Merge branch 'rtnetlink-allow-to-enslave-with-one-msg-an-up-interface'

Nicolas Dichtel says:

====================
rtnetlink: allow to enslave with one msg an up interface

The first patch fixes a regression, introduced in linux v6.1, by reverting
a patch. The second patch adds a test to verify this API.
====================

Link: https://lore.kernel.org/r/20240108094103.2001224-1-nicolas.dichtel@6wind.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

net/core/rtnetlink.c

@@ -2899,20 +2899,20 @@ static int do_setlink(const struct sk_buff *skb,
 		call_netdevice_notifiers(NETDEV_CHANGEADDR, dev);
 	}
 
-	if (tb[IFLA_MASTER]) {
-		err = do_set_master(dev, nla_get_u32(tb[IFLA_MASTER]), extack);
-		if (err)
-			goto errout;
-		status |= DO_SETLINK_MODIFIED;
-	}
-
 	if (ifm->ifi_flags || ifm->ifi_change) {
 		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)
+			goto errout;
+		status |= DO_SETLINK_MODIFIED;
+	}
+
 	if (tb[IFLA_CARRIER]) {
 		err = dev_change_carrier(dev, nla_get_u8(tb[IFLA_CARRIER]));
 		if (err)

tools/testing/selftests/net/rtnetlink.sh

@@ -28,6 +28,7 @@ ALL_TESTS="
 	kci_test_neigh_get
 	kci_test_bridge_parent_id
 	kci_test_address_proto
+	kci_test_enslave_bonding
 "
 
 devdummy="test-dummy0"
@@ -1241,6 +1242,33 @@ kci_test_address_proto()
 	return $ret
 }
 
+kci_test_enslave_bonding()
+{
+	local testns="testns"
+	local bond="bond123"
+	local dummy="dummy123"
+	local ret=0
+
+	run_cmd ip netns add "$testns"
+	if [ $ret -ne 0 ]; then
+		end_test "SKIP bonding tests: cannot add net namespace $testns"
+		return $ksft_skip
+	fi
+
+	run_cmd ip -netns $testns link add dev $bond type bond mode balance-rr
+	run_cmd ip -netns $testns link add dev $dummy type dummy
+	run_cmd ip -netns $testns link set dev $dummy up
+	run_cmd ip -netns $testns link set dev $dummy master $bond down
+	if [ $ret -ne 0 ]; then
+		end_test "FAIL: initially up interface added to a bond and set down"
+		ip netns del "$testns"
+		return 1
+	fi
+
+	end_test "PASS: enslave interface in a bond"
+	ip netns del "$testns"
+}
+
 kci_test_rtnl()
 {
 	local current_test