virtio_net: add link status handling

Allow the host to inform us that the link is down by adding
a VIRTIO_NET_F_STATUS which indicates that device status is
available in virtio_net config.

This is currently useful for simulating link down conditions
(e.g. using proposed qemu 'set_link' monitor command) but
would also be needed if we were to support device assignment
via virtio.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (added future masking)
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 5cdd0aa8bde9..f76bd4a753ef 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -21,11 +21,16 @@
 #define VIRTIO_NET_F_HOST_ECN   13      /* Host can handle TSO[6] w/ ECN in. */
 #define VIRTIO_NET_F_HOST_UFO   14      /* Host can handle UFO in. */
 #define VIRTIO_NET_F_MRG_RXBUF  15      /* Host can merge receive buffers. */
+#define VIRTIO_NET_F_STATUS     16      /* virtio_net_config.status available */
+
+#define VIRTIO_NET_S_LINK_UP    1       /* Link is up */
 
 struct virtio_net_config
 {
         /* The config defining mac address (if VIRTIO_NET_F_MAC) */
         __u8 mac[6];
+        /* See VIRTIO_NET_F_STATUS and VIRTIO_NET_S_* above */
+        __u16 status;
 } __attribute__((packed));
 
 /* This is the first element of the scatter-gather list.  If you don't