+		client: client,
+		reader: downlinkReader,
+		writer: uplinkWriter,
+	}
+	w.control = &task.Periodic{
+		Execute:  w.heartbeat,
+		Interval: time.Second * 2,
+	}
+	w.control.Start()
+	return w, nil
+}
+
+func (w *PortalWorker) heartbeat() error {
+	if w.client.Closed() {
+		return newError("client worker stopped")
+	}
+
+	if w.writer == nil {
+		return newError("already disposed")
+	}
+
+	msg := &Control{}
+	msg.FillInRandom()
+
+	if w.client.IsClosing() {
+		msg.State = Control_DRAIN
+
+		defer func() {
+			common.Close(w.writer)
+			pipe.CloseError(w.reader)
+			w.writer = nil
+		}()
+	}
+
+	b, err := proto.Marshal(msg)
+	common.Must(err)
+	var mb buf.MultiBuffer
+	common.Must2(mb.Write(b))
+	return w.writer.WriteMultiBuffer(mb)
+}
+
+func (w *PortalWorker) IsFull() bool {
+	return w.client.IsFull()
+}
+
+func (w *PortalWorker) Closed() bool {
+	return w.client.Closed()
+}

app/reverse/portal_test.go

@@ -0,0 +1,20 @@
+package reverse_test
+
+import (
+	"testing"
+
+	"v2ray.com/core/app/reverse"
+	"v2ray.com/core/common"
+)
+
+func TestStaticPickerEmpty(t *testing.T) {
+	picker, err := reverse.NewStaticMuxPicker()
+	common.Must(err)
+	worker, err := picker.PickAvailable()
+	if err == nil {
+		t.Error("expected error, but nil")
+	}
+	if worker != nil {
+		t.Error("expected nil worker, but not nil")
+	}
+}

app/reverse/reverse.go

@@ -0,0 +1,58 @@
+package reverse
+
+//go:generate errorgen
+
+import (
+	"context"
+
+	"v2ray.com/core"
+	"v2ray.com/core/common"
+	"v2ray.com/core/common/net"
+	"v2ray.com/core/features/outbound"
+	"v2ray.com/core/features/routing"
+)
+
+const (
+	internalDomain = "reverse.internal.v2ray.com"
+)
+
+func isInternalDomain(dest net.Destination) bool {
+	return dest.Address.Family().IsDomain() && dest.Address.Domain() == internalDomain
+}
+
+func init() {
+	common.Must(common.RegisterConfig((*Config)(nil), func(ctx context.Context, config interface{}) (interface{}, error) {
+		r := new(Reverse)
+		if err := core.RequireFeatures(ctx, func(d routing.Dispatcher, om outbound.Manager) error {
+			return r.Init(config.(*Config), d, om)
+		}); err != nil {
+			return nil, err
+		}
+		return r, nil
+	}))
+}
+
+type Reverse struct {
+	bridges []*Bridge
+	portals []*Portal
+}
+
+func (r *Reverse) Init(config *Config, d routing.Dispatcher, ohm outbound.Manager) error {
+	for _, bConfig := range config.BridgeConfig {
+		b, err := NewBridge(bConfig, d)
+		if err != nil {
+			return err
+		}
+		r.bridges = append(r.bridges, b)
+	}
+
+	for _, pConfig := range config.PortalConfig {
+		p, err := NewPortal(pConfig, ohm)
+		if err != nil {
+			return err
+		}
+		r.portals = append(r.portals, p)
+	}
+
+	return nil
+}

common/mux/server.go

@@ -92,6 +92,10 @@ func handle(ctx context.Context, s *Session, output buf.Writer) {
 	s.Close()
 }
 
+func (w *ServerWorker) ActiveConnections() uint32 {
+	return uint32(w.sessionManager.Size())
+}
+
 func (w *ServerWorker) handleStatusKeepAlive(meta *FrameMetadata, reader *buf.BufferedReader) error {
 	if meta.Option.Has(OptionData) {
 		return buf.Copy(NewStreamReader(reader), buf.Discard)

main/distro/all/all.go

@@ -18,6 +18,7 @@ import (
 	_ "v2ray.com/core/app/dns"
 	_ "v2ray.com/core/app/log"
 	_ "v2ray.com/core/app/policy"
+	_ "v2ray.com/core/app/reverse"
 	_ "v2ray.com/core/app/router"
 	_ "v2ray.com/core/app/stats"