From f7cfd36b8a93afd326c0d9378e99576c616bd3fc Mon Sep 17 00:00:00 2001
From: Yousong Zhou <yszhou4tech@gmail.com>
Date: Wed, 29 Apr 2015 14:21:12 +0800
Subject: [PATCH 3/7] xl2tpd-control: open control file with O_NONBLOCK.

Otherwise xl2tpd-control would block indefinitely in case xl2tpd is
not running.
---
 xl2tpd-control.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/xl2tpd-control.c
+++ b/xl2tpd-control.c
@@ -246,7 +246,7 @@ int main (int argc, char *argv[])
     print_error (DEBUG_LEVEL, "command to be passed:\n%s\n", buf);
 
     /* try to open control file for writing */
-    int control_fd = open (control_filename, O_WRONLY, 0600);
+    int control_fd = open (control_filename, O_WRONLY | O_NONBLOCK, 0600);
     if (control_fd < 0)
     {
         int errorno = errno;
@@ -265,6 +265,14 @@ int main (int argc, char *argv[])
         }
         return -1;
     }
+
+    /* turn off O_NONBLOCK */
+    if (fcntl (control_fd, F_SETFL, O_WRONLY) == -1) {
+        print_error (ERROR_LEVEL,
+            "Can not turn off nonblocking mode for control_fd: %s\n",
+            strerror(errno));
+        return -2;
+    }
     
     /* pass command to control pipe */
     if (write (control_fd, buf, ftell (mesf)) < 0)