add handler error metrics

pkg/common/metrics/conn.go

@@ -28,13 +28,13 @@ func WrapConn(service string, c net.Conn) net.Conn {
 
 func (c *serverConn) Read(b []byte) (n int, err error) {
 	n, err = c.Conn.Read(b)
-	metrics.RequestInputBytes(c.service).Add(float64(n))
+	metrics.InputBytes(c.service).Add(float64(n))
 	return
 }
 
 func (c *serverConn) Write(b []byte) (n int, err error) {
 	n, err = c.Conn.Write(b)
-	metrics.RequestOutputBytes(c.service).Add(float64(n))
+	metrics.OutputBytes(c.service).Add(float64(n))
 	return
 }
 
@@ -52,13 +52,13 @@ func WrapPacketConn(service string, pc net.PacketConn) net.PacketConn {
 
 func (c *packetConn) ReadFrom(p []byte) (n int, addr net.Addr, err error) {
 	n, addr, err = c.PacketConn.ReadFrom(p)
-	metrics.RequestInputBytes(c.service).Add(float64(n))
+	metrics.InputBytes(c.service).Add(float64(n))
 	return
 }
 
 func (c *packetConn) WriteTo(p []byte, addr net.Addr) (n int, err error) {
 	n, err = c.PacketConn.WriteTo(p, addr)
-	metrics.RequestOutputBytes(c.service).Add(float64(n))
+	metrics.OutputBytes(c.service).Add(float64(n))
 	return
 }
 
@@ -98,7 +98,7 @@ func (c *udpConn) SetWriteBuffer(n int) error {
 func (c *udpConn) Read(b []byte) (n int, err error) {
 	if nc, ok := c.PacketConn.(io.Reader); ok {
 		n, err = nc.Read(b)
-		metrics.RequestInputBytes(c.service).Add(float64(n))
+		metrics.InputBytes(c.service).Add(float64(n))
 		return
 	}
 	err = errUnsupport
@@ -107,14 +107,14 @@ func (c *udpConn) Read(b []byte) (n int, err error) {
 
 func (c *udpConn) ReadFrom(p []byte) (n int, addr net.Addr, err error) {
 	n, addr, err = c.PacketConn.ReadFrom(p)
-	metrics.RequestInputBytes(c.service).Add(float64(n))
+	metrics.InputBytes(c.service).Add(float64(n))
 	return
 }
 
 func (c *udpConn) ReadFromUDP(b []byte) (n int, addr *net.UDPAddr, err error) {
 	if nc, ok := c.PacketConn.(readUDP); ok {
 		n, addr, err = nc.ReadFromUDP(b)
-		metrics.RequestInputBytes(c.service).Add(float64(n))
+		metrics.InputBytes(c.service).Add(float64(n))
 		return
 	}
 	err = errUnsupport
@@ -124,7 +124,7 @@ func (c *udpConn) ReadFromUDP(b []byte) (n int, addr *net.UDPAddr, err error) {
 func (c *udpConn) ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *net.UDPAddr, err error) {
 	if nc, ok := c.PacketConn.(readUDP); ok {
 		n, oobn, flags, addr, err = nc.ReadMsgUDP(b, oob)
-		metrics.RequestInputBytes(c.service).Add(float64(n + oobn))
+		metrics.InputBytes(c.service).Add(float64(n + oobn))
 		return
 	}
 	err = errUnsupport
@@ -134,7 +134,7 @@ func (c *udpConn) ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *net.UDPAd
 func (c *udpConn) Write(b []byte) (n int, err error) {
 	if nc, ok := c.PacketConn.(io.Writer); ok {
 		n, err = nc.Write(b)
-		metrics.RequestOutputBytes(c.service).Add(float64(n))
+		metrics.OutputBytes(c.service).Add(float64(n))
 		return
 	}
 	err = errUnsupport
@@ -143,14 +143,14 @@ func (c *udpConn) Write(b []byte) (n int, err error) {
 
 func (c *udpConn) WriteTo(p []byte, addr net.Addr) (n int, err error) {
 	n, err = c.PacketConn.WriteTo(p, addr)
-	metrics.RequestOutputBytes(c.service).Add(float64(n))
+	metrics.OutputBytes(c.service).Add(float64(n))
 	return
 }
 
 func (c *udpConn) WriteToUDP(b []byte, addr *net.UDPAddr) (n int, err error) {
 	if nc, ok := c.PacketConn.(writeUDP); ok {
 		n, err = nc.WriteToUDP(b, addr)
-		metrics.RequestOutputBytes(c.service).Add(float64(n))
+		metrics.OutputBytes(c.service).Add(float64(n))
 		return
 	}
 	err = errUnsupport
@@ -160,7 +160,7 @@ func (c *udpConn) WriteToUDP(b []byte, addr *net.UDPAddr) (n int, err error) {
 func (c *udpConn) WriteMsgUDP(b, oob []byte, addr *net.UDPAddr) (n, oobn int, err error) {
 	if nc, ok := c.PacketConn.(writeUDP); ok {
 		n, oobn, err = nc.WriteMsgUDP(b, oob, addr)
-		metrics.RequestOutputBytes(c.service).Add(float64(n + oobn))
+		metrics.OutputBytes(c.service).Add(float64(n + oobn))
 		return
 	}
 	err = errUnsupport

pkg/common/net/relay/relay.go

@@ -1,4 +1,4 @@
-package handler
+package relay
 
 import (
 	"net"

pkg/common/net/transport.go

@@ -1,4 +1,4 @@
-package handler
+package net
 
 import (
 	"bufio"

pkg/handler/auto/handler.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/go-gost/gosocks4"
 	"github.com/go-gost/gosocks5"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/handler"
 	md "github.com/go-gost/gost/pkg/metadata"
 	"github.com/go-gost/gost/pkg/registry"
@@ -85,7 +86,7 @@ func (h *autoHandler) Init(md md.Metadata) error {
 	return nil
 }
 
-func (h *autoHandler) Handle(ctx context.Context, conn net.Conn) {
+func (h *autoHandler) Handle(ctx context.Context, conn net.Conn) error {
 	log := h.options.Logger.WithFields(map[string]any{
 		"remote": conn.RemoteAddr().String(),
 		"local":  conn.LocalAddr().String(),
@@ -104,26 +105,27 @@ func (h *autoHandler) Handle(ctx context.Context, conn net.Conn) {
 	if err != nil {
 		log.Error(err)
 		conn.Close()
-		return
+		return err
 	}
 
-	conn = handler.NewBufferReaderConn(conn, br)
+	conn = netpkg.NewBufferReaderConn(conn, br)
 	switch b[0] {
 	case gosocks4.Ver4: // socks4
 		if h.socks4Handler != nil {
-			h.socks4Handler.Handle(ctx, conn)
+			return h.socks4Handler.Handle(ctx, conn)
 		}
 	case gosocks5.Ver5: // socks5
 		if h.socks5Handler != nil {
-			h.socks5Handler.Handle(ctx, conn)
+			return h.socks5Handler.Handle(ctx, conn)
 		}
 	case relay.Version1: // relay
 		if h.relayHandler != nil {
-			h.relayHandler.Handle(ctx, conn)
+			return h.relayHandler.Handle(ctx, conn)
 		}
 	default: // http
 		if h.httpHandler != nil {
-			h.httpHandler.Handle(ctx, conn)
+			return h.httpHandler.Handle(ctx, conn)
 		}
 	}
+	return nil
 }

pkg/handler/dns/handler.go

@@ -98,7 +98,7 @@ func (h *dnsHandler) Init(md md.Metadata) (err error) {
 	return
 }
 
-func (h *dnsHandler) Handle(ctx context.Context, conn net.Conn) {
+func (h *dnsHandler) Handle(ctx context.Context, conn net.Conn) error {
 	defer conn.Close()
 
 	start := time.Now()
@@ -120,18 +120,20 @@ func (h *dnsHandler) Handle(ctx context.Context, conn net.Conn) {
 	n, err := conn.Read(*b)
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 
 	reply, err := h.exchange(ctx, (*b)[:n], log)
 	if err != nil {
-		return
+		return err
 	}
 	defer bufpool.Put(&reply)
 
 	if _, err = conn.Write(reply); err != nil {
 		log.Error(err)
+		return err
 	}
+	return nil
 }
 
 func (h *dnsHandler) exchange(ctx context.Context, msg []byte, log logger.Logger) ([]byte, error) {

pkg/handler/forward/local/handler.go

@@ -2,11 +2,13 @@ package local
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net"
 	"time"
 
 	"github.com/go-gost/gost/pkg/chain"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/handler"
 	md "github.com/go-gost/gost/pkg/metadata"
 	"github.com/go-gost/gost/pkg/registry"
@@ -59,7 +61,7 @@ func (h *forwardHandler) Forward(group *chain.NodeGroup) {
 	h.group = group
 }
 
-func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn) {
+func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn) error {
 	defer conn.Close()
 
 	start := time.Now()
@@ -77,8 +79,9 @@ func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn) {
 
 	target := h.group.Next()
 	if target == nil {
-		log.Error("no target available")
+		err := errors.New("target not available")
-		return
+		log.Error(err)
+		return err
 	}
 
 	network := "tcp"
@@ -98,15 +101,17 @@ func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn) {
 		// TODO: the router itself may be failed due to the failed node in the router,
 		// the dead marker may be a wrong operation.
 		target.Marker.Mark()
-		return
+		return err
 	}
 	defer cc.Close()
 	target.Marker.Reset()
 
 	t := time.Now()
 	log.Infof("%s <-> %s", conn.RemoteAddr(), target.Addr)
-	handler.Transport(conn, cc)
+	netpkg.Transport(conn, cc)
 	log.WithFields(map[string]any{
 		"duration": time.Since(t),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), target.Addr)
+
+	return nil
 }

pkg/handler/forward/remote/handler.go

@@ -2,11 +2,13 @@ package remote
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net"
 	"time"
 
 	"github.com/go-gost/gost/pkg/chain"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/handler"
 	md "github.com/go-gost/gost/pkg/metadata"
 	"github.com/go-gost/gost/pkg/registry"
@@ -53,7 +55,7 @@ func (h *forwardHandler) Forward(group *chain.NodeGroup) {
 	h.group = group
 }
 
-func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn) {
+func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn) error {
 	defer conn.Close()
 
 	start := time.Now()
@@ -71,8 +73,9 @@ func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn) {
 
 	target := h.group.Next()
 	if target == nil {
-		log.Error("no target available")
+		err := errors.New("target not available")
-		return
+		log.Error(err)
+		return err
 	}
 
 	network := "tcp"
@@ -92,15 +95,17 @@ func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn) {
 		// TODO: the router itself may be failed due to the failed node in the router,
 		// the dead marker may be a wrong operation.
 		target.Marker.Mark()
-		return
+		return err
 	}
 	defer cc.Close()
 	target.Marker.Reset()
 
 	t := time.Now()
 	log.Infof("%s <-> %s", conn.RemoteAddr(), target.Addr)
-	handler.Transport(conn, cc)
+	netpkg.Transport(conn, cc)
 	log.WithFields(map[string]any{
 		"duration": time.Since(t),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), target.Addr)
+
+	return nil
 }

pkg/handler/handler.go

@@ -10,7 +10,7 @@ import (
 
 type Handler interface {
 	Init(metadata.Metadata) error
-	Handle(context.Context, net.Conn)
+	Handle(context.Context, net.Conn) error
 }
 
 type Forwarder interface {

pkg/handler/http/handler.go

@@ -17,6 +17,7 @@ import (
 
 	"github.com/asaskevich/govalidator"
 	"github.com/go-gost/gost/pkg/chain"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/handler"
 	"github.com/go-gost/gost/pkg/logger"
 	md "github.com/go-gost/gost/pkg/metadata"
@@ -57,7 +58,7 @@ func (h *httpHandler) Init(md md.Metadata) error {
 	return nil
 }
 
-func (h *httpHandler) Handle(ctx context.Context, conn net.Conn) {
+func (h *httpHandler) Handle(ctx context.Context, conn net.Conn) error {
 	defer conn.Close()
 
 	start := time.Now()
@@ -75,18 +76,14 @@ func (h *httpHandler) Handle(ctx context.Context, conn net.Conn) {
 	req, err := http.ReadRequest(bufio.NewReader(conn))
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	defer req.Body.Close()
 
-	h.handleRequest(ctx, conn, req, log)
+	return h.handleRequest(ctx, conn, req, log)
-}
-
-func (h *httpHandler) handleRequest(ctx context.Context, conn net.Conn, req *http.Request, log logger.Logger) {
-	if req == nil {
-		return
 }
 
+func (h *httpHandler) handleRequest(ctx context.Context, conn net.Conn, req *http.Request, log logger.Logger) error {
 	if h.md.sni && !req.URL.IsAbs() && govalidator.IsDNSName(req.Host) {
 		req.URL.Scheme = "http"
 	}
@@ -149,30 +146,27 @@ func (h *httpHandler) handleRequest(ctx context.Context, conn net.Conn, req *htt
 		}
 		log.Info("bypass: ", addr)
 
-		resp.Write(conn)
+		return resp.Write(conn)
-		return
 	}
 
 	if !h.authenticate(conn, req, resp, log) {
-		return
+		return nil
 	}
 
 	if network == "udp" {
-		h.handleUDP(ctx, conn, network, req.Host, log)
+		return h.handleUDP(ctx, conn, network, req.Host, log)
-		return
 	}
 
 	if req.Method == "PRI" ||
 		(req.Method != http.MethodConnect && req.URL.Scheme != "http") {
 		resp.StatusCode = http.StatusBadRequest
-		resp.Write(conn)
 
 		if log.IsLevelEnabled(logger.DebugLevel) {
 			dump, _ := httputil.DumpResponse(resp, false)
 			log.Debug(string(dump))
 		}
 
-		return
+		return resp.Write(conn)
 	}
 
 	req.Header.Del("Proxy-Authorization")
@@ -180,13 +174,12 @@ func (h *httpHandler) handleRequest(ctx context.Context, conn net.Conn, req *htt
 	cc, err := h.router.Dial(ctx, network, addr)
 	if err != nil {
 		resp.StatusCode = http.StatusServiceUnavailable
-		resp.Write(conn)
 
 		if log.IsLevelEnabled(logger.DebugLevel) {
 			dump, _ := httputil.DumpResponse(resp, false)
 			log.Debug(string(dump))
 		}
-		return
+		return resp.Write(conn)
 	}
 	defer cc.Close()
 
@@ -200,22 +193,24 @@ func (h *httpHandler) handleRequest(ctx context.Context, conn net.Conn, req *htt
 		}
 		if err = resp.Write(conn); err != nil {
 			log.Error(err)
-			return
+			return err
 		}
 	} else {
 		req.Header.Del("Proxy-Connection")
 		if err = req.Write(cc); err != nil {
 			log.Error(err)
-			return
+			return err
 		}
 	}
 
 	start := time.Now()
 	log.Infof("%s <-> %s", conn.RemoteAddr(), addr)
-	handler.Transport(conn, cc)
+	netpkg.Transport(conn, cc)
 	log.WithFields(map[string]any{
 		"duration": time.Since(start),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), addr)
+
+	return nil
 }
 
 func (h *httpHandler) decodeServerName(s string) (string, error) {
@@ -292,7 +287,7 @@ func (h *httpHandler) authenticate(conn net.Conn, req *http.Request, resp *http.
 			defer cc.Close()
 
 			req.Write(cc)
-			handler.Transport(conn, cc)
+			netpkg.Transport(conn, cc)
 			return
 		case "file":
 			f, _ := os.Open(pr.Value)

pkg/handler/http/udp.go

@@ -2,17 +2,18 @@ package http
 
 import (
 	"context"
+	"errors"
 	"net"
 	"net/http"
 	"net/http/httputil"
 	"time"
 
+	"github.com/go-gost/gost/pkg/common/net/relay"
 	"github.com/go-gost/gost/pkg/common/util/socks"
-	"github.com/go-gost/gost/pkg/handler"
 	"github.com/go-gost/gost/pkg/logger"
 )
 
-func (h *httpHandler) handleUDP(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) {
+func (h *httpHandler) handleUDP(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) error {
 	log = log.WithFields(map[string]any{
 		"cmd": "udp",
 	})
@@ -28,15 +29,15 @@ func (h *httpHandler) handleUDP(ctx context.Context, conn net.Conn, network, add
 
 	if !h.md.enableUDP {
 		resp.StatusCode = http.StatusForbidden
-		resp.Write(conn)
 
 		if log.IsLevelEnabled(logger.DebugLevel) {
 			dump, _ := httputil.DumpResponse(resp, false)
 			log.Debug(string(dump))
 		}
-		log.Error("UDP relay is diabled")
 
-		return
+		log.Error("http: UDP relay is disabled")
+
+		return resp.Write(conn)
 	}
 
 	resp.StatusCode = http.StatusOK
@@ -46,24 +47,25 @@ func (h *httpHandler) handleUDP(ctx context.Context, conn net.Conn, network, add
 	}
 	if err := resp.Write(conn); err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 
 	// obtain a udp connection
 	c, err := h.router.Dial(ctx, "udp", "") // UDP association
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	defer c.Close()
 
 	pc, ok := c.(net.PacketConn)
 	if !ok {
-		log.Errorf("wrong connection type")
+		err = errors.New("wrong connection type")
-		return
+		log.Error(err)
+		return err
 	}
 
-	relay := handler.NewUDPRelay(socks.UDPTunServerConn(conn), pc).
+	relay := relay.NewUDPRelay(socks.UDPTunServerConn(conn), pc).
 		WithBypass(h.options.Bypass).
 		WithLogger(log)
 
@@ -73,4 +75,6 @@ func (h *httpHandler) handleUDP(ctx context.Context, conn net.Conn, network, add
 	log.WithFields(map[string]any{
 		"duration": time.Since(t),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), pc.LocalAddr())
+
+	return nil
 }

pkg/handler/http2/handler.go

@@ -19,6 +19,7 @@ import (
 	"time"
 
 	"github.com/go-gost/gost/pkg/chain"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/handler"
 	http2_util "github.com/go-gost/gost/pkg/internal/util/http2"
 	"github.com/go-gost/gost/pkg/logger"
@@ -60,7 +61,7 @@ func (h *http2Handler) Init(md md.Metadata) error {
 	return nil
 }
 
-func (h *http2Handler) Handle(ctx context.Context, conn net.Conn) {
+func (h *http2Handler) Handle(ctx context.Context, conn net.Conn) error {
 	defer conn.Close()
 
 	start := time.Now()
@@ -77,16 +78,17 @@ func (h *http2Handler) Handle(ctx context.Context, conn net.Conn) {
 
 	cc, ok := conn.(*http2_util.ServerConn)
 	if !ok {
-		log.Error("wrong connection type")
+		err := errors.New("wrong connection type")
-		return
+		log.Error(err)
+		return err
 	}
-	h.roundTrip(ctx, cc.Writer(), cc.Request(), log)
+	return h.roundTrip(ctx, cc.Writer(), cc.Request(), log)
 }
 
 // NOTE: there is an issue (golang/go#43989) will cause the client hangs
 // when server returns an non-200 status code,
 // May be fixed in go1.18.
-func (h *http2Handler) roundTrip(ctx context.Context, w http.ResponseWriter, req *http.Request, log logger.Logger) {
+func (h *http2Handler) roundTrip(ctx context.Context, w http.ResponseWriter, req *http.Request, log logger.Logger) error {
 	// Try to get the actual host.
 	// Compatible with GOST 2.x.
 	if v := req.Header.Get("Gost-Target"); v != "" {
@@ -129,7 +131,7 @@ func (h *http2Handler) roundTrip(ctx context.Context, w http.ResponseWriter, req
 	if h.options.Bypass != nil && h.options.Bypass.Contains(addr) {
 		w.WriteHeader(http.StatusForbidden)
 		log.Info("bypass: ", addr)
-		return
+		return nil
 	}
 
 	resp := &http.Response{
@@ -140,7 +142,7 @@ func (h *http2Handler) roundTrip(ctx context.Context, w http.ResponseWriter, req
 	}
 
 	if !h.authenticate(w, req, resp, log) {
-		return
+		return nil
 	}
 
 	// delete the proxy related headers.
@@ -151,7 +153,7 @@ func (h *http2Handler) roundTrip(ctx context.Context, w http.ResponseWriter, req
 	if err != nil {
 		log.Error(err)
 		w.WriteHeader(http.StatusServiceUnavailable)
-		return
+		return err
 	}
 	defer cc.Close()
 
@@ -168,28 +170,31 @@ func (h *http2Handler) roundTrip(ctx context.Context, w http.ResponseWriter, req
 			if err != nil {
 				log.Error(err)
 				w.WriteHeader(http.StatusInternalServerError)
-				return
+				return err
 			}
 			defer conn.Close()
 
 			start := time.Now()
 			log.Infof("%s <-> %s", conn.RemoteAddr(), addr)
-			handler.Transport(conn, cc)
+			netpkg.Transport(conn, cc)
 			log.WithFields(map[string]any{
 				"duration": time.Since(start),
 			}).Infof("%s >-< %s", conn.RemoteAddr(), addr)
 
-			return
+			return nil
 		}
 
 		start := time.Now()
 		log.Infof("%s <-> %s", req.RemoteAddr, addr)
-		handler.Transport(&readWriter{r: req.Body, w: flushWriter{w}}, cc)
+		netpkg.Transport(&readWriter{r: req.Body, w: flushWriter{w}}, cc)
 		log.WithFields(map[string]any{
 			"duration": time.Since(start),
 		}).Infof("%s >-< %s", req.RemoteAddr, addr)
-		return
+		return nil
 	}
+
+	// TODO: forward request
+	return nil
 }
 
 func (h *http2Handler) decodeServerName(s string) (string, error) {

pkg/handler/redirect/handler.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/go-gost/gost/pkg/chain"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/handler"
 	md "github.com/go-gost/gost/pkg/metadata"
 	"github.com/go-gost/gost/pkg/registry"
@@ -49,7 +50,7 @@ func (h *redirectHandler) Init(md md.Metadata) (err error) {
 	return
 }
 
-func (h *redirectHandler) Handle(ctx context.Context, conn net.Conn) {
+func (h *redirectHandler) Handle(ctx context.Context, conn net.Conn) error {
 	defer conn.Close()
 
 	start := time.Now()
@@ -78,7 +79,7 @@ func (h *redirectHandler) Handle(ctx context.Context, conn net.Conn) {
 		dstAddr, conn, err = h.getOriginalDstAddr(conn)
 		if err != nil {
 			log.Error(err)
-			return
+			return err
 		}
 	}
 
@@ -90,20 +91,22 @@ func (h *redirectHandler) Handle(ctx context.Context, conn net.Conn) {
 
 	if h.options.Bypass != nil && h.options.Bypass.Contains(dstAddr.String()) {
 		log.Info("bypass: ", dstAddr)
-		return
+		return nil
 	}
 
 	cc, err := h.router.Dial(ctx, network, dstAddr.String())
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	defer cc.Close()
 
 	t := time.Now()
 	log.Infof("%s <-> %s", conn.RemoteAddr(), dstAddr)
-	handler.Transport(conn, cc)
+	netpkg.Transport(conn, cc)
 	log.WithFields(map[string]any{
 		"duration": time.Since(t),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), dstAddr)
+
+	return nil
 }

pkg/handler/relay/bind.go

@@ -6,14 +6,15 @@ import (
 	"net"
 	"time"
 
+	netpkg "github.com/go-gost/gost/pkg/common/net"
+	net_relay "github.com/go-gost/gost/pkg/common/net/relay"
 	"github.com/go-gost/gost/pkg/common/util/mux"
 	"github.com/go-gost/gost/pkg/common/util/socks"
-	"github.com/go-gost/gost/pkg/handler"
 	"github.com/go-gost/gost/pkg/logger"
 	"github.com/go-gost/relay"
 )
 
-func (h *relayHandler) handleBind(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) {
+func (h *relayHandler) handleBind(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) error {
 	log = log.WithFields(map[string]any{
 		"dst": fmt.Sprintf("%s/%s", address, network),
 		"cmd": "bind",
@@ -28,19 +29,19 @@ func (h *relayHandler) handleBind(ctx context.Context, conn net.Conn, network, a
 
 	if !h.md.enableBind {
 		resp.Status = relay.StatusForbidden
-		resp.WriteTo(conn)
+		log.Error("relay: BIND is disabled")
-		log.Error("BIND is diabled")
+		_, err := resp.WriteTo(conn)
-		return
+		return err
 	}
 
 	if network == "tcp" {
-		h.bindTCP(ctx, conn, network, address, log)
+		return h.bindTCP(ctx, conn, network, address, log)
 	} else {
-		h.bindUDP(ctx, conn, network, address, log)
+		return h.bindUDP(ctx, conn, network, address, log)
 	}
 }
 
-func (h *relayHandler) bindTCP(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) {
+func (h *relayHandler) bindTCP(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) error {
 	resp := relay.Response{
 		Version: relay.Version1,
 		Status:  relay.StatusOK,
@@ -51,7 +52,7 @@ func (h *relayHandler) bindTCP(ctx context.Context, conn net.Conn, network, addr
 		log.Error(err)
 		resp.Status = relay.StatusServiceUnavailable
 		resp.WriteTo(conn)
-		return
+		return err
 	}
 
 	af := &relay.AddrFeature{}
@@ -67,7 +68,7 @@ func (h *relayHandler) bindTCP(ctx context.Context, conn net.Conn, network, addr
 	if _, err := resp.WriteTo(conn); err != nil {
 		log.Error(err)
 		ln.Close()
-		return
+		return err
 	}
 
 	log = log.WithFields(map[string]any{
@@ -75,10 +76,10 @@ func (h *relayHandler) bindTCP(ctx context.Context, conn net.Conn, network, addr
 	})
 	log.Debugf("bind on %s OK", ln.Addr())
 
-	h.serveTCPBind(ctx, conn, ln, log)
+	return h.serveTCPBind(ctx, conn, ln, log)
 }
 
-func (h *relayHandler) bindUDP(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) {
+func (h *relayHandler) bindUDP(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) error {
 	resp := relay.Response{
 		Version: relay.Version1,
 		Status:  relay.StatusOK,
@@ -88,7 +89,7 @@ func (h *relayHandler) bindUDP(ctx context.Context, conn net.Conn, network, addr
 	pc, err := net.ListenUDP(network, bindAddr)
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	defer pc.Close()
 
@@ -104,7 +105,7 @@ func (h *relayHandler) bindUDP(ctx context.Context, conn net.Conn, network, addr
 	resp.Features = append(resp.Features, af)
 	if _, err := resp.WriteTo(conn); err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 
 	log = log.WithFields(map[string]any{
@@ -112,25 +113,26 @@ func (h *relayHandler) bindUDP(ctx context.Context, conn net.Conn, network, addr
 	})
 	log.Debugf("bind on %s OK", pc.LocalAddr())
 
-	relay := handler.NewUDPRelay(socks.UDPTunServerConn(conn), pc).
+	r := net_relay.NewUDPRelay(socks.UDPTunServerConn(conn), pc).
 		WithBypass(h.options.Bypass).
 		WithLogger(log)
-	relay.SetBufferSize(h.md.udpBufferSize)
+	r.SetBufferSize(h.md.udpBufferSize)
 
 	t := time.Now()
 	log.Infof("%s <-> %s", conn.RemoteAddr(), pc.LocalAddr())
-	relay.Run()
+	r.Run()
 	log.WithFields(map[string]any{
 		"duration": time.Since(t),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), pc.LocalAddr())
+	return nil
 }
 
-func (h *relayHandler) serveTCPBind(ctx context.Context, conn net.Conn, ln net.Listener, log logger.Logger) {
+func (h *relayHandler) serveTCPBind(ctx context.Context, conn net.Conn, ln net.Listener, log logger.Logger) error {
 	// Upgrade connection to multiplex stream.
 	session, err := mux.ClientSession(conn)
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	defer session.Close()
 
@@ -150,7 +152,7 @@ func (h *relayHandler) serveTCPBind(ctx context.Context, conn net.Conn, ln net.L
 		rc, err := ln.Accept()
 		if err != nil {
 			log.Error(err)
-			return
+			return err
 		}
 		log.Debugf("peer %s accepted", rc.RemoteAddr())
 
@@ -183,7 +185,7 @@ func (h *relayHandler) serveTCPBind(ctx context.Context, conn net.Conn, ln net.L
 
 			t := time.Now()
 			log.Infof("%s <-> %s", c.LocalAddr(), c.RemoteAddr())
-			handler.Transport(sc, c)
+			netpkg.Transport(sc, c)
 			log.WithFields(map[string]any{"duration": time.Since(t)}).
 				Infof("%s >-< %s", c.LocalAddr(), c.RemoteAddr())
 		}(rc)

pkg/handler/relay/connect.go

@@ -2,16 +2,17 @@ package relay
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net"
 	"time"
 
-	"github.com/go-gost/gost/pkg/handler"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/logger"
 	"github.com/go-gost/relay"
 )
 
-func (h *relayHandler) handleConnect(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) {
+func (h *relayHandler) handleConnect(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) error {
 	log = log.WithFields(map[string]any{
 		"dst": fmt.Sprintf("%s/%s", address, network),
 		"cmd": "connect",
@@ -27,29 +28,30 @@ func (h *relayHandler) handleConnect(ctx context.Context, conn net.Conn, network
 	if address == "" {
 		resp.Status = relay.StatusBadRequest
 		resp.WriteTo(conn)
-		log.Error("target not specified")
+		err := errors.New("target not specified")
-		return
+		log.Error(err)
+		return err
 	}
 
 	if h.options.Bypass != nil && h.options.Bypass.Contains(address) {
 		log.Info("bypass: ", address)
 		resp.Status = relay.StatusForbidden
-		resp.WriteTo(conn)
+		_, err := resp.WriteTo(conn)
-		return
+		return err
 	}
 
 	cc, err := h.router.Dial(ctx, network, address)
 	if err != nil {
 		resp.Status = relay.StatusNetworkUnreachable
 		resp.WriteTo(conn)
-		return
+		return err
 	}
 	defer cc.Close()
 
 	if h.md.noDelay {
 		if _, err := resp.WriteTo(conn); err != nil {
 			log.Error(err)
-			return
+			return err
 		}
 	}
 
@@ -61,7 +63,7 @@ func (h *relayHandler) handleConnect(ctx context.Context, conn net.Conn, network
 		if !h.md.noDelay {
 			// cache the header
 			if _, err := resp.WriteTo(&rc.wbuf); err != nil {
-				return
+				return err
 			}
 		}
 		conn = rc
@@ -72,7 +74,7 @@ func (h *relayHandler) handleConnect(ctx context.Context, conn net.Conn, network
 		if !h.md.noDelay {
 			// cache the header
 			if _, err := resp.WriteTo(&rc.wbuf); err != nil {
-				return
+				return err
 			}
 		}
 		conn = rc
@@ -80,8 +82,10 @@ func (h *relayHandler) handleConnect(ctx context.Context, conn net.Conn, network
 
 	t := time.Now()
 	log.Infof("%s <-> %s", conn.RemoteAddr(), address)
-	handler.Transport(conn, cc)
+	netpkg.Transport(conn, cc)
 	log.WithFields(map[string]any{
 		"duration": time.Since(t),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), address)
+
+	return nil
 }

pkg/handler/relay/forward.go

@@ -2,16 +2,17 @@ package relay
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net"
 	"time"
 
-	"github.com/go-gost/gost/pkg/handler"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/logger"
 	"github.com/go-gost/relay"
 )
 
-func (h *relayHandler) handleForward(ctx context.Context, conn net.Conn, network string, log logger.Logger) {
+func (h *relayHandler) handleForward(ctx context.Context, conn net.Conn, network string, log logger.Logger) error {
 	resp := relay.Response{
 		Version: relay.Version1,
 		Status:  relay.StatusOK,
@@ -20,8 +21,9 @@ func (h *relayHandler) handleForward(ctx context.Context, conn net.Conn, network
 	if target == nil {
 		resp.Status = relay.StatusServiceUnavailable
 		resp.WriteTo(conn)
-		log.Error("no target available")
+		err := errors.New("target not available")
-		return
+		log.Error(err)
+		return err
 	}
 
 	log = log.WithFields(map[string]any{
@@ -41,7 +43,7 @@ func (h *relayHandler) handleForward(ctx context.Context, conn net.Conn, network
 		resp.WriteTo(conn)
 		log.Error(err)
 
-		return
+		return err
 	}
 	defer cc.Close()
 	target.Marker.Reset()
@@ -49,7 +51,7 @@ func (h *relayHandler) handleForward(ctx context.Context, conn net.Conn, network
 	if h.md.noDelay {
 		if _, err := resp.WriteTo(conn); err != nil {
 			log.Error(err)
-			return
+			return err
 		}
 	}
 
@@ -61,7 +63,7 @@ func (h *relayHandler) handleForward(ctx context.Context, conn net.Conn, network
 		if !h.md.noDelay {
 			// cache the header
 			if _, err := resp.WriteTo(&rc.wbuf); err != nil {
-				return
+				return err
 			}
 		}
 		conn = rc
@@ -72,7 +74,7 @@ func (h *relayHandler) handleForward(ctx context.Context, conn net.Conn, network
 		if !h.md.noDelay {
 			// cache the header
 			if _, err := resp.WriteTo(&rc.wbuf); err != nil {
-				return
+				return err
 			}
 		}
 		conn = rc
@@ -80,8 +82,10 @@ func (h *relayHandler) handleForward(ctx context.Context, conn net.Conn, network
 
 	t := time.Now()
 	log.Infof("%s <-> %s", conn.RemoteAddr(), target.Addr)
-	handler.Transport(conn, cc)
+	netpkg.Transport(conn, cc)
 	log.WithFields(map[string]any{
 		"duration": time.Since(t),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), target.Addr)
+
+	return nil
 }

pkg/handler/relay/handler.go

@@ -2,6 +2,7 @@ package relay
 
 import (
 	"context"
+	"errors"
 	"net"
 	"strconv"
 	"time"
@@ -13,6 +14,11 @@ import (
 	"github.com/go-gost/relay"
 )
 
+var (
+	ErrBadVersion = errors.New("relay: bad version")
+	ErrUnknownCmd = errors.New("relay: unknown command")
+)
+
 func init() {
 	registry.HandlerRegistry().Register("relay", NewHandler)
 }
@@ -53,7 +59,7 @@ func (h *relayHandler) Forward(group *chain.NodeGroup) {
 	h.group = group
 }
 
-func (h *relayHandler) Handle(ctx context.Context, conn net.Conn) {
+func (h *relayHandler) Handle(ctx context.Context, conn net.Conn) error {
 	defer conn.Close()
 
 	start := time.Now()
@@ -76,14 +82,15 @@ func (h *relayHandler) Handle(ctx context.Context, conn net.Conn) {
 	req := relay.Request{}
 	if _, err := req.ReadFrom(conn); err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 
 	conn.SetReadDeadline(time.Time{})
 
 	if req.Version != relay.Version1 {
-		log.Error("bad version")
+		err := ErrBadVersion
-		return
+		log.Error(err)
+		return err
 	}
 
 	var user, pass string
@@ -109,9 +116,9 @@ func (h *relayHandler) Handle(ctx context.Context, conn net.Conn) {
 	}
 	if h.options.Auther != nil && !h.options.Auther.Authenticate(user, pass) {
 		resp.Status = relay.StatusUnauthorized
-		resp.WriteTo(conn)
 		log.Error("unauthorized")
-		return
+		_, err := resp.WriteTo(conn)
+		return err
 	}
 
 	network := "tcp"
@@ -122,19 +129,19 @@ func (h *relayHandler) Handle(ctx context.Context, conn net.Conn) {
 	if h.group != nil {
 		if address != "" {
 			resp.Status = relay.StatusForbidden
-			resp.WriteTo(conn)
 			log.Error("forward mode, connect is forbidden")
-			return
+			_, err := resp.WriteTo(conn)
+			return err
 		}
 		// forward mode
-		h.handleForward(ctx, conn, network, log)
+		return h.handleForward(ctx, conn, network, log)
-		return
 	}
 
 	switch req.Flags & relay.CmdMask {
 	case 0, relay.CONNECT:
-		h.handleConnect(ctx, conn, network, address, log)
+		return h.handleConnect(ctx, conn, network, address, log)
 	case relay.BIND:
-		h.handleBind(ctx, conn, network, address, log)
+		return h.handleBind(ctx, conn, network, address, log)
 	}
+	return ErrUnknownCmd
 }

pkg/handler/sni/handler.go

@@ -13,6 +13,7 @@ import (
 
 	"github.com/go-gost/gost/pkg/chain"
 	"github.com/go-gost/gost/pkg/common/bufpool"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/handler"
 	md "github.com/go-gost/gost/pkg/metadata"
 	"github.com/go-gost/gost/pkg/registry"
@@ -70,7 +71,7 @@ func (h *sniHandler) Init(md md.Metadata) (err error) {
 	return nil
 }
 
-func (h *sniHandler) Handle(ctx context.Context, conn net.Conn) {
+func (h *sniHandler) Handle(ctx context.Context, conn net.Conn) error {
 	defer conn.Close()
 
 	start := time.Now()
@@ -89,7 +90,7 @@ func (h *sniHandler) Handle(ctx context.Context, conn net.Conn) {
 	var hdr [dissector.RecordHeaderLen]byte
 	if _, err := io.ReadFull(conn, hdr[:]); err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 
 	if hdr[0] != dissector.Handshake {
@@ -100,9 +101,9 @@ func (h *sniHandler) Handle(ctx context.Context, conn net.Conn) {
 		}
 
 		if h.httpHandler != nil {
-			h.httpHandler.Handle(ctx, conn)
+			return h.httpHandler.Handle(ctx, conn)
 		}
-		return
+		return nil
 	}
 
 	length := binary.BigEndian.Uint16(hdr[3:5])
@@ -111,14 +112,14 @@ func (h *sniHandler) Handle(ctx context.Context, conn net.Conn) {
 	defer bufpool.Put(buf)
 	if _, err := io.ReadFull(conn, (*buf)[dissector.RecordHeaderLen:]); err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	copy(*buf, hdr[:])
 
 	opaque, host, err := h.decodeHost(bytes.NewReader(*buf))
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	target := net.JoinHostPort(host, "443")
 
@@ -129,26 +130,29 @@ func (h *sniHandler) Handle(ctx context.Context, conn net.Conn) {
 
 	if h.options.Bypass != nil && h.options.Bypass.Contains(target) {
 		log.Info("bypass: ", target)
-		return
+		return nil
 	}
 
 	cc, err := h.router.Dial(ctx, "tcp", target)
 	if err != nil {
-		return
+		log.Error(err)
+		return err
 	}
 	defer cc.Close()
 
 	if _, err := cc.Write(opaque); err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 
 	t := time.Now()
 	log.Infof("%s <-> %s", conn.RemoteAddr(), target)
-	handler.Transport(conn, cc)
+	netpkg.Transport(conn, cc)
 	log.WithFields(map[string]any{
 		"duration": time.Since(t),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), target)
+
+	return nil
 }
 
 func (h *sniHandler) decodeHost(r io.Reader) (opaque []byte, host string, err error) {

pkg/handler/socks/v4/handler.go

@@ -2,17 +2,24 @@ package v4
 
 import (
 	"context"
+	"errors"
 	"net"
 	"time"
 
 	"github.com/go-gost/gosocks4"
 	"github.com/go-gost/gost/pkg/chain"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/handler"
 	"github.com/go-gost/gost/pkg/logger"
 	md "github.com/go-gost/gost/pkg/metadata"
 	"github.com/go-gost/gost/pkg/registry"
 )
 
+var (
+	ErrUnknownCmd    = errors.New("socks4: unknown command")
+	ErrUnimplemented = errors.New("socks4: unimplemented")
+)
+
 func init() {
 	registry.HandlerRegistry().Register("socks4", NewHandler)
 	registry.HandlerRegistry().Register("socks4a", NewHandler)
@@ -48,7 +55,7 @@ func (h *socks4Handler) Init(md md.Metadata) (err error) {
 	return nil
 }
 
-func (h *socks4Handler) Handle(ctx context.Context, conn net.Conn) {
+func (h *socks4Handler) Handle(ctx context.Context, conn net.Conn) error {
 	defer conn.Close()
 
 	start := time.Now()
@@ -72,7 +79,7 @@ func (h *socks4Handler) Handle(ctx context.Context, conn net.Conn) {
 	req, err := gosocks4.ReadRequest(conn)
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	log.Debug(req)
 
@@ -81,22 +88,23 @@ func (h *socks4Handler) Handle(ctx context.Context, conn net.Conn) {
 	if h.options.Auther != nil &&
 		!h.options.Auther.Authenticate(string(req.Userid), "") {
 		resp := gosocks4.NewReply(gosocks4.RejectedUserid, nil)
-		resp.Write(conn)
 		log.Debug(resp)
-		return
+		return resp.Write(conn)
 	}
 
 	switch req.Cmd {
 	case gosocks4.CmdConnect:
-		h.handleConnect(ctx, conn, req, log)
+		return h.handleConnect(ctx, conn, req, log)
 	case gosocks4.CmdBind:
-		h.handleBind(ctx, conn, req)
+		return h.handleBind(ctx, conn, req)
 	default:
-		log.Errorf("unknown cmd: %d", req.Cmd)
+		err = ErrUnknownCmd
+		log.Error(err)
+		return err
 	}
 }
 
-func (h *socks4Handler) handleConnect(ctx context.Context, conn net.Conn, req *gosocks4.Request, log logger.Logger) {
+func (h *socks4Handler) handleConnect(ctx context.Context, conn net.Conn, req *gosocks4.Request, log logger.Logger) error {
 	addr := req.Addr.String()
 
 	log = log.WithFields(map[string]any{
@@ -106,10 +114,9 @@ func (h *socks4Handler) handleConnect(ctx context.Context, conn net.Conn, req *g
 
 	if h.options.Bypass != nil && h.options.Bypass.Contains(addr) {
 		resp := gosocks4.NewReply(gosocks4.Rejected, nil)
-		resp.Write(conn)
 		log.Debug(resp)
 		log.Info("bypass: ", addr)
-		return
+		return resp.Write(conn)
 	}
 
 	cc, err := h.router.Dial(ctx, "tcp", addr)
@@ -117,7 +124,7 @@ func (h *socks4Handler) handleConnect(ctx context.Context, conn net.Conn, req *g
 		resp := gosocks4.NewReply(gosocks4.Failed, nil)
 		resp.Write(conn)
 		log.Debug(resp)
-		return
+		return err
 	}
 
 	defer cc.Close()
@@ -125,18 +132,21 @@ func (h *socks4Handler) handleConnect(ctx context.Context, conn net.Conn, req *g
 	resp := gosocks4.NewReply(gosocks4.Granted, nil)
 	if err := resp.Write(conn); err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	log.Debug(resp)
 
 	t := time.Now()
 	log.Infof("%s <-> %s", conn.RemoteAddr(), addr)
-	handler.Transport(conn, cc)
+	netpkg.Transport(conn, cc)
 	log.WithFields(map[string]any{
 		"duration": time.Since(t),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), addr)
+
+	return nil
 }
 
-func (h *socks4Handler) handleBind(ctx context.Context, conn net.Conn, req *gosocks4.Request) {
+func (h *socks4Handler) handleBind(ctx context.Context, conn net.Conn, req *gosocks4.Request) error {
 	// TODO: bind
+	return ErrUnimplemented
 }

pkg/handler/socks/v5/bind.go

@@ -7,11 +7,11 @@ import (
 	"time"
 
 	"github.com/go-gost/gosocks5"
-	"github.com/go-gost/gost/pkg/handler"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/logger"
 )
 
-func (h *socks5Handler) handleBind(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) {
+func (h *socks5Handler) handleBind(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) error {
 	log = log.WithFields(map[string]any{
 		"dst": fmt.Sprintf("%s/%s", address, network),
 		"cmd": "bind",
@@ -21,17 +21,16 @@ func (h *socks5Handler) handleBind(ctx context.Context, conn net.Conn, network,
 
 	if !h.md.enableBind {
 		reply := gosocks5.NewReply(gosocks5.NotAllowed, nil)
-		reply.Write(conn)
 		log.Debug(reply)
-		log.Error("BIND is diabled")
+		log.Error("socks5: BIND is disabled")
-		return
+		return reply.Write(conn)
 	}
 
 	// BIND does not support chain.
-	h.bindLocal(ctx, conn, network, address, log)
+	return h.bindLocal(ctx, conn, network, address, log)
 }
 
-func (h *socks5Handler) bindLocal(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) {
+func (h *socks5Handler) bindLocal(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) error {
 	ln, err := net.Listen(network, address) // strict mode: if the port already in use, it will return error
 	if err != nil {
 		log.Error(err)
@@ -40,7 +39,7 @@ func (h *socks5Handler) bindLocal(ctx context.Context, conn net.Conn, network, a
 			log.Error(err)
 		}
 		log.Debug(reply)
-		return
+		return err
 	}
 
 	socksAddr := gosocks5.Addr{}
@@ -55,7 +54,7 @@ func (h *socks5Handler) bindLocal(ctx context.Context, conn net.Conn, network, a
 	if err := reply.Write(conn); err != nil {
 		log.Error(err)
 		ln.Close()
-		return
+		return err
 	}
 	log.Debug(reply)
 
@@ -66,6 +65,7 @@ func (h *socks5Handler) bindLocal(ctx context.Context, conn net.Conn, network, a
 	log.Debugf("bind on %s OK", ln.Addr())
 
 	h.serveBind(ctx, conn, ln, log)
+	return nil
 }
 
 func (h *socks5Handler) serveBind(ctx context.Context, conn net.Conn, ln net.Listener, log logger.Logger) {
@@ -95,7 +95,7 @@ func (h *socks5Handler) serveBind(ctx context.Context, conn net.Conn, ln net.Lis
 			defer close(errc)
 			defer pc1.Close()
 
-			errc <- handler.Transport(conn, pc1)
+			errc <- netpkg.Transport(conn, pc1)
 		}()
 
 		return errc
@@ -135,7 +135,7 @@ func (h *socks5Handler) serveBind(ctx context.Context, conn net.Conn, ln net.Lis
 
 		start := time.Now()
 		log.Infof("%s <-> %s", rc.LocalAddr(), rc.RemoteAddr())
-		handler.Transport(pc2, rc)
+		netpkg.Transport(pc2, rc)
 		log.WithFields(map[string]any{"duration": time.Since(start)}).
 			Infof("%s >-< %s", rc.LocalAddr(), rc.RemoteAddr())
 

pkg/handler/socks/v5/connect.go

@@ -7,11 +7,11 @@ import (
 	"time"
 
 	"github.com/go-gost/gosocks5"
-	"github.com/go-gost/gost/pkg/handler"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/logger"
 )
 
-func (h *socks5Handler) handleConnect(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) {
+func (h *socks5Handler) handleConnect(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) error {
 	log = log.WithFields(map[string]any{
 		"dst": fmt.Sprintf("%s/%s", address, network),
 		"cmd": "connect",
@@ -20,18 +20,17 @@ func (h *socks5Handler) handleConnect(ctx context.Context, conn net.Conn, networ
 
 	if h.options.Bypass != nil && h.options.Bypass.Contains(address) {
 		resp := gosocks5.NewReply(gosocks5.NotAllowed, nil)
-		resp.Write(conn)
 		log.Debug(resp)
 		log.Info("bypass: ", address)
-		return
+		return resp.Write(conn)
 	}
 
 	cc, err := h.router.Dial(ctx, network, address)
 	if err != nil {
 		resp := gosocks5.NewReply(gosocks5.NetUnreachable, nil)
-		resp.Write(conn)
 		log.Debug(resp)
-		return
+		resp.Write(conn)
+		return err
 	}
 
 	defer cc.Close()
@@ -39,14 +38,16 @@ func (h *socks5Handler) handleConnect(ctx context.Context, conn net.Conn, networ
 	resp := gosocks5.NewReply(gosocks5.Succeeded, nil)
 	if err := resp.Write(conn); err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	log.Debug(resp)
 
 	t := time.Now()
 	log.Infof("%s <-> %s", conn.RemoteAddr(), address)
-	handler.Transport(conn, cc)
+	netpkg.Transport(conn, cc)
 	log.WithFields(map[string]any{
 		"duration": time.Since(t),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), address)
+
+	return nil
 }

pkg/handler/socks/v5/handler.go

@@ -2,6 +2,7 @@ package v5
 
 import (
 	"context"
+	"errors"
 	"net"
 	"time"
 
@@ -13,6 +14,10 @@ import (
 	"github.com/go-gost/gost/pkg/registry"
 )
 
+var (
+	ErrUnknownCmd = errors.New("socks5: unknown command")
+)
+
 func init() {
 	registry.HandlerRegistry().Register("socks5", NewHandler)
 	registry.HandlerRegistry().Register("socks", NewHandler)
@@ -56,7 +61,7 @@ func (h *socks5Handler) Init(md md.Metadata) (err error) {
 	return
 }
 
-func (h *socks5Handler) Handle(ctx context.Context, conn net.Conn) {
+func (h *socks5Handler) Handle(ctx context.Context, conn net.Conn) error {
 	defer conn.Close()
 
 	start := time.Now()
@@ -81,7 +86,7 @@ func (h *socks5Handler) Handle(ctx context.Context, conn net.Conn) {
 	req, err := gosocks5.ReadRequest(conn)
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	log.Debug(req)
 	conn.SetReadDeadline(time.Time{})
@@ -90,20 +95,21 @@ func (h *socks5Handler) Handle(ctx context.Context, conn net.Conn) {
 
 	switch req.Cmd {
 	case gosocks5.CmdConnect:
-		h.handleConnect(ctx, conn, "tcp", address, log)
+		return h.handleConnect(ctx, conn, "tcp", address, log)
 	case gosocks5.CmdBind:
-		h.handleBind(ctx, conn, "tcp", address, log)
+		return h.handleBind(ctx, conn, "tcp", address, log)
 	case socks.CmdMuxBind:
-		h.handleMuxBind(ctx, conn, "tcp", address, log)
+		return h.handleMuxBind(ctx, conn, "tcp", address, log)
 	case gosocks5.CmdUdp:
-		h.handleUDP(ctx, conn, log)
+		return h.handleUDP(ctx, conn, log)
 	case socks.CmdUDPTun:
-		h.handleUDPTun(ctx, conn, "udp", address, log)
+		return h.handleUDPTun(ctx, conn, "udp", address, log)
 	default:
-		log.Errorf("unknown cmd: %d", req.Cmd)
+		err = ErrUnknownCmd
+		log.Error(err)
 		resp := gosocks5.NewReply(gosocks5.CmdUnsupported, nil)
 		resp.Write(conn)
 		log.Debug(resp)
-		return
+		return err
 	}
 }

pkg/handler/socks/v5/mbind.go

@@ -7,12 +7,12 @@ import (
 	"time"
 
 	"github.com/go-gost/gosocks5"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/common/util/mux"
-	"github.com/go-gost/gost/pkg/handler"
 	"github.com/go-gost/gost/pkg/logger"
 )
 
-func (h *socks5Handler) handleMuxBind(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) {
+func (h *socks5Handler) handleMuxBind(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) error {
 	log = log.WithFields(map[string]any{
 		"dst": fmt.Sprintf("%s/%s", address, network),
 		"cmd": "mbind",
@@ -22,16 +22,15 @@ func (h *socks5Handler) handleMuxBind(ctx context.Context, conn net.Conn, networ
 
 	if !h.md.enableBind {
 		reply := gosocks5.NewReply(gosocks5.NotAllowed, nil)
-		reply.Write(conn)
 		log.Debug(reply)
-		log.Error("BIND is diabled")
+		log.Error("socks5: BIND is disabled")
-		return
+		return reply.Write(conn)
 	}
 
-	h.muxBindLocal(ctx, conn, network, address, log)
+	return h.muxBindLocal(ctx, conn, network, address, log)
 }
 
-func (h *socks5Handler) muxBindLocal(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) {
+func (h *socks5Handler) muxBindLocal(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) error {
 	ln, err := net.Listen(network, address) // strict mode: if the port already in use, it will return error
 	if err != nil {
 		log.Error(err)
@@ -40,7 +39,7 @@ func (h *socks5Handler) muxBindLocal(ctx context.Context, conn net.Conn, network
 			log.Error(err)
 		}
 		log.Debug(reply)
-		return
+		return err
 	}
 
 	socksAddr := gosocks5.Addr{}
@@ -56,7 +55,7 @@ func (h *socks5Handler) muxBindLocal(ctx context.Context, conn net.Conn, network
 	if err := reply.Write(conn); err != nil {
 		log.Error(err)
 		ln.Close()
-		return
+		return err
 	}
 	log.Debug(reply)
 
@@ -66,15 +65,15 @@ func (h *socks5Handler) muxBindLocal(ctx context.Context, conn net.Conn, network
 
 	log.Debugf("bind on %s OK", ln.Addr())
 
-	h.serveMuxBind(ctx, conn, ln, log)
+	return h.serveMuxBind(ctx, conn, ln, log)
 }
 
-func (h *socks5Handler) serveMuxBind(ctx context.Context, conn net.Conn, ln net.Listener, log logger.Logger) {
+func (h *socks5Handler) serveMuxBind(ctx context.Context, conn net.Conn, ln net.Listener, log logger.Logger) error {
 	// Upgrade connection to multiplex stream.
 	session, err := mux.ClientSession(conn)
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	defer session.Close()
 
@@ -94,7 +93,7 @@ func (h *socks5Handler) serveMuxBind(ctx context.Context, conn net.Conn, ln net.
 		rc, err := ln.Accept()
 		if err != nil {
 			log.Error(err)
-			return
+			return err
 		}
 		log.Debugf("peer %s accepted", rc.RemoteAddr())
 
@@ -126,7 +125,7 @@ func (h *socks5Handler) serveMuxBind(ctx context.Context, conn net.Conn, ln net.
 
 			t := time.Now()
 			log.Infof("%s <-> %s", c.LocalAddr(), c.RemoteAddr())
-			handler.Transport(sc, c)
+			netpkg.Transport(sc, c)
 			log.WithFields(map[string]any{"duration": time.Since(t)}).
 				Infof("%s >-< %s", c.LocalAddr(), c.RemoteAddr())
 		}(rc)

pkg/handler/socks/v5/udp.go

@@ -2,6 +2,7 @@ package v5
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -9,22 +10,21 @@ import (
 	"time"
 
 	"github.com/go-gost/gosocks5"
+	"github.com/go-gost/gost/pkg/common/net/relay"
 	"github.com/go-gost/gost/pkg/common/util/socks"
-	"github.com/go-gost/gost/pkg/handler"
 	"github.com/go-gost/gost/pkg/logger"
 )
 
-func (h *socks5Handler) handleUDP(ctx context.Context, conn net.Conn, log logger.Logger) {
+func (h *socks5Handler) handleUDP(ctx context.Context, conn net.Conn, log logger.Logger) error {
 	log = log.WithFields(map[string]any{
 		"cmd": "udp",
 	})
 
 	if !h.md.enableUDP {
 		reply := gosocks5.NewReply(gosocks5.NotAllowed, nil)
-		reply.Write(conn)
 		log.Debug(reply)
-		log.Error("UDP relay is diabled")
+		log.Error("socks5: UDP relay is disabled")
-		return
+		return reply.Write(conn)
 	}
 
 	cc, err := net.ListenUDP("udp", nil)
@@ -33,7 +33,7 @@ func (h *socks5Handler) handleUDP(ctx context.Context, conn net.Conn, log logger
 		reply := gosocks5.NewReply(gosocks5.Failure, nil)
 		reply.Write(conn)
 		log.Debug(reply)
-		return
+		return err
 	}
 	defer cc.Close()
 
@@ -44,7 +44,7 @@ func (h *socks5Handler) handleUDP(ctx context.Context, conn net.Conn, log logger
 	reply := gosocks5.NewReply(gosocks5.Succeeded, &saddr)
 	if err := reply.Write(conn); err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	log.Debug(reply)
 
@@ -57,26 +57,29 @@ func (h *socks5Handler) handleUDP(ctx context.Context, conn net.Conn, log logger
 	c, err := h.router.Dial(ctx, "udp", "") // UDP association
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	defer c.Close()
 
 	pc, ok := c.(net.PacketConn)
 	if !ok {
-		log.Errorf("wrong connection type")
+		err := errors.New("socks5: wrong connection type")
-		return
+		log.Error(err)
+		return err
 	}
 
-	relay := handler.NewUDPRelay(socks.UDPConn(cc, h.md.udpBufferSize), pc).
+	r := relay.NewUDPRelay(socks.UDPConn(cc, h.md.udpBufferSize), pc).
 		WithBypass(h.options.Bypass).
 		WithLogger(log)
-	relay.SetBufferSize(h.md.udpBufferSize)
+	r.SetBufferSize(h.md.udpBufferSize)
 
-	go relay.Run()
+	go r.Run()
 
 	t := time.Now()
 	log.Infof("%s <-> %s", conn.RemoteAddr(), cc.LocalAddr())
 	io.Copy(ioutil.Discard, conn)
 	log.WithFields(map[string]any{"duration": time.Since(t)}).
 		Infof("%s >-< %s", conn.RemoteAddr(), cc.LocalAddr())
+
+	return nil
 }

pkg/handler/socks/v5/udp_tun.go

@@ -6,12 +6,12 @@ import (
 	"time"
 
 	"github.com/go-gost/gosocks5"
+	"github.com/go-gost/gost/pkg/common/net/relay"
 	"github.com/go-gost/gost/pkg/common/util/socks"
-	"github.com/go-gost/gost/pkg/handler"
 	"github.com/go-gost/gost/pkg/logger"
 )
 
-func (h *socks5Handler) handleUDPTun(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) {
+func (h *socks5Handler) handleUDPTun(ctx context.Context, conn net.Conn, network, address string, log logger.Logger) error {
 	log = log.WithFields(map[string]any{
 		"cmd": "udp-tun",
 	})
@@ -25,26 +25,24 @@ func (h *socks5Handler) handleUDPTun(ctx context.Context, conn net.Conn, network
 		// relay mode
 		if !h.md.enableUDP {
 			reply := gosocks5.NewReply(gosocks5.NotAllowed, nil)
-			reply.Write(conn)
 			log.Debug(reply)
-			log.Error("UDP relay is diabled")
+			log.Error("socks5: UDP relay is disabled")
-			return
+			return reply.Write(conn)
 		}
 	} else {
 		// BIND mode
 		if !h.md.enableBind {
 			reply := gosocks5.NewReply(gosocks5.NotAllowed, nil)
-			reply.Write(conn)
 			log.Debug(reply)
-			log.Error("BIND is diabled")
+			log.Error("socks5: BIND is disabled")
-			return
+			return reply.Write(conn)
 		}
 	}
 
 	pc, err := net.ListenUDP(network, bindAddr)
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	defer pc.Close()
 
@@ -53,20 +51,22 @@ func (h *socks5Handler) handleUDPTun(ctx context.Context, conn net.Conn, network
 	reply := gosocks5.NewReply(gosocks5.Succeeded, &saddr)
 	if err := reply.Write(conn); err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	log.Debug(reply)
 	log.Debugf("bind on %s OK", pc.LocalAddr())
 
-	relay := handler.NewUDPRelay(socks.UDPTunServerConn(conn), pc).
+	r := relay.NewUDPRelay(socks.UDPTunServerConn(conn), pc).
 		WithBypass(h.options.Bypass).
 		WithLogger(log)
-	relay.SetBufferSize(h.md.udpBufferSize)
+	r.SetBufferSize(h.md.udpBufferSize)
 
 	t := time.Now()
 	log.Infof("%s <-> %s", conn.RemoteAddr(), pc.LocalAddr())
-	relay.Run()
+	r.Run()
 	log.WithFields(map[string]any{
 		"duration": time.Since(t),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), pc.LocalAddr())
+
+	return nil
 }

pkg/handler/ss/handler.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/go-gost/gosocks5"
 	"github.com/go-gost/gost/pkg/chain"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/common/util/ss"
 	"github.com/go-gost/gost/pkg/handler"
 	md "github.com/go-gost/gost/pkg/metadata"
@@ -59,7 +60,7 @@ func (h *ssHandler) Init(md md.Metadata) (err error) {
 	return
 }
 
-func (h *ssHandler) Handle(ctx context.Context, conn net.Conn) {
+func (h *ssHandler) Handle(ctx context.Context, conn net.Conn) error {
 	defer conn.Close()
 
 	start := time.Now()
@@ -87,7 +88,7 @@ func (h *ssHandler) Handle(ctx context.Context, conn net.Conn) {
 	if _, err := addr.ReadFrom(conn); err != nil {
 		log.Error(err)
 		io.Copy(ioutil.Discard, conn)
-		return
+		return err
 	}
 
 	log = log.WithFields(map[string]any{
@@ -98,19 +99,21 @@ func (h *ssHandler) Handle(ctx context.Context, conn net.Conn) {
 
 	if h.options.Bypass != nil && h.options.Bypass.Contains(addr.String()) {
 		log.Info("bypass: ", addr.String())
-		return
+		return nil
 	}
 
 	cc, err := h.router.Dial(ctx, "tcp", addr.String())
 	if err != nil {
-		return
+		return err
 	}
 	defer cc.Close()
 
 	t := time.Now()
 	log.Infof("%s <-> %s", conn.RemoteAddr(), addr)
-	handler.Transport(conn, cc)
+	netpkg.Transport(conn, cc)
 	log.WithFields(map[string]any{
 		"duration": time.Since(t),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), addr)
+
+	return nil
 }

pkg/handler/ss/udp/handler.go

@@ -2,6 +2,7 @@ package ss
 
 import (
 	"context"
+	"errors"
 	"net"
 	"time"
 
@@ -60,7 +61,7 @@ func (h *ssuHandler) Init(md md.Metadata) (err error) {
 	return
 }
 
-func (h *ssuHandler) Handle(ctx context.Context, conn net.Conn) {
+func (h *ssuHandler) Handle(ctx context.Context, conn net.Conn) error {
 	defer conn.Close()
 
 	start := time.Now()
@@ -95,14 +96,15 @@ func (h *ssuHandler) Handle(ctx context.Context, conn net.Conn) {
 	c, err := h.router.Dial(ctx, "udp", "") // UDP association
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 	defer c.Close()
 
 	cc, ok := c.(net.PacketConn)
 	if !ok {
-		log.Errorf("wrong connection type")
+		err := errors.New("ss: wrong connection type")
-		return
+		log.Error(err)
+		return err
 	}
 
 	t := time.Now()
@@ -110,6 +112,8 @@ func (h *ssuHandler) Handle(ctx context.Context, conn net.Conn) {
 	h.relayPacket(pc, cc, log)
 	log.WithFields(map[string]any{"duration": time.Since(t)}).
 		Infof("%s >-< %s", conn.LocalAddr(), cc.LocalAddr())
+
+	return nil
 }
 
 func (h *ssuHandler) relayPacket(pc1, pc2 net.PacketConn, log logger.Logger) (err error) {

pkg/handler/sshd/handler.go

@@ -3,12 +3,14 @@ package ssh
 import (
 	"context"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"net"
 	"strconv"
 	"time"
 
 	"github.com/go-gost/gost/pkg/chain"
+	netpkg "github.com/go-gost/gost/pkg/common/net"
 	"github.com/go-gost/gost/pkg/handler"
 	sshd_util "github.com/go-gost/gost/pkg/internal/util/sshd"
 	"github.com/go-gost/gost/pkg/logger"
@@ -56,7 +58,7 @@ func (h *forwardHandler) Init(md md.Metadata) (err error) {
 	return nil
 }
 
-func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn) {
+func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn) error {
 	defer conn.Close()
 
 	log := h.options.Logger.WithFields(map[string]any{
@@ -66,16 +68,17 @@ func (h *forwardHandler) Handle(ctx context.Context, conn net.Conn) {
 
 	switch cc := conn.(type) {
 	case *sshd_util.DirectForwardConn:
-		h.handleDirectForward(ctx, cc, log)
+		return h.handleDirectForward(ctx, cc, log)
 	case *sshd_util.RemoteForwardConn:
-		h.handleRemoteForward(ctx, cc, log)
+		return h.handleRemoteForward(ctx, cc, log)
 	default:
-		log.Error("wrong connection type")
+		err := errors.New("sshd: wrong connection type")
-		return
+		log.Error(err)
+		return err
 	}
 }
 
-func (h *forwardHandler) handleDirectForward(ctx context.Context, conn *sshd_util.DirectForwardConn, log logger.Logger) {
+func (h *forwardHandler) handleDirectForward(ctx context.Context, conn *sshd_util.DirectForwardConn, log logger.Logger) error {
 	targetAddr := conn.DstAddr()
 
 	log = log.WithFields(map[string]any{
@@ -87,28 +90,33 @@ func (h *forwardHandler) handleDirectForward(ctx context.Context, conn *sshd_uti
 
 	if h.options.Bypass != nil && h.options.Bypass.Contains(targetAddr) {
 		log.Infof("bypass %s", targetAddr)
-		return
+		return nil
 	}
 
 	cc, err := h.router.Dial(ctx, "tcp", targetAddr)
 	if err != nil {
-		return
+		return err
 	}
 	defer cc.Close()
 
 	t := time.Now()
 	log.Infof("%s <-> %s", cc.LocalAddr(), targetAddr)
-	handler.Transport(conn, cc)
+	netpkg.Transport(conn, cc)
 	log.WithFields(map[string]any{
 		"duration": time.Since(t),
 	}).Infof("%s >-< %s", cc.LocalAddr(), targetAddr)
+
+	return nil
 }
 
-func (h *forwardHandler) handleRemoteForward(ctx context.Context, conn *sshd_util.RemoteForwardConn, log logger.Logger) {
+func (h *forwardHandler) handleRemoteForward(ctx context.Context, conn *sshd_util.RemoteForwardConn, log logger.Logger) error {
 	req := conn.Request()
 
 	t := tcpipForward{}
-	ssh.Unmarshal(req.Payload, &t)
+	if err := ssh.Unmarshal(req.Payload, &t); err != nil {
+		log.Error(err)
+		return err
+	}
 
 	network := "tcp"
 	addr := net.JoinHostPort(t.Host, strconv.Itoa(int(t.Port)))
@@ -125,7 +133,7 @@ func (h *forwardHandler) handleRemoteForward(ctx context.Context, conn *sshd_uti
 	if err != nil {
 		log.Error(err)
 		req.Reply(false, nil)
-		return
+		return err
 	}
 	defer ln.Close()
 
@@ -149,7 +157,7 @@ func (h *forwardHandler) handleRemoteForward(ctx context.Context, conn *sshd_uti
 	}()
 	if err != nil {
 		log.Error(err)
-		return
+		return err
 	}
 
 	sshConn := conn.Conn()
@@ -191,7 +199,7 @@ func (h *forwardHandler) handleRemoteForward(ctx context.Context, conn *sshd_uti
 
 				t := time.Now()
 				log.Infof("%s <-> %s", conn.LocalAddr(), conn.RemoteAddr())
-				handler.Transport(ch, conn)
+				netpkg.Transport(ch, conn)
 				log.WithFields(map[string]any{
 					"duration": time.Since(t),
 				}).Infof("%s >-< %s", conn.LocalAddr(), conn.RemoteAddr())
@@ -205,6 +213,8 @@ func (h *forwardHandler) handleRemoteForward(ctx context.Context, conn *sshd_uti
 	log.WithFields(map[string]any{
 		"duration": time.Since(tm),
 	}).Infof("%s >-< %s", conn.RemoteAddr(), addr)
+
+	return nil
 }
 
 func getHostPortFromAddr(addr net.Addr) (host string, port int, err error) {

pkg/handler/tap/handler.go

@@ -76,15 +76,16 @@ func (h *tapHandler) Forward(group *chain.NodeGroup) {
 	h.group = group
 }
 
-func (h *tapHandler) Handle(ctx context.Context, conn net.Conn) {
+func (h *tapHandler) Handle(ctx context.Context, conn net.Conn) error {
 	defer os.Exit(0)
 	defer conn.Close()
 
 	log := h.options.Logger
 	cc, ok := conn.(*tap_util.Conn)
 	if !ok || cc.Config() == nil {
-		log.Error("invalid connection")
+		err := errors.New("tap: wrong connection type")
-		return
+		log.Error(err)
+		return err
 	}
 
 	start := time.Now()
@@ -109,7 +110,7 @@ func (h *tapHandler) Handle(ctx context.Context, conn net.Conn) {
 		raddr, err = net.ResolveUDPAddr(network, target.Addr)
 		if err != nil {
 			log.Error(err)
-			return
+			return err
 		}
 		log = log.WithFields(map[string]any{
 			"dst": fmt.Sprintf("%s/%s", raddr.String(), raddr.Network()),
@@ -118,6 +119,7 @@ func (h *tapHandler) Handle(ctx context.Context, conn net.Conn) {
 	}
 
 	h.handleLoop(ctx, conn, raddr, cc.Config(), log)
+	return nil
 }
 
 func (h *tapHandler) handleLoop(ctx context.Context, conn net.Conn, addr net.Addr, config *tap_util.Config, log logger.Logger) {

pkg/handler/tun/handler.go

@@ -78,7 +78,7 @@ func (h *tunHandler) Forward(group *chain.NodeGroup) {
 	h.group = group
 }
 
-func (h *tunHandler) Handle(ctx context.Context, conn net.Conn) {
+func (h *tunHandler) Handle(ctx context.Context, conn net.Conn) error {
 	defer os.Exit(0)
 	defer conn.Close()
 
@@ -86,8 +86,9 @@ func (h *tunHandler) Handle(ctx context.Context, conn net.Conn) {
 
 	cc, ok := conn.(*tun_util.Conn)
 	if !ok || cc.Config() == nil {
-		log.Error("invalid connection")
+		err := errors.New("tun: wrong connection type")
-		return
+		log.Error(err)
+		return err
 	}
 
 	start := time.Now()
@@ -112,7 +113,7 @@ func (h *tunHandler) Handle(ctx context.Context, conn net.Conn) {
 		raddr, err = net.ResolveUDPAddr(network, target.Addr)
 		if err != nil {
 			log.Error(err)
-			return
+			return err
 		}
 		log = log.WithFields(map[string]any{
 			"dst": fmt.Sprintf("%s/%s", raddr.String(), raddr.Network()),
@@ -121,6 +122,7 @@ func (h *tunHandler) Handle(ctx context.Context, conn net.Conn) {
 	}
 
 	h.handleLoop(ctx, conn, raddr, cc.Config(), log)
+	return nil
 }
 
 func (h *tunHandler) handleLoop(ctx context.Context, conn net.Conn, addr net.Addr, config *tun_util.Config, log logger.Logger) {

pkg/metrics/metrics.go

@@ -5,16 +5,33 @@ import (
 )
 
 var (
-	global = newMetrics()
+	metrics = newMetrics()
 )
 
+type Gauge interface {
+	Inc()
+	Dec()
+	Add(float64)
+	Set(float64)
+}
+
+type Counter interface {
+	Inc()
+	Add(float64)
+}
+
+type Observer interface {
+	Observe(float64)
+}
+
 type Metrics struct {
 	services         prometheus.Gauge
 	requests         *prometheus.CounterVec
 	requestsInFlight *prometheus.GaugeVec
 	requestSeconds   *prometheus.HistogramVec
-	requestInputBytes  *prometheus.CounterVec
+	inputBytes       *prometheus.CounterVec
-	requestOutputBytes *prometheus.CounterVec
+	outputBytes      *prometheus.CounterVec
+	handlerErrors    *prometheus.CounterVec
 }
 
 func newMetrics() *Metrics {
@@ -44,20 +61,26 @@ func newMetrics() *Metrics {
 				Name: "gost_service_request_duration_seconds",
 				Help: "Distribution of request latencies",
 				Buckets: []float64{
-					.005, .01, .025, .05, .1, .25, .5, 1, 2.5, 5, 10, 15, 20, 30,
+					.005, .01, .025, .05, .1, .25, .5, 1, 2.5, 5, 10, 15, 30, 60,
 				},
 			},
 			[]string{"service"}),
-		requestInputBytes: prometheus.NewCounterVec(
+		inputBytes: prometheus.NewCounterVec(
 			prometheus.CounterOpts{
-				Name: "gost_service_request_transfer_input_bytes_total",
+				Name: "gost_service_transfer_input_bytes_total",
-				Help: "Total request input data transfer size in bytes",
+				Help: "Total service input data transfer size in bytes",
 			},
 			[]string{"service"}),
-		requestOutputBytes: prometheus.NewCounterVec(
+		outputBytes: prometheus.NewCounterVec(
 			prometheus.CounterOpts{
-				Name: "gost_service_request_transfer_output_bytes_total",
+				Name: "gost_service_transfer_output_bytes_total",
-				Help: "Total request output data transfer size in bytes",
+				Help: "Total service output data transfer size in bytes",
+			},
+			[]string{"service"}),
+		handlerErrors: prometheus.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "gost_service_handler_errors_total",
+				Help: "Total service handler errors",
 			},
 			[]string{"service"}),
 	}
@@ -65,31 +88,35 @@ func newMetrics() *Metrics {
 	prometheus.MustRegister(m.requests)
 	prometheus.MustRegister(m.requestsInFlight)
 	prometheus.MustRegister(m.requestSeconds)
-	prometheus.MustRegister(m.requestInputBytes)
+	prometheus.MustRegister(m.inputBytes)
-	prometheus.MustRegister(m.requestOutputBytes)
+	prometheus.MustRegister(m.outputBytes)
 	return m
 }
 
-func Services() prometheus.Gauge {
+func Services() Gauge {
-	return global.services
+	return metrics.services
 }
 
-func Requests(service string) prometheus.Counter {
+func Requests(service string) Counter {
-	return global.requests.With(prometheus.Labels{"service": service})
+	return metrics.requests.With(prometheus.Labels{"service": service})
 }
 
-func RequestsInFlight(service string) prometheus.Gauge {
+func RequestsInFlight(service string) Gauge {
-	return global.requestsInFlight.With(prometheus.Labels{"service": service})
+	return metrics.requestsInFlight.With(prometheus.Labels{"service": service})
 }
 
-func RequestSeconds(service string) prometheus.Observer {
+func RequestSeconds(service string) Observer {
-	return global.requestSeconds.With(prometheus.Labels{"service": service})
+	return metrics.requestSeconds.With(prometheus.Labels{"service": service})
 }
 
-func RequestInputBytes(service string) prometheus.Counter {
+func InputBytes(service string) Counter {
-	return global.requestInputBytes.With(prometheus.Labels{"service": service})
+	return metrics.inputBytes.With(prometheus.Labels{"service": service})
 }
 
-func RequestOutputBytes(service string) prometheus.Counter {
+func OutputBytes(service string) Counter {
-	return global.requestOutputBytes.With(prometheus.Labels{"service": service})
+	return metrics.outputBytes.With(prometheus.Labels{"service": service})
+}
+
+func HandlerErrors(service string) Counter {
+	return metrics.handlerErrors.With(prometheus.Labels{"service": service})
 }

pkg/service/service.go

@@ -10,7 +10,6 @@ import (
 	"github.com/go-gost/gost/pkg/listener"
 	"github.com/go-gost/gost/pkg/logger"
 	"github.com/go-gost/gost/pkg/metrics"
-	"github.com/prometheus/client_golang/prometheus"
 )
 
 type options struct {
@@ -105,11 +104,14 @@ func (s *service) Serve() error {
 			metrics.RequestsInFlight(s.name).Inc()
 			defer metrics.RequestsInFlight(s.name).Dec()
 
-			timer := prometheus.NewTimer(
+			start := time.Now()
-				metrics.RequestSeconds(s.name))
+			defer func() {
-			defer timer.ObserveDuration()
+				metrics.RequestSeconds(s.name).Observe(time.Since(start).Seconds())
+			}()
 
-			s.handler.Handle(context.Background(), conn)
+			if err := s.handler.Handle(context.Background(), conn); err != nil {
+				metrics.HandlerErrors(s.name).Inc()
+			}
 		}()
 	}
 }