tap: fix net_init_tap() return code

net_init_tap intends to return 0 for success and -1 on error.  However,
when net_init_tap() succeeds for a multi-queue device, it returns 1,
because of this code where ret becomes 1 when g_unix_set_fd_nonblocking
succeeds:

        ret = g_unix_set_fd_nonblocking(fd, true, NULL);
        if (!ret) {
            ... error ...
    free_fail:
        ...
        return ret;

Luckily, the only current call site checks for negative, rather than non-zero:

  net_client_init1()
      if (net_client_init_fun[](...) < 0)

Also, in the unlikely case that g_unix_set_fd_nonblocking fails and returns
false, ret=0 is returned, and net_client_init1 will use a broken interface.

Fix it to be future proof.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/tap.c b/net/tap.c
index 2a85936019..f7df702f97 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -895,8 +895,8 @@ int net_init_tap(const Netdev *netdev, const char *name,
                 goto free_fail;
             }
 
-            ret = g_unix_set_fd_nonblocking(fd, true, NULL);
-            if (!ret) {
+            if (!g_unix_set_fd_nonblocking(fd, true, NULL)) {
+                ret = -1;
                 error_setg_errno(errp, errno, "%s: Can't use file descriptor %d",
                                  name, fd);
                 goto free_fail;