src/udev/udev-ctrl.c: restore accept4_fallback code

This code was accidentally removed in commit

    601c4e8ce69338652b3c9178386cbc05de8bae8d

We restore it here.  Since most modern systems have accept4()
this code will seldom be triggered.  You can test by configuring
as follows:

    ac_cv_have_decl_accept4="no" ./configure

Signed-off-by: Anthony G. Basile <blueness@gentoo.org>

1 files changed, 18 insertions, 1 deletions

diff --git a/src/udev/udev-ctrl.c b/src/udev/udev-ctrl.c
index d8c57b216e..fe318586fc 100644
--- a/src/udev/udev-ctrl.c
+++ b/src/udev/udev-ctrl.c
@@ -10,6 +10,7 @@
  */
 
 #include <errno.h>
+#include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stddef.h>
@@ -177,6 +178,18 @@ int udev_ctrl_get_fd(struct udev_ctrl *uctrl)
         return uctrl->sock;
 }
 
+static inline accept4_fallback(int sockfd)
+{
+        int fd;
+
+        if ((fd = accept(sockfd, NULL, NULL)) >= 0) {
+                fcntl(fd, F_SETFL, O_NONBLOCK);
+                fcntl(fd, F_SETFD, FD_CLOEXEC);
+        }
+
+        return fd;
+}
+
 struct udev_ctrl_connection *udev_ctrl_get_connection(struct udev_ctrl *uctrl)
 {
         struct udev_ctrl_connection *conn;
@@ -192,8 +205,12 @@ struct udev_ctrl_connection *udev_ctrl_get_connection(struct udev_ctrl *uctrl)
 
 #if HAVE_DECL_ACCEPT4
         conn->sock = accept4(uctrl->sock, NULL, NULL, SOCK_CLOEXEC|SOCK_NONBLOCK);
+
+        /* Fallback path when accept4() is unavailable */
+        if ( conn->sock < 0 && (errno == ENOSYS || errno == ENOTSUP) )
+                conn->sock = accept4_fallback(uctrl->sock);
 #else
-        conn->sock = accept(uctrl->sock, NULL, NULL);
+        conn->sock = accept4_fallback(uctrl->sock);
 #endif
 
         if (conn->sock < 0) {