Move checks to the top of the function to simplify further
refactoring. Merge duplicated checks.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
---
 net/tap.c | 53 +++++++++++++++++++++++------------------------------
 1 file changed, 23 insertions(+), 30 deletions(-)

diff --git a/net/tap.c b/net/tap.c
index 55b8b33ea8..331a779585 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -841,16 +841,30 @@ int net_init_tap(const Netdev *netdev, const char *name,
         return -1;
     }
 
-    if (tap->fd) {
-        if (tap->ifname || tap->script || tap->downscript ||
-            tap->has_vnet_hdr || tap->helper || tap->has_queues ||
-            tap->fds || tap->vhostfds) {
-            error_setg(errp, "ifname=, script=, downscript=, vnet_hdr=, "
-                       "helper=, queues=, fds=, and vhostfds= "
-                       "are invalid with fd=");
-            return -1;
-        }
+    if (tap->has_queues + !!tap->helper + !!tap->fds + !!tap->fd > 1) {
+        error_setg(errp, "queues=, helper=, fds= and fd= are mutual exclusive");
+        return -1;
+    }
 
+    if ((tap->fd || tap->fds || tap->helper) &&
+        (tap->ifname || tap->script || tap->downscript ||
+         tap->has_vnet_hdr)) {
+        error_setg(errp, "ifname=, script=, downscript=, vnet_hdr= "
+                   "are invalid with fd=/fds=/helper=");
+        return -1;
+    }
+
+    if (tap->vhostfds && !tap->fds) {
+        error_setg(errp, "vhostfds= is invalid if fds= wasn't specified");
+        return -1;
+    }
+
+    if (tap->vhostfd && tap->fds) {
+        error_setg(errp, "vhostfd= is invalid with fds=");
+        return -1;
+    }
+
+    if (tap->fd) {
         fd = monitor_fd_param(monitor_cur(), tap->fd, errp);
         if (fd == -1) {
             return -1;
@@ -878,15 +892,6 @@ int net_init_tap(const Netdev *netdev, const char *name,
         char **vhost_fds;
         int nfds = 0, nvhosts = 0;
 
-        if (tap->ifname || tap->script || tap->downscript ||
-            tap->has_vnet_hdr || tap->helper || tap->has_queues ||
-            tap->vhostfd) {
-            error_setg(errp, "ifname=, script=, downscript=, vnet_hdr=, "
-                       "helper=, queues=, and vhostfd= "
-                       "are invalid with fds=");
-            return -1;
-        }
-
         fds = g_new0(char *, MAX_TAP_QUEUES);
         vhost_fds = g_new0(char *, MAX_TAP_QUEUES);
 
@@ -946,13 +951,6 @@ free_fail:
         g_free(vhost_fds);
         return ret;
     } else if (tap->helper) {
-        if (tap->ifname || tap->script || tap->downscript ||
-            tap->has_vnet_hdr || tap->has_queues || tap->vhostfds) {
-            error_setg(errp, "ifname=, script=, downscript=, vnet_hdr=, "
-                       "queues=, and vhostfds= are invalid with helper=");
-            return -1;
-        }
-
         fd = net_bridge_run_helper(tap->helper,
                                    tap->br ?: DEFAULT_BRIDGE_INTERFACE,
                                    errp);
@@ -981,11 +979,6 @@ free_fail:
         g_autofree char *downscript =
             tap_parse_script(tap->downscript, DEFAULT_NETWORK_DOWN_SCRIPT);
 
-        if (tap->vhostfds) {
-            error_setg(errp, "vhostfds= is invalid if fds= wasn't specified");
-            return -1;
-        }
-
         if (tap->ifname) {
             pstrcpy(ifname, sizeof ifname, tap->ifname);
         } else {
-- 
2.52.0