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>

2 files changed, 47 insertions, 1 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 30ae6d9a12af..9b33d6ebf542 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -42,6 +42,7 @@ struct virtnet_info
         struct virtqueue *rvq, *svq;
         struct net_device *dev;
         struct napi_struct napi;
+        unsigned int status;
 
         /* The skb we couldn't send because buffers were full. */
         struct sk_buff *last_xmit_skb;
@@ -611,6 +612,7 @@ static struct ethtool_ops virtnet_ethtool_ops = {
         .set_tx_csum = virtnet_set_tx_csum,
         .set_sg = ethtool_op_set_sg,
         .set_tso = ethtool_op_set_tso,
+        .get_link = ethtool_op_get_link,
 };
 
 #define MIN_MTU 68
@@ -636,6 +638,41 @@ static const struct net_device_ops virtnet_netdev = {
 #endif
 };
 
+static void virtnet_update_status(struct virtnet_info *vi)
+{
+        u16 v;
+
+        if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS))
+                return;
+
+        vi->vdev->config->get(vi->vdev,
+                              offsetof(struct virtio_net_config, status),
+                              &v, sizeof(v));
+
+        /* Ignore unknown (future) status bits */
+        v &= VIRTIO_NET_S_LINK_UP;
+
+        if (vi->status == v)
+                return;
+
+        vi->status = v;
+
+        if (vi->status & VIRTIO_NET_S_LINK_UP) {
+                netif_carrier_on(vi->dev);
+                netif_wake_queue(vi->dev);
+        } else {
+                netif_carrier_off(vi->dev);
+                netif_stop_queue(vi->dev);
+        }
+}
+
+static void virtnet_config_changed(struct virtio_device *vdev)
+{
+        struct virtnet_info *vi = vdev->priv;
+
+        virtnet_update_status(vi);
+}
+
 static int virtnet_probe(struct virtio_device *vdev)
 {
         int err;
@@ -738,6 +775,9 @@ static int virtnet_probe(struct virtio_device *vdev)
                 goto unregister;
         }
 
+        vi->status = VIRTIO_NET_S_LINK_UP;
+        virtnet_update_status(vi);
+
         pr_debug("virtnet: registered device %s\n", dev->name);
         return 0;
 
@@ -793,7 +833,7 @@ static unsigned int features[] = {
         VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_UFO, VIRTIO_NET_F_HOST_TSO6,
         VIRTIO_NET_F_HOST_ECN, VIRTIO_NET_F_GUEST_TSO4, VIRTIO_NET_F_GUEST_TSO6,
         VIRTIO_NET_F_GUEST_ECN, /* We don't yet handle UFO input. */
-        VIRTIO_NET_F_MRG_RXBUF,
+        VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS,
         VIRTIO_F_NOTIFY_ON_EMPTY,
 };
 
@@ -805,6 +845,7 @@ static struct virtio_driver virtio_net = {
         .id_table =     id_table,
         .probe =        virtnet_probe,
         .remove =       __devexit_p(virtnet_remove),
+        .config_changed = virtnet_config_changed,
 };
 
 static int __init init(void)
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