Support calling from inside via vsock

kernel/comps/virtio/src/dma_buf.rs

@@ -3,6 +3,8 @@
 use aster_frame::mm::{DmaCoherent, DmaStream, DmaStreamSlice, HasDaddr};
 use aster_network::{DmaSegment, RxBuffer, TxBuffer};
 
+use crate::device;
+
 /// A DMA-capable buffer.
 ///
 /// Any type implements this trait should also implements `HasDaddr` trait,
@@ -48,3 +50,15 @@ impl DmaBuf for RxBuffer {
         self.buf_len()
     }
 }
+
+impl DmaBuf for device::socket::buffer::TxBuffer {
+    fn len(&self) -> usize {
+        self.nbytes()
+    }
+}
+
+impl DmaBuf for device::socket::buffer::RxBuffer {
+    fn len(&self) -> usize {
+        self.buf_len()
+    }
+}