From 974dc36a87274d7bae13e7dddd3364fecf5b3e7c Mon Sep 17 00:00:00 2001
From: Helmut Schaa <helmut.schaa@googlemail.com>
Date: Wed, 8 Jan 2014 13:48:49 +0100
Subject: [PATCH] netdev-linux: Let interface flag survive internal port setup

Due to a race condition when bringing up an internal port on Linux
some interface flags (e.g. IFF_MULTICAST) are falsely reset. This
happens because netlink events may be processed after the according
netdev has been brought up (which sets interface flags).

Fix this by reading the interface flags just before updating them
if they have not been updated by from the kernel yet.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
---
 lib/netdev-linux.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/lib/netdev-linux.c
+++ b/lib/netdev-linux.c
@@ -3546,7 +3546,13 @@ update_flags(struct netdev_linux *netdev
     unsigned int old_flags, new_flags;
     int error = 0;
 
-    old_flags = netdev->ifi_flags;
+    if (!(netdev->cache_valid & VALID_DRVINFO)) {
+        /* Most likely the debvice flags are not in sync yet, fetch them now */
+        get_flags(&netdev->up, &old_flags);
+    } else {
+        old_flags = netdev->ifi_flags;
+    }
+
     *old_flagsp = iff_to_nd_flags(old_flags);
     new_flags = (old_flags & ~nd_to_iff_flags(off)) | nd_to_iff_flags(on);
     if (new_flags != old_flags) {
