Improve read waiter interface

transport/fakeip/packet_wait.go

@@ -0,0 +1,37 @@
+package fakeip
+
+import (
+	"github.com/sagernet/sing/common/buf"
+	"github.com/sagernet/sing/common/bufio"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+)
+
+func (c *NATPacketConn) CreatePacketReadWaiter() (N.PacketReadWaiter, bool) {
+	waiter, created := bufio.CreatePacketReadWaiter(c.PacketConn)
+	if !created {
+		return nil, false
+	}
+	return &waitNATPacketConn{c, waiter}, true
+}
+
+type waitNATPacketConn struct {
+	*NATPacketConn
+	waiter N.PacketReadWaiter
+}
+
+func (c *waitNATPacketConn) InitializeReadWaiter(newBuffer func() *buf.Buffer) {
+	c.waiter.InitializeReadWaiter(newBuffer)
+}
+
+func (c *waitNATPacketConn) WaitReadPacket() (destination M.Socksaddr, err error) {
+	destination, err = c.waiter.WaitReadPacket()
+	if socksaddrWithoutPort(destination) == c.origin {
+		destination = M.Socksaddr{
+			Addr: c.destination.Addr,
+			Fqdn: c.destination.Fqdn,
+			Port: destination.Port,
+		}
+	}
+	return
+}