Feature: SOCKS4/SOCKS4A Inbound Compatible Support (#1491)

listener/listener.go

@@ -139,7 +139,7 @@ func ReCreateSocks(port int, tcpIn chan<- C.ConnContext, udpIn chan<- *inbound.P
 	socksListener = tcpListener
 	socksUDPListener = udpListener
 
-	log.Infoln("SOCKS5 proxy listening at: %s", socksListener.Address())
+	log.Infoln("SOCKS proxy listening at: %s", socksListener.Address())
 	return nil
 }
 
@@ -271,7 +271,7 @@ func ReCreateMixed(port int, tcpIn chan<- C.ConnContext, udpIn chan<- *inbound.P
 		return err
 	}
 
-	log.Infoln("Mixed(http+socks5) proxy listening at: %s", mixedListener.Address())
+	log.Infoln("Mixed(http+socks) proxy listening at: %s", mixedListener.Address())
 	return nil
 }
 

listener/mixed/mixed.go

@@ -9,6 +9,7 @@ import (
 	C "github.com/Dreamacro/clash/constant"
 	"github.com/Dreamacro/clash/listener/http"
 	"github.com/Dreamacro/clash/listener/socks"
+	"github.com/Dreamacro/clash/transport/socks4"
 	"github.com/Dreamacro/clash/transport/socks5"
 )
 
@@ -58,10 +59,12 @@ func handleConn(conn net.Conn, in chan<- C.ConnContext, cache *cache.Cache) {
 		return
 	}
 
-	if head[0] == socks5.Version {
-		socks.HandleSocks(bufConn, in)
-		return
+	switch head[0] {
+	case socks4.Version:
+		socks.HandleSocks4(bufConn, in)
+	case socks5.Version:
+		socks.HandleSocks5(bufConn, in)
+	default:
+		http.HandleConn(bufConn, in, cache)
 	}
-
-	http.HandleConn(bufConn, in, cache)
 }

listener/socks/tcp.go

@@ -6,8 +6,10 @@ import (
 	"net"
 
 	"github.com/Dreamacro/clash/adapter/inbound"
+	N "github.com/Dreamacro/clash/common/net"
 	C "github.com/Dreamacro/clash/constant"
 	authStore "github.com/Dreamacro/clash/listener/auth"
+	"github.com/Dreamacro/clash/transport/socks4"
 	"github.com/Dreamacro/clash/transport/socks5"
 )
 
@@ -33,7 +35,7 @@ func New(addr string, in chan<- C.ConnContext) (*Listener, error) {
 				}
 				continue
 			}
-			go HandleSocks(c, in)
+			go handleSocks(c, in)
 		}
 	}()
 
@@ -49,7 +51,37 @@ func (l *Listener) Address() string {
 	return l.address
 }
 
-func HandleSocks(conn net.Conn, in chan<- C.ConnContext) {
+func handleSocks(conn net.Conn, in chan<- C.ConnContext) {
+	bufConn := N.NewBufferedConn(conn)
+	head, err := bufConn.Peek(1)
+	if err != nil {
+		conn.Close()
+		return
+	}
+
+	switch head[0] {
+	case socks4.Version:
+		HandleSocks4(bufConn, in)
+	case socks5.Version:
+		HandleSocks5(bufConn, in)
+	default:
+		conn.Close()
+	}
+}
+
+func HandleSocks4(conn net.Conn, in chan<- C.ConnContext) {
+	addr, _, err := socks4.ServerHandshake(conn, authStore.Authenticator())
+	if err != nil {
+		conn.Close()
+		return
+	}
+	if c, ok := conn.(*net.TCPConn); ok {
+		c.SetKeepAlive(true)
+	}
+	in <- inbound.NewSocket(socks5.ParseAddr(addr), conn, C.SOCKS)
+}
+
+func HandleSocks5(conn net.Conn, in chan<- C.ConnContext) {
 	target, command, err := socks5.ServerHandshake(conn, authStore.Authenticator())
 	if err != nil {
 		conn.Close()