tap: add API to retrieve vhost net header

will be used by virtio-net for vhost net support

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

net/tap.c

@@ -488,3 +488,10 @@ int net_init_tap(QemuOpts *opts, Monitor *mon, const char *name, VLANState *vlan
 
     return 0;
 }
+
+VHostNetState *tap_get_vhost_net(VLANClientState *nc)
+{
+    TAPState *s = DO_UPCAST(TAPState, nc, nc);
+    assert(nc->info->type == NET_CLIENT_TYPE_TAP);
+    return s->vhost_net;
+}

net/tap.h

@@ -50,4 +50,7 @@ void tap_fd_set_offload(int fd, int csum, int tso4, int tso6, int ecn, int ufo);
 
 int tap_get_fd(VLANClientState *vc);
 
+struct vhost_net;
+struct vhost_net *tap_get_vhost_net(VLANClientState *vc);
+
 #endif /* QEMU_NET_TAP_H */