netdev - [PATCH net 0/4] vxlan: fix default fdb entry user-space notify ordering/race

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Date:   Fri, 20 Jul 2018 13:21:00 -0700
From:   Roopa Prabhu <roopa@...ulusnetworks.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org
Subject: [PATCH net 0/4] vxlan: fix default fdb entry user-space notify ordering/race

From: Roopa Prabhu <roopa@...ulusnetworks.com>

Problem:
In vxlan_newlink, a default fdb entry is added before register_netdev.
The default fdb creation function notifies user-space of the
fdb entry on the vxlan device which user-space does not know about yet.
(RTM_NEWNEIGH goes before RTM_NEWLINK for the same ifindex).

This series fixes the user-space netlink notification ordering issue
with the following changes:
- decouple fdb notify from fdb create.
- Move fdb notify after register_netdev.
- modify rtnl_configure_link to allow configuring a link early.
- Call rtnl_configure_link in vxlan newlink handler to notify
userspace about the newlink before fdb notify and
hence avoiding the user-space race.

Fixes: afbd8bae9c79 ("vxlan: add implicit fdb entry for default destination")
Signed-off-by: Roopa Prabhu <roopa@...ulusnetworks.com>

Roopa Prabhu (4):
  vxlan: add new fdb alloc and create helpers
  vxlan: make netlink notify in vxlan_fdb_destroy optional
  rtnetlink: add rtnl_link_state check in rtnl_configure_link
  vxlan: fix default fdb netlink notify ordering during netdev create

 drivers/net/vxlan.c  | 130 ++++++++++++++++++++++++++++++++++-----------------
 net/core/rtnetlink.c |   9 ++--
 2 files changed, 94 insertions(+), 45 deletions(-)

-- 
Dave, I am sending this series against net on your request on my net-next series.
https://marc.info/?l=linux-netdev&m=153098151929102&w=2
I did not know how long to wait before i send it to net. So sending it now.
As you also noted it is a very old bug. If you have changed your mind about stable or
if this is too early for net and you think we should soak it more in net-next,
pls feel free to drop. also, i will be happy to do a stable backport if needed. thanks.