net: Add get_vhost_net callback to NetClientInfo

The get_vhost_net() function previously contained a large switch
statement to find the VHostNetState pointer based on the net
client's type. This created a tight coupling, requiring the generic
vhost layer to be aware of every specific backend that supported
vhost, such as tap, vhost-user, and vhost-vdpa.

This approach is not scalable and requires modifying a central function
for any new backend. It also forced each backend to expose its internal
getter function in a public header file.

This patch refactors the logic by introducing a new get_vhost_net
function pointer to the NetClientInfo struct. The central
get_vhost_net() function is now a simple, generic dispatcher that
invokes the callback provided by the net client.

Each backend now implements its own private getter and registers it in
its NetClientInfo.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

1 files changed, 4 insertions, 27 deletions

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index cb87056397..db8b97b753 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -649,41 +649,18 @@ void vhost_net_config_mask(VHostNetState *net, VirtIODevice *dev, bool mask)
 {
     vhost_config_mask(&net->dev, dev, mask);
 }
+
 VHostNetState *get_vhost_net(NetClientState *nc)
 {
-    VHostNetState *vhost_net = 0;
-
     if (!nc) {
         return 0;
     }
 
-    switch (nc->info->type) {
-    case NET_CLIENT_DRIVER_TAP:
-        vhost_net = tap_get_vhost_net(nc);
-        /*
-         * tap_get_vhost_net() can return NULL if a tap net-device backend is
-         * created with 'vhost=off' option, 'vhostforce=off' or no vhost or
-         * vhostforce or vhostfd options at all. Please see net_init_tap_one().
-         * Hence, we omit the assertion here.
-         */
-        break;
-#ifdef CONFIG_VHOST_NET_USER
-    case NET_CLIENT_DRIVER_VHOST_USER:
-        vhost_net = vhost_user_get_vhost_net(nc);
-        assert(vhost_net);
-        break;
-#endif
-#ifdef CONFIG_VHOST_NET_VDPA
-    case NET_CLIENT_DRIVER_VHOST_VDPA:
-        vhost_net = vhost_vdpa_get_vhost_net(nc);
-        assert(vhost_net);
-        break;
-#endif
-    default:
-        break;
+    if (nc->info->get_vhost_net) {
+        return nc->info->get_vhost_net(nc);
     }
 
-    return vhost_net;
+    return NULL;
 }
 
 int vhost_net_set_vring_enable(NetClientState *nc, int enable)