Split the function into separate net_tap_new() and net_tap_set_fd().

We start move to the following picture:

net_tap_new() - take QAPI @tap parameter, but don't have @fd,
initialize the net client, called during initialization.

net_tap_setup() - don't have @tap (QAPI), but have @fd parameter,
may be called at later point.

In this commit we introduce the first function.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Maksim Davydov <davydov-max@yandex-team.ru>
---
 net/tap.c | 31 +++++++++++++++++--------------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/net/tap.c b/net/tap.c
index 05f7480334..f5830f4b00 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -412,19 +412,20 @@ static NetClientInfo net_tap_info = {
     .get_vhost_net = tap_get_vhost_net,
 };
 
-static TAPState *net_tap_fd_init(NetClientState *peer,
-                                 const char *model,
-                                 const char *name,
-                                 int fd,
-                                 int vnet_hdr)
+static TAPState *net_tap_new(NetClientState *peer, const char *model,
+                             const char *name)
 {
-    NetOffloads ol = {};
-    NetClientState *nc;
-    TAPState *s;
+    NetClientState *nc = qemu_new_net_client(&net_tap_info, peer, model, name);
+    TAPState *s = DO_UPCAST(TAPState, nc, nc);
 
-    nc = qemu_new_net_client(&net_tap_info, peer, model, name);
+    s->fd = -1;
 
-    s = DO_UPCAST(TAPState, nc, nc);
+    return s;
+}
+
+static void net_tap_set_fd(TAPState *s, int fd, int vnet_hdr)
+{
+    NetOffloads ol = {};
 
     s->fd = fd;
     s->host_vnet_hdr_len = vnet_hdr ? sizeof(struct virtio_net_hdr) : 0;
@@ -443,8 +444,6 @@ static TAPState *net_tap_fd_init(NetClientState *peer,
     }
     tap_read_poll(s, true);
     s->vhost_net = NULL;
-
-    return s;
 }
 
 static void close_all_fds_after_fork(int excluded_fd)
@@ -661,7 +660,9 @@ int net_init_bridge(const Netdev *netdev, const char *name,
         close(fd);
         return -1;
     }
-    s = net_tap_fd_init(peer, "bridge", name, fd, vnet_hdr);
+
+    s = net_tap_new(peer, "bridge", name);
+    net_tap_set_fd(s, fd, vnet_hdr);
 
     qemu_set_info_str(&s->nc, "helper=%s,br=%s", helper, br);
 
@@ -701,12 +702,14 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer,
                              const char *downscript, const char *vhostfdname,
                              int vnet_hdr, int fd, Error **errp)
 {
-    TAPState *s = net_tap_fd_init(peer, model, name, fd, vnet_hdr);
+    TAPState *s = net_tap_new(peer, model, name);
     int vhostfd;
     bool sndbuf_required = tap->has_sndbuf;
     int sndbuf =
         (tap->has_sndbuf && tap->sndbuf) ? MIN(tap->sndbuf, INT_MAX) : INT_MAX;
 
+    net_tap_set_fd(s, fd, vnet_hdr);
+
     if (!tap_set_sndbuf(fd, sndbuf, sndbuf_required ? errp : NULL) &&
         sndbuf_required) {
         goto failed;
-- 
2.48.1