Fix UDP domain destination lost in outbound groups

common/interrupt/conn.go

@@ -4,29 +4,16 @@ import (
 	"net"
 
 	"github.com/sagernet/sing/common/bufio"
+	N "github.com/sagernet/sing/common/network"
 	"github.com/sagernet/sing/common/x/list"
 )
 
-/*type GroupedConn interface {
-	MarkAsInternal()
-}
-
-func MarkAsInternal(conn any) {
-	if groupedConn, isGroupConn := common.Cast[GroupedConn](conn); isGroupConn {
-		groupedConn.MarkAsInternal()
-	}
-}*/
-
 type Conn struct {
 	net.Conn
 	group   *Group
 	element *list.Element[*groupConnItem]
 }
 
-/*func (c *Conn) MarkAsInternal() {
-	c.element.Value.internal = true
-}*/
-
 func (c *Conn) Close() error {
 	c.group.access.Lock()
 	defer c.group.access.Unlock()
@@ -47,20 +34,20 @@ func (c *Conn) Upstream() any {
 }
 
 type PacketConn struct {
-	net.PacketConn
+	N.NetPacketConn
 	group   *Group
 	element *list.Element[*groupConnItem]
 }
 
-/*func (c *PacketConn) MarkAsInternal() {
-	c.element.Value.internal = true
-}*/
+func newPacketConn(group *Group, conn net.PacketConn, element *list.Element[*groupConnItem]) *PacketConn {
+	return &PacketConn{NetPacketConn: bufio.NewPacketConn(conn), group: group, element: element}
+}
 
 func (c *PacketConn) Close() error {
 	c.group.access.Lock()
 	defer c.group.access.Unlock()
 	c.group.connections.Remove(c.element)
-	return c.PacketConn.Close()
+	return c.NetPacketConn.Close()
 }
 
 func (c *PacketConn) ReaderReplaceable() bool {
@@ -72,5 +59,5 @@ func (c *PacketConn) WriterReplaceable() bool {
 }
 
 func (c *PacketConn) Upstream() any {
-	return bufio.NewPacketConn(c.PacketConn)
+	return c.NetPacketConn
 }

common/interrupt/group.go

@@ -33,7 +33,7 @@ func (g *Group) NewPacketConn(conn net.PacketConn, isExternal bool) net.PacketCo
 	g.access.Lock()
 	defer g.access.Unlock()
 	item := g.connections.PushBack(&groupConnItem{conn, isExternal})
-	return &PacketConn{PacketConn: conn, group: g, element: item}
+	return newPacketConn(g, conn, item)
 }
 
 func (g *Group) Interrupt(interruptExternalConnections bool) {