diff --git a/format.go b/format.go
deleted file mode 100644
index cb9e463..0000000
--- a/format.go
+++ /dev/null
@@ -1,7 +0,0 @@
-package tun
-
-//go:generate go install -v mvdan.cc/gofumpt@latest
-//go:generate go install -v github.com/daixiang0/gci@v0.4.0
-//go:generate gofumpt -l -w .
-//go:generate gofmt -s -w .
-//go:generate gci write -s "standard,prefix(github.com/sagernet/),default" .
diff --git a/gvisor_udp.go b/gvisor_udp.go
index 82adce8..3708b9c 100644
--- a/gvisor_udp.go
+++ b/gvisor_udp.go
@@ -39,40 +39,45 @@ func (f *UDPForwarder) HandlePacket(id stack.TransportEndpointID, pkt *stack.Pac
 	var upstreamMetadata M.Metadata
 	upstreamMetadata.Source = M.SocksaddrFrom(M.AddrFromIP(net.IP(id.RemoteAddress)), id.RemotePort)
 	upstreamMetadata.Destination = M.SocksaddrFrom(M.AddrFromIP(net.IP(id.LocalAddress)), id.LocalPort)
-
+	var netProto tcpip.NetworkProtocolNumber
+	if upstreamMetadata.Source.IsIPv4() {
+		netProto = header.IPv4ProtocolNumber
+	} else {
+		netProto = header.IPv6ProtocolNumber
+	}
 	f.udpNat.NewPacket(
 		f.ctx,
 		upstreamMetadata.Source.AddrPort(),
 		buf.As(pkt.Data().AsRange().ToSlice()),
 		upstreamMetadata,
 		func(natConn N.PacketConn) N.PacketWriter {
-			return &UDPBackWriter{f.stack, id.RemoteAddress, id.RemotePort}
+			return &UDPBackWriter{f.stack, id.RemoteAddress, id.RemotePort, netProto}
 		},
 	)
 	return true
 }
 
 type UDPBackWriter struct {
-	stack      *stack.Stack
-	source     tcpip.Address
-	sourcePort uint16
+	stack         *stack.Stack
+	source        tcpip.Address
+	sourcePort    uint16
+	sourceNetwork tcpip.NetworkProtocolNumber
 }
 
 func (w *UDPBackWriter) WritePacket(buffer *buf.Buffer, destination M.Socksaddr) error {
 	defer buffer.Release()
 
-	var netProto tcpip.NetworkProtocolNumber
-	if destination.IsIPv4() {
-		netProto = header.IPv4ProtocolNumber
-	} else {
-		netProto = header.IPv6ProtocolNumber
+	if w.sourceNetwork == header.IPv4ProtocolNumber && destination.Addr.Is4In6() {
+		destination = destination.Unwrap()
+	} else if w.sourceNetwork == header.IPv6ProtocolNumber && destination.Addr.Is4() {
+		destination = M.SocksaddrFrom(netip.AddrFrom16(destination.Addr.As16()), destination.Port)
 	}
 
 	route, err := w.stack.FindRoute(
 		defaultNIC,
 		tcpip.Address(destination.Addr.AsSlice()),
 		w.source,
-		netProto,
+		w.sourceNetwork,
 		false,
 	)
 	if err != nil {
@@ -95,7 +100,7 @@ func (w *UDPBackWriter) WritePacket(buffer *buf.Buffer, destination M.Socksaddr)
 		Length:  pLen,
 	})
 
-	if route.RequiresTXTransportChecksum() && netProto == header.IPv6ProtocolNumber {
+	if route.RequiresTXTransportChecksum() && w.sourceNetwork == header.IPv6ProtocolNumber {
 		xsum := udpHdr.CalculateChecksum(header.ChecksumCombine(
 			route.PseudoHeaderChecksum(header.UDPProtocolNumber, pLen),
 			packet.Data().AsRange().Checksum(),
diff --git a/monitor_shared.go b/monitor_shared.go
index 6980de5..cf451b4 100644
--- a/monitor_shared.go
+++ b/monitor_shared.go
@@ -5,9 +5,9 @@ package tun
 import (
 	"context"
 	"sync"
+	"time"
 
 	"github.com/sagernet/sing/common/x/list"
-	"time"
 )
 
 func (m *networkUpdateMonitor) RegisterCallback(callback NetworkUpdateCallback) *list.Element[NetworkUpdateCallback] {
diff --git a/packages_android.go b/packages_android.go
index 2206123..ddf5480 100644
--- a/packages_android.go
+++ b/packages_android.go
@@ -8,11 +8,11 @@ import (
 	"os"
 	"strconv"
 
+	"github.com/sagernet/abx-go"
 	"github.com/sagernet/sing/common"
 	E "github.com/sagernet/sing/common/exceptions"
 
 	"github.com/fsnotify/fsnotify"
-	"github.com/sagernet/abx-go"
 )
 
 type packageManager struct {