Feature: support proxy-group in relay (#597)

README.md

@@ -273,7 +273,7 @@ proxies:
     # skip-cert-verify: true
 
 proxy-groups:
-  # relay chains the proxies. proxies shall not contain a proxy-group. No UDP support.
+  # relay chains the proxies. proxies shall not contain a relay. No UDP support.
   # Traffic: clash <-> http <-> vmess <-> ss1 <-> ss2 <-> Internet
   - name: "relay"
     type: relay

adapters/outbound/base.go

@@ -53,6 +53,10 @@ func (b *Base) Addr() string {
 	return b.addr
 }
 
+func (b *Base) Unwrap(metadata *C.Metadata) C.Proxy {
+	return nil
+}
+
 func NewBase(name string, addr string, tp C.AdapterType, udp bool) *Base {
 	return &Base{name, addr, tp, udp}
 }

adapters/outboundgroup/fallback.go

@@ -56,6 +56,11 @@ func (f *Fallback) MarshalJSON() ([]byte, error) {
 	})
 }
 
+func (f *Fallback) Unwrap(metadata *C.Metadata) C.Proxy {
+	proxy := f.findAliveProxy()
+	return proxy
+}
+
 func (f *Fallback) proxies() []C.Proxy {
 	elm, _, _ := f.single.Do(func() (interface{}, error) {
 		return getProvidersProxies(f.providers), nil

adapters/outboundgroup/loadbalance.go

@@ -59,18 +59,9 @@ func (lb *LoadBalance) DialContext(ctx context.Context, metadata *C.Metadata) (c
 		}
 	}()
 
-	key := uint64(murmur3.Sum32([]byte(getKey(metadata))))
-	proxies := lb.proxies()
-	buckets := int32(len(proxies))
-	for i := 0; i < lb.maxRetry; i, key = i+1, key+1 {
-		idx := jumpHash(key, buckets)
-		proxy := proxies[idx]
-		if proxy.Alive() {
-			c, err = proxy.DialContext(ctx, metadata)
-			return
-		}
-	}
-	c, err = proxies[0].DialContext(ctx, metadata)
+	proxy := lb.Unwrap(metadata)
+
+	c, err = proxy.DialContext(ctx, metadata)
 	return
 }
 
@@ -81,22 +72,28 @@ func (lb *LoadBalance) DialUDP(metadata *C.Metadata) (pc C.PacketConn, err error
 		}
 	}()
 
+	proxy := lb.Unwrap(metadata)
+
+	return proxy.DialUDP(metadata)
+}
+
+func (lb *LoadBalance) SupportUDP() bool {
+	return true
+}
+
+func (lb *LoadBalance) Unwrap(metadata *C.Metadata) C.Proxy {
 	key := uint64(murmur3.Sum32([]byte(getKey(metadata))))
 	proxies := lb.proxies()
 	buckets := int32(len(proxies))
 	for i := 0; i < lb.maxRetry; i, key = i+1, key+1 {
 		idx := jumpHash(key, buckets)
 		proxy := proxies[idx]
 		if proxy.Alive() {
-			return proxy.DialUDP(metadata)
+			return proxy
 		}
 	}
 
-	return proxies[0].DialUDP(metadata)
-}
-
-func (lb *LoadBalance) SupportUDP() bool {
-	return true
+	return proxies[0]
 }
 
 func (lb *LoadBalance) proxies() []C.Proxy {

adapters/outboundgroup/relay.go

@@ -20,7 +20,7 @@ type Relay struct {
 }
 
 func (r *Relay) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
-	proxies := r.proxies()
+	proxies := r.proxies(metadata)
 	if len(proxies) == 0 {
 		return nil, errors.New("Proxy does not exist")
 	}
@@ -58,7 +58,7 @@ func (r *Relay) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn,
 
 func (r *Relay) MarshalJSON() ([]byte, error) {
 	var all []string
-	for _, proxy := range r.proxies() {
+	for _, proxy := range r.rawProxies() {
 		all = append(all, proxy.Name())
 	}
 	return json.Marshal(map[string]interface{}{
@@ -67,14 +67,28 @@ func (r *Relay) MarshalJSON() ([]byte, error) {
 	})
 }
 
-func (r *Relay) proxies() []C.Proxy {
+func (r *Relay) rawProxies() []C.Proxy {
 	elm, _, _ := r.single.Do(func() (interface{}, error) {
 		return getProvidersProxies(r.providers), nil
 	})
 
 	return elm.([]C.Proxy)
 }
 
+func (r *Relay) proxies(metadata *C.Metadata) []C.Proxy {
+	proxies := r.rawProxies()
+
+	for n, proxy := range proxies {
+		subproxy := proxy.Unwrap(metadata)
+		for subproxy != nil {
+			proxies[n] = subproxy
+			subproxy = subproxy.Unwrap(metadata)
+		}
+	}
+
+	return proxies
+}
+
 func NewRelay(name string, providers []provider.ProxyProvider) *Relay {
 	return &Relay{
 		Base:      outbound.NewBase(name, "", C.Relay, false),

adapters/outboundgroup/selector.go

@@ -67,6 +67,10 @@ func (s *Selector) Set(name string) error {
 	return errors.New("Proxy does not exist")
 }
 
+func (s *Selector) Unwrap(metadata *C.Metadata) C.Proxy {
+	return s.selectedProxy()
+}
+
 func (s *Selector) selectedProxy() C.Proxy {
 	elm, _, _ := s.single.Do(func() (interface{}, error) {
 		proxies := getProvidersProxies(s.providers)

adapters/outboundgroup/urltest.go

@@ -38,6 +38,10 @@ func (u *URLTest) DialUDP(metadata *C.Metadata) (C.PacketConn, error) {
 	return pc, err
 }
 
+func (u *URLTest) Unwrap(metadata *C.Metadata) C.Proxy {
+	return u.fast()
+}
+
 func (u *URLTest) proxies() []C.Proxy {
 	elm, _, _ := u.single.Do(func() (interface{}, error) {
 		return getProvidersProxies(u.providers), nil

constant/adapters.go

@@ -69,6 +69,8 @@ type ProxyAdapter interface {
 	SupportUDP() bool
 	MarshalJSON() ([]byte, error)
 	Addr() string
+	// Unwrap extracts the proxy from a proxy-group. It returns nil when nothing to extract.
+	Unwrap(metadata *Metadata) Proxy
 }
 
 type DelayHistory struct {