net: introduce control client

This patch introduces a boolean for the device has control queue which
can accepts control command via network queue.

The first user would be the control virtqueue support for vhost.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20211020045600.16082-6-jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

include/net/net.h

@@ -105,6 +105,7 @@ struct NetClientState {
     int vnet_hdr_len;
     bool is_netdev;
     bool do_not_pad; /* do not pad to the minimum ethernet frame length */
+    bool is_datapath;
     QTAILQ_HEAD(, NetFilterState) filters;
 };
 
@@ -136,6 +137,10 @@ NetClientState *qemu_new_net_client(NetClientInfo *info,
                                     NetClientState *peer,
                                     const char *model,
                                     const char *name);
+NetClientState *qemu_new_net_control_client(NetClientInfo *info,
+                                        NetClientState *peer,
+                                        const char *model,
+                                        const char *name);
 NICState *qemu_new_nic(NetClientInfo *info,
                        NICConf *conf,
                        const char *model,

net/net.c

@@ -239,7 +239,8 @@ static void qemu_net_client_setup(NetClientState *nc,
                                   NetClientState *peer,
                                   const char *model,
                                   const char *name,
-                                  NetClientDestructor *destructor)
+                                  NetClientDestructor *destructor,
+                                  bool is_datapath)
 {
     nc->info = info;
     nc->model = g_strdup(model);
@@ -258,6 +259,7 @@ static void qemu_net_client_setup(NetClientState *nc,
 
     nc->incoming_queue = qemu_new_net_queue(qemu_deliver_packet_iov, nc);
     nc->destructor = destructor;
+    nc->is_datapath = is_datapath;
     QTAILQ_INIT(&nc->filters);
 }
 
@@ -272,7 +274,23 @@ NetClientState *qemu_new_net_client(NetClientInfo *info,
 
     nc = g_malloc0(info->size);
     qemu_net_client_setup(nc, info, peer, model, name,
-                          qemu_net_client_destructor);
+                          qemu_net_client_destructor, true);
+
+    return nc;
+}
+
+NetClientState *qemu_new_net_control_client(NetClientInfo *info,
+                                            NetClientState *peer,
+                                            const char *model,
+                                            const char *name)
+{
+    NetClientState *nc;
+
+    assert(info->size >= sizeof(NetClientState));
+
+    nc = g_malloc0(info->size);
+    qemu_net_client_setup(nc, info, peer, model, name,
+                          qemu_net_client_destructor, false);
 
     return nc;
 }
@@ -297,7 +315,7 @@ NICState *qemu_new_nic(NetClientInfo *info,
 
     for (i = 0; i < queues; i++) {
         qemu_net_client_setup(&nic->ncs[i], info, peers[i], model, name,
-                              NULL);
+                              NULL, true);
         nic->ncs[i].queue_index = i;
     }