[RFC] virtio: enforce link up

[Vincent Jardin]

Using interface's settings, let's enforce an always on link up.

Signed-off-by: Vincent Jardin <vincent.jar...@ekinops.com>
---
 hw/net/virtio-net.c            | 8 ++++++++
 include/hw/virtio/virtio-net.h | 2 ++
 2 files changed, 10 insertions(+)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 29e33ea5ed..e731b4fdea 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -78,6 +78,9 @@
    tso/gso/gro 'off'. */
 #define VIRTIO_NET_RSC_DEFAULT_INTERVAL 300000
 
+/* force always link up */
+#define VIRTIO_NET_LINK_UP false
+
 #define VIRTIO_NET_RSS_SUPPORTED_HASHES (VIRTIO_NET_RSS_HASH_TYPE_IPv4 | \
                                          VIRTIO_NET_RSS_HASH_TYPE_TCPv4 | \
                                          VIRTIO_NET_RSS_HASH_TYPE_UDPv4 | \
@@ -447,6 +450,9 @@ static void virtio_net_set_link_status(NetClientState *nc)
     else
         n->status |= VIRTIO_NET_S_LINK_UP;
 
+    if (n->net_conf.link_up)
+        n->status |= VIRTIO_NET_S_LINK_UP;
+
     if (n->status != old_status)
         virtio_notify_config(vdev);
 
@@ -3947,6 +3953,8 @@ static Property virtio_net_properties[] = {
                       VIRTIO_NET_F_GUEST_USO6, true),
     DEFINE_PROP_BIT64("host_uso", VirtIONet, host_features,
                       VIRTIO_NET_F_HOST_USO, true),
+    DEFINE_PROP_BOOL("link_up", VirtIONet, net_conf.link_up,
+                       VIRTIO_NET_LINK_UP),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
index 55977f01f0..385bebab34 100644
--- a/include/hw/virtio/virtio-net.h
+++ b/include/hw/virtio/virtio-net.h
@@ -56,6 +56,7 @@ typedef struct virtio_net_conf
     char *duplex_str;
     uint8_t duplex;
     char *primary_id_str;
+    bool link_up; /* if set enforce link up, never down */
 } virtio_net_conf;
 
 /* Coalesced packets type & status */
@@ -180,6 +181,7 @@ struct VirtIONet {
     size_t guest_hdr_len;
     uint64_t host_features;
     uint32_t rsc_timeout;
+    uint32_t link_up; /* if set enforce link up, never down */
     uint8_t rsc4_enabled;
     uint8_t rsc6_enabled;
     uint8_t has_ufo;
-- 
2.34.1