net: tap: use qemu_set_nonblock

The fcntl will change the flags directly, use qemu_set_nonblock()
instead.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Li Qiang <liq3ea@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

net/tap.c

@@ -592,7 +592,7 @@ int net_init_bridge(const Netdev *netdev, const char *name,
         return -1;
     }
 
-    fcntl(fd, F_SETFL, O_NONBLOCK);
+    qemu_set_nonblock(fd);
     vnet_hdr = tap_probe_vnet_hdr(fd);
     s = net_tap_fd_init(peer, "bridge", name, fd, vnet_hdr);
 
@@ -707,7 +707,7 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer,
                 }
                 return;
             }
-            fcntl(vhostfd, F_SETFL, O_NONBLOCK);
+            qemu_set_nonblock(vhostfd);
         }
         options.opaque = (void *)(uintptr_t)vhostfd;
 
@@ -791,7 +791,7 @@ int net_init_tap(const Netdev *netdev, const char *name,
             return -1;
         }
 
-        fcntl(fd, F_SETFL, O_NONBLOCK);
+        qemu_set_nonblock(fd);
 
         vnet_hdr = tap_probe_vnet_hdr(fd);
 
@@ -839,7 +839,7 @@ int net_init_tap(const Netdev *netdev, const char *name,
                 goto free_fail;
             }
 
-            fcntl(fd, F_SETFL, O_NONBLOCK);
+            qemu_set_nonblock(fd);
 
             if (i == 0) {
                 vnet_hdr = tap_probe_vnet_hdr(fd);
@@ -887,7 +887,7 @@ free_fail:
             return -1;
         }
 
-        fcntl(fd, F_SETFL, O_NONBLOCK);
+        qemu_set_nonblock(fd);
         vnet_hdr = tap_probe_vnet_hdr(fd);
 
         net_init_tap_one(tap, peer, "bridge", name, ifname,