netdev - [PATCH net-next] tun: Consistently configure generic netdev params via rtnetlink

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Message-Id: <1539109261-8414-1-git-send-email-serhe.popovych@gmail.com>
Date:   Tue,  9 Oct 2018 21:21:01 +0300
From:   Serhey Popovych <serhe.popovych@...il.com>
To:     netdev@...r.kernel.org
Cc:     ebiederm@...ssion.com
Subject: [PATCH net-next] tun: Consistently configure generic netdev params via rtnetlink

Configuring generic network device parameters on tun will fail in
presence of IFLA_INFO_KIND attribute in IFLA_LINKINFO nested attribute
since tun_validate() always return failure.

This can be visualized with following ip-link(8) command sequences:

  # ip link set dev tun0 group 100
  # ip link set dev tun0 group 100 type tun
  RTNETLINK answers: Invalid argument

with contrast to dummy and veth drivers:

  # ip link set dev dummy0 group 100
  # ip link set dev dummy0 type dummy

  # ip link set dev veth0 group 100
  # ip link set dev veth0 group 100 type veth

Fix by returning zero in tun_validate() when @data is NULL that is
always in case since rtnl_link_ops->maxtype is zero in tun driver.

Fixes: f019a7a594d9 ("tun: Implement ip link del tunXXX")
Signed-off-by: Serhey Popovych <serhe.popovych@...il.com>
---
 drivers/net/tun.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index b174342..a3e8a43 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2298,6 +2298,8 @@ static void tun_setup(struct net_device *dev)
 static int tun_validate(struct nlattr *tb[], struct nlattr *data[],
 			struct netlink_ext_ack *extack)
 {
+	if (!data)
+		return 0;
 	return -EINVAL;
 }
 
-- 
1.8.3.1