Feature: support relay (proxy chains) (#539)

README.md

@@ -255,6 +255,16 @@ proxies:
     # skip-cert-verify: true
 
 proxy-groups:
+  # relay chains the proxies. proxies shall not contain a proxy-group. No UDP support.
+  # Traffic: clash <-> http <-> vmess <-> ss1 <-> ss2 <-> Internet
+  - name: "relay"
+    type: relay
+    proxies:
+      - http
+      - vmess
+      - ss1
+      - ss2
+
   # url-test select which proxy will be used by benchmarking speed to a URL.
   - name: "auto"
     type: url-test

adapters/outbound/base.go

@@ -18,6 +18,7 @@ var (
 
 type Base struct {
 	name string
+	addr string
 	tp   C.AdapterType
 	udp  bool
 }
@@ -30,6 +31,10 @@ func (b *Base) Type() C.AdapterType {
 	return b.tp
 }
 
+func (b *Base) StreamConn(c net.Conn, metadata *C.Metadata) (net.Conn, error) {
+	return c, errors.New("no support")
+}
+
 func (b *Base) DialUDP(metadata *C.Metadata) (C.PacketConn, error) {
 	return nil, errors.New("no support")
 }
@@ -44,8 +49,12 @@ func (b *Base) MarshalJSON() ([]byte, error) {
 	})
 }
 
-func NewBase(name string, tp C.AdapterType, udp bool) *Base {
-	return &Base{name, tp, udp}
+func (b *Base) Addr() string {
+	return b.addr
+}
+
+func NewBase(name string, addr string, tp C.AdapterType, udp bool) *Base {
+	return &Base{name, addr, tp, udp}
 }
 
 type conn struct {
@@ -61,7 +70,7 @@ func (c *conn) AppendToChains(a C.ProxyAdapter) {
 	c.chain = append(c.chain, a.Name())
 }
 
-func newConn(c net.Conn, a C.ProxyAdapter) C.Conn {
+func NewConn(c net.Conn, a C.ProxyAdapter) C.Conn {
 	return &conn{c, []string{a.Name()}}
 }
 

adapters/outbound/direct.go

@@ -24,7 +24,7 @@ func (d *Direct) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn,
 		return nil, err
 	}
 	tcpKeepAlive(c)
-	return newConn(c, d), nil
+	return NewConn(c, d), nil
 }
 
 func (d *Direct) DialUDP(metadata *C.Metadata) (C.PacketConn, error) {

adapters/outbound/http.go

@@ -19,7 +19,6 @@ import (
 
 type Http struct {
 	*Base
-	addr      string
 	user      string
 	pass      string
 	tlsConfig *tls.Config
@@ -35,23 +34,35 @@ type HttpOption struct {
 	SkipCertVerify bool   `proxy:"skip-cert-verify,omitempty"`
 }
 
-func (h *Http) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
-	c, err := dialer.DialContext(ctx, "tcp", h.addr)
-	if err == nil && h.tlsConfig != nil {
+func (h *Http) StreamConn(c net.Conn, metadata *C.Metadata) (net.Conn, error) {
+	if h.tlsConfig != nil {
 		cc := tls.Client(c, h.tlsConfig)
-		err = cc.Handshake()
+		err := cc.Handshake()
 		c = cc
+		if err != nil {
+			return nil, fmt.Errorf("%s connect error: %w", h.addr, err)
+		}
 	}
 
+	if err := h.shakeHand(metadata, c); err != nil {
+		return nil, err
+	}
+	return c, nil
+}
+
+func (h *Http) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
+	c, err := dialer.DialContext(ctx, "tcp", h.addr)
 	if err != nil {
 		return nil, fmt.Errorf("%s connect error: %w", h.addr, err)
 	}
 	tcpKeepAlive(c)
-	if err := h.shakeHand(metadata, c); err != nil {
+
+	c, err = h.StreamConn(c, metadata)
+	if err != nil {
 		return nil, err
 	}
 
-	return newConn(c, h), nil
+	return NewConn(c, h), nil
 }
 
 func (h *Http) shakeHand(metadata *C.Metadata, rw io.ReadWriter) error {
@@ -113,9 +124,9 @@ func NewHttp(option HttpOption) *Http {
 	return &Http{
 		Base: &Base{
 			name: option.Name,
+			addr: net.JoinHostPort(option.Server, strconv.Itoa(option.Port)),
 			tp:   C.Http,
 		},
-		addr:      net.JoinHostPort(option.Server, strconv.Itoa(option.Port)),
 		user:      option.UserName,
 		pass:      option.Password,
 		tlsConfig: tlsConfig,

adapters/outbound/reject.go

@@ -15,7 +15,7 @@ type Reject struct {
 }
 
 func (r *Reject) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
-	return newConn(&NopConn{}, r), nil
+	return NewConn(&NopConn{}, r), nil
 }
 
 func (r *Reject) DialUDP(metadata *C.Metadata) (C.PacketConn, error) {

adapters/outbound/shadowsocks.go

@@ -21,7 +21,6 @@ import (
 
 type ShadowSocks struct {
 	*Base
-	server string
 	cipher core.Cipher
 
 	// obfs
@@ -60,28 +59,34 @@ type v2rayObfsOption struct {
 	Mux            bool              `obfs:"mux,omitempty"`
 }
 
-func (ss *ShadowSocks) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
-	c, err := dialer.DialContext(ctx, "tcp", ss.server)
-	if err != nil {
-		return nil, fmt.Errorf("%s connect error: %w", ss.server, err)
-	}
-	tcpKeepAlive(c)
+func (ss *ShadowSocks) StreamConn(c net.Conn, metadata *C.Metadata) (net.Conn, error) {
 	switch ss.obfsMode {
 	case "tls":
 		c = obfs.NewTLSObfs(c, ss.obfsOption.Host)
 	case "http":
-		_, port, _ := net.SplitHostPort(ss.server)
+		_, port, _ := net.SplitHostPort(ss.addr)
 		c = obfs.NewHTTPObfs(c, ss.obfsOption.Host, port)
 	case "websocket":
 		var err error
 		c, err = v2rayObfs.NewV2rayObfs(c, ss.v2rayOption)
 		if err != nil {
-			return nil, fmt.Errorf("%s connect error: %w", ss.server, err)
+			return nil, fmt.Errorf("%s connect error: %w", ss.addr, err)
 		}
 	}
 	c = ss.cipher.StreamConn(c)
-	_, err = c.Write(serializesSocksAddr(metadata))
-	return newConn(c, ss), err
+	_, err := c.Write(serializesSocksAddr(metadata))
+	return c, err
+}
+
+func (ss *ShadowSocks) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
+	c, err := dialer.DialContext(ctx, "tcp", ss.addr)
+	if err != nil {
+		return nil, fmt.Errorf("%s connect error: %w", ss.addr, err)
+	}
+	tcpKeepAlive(c)
+
+	c, err = ss.StreamConn(c, metadata)
+	return NewConn(c, ss), err
 }
 
 func (ss *ShadowSocks) DialUDP(metadata *C.Metadata) (C.PacketConn, error) {
@@ -90,7 +95,7 @@ func (ss *ShadowSocks) DialUDP(metadata *C.Metadata) (C.PacketConn, error) {
 		return nil, err
 	}
 
-	addr, err := resolveUDPAddr("udp", ss.server)
+	addr, err := resolveUDPAddr("udp", ss.addr)
 	if err != nil {
 		return nil, err
 	}
@@ -106,12 +111,12 @@ func (ss *ShadowSocks) MarshalJSON() ([]byte, error) {
 }
 
 func NewShadowSocks(option ShadowSocksOption) (*ShadowSocks, error) {
-	server := net.JoinHostPort(option.Server, strconv.Itoa(option.Port))
+	addr := net.JoinHostPort(option.Server, strconv.Itoa(option.Port))
 	cipher := option.Cipher
 	password := option.Password
 	ciph, err := core.PickCipher(cipher, nil, password)
 	if err != nil {
-		return nil, fmt.Errorf("ss %s initialize error: %w", server, err)
+		return nil, fmt.Errorf("ss %s initialize error: %w", addr, err)
 	}
 
 	var v2rayOption *v2rayObfs.Option
@@ -133,22 +138,22 @@ func NewShadowSocks(option ShadowSocksOption) (*ShadowSocks, error) {
 	if option.Plugin == "obfs" {
 		opts := simpleObfsOption{Host: "bing.com"}
 		if err := decoder.Decode(option.PluginOpts, &opts); err != nil {
-			return nil, fmt.Errorf("ss %s initialize obfs error: %w", server, err)
+			return nil, fmt.Errorf("ss %s initialize obfs error: %w", addr, err)
 		}
 
 		if opts.Mode != "tls" && opts.Mode != "http" {
-			return nil, fmt.Errorf("ss %s obfs mode error: %s", server, opts.Mode)
+			return nil, fmt.Errorf("ss %s obfs mode error: %s", addr, opts.Mode)
 		}
 		obfsMode = opts.Mode
 		obfsOption = &opts
 	} else if option.Plugin == "v2ray-plugin" {
 		opts := v2rayObfsOption{Host: "bing.com", Mux: true}
 		if err := decoder.Decode(option.PluginOpts, &opts); err != nil {
-			return nil, fmt.Errorf("ss %s initialize v2ray-plugin error: %w", server, err)
+			return nil, fmt.Errorf("ss %s initialize v2ray-plugin error: %w", addr, err)
 		}
 
 		if opts.Mode != "websocket" {
-			return nil, fmt.Errorf("ss %s obfs mode error: %s", server, opts.Mode)
+			return nil, fmt.Errorf("ss %s obfs mode error: %s", addr, opts.Mode)
 		}
 		obfsMode = opts.Mode
 
@@ -172,10 +177,10 @@ func NewShadowSocks(option ShadowSocksOption) (*ShadowSocks, error) {
 	return &ShadowSocks{
 		Base: &Base{
 			name: option.Name,
+			addr: addr,
 			tp:   C.Shadowsocks,
 			udp:  option.UDP,
 		},
-		server: server,
 		cipher: ciph,
 
 		obfsMode:    obfsMode,

adapters/outbound/snell.go

@@ -15,7 +15,6 @@ import (
 
 type Snell struct {
 	*Base
-	server     string
 	psk        []byte
 	obfsOption *simpleObfsOption
 }
@@ -28,45 +27,51 @@ type SnellOption struct {
 	ObfsOpts map[string]interface{} `proxy:"obfs-opts,omitempty"`
 }
 
-func (s *Snell) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
-	c, err := dialer.DialContext(ctx, "tcp", s.server)
-	if err != nil {
-		return nil, fmt.Errorf("%s connect error: %w", s.server, err)
-	}
-	tcpKeepAlive(c)
+func (s *Snell) StreamConn(c net.Conn, metadata *C.Metadata) (net.Conn, error) {
 	switch s.obfsOption.Mode {
 	case "tls":
 		c = obfs.NewTLSObfs(c, s.obfsOption.Host)
 	case "http":
-		_, port, _ := net.SplitHostPort(s.server)
+		_, port, _ := net.SplitHostPort(s.addr)
 		c = obfs.NewHTTPObfs(c, s.obfsOption.Host, port)
 	}
 	c = snell.StreamConn(c, s.psk)
 	port, _ := strconv.Atoi(metadata.DstPort)
-	err = snell.WriteHeader(c, metadata.String(), uint(port))
-	return newConn(c, s), err
+	err := snell.WriteHeader(c, metadata.String(), uint(port))
+	return c, err
+}
+
+func (s *Snell) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
+	c, err := dialer.DialContext(ctx, "tcp", s.addr)
+	if err != nil {
+		return nil, fmt.Errorf("%s connect error: %w", s.addr, err)
+	}
+	tcpKeepAlive(c)
+
+	c, err = s.StreamConn(c, metadata)
+	return NewConn(c, s), err
 }
 
 func NewSnell(option SnellOption) (*Snell, error) {
-	server := net.JoinHostPort(option.Server, strconv.Itoa(option.Port))
+	addr := net.JoinHostPort(option.Server, strconv.Itoa(option.Port))
 	psk := []byte(option.Psk)
 
 	decoder := structure.NewDecoder(structure.Option{TagName: "obfs", WeaklyTypedInput: true})
 	obfsOption := &simpleObfsOption{Host: "bing.com"}
 	if err := decoder.Decode(option.ObfsOpts, obfsOption); err != nil {
-		return nil, fmt.Errorf("snell %s initialize obfs error: %w", server, err)
+		return nil, fmt.Errorf("snell %s initialize obfs error: %w", addr, err)
 	}
 
 	if obfsOption.Mode != "tls" && obfsOption.Mode != "http" {
-		return nil, fmt.Errorf("snell %s obfs mode error: %s", server, obfsOption.Mode)
+		return nil, fmt.Errorf("snell %s obfs mode error: %s", addr, obfsOption.Mode)
 	}
 
 	return &Snell{
 		Base: &Base{
 			name: option.Name,
+			addr: addr,
 			tp:   C.Snell,
 		},
-		server:     server,
 		psk:        psk,
 		obfsOption: obfsOption,
 	}, nil

adapters/outbound/socks5.go

@@ -17,7 +17,6 @@ import (
 
 type Socks5 struct {
 	*Base
-	addr           string
 	user           string
 	pass           string
 	tls            bool
@@ -36,19 +35,16 @@ type Socks5Option struct {
 	SkipCertVerify bool   `proxy:"skip-cert-verify,omitempty"`
 }
 
-func (ss *Socks5) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
-	c, err := dialer.DialContext(ctx, "tcp", ss.addr)
-
-	if err == nil && ss.tls {
+func (ss *Socks5) StreamConn(c net.Conn, metadata *C.Metadata) (net.Conn, error) {
+	if ss.tls {
 		cc := tls.Client(c, ss.tlsConfig)
-		err = cc.Handshake()
+		err := cc.Handshake()
 		c = cc
+		if err != nil {
+			return nil, fmt.Errorf("%s connect error: %w", ss.addr, err)
+		}
 	}
 
-	if err != nil {
-		return nil, fmt.Errorf("%s connect error: %w", ss.addr, err)
-	}
-	tcpKeepAlive(c)
 	var user *socks5.User
 	if ss.user != "" {
 		user = &socks5.User{
@@ -59,7 +55,22 @@ func (ss *Socks5) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn
 	if _, err := socks5.ClientHandshake(c, serializesSocksAddr(metadata), socks5.CmdConnect, user); err != nil {
 		return nil, err
 	}
-	return newConn(c, ss), nil
+	return c, nil
+}
+
+func (ss *Socks5) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
+	c, err := dialer.DialContext(ctx, "tcp", ss.addr)
+	if err != nil {
+		return nil, fmt.Errorf("%s connect error: %w", ss.addr, err)
+	}
+	tcpKeepAlive(c)
+
+	c, err = ss.StreamConn(c, metadata)
+	if err != nil {
+		return nil, err
+	}
+
+	return NewConn(c, ss), nil
 }
 
 func (ss *Socks5) DialUDP(metadata *C.Metadata) (_ C.PacketConn, err error) {
@@ -127,10 +138,10 @@ func NewSocks5(option Socks5Option) *Socks5 {
 	return &Socks5{
 		Base: &Base{
 			name: option.Name,
+			addr: net.JoinHostPort(option.Server, strconv.Itoa(option.Port)),
 			tp:   C.Socks5,
 			udp:  option.UDP,
 		},
-		addr:           net.JoinHostPort(option.Server, strconv.Itoa(option.Port)),
 		user:           option.UserName,
 		pass:           option.Password,
 		tls:            option.TLS,

adapters/outbound/trojan.go

@@ -14,7 +14,6 @@ import (
 
 type Trojan struct {
 	*Base
-	server   string
 	instance *trojan.Trojan
 }
 
@@ -29,32 +28,41 @@ type TrojanOption struct {
 	UDP            bool     `proxy:"udp,omitempty"`
 }
 
-func (t *Trojan) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
-	c, err := dialer.DialContext(ctx, "tcp", t.server)
+func (t *Trojan) StreamConn(c net.Conn, metadata *C.Metadata) (net.Conn, error) {
+	c, err := t.instance.StreamConn(c)
 	if err != nil {
-		return nil, fmt.Errorf("%s connect error: %w", t.server, err)
-	}
-	tcpKeepAlive(c)
-	c, err = t.instance.StreamConn(c)
-	if err != nil {
-		return nil, fmt.Errorf("%s connect error: %w", t.server, err)
+		return nil, fmt.Errorf("%s connect error: %w", t.addr, err)
 	}
 
 	err = t.instance.WriteHeader(c, trojan.CommandTCP, serializesSocksAddr(metadata))
-	return newConn(c, t), err
+	return c, err
+}
+
+func (t *Trojan) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
+	c, err := dialer.DialContext(ctx, "tcp", t.addr)
+	if err != nil {
+		return nil, fmt.Errorf("%s connect error: %w", t.addr, err)
+	}
+	tcpKeepAlive(c)
+	c, err = t.StreamConn(c, metadata)
+	if err != nil {
+		return nil, err
+	}
+
+	return NewConn(c, t), err
 }
 
 func (t *Trojan) DialUDP(metadata *C.Metadata) (C.PacketConn, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), tcpTimeout)
 	defer cancel()
-	c, err := dialer.DialContext(ctx, "tcp", t.server)
+	c, err := dialer.DialContext(ctx, "tcp", t.addr)
 	if err != nil {
-		return nil, fmt.Errorf("%s connect error: %w", t.server, err)
+		return nil, fmt.Errorf("%s connect error: %w", t.addr, err)
 	}
 	tcpKeepAlive(c)
 	c, err = t.instance.StreamConn(c)
 	if err != nil {
-		return nil, fmt.Errorf("%s connect error: %w", t.server, err)
+		return nil, fmt.Errorf("%s connect error: %w", t.addr, err)
 	}
 
 	err = t.instance.WriteHeader(c, trojan.CommandUDP, serializesSocksAddr(metadata))
@@ -73,7 +81,7 @@ func (t *Trojan) MarshalJSON() ([]byte, error) {
 }
 
 func NewTrojan(option TrojanOption) (*Trojan, error) {
-	server := net.JoinHostPort(option.Server, strconv.Itoa(option.Port))
+	addr := net.JoinHostPort(option.Server, strconv.Itoa(option.Port))
 
 	tOption := &trojan.Option{
 		Password:           option.Password,
@@ -90,10 +98,10 @@ func NewTrojan(option TrojanOption) (*Trojan, error) {
 	return &Trojan{
 		Base: &Base{
 			name: option.Name,
+			addr: addr,
 			tp:   C.Trojan,
 			udp:  option.UDP,
 		},
-		server:   server,
 		instance: trojan.New(tOption),
 	}, nil
 }

adapters/outbound/vmess.go

@@ -16,7 +16,6 @@ import (
 
 type Vmess struct {
 	*Base
-	server string
 	client *vmess.Client
 }
 
@@ -35,14 +34,19 @@ type VmessOption struct {
 	SkipCertVerify bool              `proxy:"skip-cert-verify,omitempty"`
 }
 
+func (v *Vmess) StreamConn(c net.Conn, metadata *C.Metadata) (net.Conn, error) {
+	return v.client.New(c, parseVmessAddr(metadata))
+}
+
 func (v *Vmess) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
-	c, err := dialer.DialContext(ctx, "tcp", v.server)
+	c, err := dialer.DialContext(ctx, "tcp", v.addr)
 	if err != nil {
-		return nil, fmt.Errorf("%s connect error", v.server)
+		return nil, fmt.Errorf("%s connect error", v.addr)
 	}
 	tcpKeepAlive(c)
-	c, err = v.client.New(c, parseVmessAddr(metadata))
-	return newConn(c, v), err
+
+	c, err = v.StreamConn(c, metadata)
+	return NewConn(c, v), err
 }
 
 func (v *Vmess) DialUDP(metadata *C.Metadata) (C.PacketConn, error) {
@@ -57,9 +61,9 @@ func (v *Vmess) DialUDP(metadata *C.Metadata) (C.PacketConn, error) {
 
 	ctx, cancel := context.WithTimeout(context.Background(), tcpTimeout)
 	defer cancel()
-	c, err := dialer.DialContext(ctx, "tcp", v.server)
+	c, err := dialer.DialContext(ctx, "tcp", v.addr)
 	if err != nil {
-		return nil, fmt.Errorf("%s connect error", v.server)
+		return nil, fmt.Errorf("%s connect error", v.addr)
 	}
 	tcpKeepAlive(c)
 	c, err = v.client.New(c, parseVmessAddr(metadata))
@@ -91,10 +95,10 @@ func NewVmess(option VmessOption) (*Vmess, error) {
 	return &Vmess{
 		Base: &Base{
 			name: option.Name,
+			addr: net.JoinHostPort(option.Server, strconv.Itoa(option.Port)),
 			tp:   C.Vmess,
 			udp:  true,
 		},
-		server: net.JoinHostPort(option.Server, strconv.Itoa(option.Port)),
 		client: client,
 	}, nil
 }

adapters/outboundgroup/fallback.go

@@ -77,7 +77,7 @@ func (f *Fallback) findAliveProxy() C.Proxy {
 
 func NewFallback(name string, providers []provider.ProxyProvider) *Fallback {
 	return &Fallback{
-		Base:      outbound.NewBase(name, C.Fallback, false),
+		Base:      outbound.NewBase(name, "", C.Fallback, false),
 		single:    singledo.NewSingle(defaultGetProxiesDuration),
 		providers: providers,
 	}

adapters/outboundgroup/loadbalance.go

@@ -120,7 +120,7 @@ func (lb *LoadBalance) MarshalJSON() ([]byte, error) {
 
 func NewLoadBalance(name string, providers []provider.ProxyProvider) *LoadBalance {
 	return &LoadBalance{
-		Base:      outbound.NewBase(name, C.LoadBalance, false),
+		Base:      outbound.NewBase(name, "", C.LoadBalance, false),
 		single:    singledo.NewSingle(defaultGetProxiesDuration),
 		maxRetry:  3,
 		providers: providers,

adapters/outboundgroup/parser.go

@@ -64,7 +64,7 @@ func ParseProxyGroup(config map[string]interface{}, proxyMap map[string]C.Proxy,
 			providers = append(providers, pd)
 		} else {
 			// select don't need health check
-			if groupOption.Type == "select" {
+			if groupOption.Type == "select" || groupOption.Type == "relay" {
 				hc := provider.NewHealthCheck(ps, "", 0)
 				pd, err := provider.NewCompatibleProvider(groupName, ps, hc)
 				if err != nil {
@@ -108,6 +108,8 @@ func ParseProxyGroup(config map[string]interface{}, proxyMap map[string]C.Proxy,
 		group = NewFallback(groupName, providers)
 	case "load-balance":
 		group = NewLoadBalance(groupName, providers)
+	case "relay":
+		group = NewRelay(groupName, providers)
 	default:
 		return nil, fmt.Errorf("%w: %s", errType, groupOption.Type)
 	}

adapters/outboundgroup/relay.go

@@ -0,0 +1,84 @@
+package outboundgroup
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+
+	"github.com/Dreamacro/clash/adapters/outbound"
+	"github.com/Dreamacro/clash/adapters/provider"
+	"github.com/Dreamacro/clash/common/singledo"
+	"github.com/Dreamacro/clash/component/dialer"
+	C "github.com/Dreamacro/clash/constant"
+)
+
+type Relay struct {
+	*outbound.Base
+	single    *singledo.Single
+	providers []provider.ProxyProvider
+}
+
+func (r *Relay) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
+	proxies := r.proxies()
+	if len(proxies) == 0 {
+		return nil, errors.New("Proxy does not exist")
+	}
+	first := proxies[0]
+	last := proxies[len(proxies)-1]
+
+	c, err := dialer.DialContext(ctx, "tcp", first.Addr())
+	if err != nil {
+		return nil, fmt.Errorf("%s connect error: %w", first.Addr(), err)
+	}
+	tcpKeepAlive(c)
+
+	var currentMeta *C.Metadata
+	for _, proxy := range proxies[1:] {
+		currentMeta, err = addrToMetadata(proxy.Addr())
+		if err != nil {
+			return nil, err
+		}
+
+		c, err = first.StreamConn(c, currentMeta)
+		if err != nil {
+			return nil, fmt.Errorf("%s connect error: %w", first.Addr(), err)
+		}
+
+		first = proxy
+	}
+
+	c, err = last.StreamConn(c, metadata)
+	if err != nil {
+		return nil, fmt.Errorf("%s connect error: %w", last.Addr(), err)
+	}
+
+	return outbound.NewConn(c, r), nil
+}
+
+func (r *Relay) MarshalJSON() ([]byte, error) {
+	var all []string
+	for _, proxy := range r.proxies() {
+		all = append(all, proxy.Name())
+	}
+	return json.Marshal(map[string]interface{}{
+		"type": r.Type().String(),
+		"all":  all,
+	})
+}
+
+func (r *Relay) proxies() []C.Proxy {
+	elm, _, _ := r.single.Do(func() (interface{}, error) {
+		return getProvidersProxies(r.providers), nil
+	})
+
+	return elm.([]C.Proxy)
+}
+
+func NewRelay(name string, providers []provider.ProxyProvider) *Relay {
+	return &Relay{
+		Base:      outbound.NewBase(name, "", C.Relay, false),
+		single:    singledo.NewSingle(defaultGetProxiesDuration),
+		providers: providers,
+	}
+}

adapters/outboundgroup/selector.go

@@ -77,7 +77,7 @@ func (s *Selector) proxies() []C.Proxy {
 func NewSelector(name string, providers []provider.ProxyProvider) *Selector {
 	selected := providers[0].Proxies()[0]
 	return &Selector{
-		Base:      outbound.NewBase(name, C.Selector, false),
+		Base:      outbound.NewBase(name, "", C.Selector, false),
 		single:    singledo.NewSingle(defaultGetProxiesDuration),
 		providers: providers,
 		selected:  selected,

adapters/outboundgroup/urltest.go

@@ -86,7 +86,7 @@ func (u *URLTest) MarshalJSON() ([]byte, error) {
 
 func NewURLTest(name string, providers []provider.ProxyProvider) *URLTest {
 	return &URLTest{
-		Base:       outbound.NewBase(name, C.URLTest, false),
+		Base:       outbound.NewBase(name, "", C.URLTest, false),
 		single:     singledo.NewSingle(defaultGetProxiesDuration),
 		fastSingle: singledo.NewSingle(time.Second * 10),
 		providers:  providers,

adapters/outboundgroup/util.go

@@ -0,0 +1,53 @@
+package outboundgroup
+
+import (
+	"fmt"
+	"net"
+	"time"
+
+	C "github.com/Dreamacro/clash/constant"
+)
+
+func addrToMetadata(rawAddress string) (addr *C.Metadata, err error) {
+	host, port, err := net.SplitHostPort(rawAddress)
+	if err != nil {
+		err = fmt.Errorf("addrToMetadata failed: %w", err)
+		return
+	}
+
+	ip := net.ParseIP(host)
+	if ip != nil {
+		if ip.To4() != nil {
+			addr = &C.Metadata{
+				AddrType: C.AtypIPv4,
+				Host:     "",
+				DstIP:    ip,
+				DstPort:  port,
+			}
+			return
+		} else {
+			addr = &C.Metadata{
+				AddrType: C.AtypIPv6,
+				Host:     "",
+				DstIP:    ip,
+				DstPort:  port,
+			}
+			return
+		}
+	} else {
+		addr = &C.Metadata{
+			AddrType: C.AtypDomainName,
+			Host:     host,
+			DstIP:    nil,
+			DstPort:  port,
+		}
+		return
+	}
+}
+
+func tcpKeepAlive(c net.Conn) {
+	if tcp, ok := c.(*net.TCPConn); ok {
+		tcp.SetKeepAlive(true)
+		tcp.SetKeepAlivePeriod(30 * time.Second)
+	}
+}

constant/adapters.go

@@ -19,6 +19,7 @@ const (
 	Vmess
 	Trojan
 
+	Relay
 	Selector
 	Fallback
 	URLTest
@@ -62,10 +63,12 @@ type PacketConn interface {
 type ProxyAdapter interface {
 	Name() string
 	Type() AdapterType
+	StreamConn(c net.Conn, metadata *Metadata) (net.Conn, error)
 	DialContext(ctx context.Context, metadata *Metadata) (Conn, error)
 	DialUDP(metadata *Metadata) (PacketConn, error)
 	SupportUDP() bool
 	MarshalJSON() ([]byte, error)
+	Addr() string
 }
 
 type DelayHistory struct {
@@ -105,6 +108,8 @@ func (at AdapterType) String() string {
 	case Trojan:
 		return "Trojan"
 
+	case Relay:
+		return "Relay"
 	case Selector:
 		return "Selector"
 	case Fallback: