On Tue, Jan 02, 2024 at 01:14:21PM +0100, Nicolas Dichtel wrote:

Le 01/01/2024 à 23:10, Phil Sutter a écrit :

quoted

On Fri, Dec 29, 2023 at 11:08:35AM +0100, Nicolas Dichtel wrote:

quoted

The below commit adds support for:

quoted

ip link set dummy0 down
ip link set dummy0 master bond0 up

but breaks the opposite:

quoted

ip link set dummy0 up
ip link set dummy0 master bond0 down

Let's add a workaround to have both commands working.

Cc: stable@vger.kernel.org
Fixes: a4abfa627c38 ("net: rtnetlink: Enslave device before bringing it up")
Signed-off-by: Nicolas Dichtel <redacted>
---
 net/core/rtnetlink.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index e8431c6c8490..dd79693c2d91 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c

@@ -2905,6 +2905,14 @@ static int do_setlink(const struct sk_buff *skb,
 		call_netdevice_notifiers(NETDEV_CHANGEADDR, dev);
 	}
 
+	/* Backward compat: enable to set interface down before enslaving it */
+	if (!(ifm->ifi_flags & IFF_UP) && ifm->ifi_change & IFF_UP) {
+		err = dev_change_flags(dev, rtnl_dev_combine_flags(dev, ifm),
+				       extack);
+		if (err < 0)
+			goto errout;
+	}
+
 	if (tb[IFLA_MASTER]) {
 		err = do_set_master(dev, nla_get_u32(tb[IFLA_MASTER]), extack);
 		if (err)

Doesn't this merely revert to the old behaviour of setting the interface
up before enslaving if both IFF_UP and IFLA_MASTER are present? Did you
test this with a bond-type master?

Yes, both command sequences (cf commit log) work after the patch.
dev_change_flags() is called before do_set_master() only if the user asks to
remove the flag IFF_UP.

Ah, indeed! I should have looked at rtnl_dev_combine_flags() before
commenting. When submitting v2, feel free to add my:

Acked-by: Phil Sutter <phil@nwl.cc>

Thanks, Phil