endpoint: Drop packets to non-IP destinations

common/iponly/conn.go

@@ -0,0 +1,95 @@
+package iponly
+
+import (
+	"net"
+	"os"
+
+	"github.com/sagernet/sing/common/buf"
+	"github.com/sagernet/sing/common/bufio"
+	"github.com/sagernet/sing/common/logger"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+)
+
+type PacketConn struct {
+	N.NetPacketConn
+	logger logger.Logger
+}
+
+func NewPacketConn(logger logger.Logger, conn net.PacketConn) *PacketConn {
+	return &PacketConn{
+		NetPacketConn: bufio.NewPacketConn(conn),
+		logger:        logger,
+	}
+}
+
+func (c *PacketConn) WriteTo(p []byte, addr net.Addr) (n int, err error) {
+	destination := M.SocksaddrFromNet(addr)
+	if !destination.IsIP() {
+		c.logger.Debug("dropped packet to non-IP destination ", destination)
+		return len(p), nil
+	}
+	return c.NetPacketConn.WriteTo(p, addr)
+}
+
+func (c *PacketConn) WritePacket(buffer *buf.Buffer, destination M.Socksaddr) error {
+	if !destination.IsIP() {
+		buffer.Release()
+		c.logger.Debug("dropped packet to non-IP destination ", destination)
+		return nil
+	}
+	return c.NetPacketConn.WritePacket(buffer, destination)
+}
+
+func (c *PacketConn) CreatePacketBatchWriter() (N.PacketBatchWriter, bool) {
+	writer, created := bufio.CreatePacketBatchWriter(c.NetPacketConn)
+	if !created {
+		return nil, false
+	}
+	return &packetBatchWriter{c, writer}, true
+}
+
+func (c *PacketConn) CreateConnectedPacketBatchWriter() (N.ConnectedPacketBatchWriter, bool) {
+	return bufio.CreateConnectedPacketBatchWriter(c.NetPacketConn)
+}
+
+func (c *PacketConn) ReaderReplaceable() bool {
+	return true
+}
+
+func (c *PacketConn) Upstream() any {
+	return c.NetPacketConn
+}
+
+type packetBatchWriter struct {
+	*PacketConn
+	writer N.PacketBatchWriter
+}
+
+func (w *packetBatchWriter) WritePacketBatch(buffers []*buf.Buffer, destinations []M.Socksaddr) error {
+	if len(buffers) == 0 || len(buffers) != len(destinations) {
+		buf.ReleaseMulti(buffers)
+		return os.ErrInvalid
+	}
+	writeIndex := 0
+	for index, destination := range destinations {
+		if !destination.IsIP() {
+			buffers[index].Release()
+			w.logger.Debug("dropped packet to non-IP destination ", destination)
+			continue
+		}
+		buffers[writeIndex] = buffers[index]
+		destinations[writeIndex] = destination
+		writeIndex++
+	}
+	if writeIndex == 0 {
+		return nil
+	}
+	return w.writer.WritePacketBatch(buffers[:writeIndex], destinations[:writeIndex])
+}
+
+var (
+	_ N.NetPacketConn                    = (*PacketConn)(nil)
+	_ N.PacketBatchWriteCreator          = (*PacketConn)(nil)
+	_ N.ConnectedPacketBatchWriteCreator = (*PacketConn)(nil)
+)