Add pac support for mixed server

cli/ss-local/main.go

@@ -11,6 +11,7 @@ import (
 	"os"
 	"os/signal"
 	"runtime/debug"
+	"strconv"
 	"strings"
 	"syscall"
 	"time"
@@ -30,6 +31,7 @@ import (
 	"github.com/sagernet/sing/protocol/shadowsocks/shadowaead"
 	"github.com/sagernet/sing/protocol/shadowsocks/shadowaead_2022"
 	"github.com/sagernet/sing/protocol/socks"
+	"github.com/sagernet/sing/protocol/wapd"
 	"github.com/sagernet/sing/transport/mixed"
 	"github.com/sagernet/sing/transport/system"
 	"github.com/sirupsen/logrus"
@@ -52,6 +54,7 @@ type flags struct {
 	UseSystemRNG       bool   `json:"use_system_rng"`
 	ReducedSaltEntropy bool   `json:"reduced_salt_entropy"`
 	ConfigFile         string
+	WAPD               bool
 }
 
 func main() {
@@ -88,6 +91,7 @@ Only available with Linux kernel > 3.7.0.`)
 	command.Flags().BoolVarP(&f.Verbose, "verbose", "v", true, "Enable verbose mode.")
 	command.Flags().BoolVar(&f.UseSystemRNG, "use-system-rng", false, "Use system random number generator.")
 	command.Flags().BoolVar(&f.ReducedSaltEntropy, "reduced-salt-entropy", false, "Remapping salt to printable chars.")
+	command.Flags().BoolVar(&f.WAPD, "wapd", false, "Listen WADP server.")
 
 	err := command.Execute()
 	if err != nil {
@@ -102,6 +106,7 @@ type LocalClient struct {
 	method shadowsocks.Method
 	dialer net.Dialer
 	bypass string
+	wapd   *wapd.Listener
 }
 
 func NewLocalClient(f *flags) (*LocalClient, error) {
@@ -247,6 +252,10 @@ func NewLocalClient(f *flags) (*LocalClient, error) {
 
 	client.Listener = mixed.NewListener(netip.AddrPortFrom(bind, f.LocalPort), nil, transproxyMode, client)
 
+	if f.WAPD {
+		client.wapd = wapd.NewListener(netip.MustParseAddr("255.255.255.255"), "http://127.0.0.1:"+strconv.Itoa(int(f.LocalPort))+"/proxy.pac", client)
+	}
+
 	if f.Bypass != "" {
 		err := geoip.LoadMMDB("Country.mmdb")
 		if err != nil {
@@ -373,6 +382,14 @@ func Run(cmd *cobra.Command, flags *flags) {
 		logrus.Fatal(err)
 	}
 
+	if client.wapd != nil {
+		err = client.wapd.Start()
+	}
+
+	if err != nil {
+		logrus.Fatal(err)
+	}
+
 	logrus.Info("mixed server started at ", client.Listener.TCPListener.Addr())
 
 	osSignals := make(chan os.Signal, 1)
@@ -383,6 +400,7 @@ func Run(cmd *cobra.Command, flags *flags) {
 }
 
 func (c *LocalClient) HandleError(err error) {
+	common.Close(err)
 	if E.IsClosed(err) {
 		return
 	}

cli/uot-local/main.go

@@ -9,6 +9,7 @@ import (
 	"syscall"
 
 	"github.com/sagernet/sing"
+	"github.com/sagernet/sing/common"
 	E "github.com/sagernet/sing/common/exceptions"
 	M "github.com/sagernet/sing/common/metadata"
 	"github.com/sagernet/sing/common/redir"
@@ -133,6 +134,7 @@ func (c *localClient) NewPacketConnection(conn socks.PacketConn, _ M.Metadata) e
 }
 
 func (c *localClient) OnError(err error) {
+	common.Close(err)
 	if E.IsClosed(err) {
 		return
 	}

common/cond.go

@@ -96,20 +96,33 @@ func Must1(_ any, err error) {
 	}
 }
 
-func Close(closers ...any) {
+func Close(closers ...any) error {
+	var retErr error
 	for _, closer := range closers {
 		if closer == nil {
 			continue
 		}
+		var err error
 		switch c := closer.(type) {
 		case io.Closer:
-			c.Close()
+			err = c.Close()
 		}
 		switch c := closer.(type) {
 		case ReaderWithUpstream:
-			Close(c.Upstream())
+			err = Close(c.Upstream())
 		case WriterWithUpstream:
-			Close(c.Upstream())
+			err = Close(c.Upstream())
+		}
+		if err != nil {
+			retErr = err
 		}
 	}
+	return retErr
+}
+
+func CloseError(closer any, err error) error {
+	if err == nil {
+		return nil
+	}
+	return Close(closer)
 }

common/metadata/network.go

@@ -0,0 +1,10 @@
+package metadata
+
+import "net/netip"
+
+func NetworkFromNetAddr(network string, addr netip.Addr) string {
+	if addr.Is4() && (addr.IsUnspecified() || addr.IsGlobalUnicast() || addr.IsLinkLocalUnicast()) {
+		return network + "4"
+	}
+	return network
+}

go.mod

@@ -3,6 +3,7 @@ module github.com/sagernet/sing
 go 1.18
 
 require (
+	github.com/insomniacslk/dhcp v0.0.0-20220405050111-12fbdcb11b41
 	github.com/klauspost/compress v1.15.1
 	github.com/openacid/low v0.1.21
 	github.com/oschwald/geoip2-golang v1.7.0
@@ -33,6 +34,7 @@ require (
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/riobard/go-bloom v0.0.0-20200614022211-cdc8013cb5b3 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
+	github.com/u-root/uio v0.0.0-20210528114334-82958018845c // indirect
 	golang.org/x/exp v0.0.0-20220303212507-bbda1eaf7a17 // indirect
 	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
 )

go.sum

@@ -5,19 +5,41 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
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+github.com/fanliao/go-promise v0.0.0-20141029170127-1890db352a72/go.mod h1:PjfxuH4FZdUyfMdtBio2lsRr1AKEaVPwelzuHuh8Lqc=
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+github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
+github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
+github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
+github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
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+github.com/mdlayher/raw v0.0.0-20190606142536-fef19f00fc18/go.mod h1:7EpbotpCmVZcu+KCX4g9WaRNuu11uyhiW7+Le1dKawg=
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@@ -42,10 +64,13 @@ github.com/seiflotfy/cuckoofilter v0.0.0-20201222105146-bc6005554a0c h1:pqy40B3M
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+github.com/smartystreets/goconvey v1.6.4/go.mod h1:syvi0/a8iFYH4r/RixwvyeAJjdLS9QV7WQ/tjFTllLA=
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+github.com/stretchr/objx v0.1.0 h1:4G4v2dO3VZwixGIRoQ5Lfboy6nUhCyYzaqnIAPPhYs4=
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@@ -54,21 +79,51 @@ github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
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+golang.org/x/sys v0.0.0-20191008105621-543471e840be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200202164722-d101bd2416d5/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20201009025420-dfb3f7c4e634/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20201101102859-da207088b7d1/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210525143221-35b2ab0089ea/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220408201424-a24fb2fb8a0f h1:8w7RhxzTVgUzw/AH/9mUV5q0vMgy40SQRursCcfmkCw=
 golang.org/x/sys v0.0.0-20220408201424-a24fb2fb8a0f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/tools v0.0.0-20190328211700-ab21143f2384/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
 golang.zx2c4.com/wireguard v0.0.0-20220407013110-ef5c587f782d h1:q4JksJ2n0fmbXC0Aj0eOs6E0AcPqnKglxWXWFqGD6x0=

protocol/http/listener.go

@@ -12,7 +12,6 @@ import (
 	_ "unsafe"
 
 	"github.com/sagernet/sing/common/auth"
-	"github.com/sagernet/sing/common/buf"
 	E "github.com/sagernet/sing/common/exceptions"
 	M "github.com/sagernet/sing/common/metadata"
 	"github.com/sagernet/sing/transport/tcp"
@@ -22,14 +21,9 @@ type Handler interface {
 	tcp.Handler
 }
 
-func HandleConnection(conn *buf.BufferedConn, authenticator auth.Authenticator, handler Handler) error {
+func HandleRequest(request *http.Request, conn net.Conn, authenticator auth.Authenticator, handler Handler, metadata M.Metadata) error {
 	var httpClient *http.Client
 	for {
-		request, err := readRequest(conn.Reader())
-		if err != nil {
-			return E.Cause(err, "read http request")
-		}
-
 		if authenticator != nil {
 			var authOk bool
 			authorization := request.Header.Get("Proxy-Authorization")
@@ -39,7 +33,7 @@ func HandleConnection(conn *buf.BufferedConn, authenticator auth.Authenticator,
 				authOk = authenticator.Verify(userPswdArr[0], userPswdArr[1])
 			}
 			if !authOk {
-				err = responseWith(request, http.StatusProxyAuthRequired).Write(conn)
+				err := responseWith(request, http.StatusProxyAuthRequired).Write(conn)
 				if err != nil {
 					return err
 				}
@@ -61,9 +55,8 @@ func HandleConnection(conn *buf.BufferedConn, authenticator auth.Authenticator,
 			if err != nil {
 				return E.Cause(err, "write http response")
 			}
-			return handler.NewConnection(conn, M.Metadata{
+			metadata.Destination = destination
-				Destination: destination,
+			return handler.NewConnection(conn, metadata)
-			})
 		}
 
 		keepAlive := strings.TrimSpace(strings.ToLower(request.Header.Get("Proxy-Connection"))) == "keep-alive"
@@ -101,11 +94,10 @@ func HandleConnection(conn *buf.BufferedConn, authenticator auth.Authenticator,
 
 						left, right := net.Pipe()
 						go func() {
-							err = handler.NewConnection(right, M.Metadata{
+							metadata.Destination = destination
-								Destination: destination,
+							err = handler.NewConnection(right, metadata)
-							})
 							if err != nil {
-								handler.HandleError(err)
+								handler.HandleError(&tcp.Error{Conn: right, Cause: err})
 							}
 						}()
 						return left, nil
@@ -137,11 +129,15 @@ func HandleConnection(conn *buf.BufferedConn, authenticator auth.Authenticator,
 		if err != nil {
 			return err
 		}
+
+		if !keepAlive {
+			return conn.Close()
+		}
 	}
 }
 
-//go:linkname readRequest net/http.ReadRequest
+//go:linkname ReadRequest net/http.ReadRequest
-func readRequest(b *bufio.Reader) (req *http.Request, err error)
+func ReadRequest(b *bufio.Reader) (req *http.Request, err error)
 
 func removeHopByHopHeaders(header http.Header) {
 	// Strip hop-by-hop header based on RFC:

protocol/socks/listener.go

@@ -35,7 +35,7 @@ func NewListener(bind netip.AddrPort, authenticator auth.Authenticator, handler
 }
 
 func (l *Listener) NewConnection(conn net.Conn, metadata M.Metadata) error {
-	return HandleConnection(conn, l.bindAddr, l.authenticator, l.handler)
+	return HandleConnection(conn, l.authenticator, l.bindAddr, l.handler, metadata)
 }
 
 func (l *Listener) Start() error {
@@ -50,7 +50,7 @@ func (l *Listener) HandleError(err error) {
 	l.handler.HandleError(err)
 }
 
-func HandleConnection(conn net.Conn, bind netip.Addr, authenticator auth.Authenticator, handler Handler) error {
+func HandleConnection(conn net.Conn, authenticator auth.Authenticator, bind netip.Addr, handler Handler, metadata M.Metadata) error {
 	authRequest, err := ReadAuthRequest(conn)
 	if err != nil {
 		return E.Cause(err, "read socks auth request")
@@ -72,7 +72,7 @@ func HandleConnection(conn net.Conn, bind netip.Addr, authenticator auth.Authent
 	}
 	err = WriteAuthResponse(conn, &AuthResponse{
 		Version: authRequest.Version,
-		Method:  AuthTypeNotRequired,
+		Method:  authMethod,
 	})
 	if err != nil {
 		return E.Cause(err, "write socks auth response")
@@ -109,9 +109,8 @@ func HandleConnection(conn net.Conn, bind netip.Addr, authenticator auth.Authent
 		if err != nil {
 			return E.Cause(err, "write socks response")
 		}
-		return handler.NewConnection(conn, M.Metadata{
+		metadata.Destination = request.Destination
-			Destination: request.Destination,
+		return handler.NewConnection(conn, metadata)
-		})
 	case CommandUDPAssociate:
 		network := "udp"
 		if bind.Is4() {
@@ -130,15 +129,12 @@ func HandleConnection(conn net.Conn, bind netip.Addr, authenticator auth.Authent
 		if err != nil {
 			return E.Cause(err, "write socks response")
 		}
+		metadata.Destination = request.Destination
 		go func() {
-			err := handler.NewPacketConnection(NewPacketConn(conn, udpConn), M.Metadata{
+			err := handler.NewPacketConnection(NewPacketConn(conn, udpConn), metadata)
-				Source:      M.AddrPortFromNetAddr(conn.RemoteAddr()),
-				Destination: request.Destination,
-			})
 			if err != nil {
 				handler.HandleError(err)
 			}
-			conn.Close()
 		}()
 		return common.Error(io.Copy(io.Discard, conn))
 	default:

protocol/wapd/listener.go

@@ -0,0 +1,52 @@
+package wapd
+
+import (
+	"fmt"
+	"net/netip"
+
+	"github.com/insomniacslk/dhcp/dhcpv4"
+	_ "github.com/insomniacslk/dhcp/dhcpv6"
+	"github.com/sagernet/sing/common/buf"
+	E "github.com/sagernet/sing/common/exceptions"
+	M "github.com/sagernet/sing/common/metadata"
+	"github.com/sagernet/sing/transport/udp"
+	"github.com/sirupsen/logrus"
+)
+
+type Listener struct {
+	*udp.Listener
+	E.Handler
+	option dhcpv4.Option
+}
+
+func NewListener(bind netip.Addr, proxyURL string, errorHandler E.Handler) *Listener {
+	l := &Listener{
+		Handler: errorHandler,
+		option: dhcpv4.Option{
+			Code:  OptionCode,
+			Value: dhcpv4.String(fmt.Sprint(proxyURL)),
+		},
+	}
+	l.Listener = udp.NewUDPListener(netip.AddrPortFrom(bind, dhcpv4.ServerPort), l)
+	return l
+}
+
+func (l *Listener) NewPacket(packet *buf.Buffer, metadata M.Metadata) error {
+	request, err := dhcpv4.FromBytes(packet.Bytes())
+	if err != nil {
+		return E.Cause(err, "bad dhcpv4 packet")
+	}
+	logrus.Trace("DHCPv4 request ", request)
+	if !request.IsOptionRequested(OptionCode) {
+		return nil
+	}
+	reply, err := dhcpv4.NewReplyFromRequest(request, dhcpv4.WithOption(l.option))
+	if err != nil {
+		return E.Cause(err, "create response")
+	}
+	_, err = l.WriteTo(reply.ToBytes(), metadata.Source.UDPAddr())
+	if err != nil {
+		return E.Cause(err, "write response")
+	}
+	return nil
+}

protocol/wapd/protocol.go

@@ -0,0 +1,13 @@
+package wapd
+
+var OptionCode = optionCode{}
+
+type optionCode struct{}
+
+func (C optionCode) Code() uint8 {
+	return 252
+}
+
+func (C optionCode) String() string {
+	return "Web Proxy Auto-Discovery Protocol"
+}

transport/mixed/listener.go

@@ -1,11 +1,17 @@
 package mixed
 
 import (
+	"io"
 	"net"
+	netHttp "net/http"
 	"net/netip"
+	"strings"
 
+	"github.com/sagernet/sing"
+	"github.com/sagernet/sing/common"
 	"github.com/sagernet/sing/common/auth"
 	"github.com/sagernet/sing/common/buf"
+	E "github.com/sagernet/sing/common/exceptions"
 	M "github.com/sagernet/sing/common/metadata"
 	"github.com/sagernet/sing/common/redir"
 	"github.com/sagernet/sing/common/udpnat"
@@ -53,11 +59,40 @@ func (l *Listener) NewConnection(conn net.Conn, metadata M.Metadata) error {
 		return err
 	}
 	switch header[0] {
-	case socks.Version4, socks.Version5:
+	case socks.Version4:
-		return socks.HandleConnection(bufConn, l.bindAddr, l.authenticator, l.handler)
+		return E.New("socks4 request dropped (TODO)")
-	default:
+	case socks.Version5:
-		return http.HandleConnection(bufConn, l.authenticator, l.handler)
+		return socks.HandleConnection(bufConn, l.authenticator, l.bindAddr, l.handler, metadata)
 	}
+
+	request, err := http.ReadRequest(bufConn.Reader())
+	if err != nil {
+		return E.Cause(err, "read http request")
+	}
+
+	if request.Method == "GET" && request.URL.Path == "/proxy.pac" {
+		content := newPAC(M.AddrPortFromNetAddr(conn.LocalAddr()))
+		response := &netHttp.Response{
+			StatusCode: 200,
+			Status:     netHttp.StatusText(200),
+			Proto:      request.Proto,
+			ProtoMajor: request.ProtoMajor,
+			ProtoMinor: request.ProtoMinor,
+			Header: netHttp.Header{
+				"Content-Type": {"application/x-ns-proxy-autoconfig"},
+				"Server":       {sing.VersionStr},
+			},
+			ContentLength: int64(len(content)),
+			Body:          io.NopCloser(strings.NewReader(content)),
+		}
+		err = response.Write(bufConn)
+		if err != nil {
+			return E.Cause(err, "write pac response")
+		}
+		return nil
+	}
+
+	return http.HandleRequest(request, bufConn, l.authenticator, l.handler, metadata)
 }
 
 func (l *Listener) NewPacket(packet *buf.Buffer, metadata M.Metadata) error {
@@ -80,9 +115,8 @@ func (l *Listener) Start() error {
 }
 
 func (l *Listener) Close() error {
-	l.TCPListener.Close()
+	return common.Close(
-	if l.UDPListener != nil {
+		l.TCPListener,
-		l.UDPListener.Close()
+		l.UDPListener,
-	}
+	)
-	return nil
 }

transport/mixed/pac.go

@@ -0,0 +1,19 @@
+package mixed
+
+import M "github.com/sagernet/sing/common/metadata"
+
+/*func newPAC(proxyAddr *M.AddrPort) string {
+	return `
+function FindProxyForURL(url, host) {
+    return "SOCKS5 ` + proxyAddr.String() + `;SOCKS ` + proxyAddr.String() + `; PROXY ` + proxyAddr.String() + `";
+}`
+}
+*/
+
+func newPAC(proxyAddr *M.AddrPort) string {
+	// TODO: socks4 not supported
+	return `
+function FindProxyForURL(url, host) {
+    return "SOCKS5 ` + proxyAddr.String() + `; PROXY ` + proxyAddr.String() + `";
+}`
+}

transport/tcp/handler.go

@@ -23,6 +23,23 @@ type Listener struct {
 	*net.TCPListener
 }
 
+type Error struct {
+	Conn  net.Conn
+	Cause error
+}
+
+func (e *Error) Error() string {
+	return e.Cause.Error()
+}
+
+func (e *Error) Unwrap() error {
+	return e.Cause
+}
+
+func (e *Error) Close() error {
+	return common.Close(e.Conn)
+}
+
 func NewTCPListener(listen netip.AddrPort, handler Handler, options ...Option) *Listener {
 	listener := &Listener{
 		bind:    listen,
@@ -35,11 +52,7 @@ func NewTCPListener(listen netip.AddrPort, handler Handler, options ...Option) *
 }
 
 func (l *Listener) Start() error {
-	network := "tcp"
+	tcpListener, err := net.ListenTCP(M.NetworkFromNetAddr("tcp", l.bind.Addr()), net.TCPAddrFromAddrPort(l.bind))
-	if l.bind.Addr() == netip.IPv4Unspecified() {
-		network = "tcp4"
-	}
-	tcpListener, err := net.ListenTCP(network, net.TCPAddrFromAddrPort(l.bind))
 	if err != nil {
 		return err
 	}
@@ -73,7 +86,9 @@ func (l *Listener) loop() {
 			l.Close()
 			return
 		}
-		var metadata M.Metadata
+		metadata := M.Metadata{
+			Source: M.AddrPortFromNetAddr(tcpConn.RemoteAddr()),
+		}
 		switch l.trans {
 		case redir.ModeRedirect:
 			metadata.Destination, _ = redir.GetOriginalDestination(tcpConn)
@@ -86,9 +101,9 @@ func (l *Listener) loop() {
 			}
 		}
 		go func() {
-			err := l.handler.NewConnection(tcpConn, metadata)
+			hErr := l.handler.NewConnection(tcpConn, metadata)
-			if err != nil {
+			if hErr != nil {
-				l.handler.HandleError(err)
+				l.handler.HandleError(&Error{Conn: tcpConn, Cause: hErr})
 			}
 		}()
 	}

transport/udp/udp.go

@@ -19,6 +19,7 @@ type Handler interface {
 type Listener struct {
 	*net.UDPConn
 	handler Handler
+	network string
 	bind    netip.AddrPort
 	tproxy  bool
 }
@@ -35,11 +36,7 @@ func NewUDPListener(listen netip.AddrPort, handler Handler, options ...Option) *
 }
 
 func (l *Listener) Start() error {
-	network := "udp"
+	udpConn, err := net.ListenUDP(M.NetworkFromNetAddr("udp", l.bind.Addr()), net.UDPAddrFromAddrPort(l.bind))
-	if l.bind.Addr() == netip.IPv4Unspecified() {
-		network = "udp4"
-	}
-	udpConn, err := net.ListenUDP(network, net.UDPAddrFromAddrPort(l.bind))
 	if err != nil {
 		return err
 	}