virtio-net: Enable filtering based on MAC, promisc, broadcast and allmulti

index c5d9952..99e582f 100644
@@ -273,6 +273,25 @@ static int receive_header(VirtIONet *n, struct iovec *iov, int iovcnt,
     return offset;
 }
 
+static int receive_filter(VirtIONet *n, const uint8_t *buf, int size)
+{
+    static uint8_t bcast[] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
+
+    if (n->promisc)
+        return 1;
+
+    if ((buf[0] & 1) && n->allmulti)
+        return 1;
+
+    if (!memcmp(buf, bcast, sizeof(bcast)))
+        return 1;
+
+    if (!memcmp(buf, n->mac, 6))
+        return 1;
+
+    return 0;
+}
+
 static void virtio_net_receive(void *opaque, const uint8_t *buf, int size)
 {
     VirtIONet *n = opaque;

@@ -282,6 +301,9 @@ static void virtio_net_receive(void *opaque, const uint8_t *buf, int size)
     if (!do_virtio_net_can_receive(n, size))
         return;
 
+    if (!receive_filter(n, buf, size))
+        return;
+
     /* hdr_len refers to the header we supply to the guest */
     hdr_len = n->mergeable_rx_bufs ?
         sizeof(struct virtio_net_hdr_mrg_rxbuf) : sizeof(struct virtio_net_hdr);