utils: add fd_cloexec()

src/lxc/utils.c

@@ -2686,3 +2686,25 @@ void remove_trailing_newlines(char *l)
 	while (--p >= l && *p == '\n')
 		*p = '\0';
 }
+
+int fd_cloexec(int fd, bool cloexec)
+{
+	int oflags, nflags;
+
+	oflags = fcntl(fd, F_GETFD, 0);
+	if (oflags < 0)
+		return -errno;
+
+	if (cloexec)
+		nflags = oflags | FD_CLOEXEC;
+	else
+		nflags = oflags & ~FD_CLOEXEC;
+
+	if (nflags == oflags)
+		return 0;
+
+	if (fcntl(fd, F_SETFD, nflags) < 0)
+		return -errno;
+
+	return 0;
+}

src/lxc/utils.h

@@ -615,5 +615,6 @@ static inline pid_t lxc_raw_gettid(void)
 
 /* Set a signal the child process will receive after the parent has died. */
 extern int lxc_set_death_signal(int signal);
+extern int fd_cloexec(int fd, bool cloexec);
 
 #endif /* __LXC_UTILS_H */