[PATCH net-next v4 0/3] net: notify users when an iface cannot change its netns

@@ -1148,6 +1148,9 @@ attribute-sets:
         name: max-pacing-offload-horizon
         type: uint
         doc: EDT offload horizon supported by the device (in nsec).
+      -
+        name: netns-immutable
+        type: u8
   -
     name: af-spec-attrs
     attributes:

@@ -378,6 +378,7 @@ enum {
 	IFLA_GRO_IPV4_MAX_SIZE,
 	IFLA_DPLL_PIN,
 	IFLA_MAX_PACING_OFFLOAD_HORIZON,
+	IFLA_NETNS_IMMUTABLE,
 	__IFLA_MAX
 };
 

@@ -1292,6 +1292,7 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
 	       + nla_total_size(4) /* IFLA_TSO_MAX_SEGS */
 	       + nla_total_size(1) /* IFLA_OPERSTATE */
 	       + nla_total_size(1) /* IFLA_LINKMODE */
+	       + nla_total_size(1) /* IFLA_NETNS_IMMUTABLE */
 	       + nla_total_size(4) /* IFLA_CARRIER_CHANGES */
 	       + nla_total_size(4) /* IFLA_LINK_NETNSID */
 	       + nla_total_size(4) /* IFLA_GROUP */

@@ -2046,6 +2047,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
 		       netif_running(dev) ? READ_ONCE(dev->operstate) :
 					    IF_OPER_DOWN) ||
 	    nla_put_u8(skb, IFLA_LINKMODE, READ_ONCE(dev->link_mode)) ||
+	    nla_put_u8(skb, IFLA_NETNS_IMMUTABLE, dev->netns_immutable) ||
 	    nla_put_u32(skb, IFLA_MTU, READ_ONCE(dev->mtu)) ||
 	    nla_put_u32(skb, IFLA_MIN_MTU, READ_ONCE(dev->min_mtu)) ||
 	    nla_put_u32(skb, IFLA_MAX_MTU, READ_ONCE(dev->max_mtu)) ||

@@ -2234,6 +2236,7 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
 	[IFLA_ALLMULTI]		= { .type = NLA_REJECT },
 	[IFLA_GSO_IPV4_MAX_SIZE]	= NLA_POLICY_MIN(NLA_U32, MAX_TCP_HEADER + 1),
 	[IFLA_GRO_IPV4_MAX_SIZE]	= { .type = NLA_U32 },
+	[IFLA_NETNS_IMMUTABLE]	= { .type = NLA_REJECT },
 };
 
 static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {

@@ -4156,12 +4156,13 @@ int dev_change_flags(struct net_device *dev, unsigned int flags,
 int dev_set_alias(struct net_device *, const char *, size_t);
 int dev_get_alias(const struct net_device *, char *, size_t);
 int __dev_change_net_namespace(struct net_device *dev, struct net *net,
-			       const char *pat, int new_ifindex);
+			       const char *pat, int new_ifindex,
+			       struct netlink_ext_ack *extack);
 static inline
 int dev_change_net_namespace(struct net_device *dev, struct net *net,
 			     const char *pat)
 {
-	return __dev_change_net_namespace(dev, net, pat, 0);
+	return __dev_change_net_namespace(dev, net, pat, 0, NULL);
 }
 int __dev_set_mtu(struct net_device *, int);
 int dev_set_mtu(struct net_device *, int);

@@ -12003,6 +12003,7 @@ EXPORT_SYMBOL(unregister_netdev);
  *	      is already taken in the destination network namespace.
  *	@new_ifindex: If not zero, specifies device index in the target
  *	              namespace.
+ *	@extack: netlink extended ack
  *
  *	This function shuts down a device interface and moves it
  *	to a new network namespace. On success 0 is returned, on

@@ -12012,7 +12013,8 @@ EXPORT_SYMBOL(unregister_netdev);
  */
 
 int __dev_change_net_namespace(struct net_device *dev, struct net *net,
-			       const char *pat, int new_ifindex)
+			       const char *pat, int new_ifindex,
+			       struct netlink_ext_ack *extack)
 {
 	struct netdev_name_node *name_node;
 	struct net *net_old = dev_net(dev);

@@ -12023,12 +12025,16 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 
 	/* Don't allow namespace local devices to be moved. */
 	err = -EINVAL;
-	if (dev->netns_immutable)
+	if (dev->netns_immutable) {
+		NL_SET_ERR_MSG(extack, "The interface netns is immutable");
 		goto out;
+	}
 
 	/* Ensure the device has been registered */
-	if (dev->reg_state != NETREG_REGISTERED)
+	if (dev->reg_state != NETREG_REGISTERED) {
+		NL_SET_ERR_MSG(extack, "The interface isn't registered");
 		goto out;
+	}
 
 	/* Get out if there is nothing todo */
 	err = 0;

@@ -12041,30 +12047,48 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 	err = -EEXIST;
 	if (netdev_name_in_use(net, dev->name)) {
 		/* We get here if we can't use the current device name */
-		if (!pat)
+		if (!pat) {
+			NL_SET_ERR_MSG(extack,
+				       "An interface with the same name exists in the target netns");
 			goto out;
+		}
 		err = dev_prep_valid_name(net, dev, pat, new_name, EEXIST);
-		if (err < 0)
+		if (err < 0) {
+			NL_SET_ERR_MSG_FMT(extack,
+					   "Unable to use '%s' for the new interface name",
+					   pat);
 			goto out;
+		}
 	}
 	/* Check that none of the altnames conflicts. */
 	err = -EEXIST;
 	netdev_for_each_altname(dev, name_node)
-		if (netdev_name_in_use(net, name_node->name))
+		if (netdev_name_in_use(net, name_node->name)) {
+			NL_SET_ERR_MSG_FMT(extack,
+					   "An interface with the altname %s exists in the target netns",
+					   name_node->name);
 			goto out;
+		}
 
 	/* Check that new_ifindex isn't used yet. */
 	if (new_ifindex) {
 		err = dev_index_reserve(net, new_ifindex);
-		if (err < 0)
+		if (err < 0) {
+			NL_SET_ERR_MSG_FMT(extack,
+					   "The ifindex %d is not available in the target netns",
+					   new_ifindex);
 			goto out;
+		}
 	} else {
 		/* If there is an ifindex conflict assign a new one */
 		err = dev_index_reserve(net, dev->ifindex);
 		if (err == -EBUSY)
 			err = dev_index_reserve(net, 0);
-		if (err < 0)
+		if (err < 0) {
+			NL_SET_ERR_MSG(extack,
+				       "Unable to allocate a new ifindex in the target netns");
 			goto out;
+		}
 		new_ifindex = err;
 	}
 

@@ -3028,7 +3028,7 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev,
 
 		new_ifindex = nla_get_s32_default(tb[IFLA_NEW_IFINDEX], 0);
 
-		err = __dev_change_net_namespace(dev, tgt_net, pat, new_ifindex);
+		err = __dev_change_net_namespace(dev, tgt_net, pat, new_ifindex, extack);
 		if (err)
 			goto errout;
 

@@ -167,7 +167,7 @@ unsigned:1                          wol_enabled
 unsigned:1                          threaded                                                            napi_poll(napi_enable,dev_set_threaded)
 unsigned_long:1                     see_all_hwtstamp_requests
 unsigned_long:1                     change_proto_down
-unsigned_long:1                     netns_local
+unsigned_long:1                     netns_immutable
 unsigned_long:1                     fcoe_mtu
 struct list_head                    net_notifier_list
 struct macsec_ops*                  macsec_ops

@@ -137,7 +137,7 @@ would be sub-port 0 on port 1 on switch 1.
 Port Features
 ^^^^^^^^^^^^^
 
-dev->netns_local
+dev->netns_immutable
 
 If the switchdev driver (and device) only supports offloading of the default
 network namespace (netns), the driver should set this private flag to prevent

@@ -3099,7 +3099,7 @@ static void amt_link_setup(struct net_device *dev)
 	dev->addr_len		= 0;
 	dev->priv_flags		|= IFF_NO_QUEUE;
 	dev->lltx		= true;
-	dev->netns_local	= true;
+	dev->netns_immutable	= true;
 	dev->features		|= NETIF_F_GSO_SOFTWARE;
 	dev->hw_features	|= NETIF_F_SG | NETIF_F_HW_CSUM;
 	dev->hw_features	|= NETIF_F_FRAGLIST | NETIF_F_RXCSUM;

@@ -6025,7 +6025,7 @@ void bond_setup(struct net_device *bond_dev)
 	bond_dev->lltx = true;
 
 	/* Don't allow bond devices to change network namespaces. */
-	bond_dev->netns_local = true;
+	bond_dev->netns_immutable = true;
 
 	/* By default, we declare the bond to be fully
 	 * VLAN hardware accelerated capable. Special

@@ -1599,7 +1599,7 @@ static int adin1110_probe_netdevs(struct adin1110_priv *priv)
 		netdev->netdev_ops = &adin1110_netdev_ops;
 		netdev->ethtool_ops = &adin1110_ethtool_ops;
 		netdev->priv_flags |= IFF_UNICAST_FLT;
-		netdev->netns_local = true;
+		netdev->netns_immutable = true;
 
 		port_priv->phydev = get_phy_device(priv->mii_bus, i + 1, false);
 		if (IS_ERR(port_priv->phydev)) {

@@ -634,7 +634,7 @@ static int prestera_port_create(struct prestera_switch *sw, u32 id)
 		goto err_dl_port_register;
 
 	dev->features |= NETIF_F_HW_TC;
-	dev->netns_local = true;
+	dev->netns_immutable = true;
 	dev->netdev_ops = &prestera_netdev_ops;
 	dev->ethtool_ops = &prestera_ethtool_ops;
 	SET_NETDEV_DEV(dev, sw->dev->dev);

@@ -4421,9 +4421,9 @@ static netdev_features_t mlx5e_fix_features(struct net_device *netdev,
 
 	if (mlx5e_is_uplink_rep(priv)) {
 		features = mlx5e_fix_uplink_rep_features(netdev, features);
-		netdev->netns_local = true;
+		netdev->netns_immutable = true;
 	} else {
-		netdev->netns_local = false;
+		netdev->netns_immutable = false;
 	}
 
 	mutex_unlock(&priv->state_lock);

@@ -905,7 +905,7 @@ static void mlx5e_build_rep_netdev(struct net_device *netdev,
 
 	netdev->features |= netdev->hw_features;
 
-	netdev->netns_local = true;
+	netdev->netns_immutable = true;
 }
 
 static int mlx5e_init_rep(struct mlx5_core_dev *mdev,

@@ -1579,7 +1579,7 @@ static int mlxsw_sp_port_create(struct mlxsw_sp *mlxsw_sp, u16 local_port,
 			    NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM;
 	dev->vlan_features |= NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM;
 	dev->lltx = true;
-	dev->netns_local = true;
+	dev->netns_immutable = true;
 
 	dev->min_mtu = ETH_MIN_MTU;
 	dev->max_mtu = MLXSW_PORT_MAX_MTU - MLXSW_PORT_ETH_FRAME_HDR;

@@ -2576,7 +2576,7 @@ static int rocker_probe_port(struct rocker *rocker, unsigned int port_number)
 	rocker_carrier_init(rocker_port);
 
 	dev->features |= NETIF_F_SG;
-	dev->netns_local = true;
+	dev->netns_immutable = true;
 
 	/* MTU range: 68 - 9000 */
 	dev->min_mtu = ROCKER_PORT_MIN_MTU;

@@ -1409,7 +1409,7 @@ static int cpsw_create_ports(struct cpsw_common *cpsw)
 
 		ndev->features |= NETIF_F_HW_VLAN_CTAG_FILTER |
 				  NETIF_F_HW_VLAN_CTAG_RX | NETIF_F_HW_TC;
-		ndev->netns_local = true;
+		ndev->netns_immutable = true;
 
 		ndev->xdp_features = NETDEV_XDP_ACT_BASIC |
 				     NETDEV_XDP_ACT_REDIRECT |

@@ -172,7 +172,7 @@ static void gen_lo_setup(struct net_device *dev,
 	dev->flags		= IFF_LOOPBACK;
 	dev->priv_flags		|= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE;
 	dev->lltx		= true;
-	dev->netns_local	= true;
+	dev->netns_immutable	= true;
 	netif_keep_dst(dev);
 	dev->hw_features	= NETIF_F_GSO_SOFTWARE;
 	dev->features		= NETIF_F_SG | NETIF_F_FRAGLIST

@@ -734,7 +734,7 @@ struct failover *net_failover_create(struct net_device *standby_dev)
 	failover_dev->lltx = true;
 
 	/* Don't allow failover devices to change network namespaces. */
-	failover_dev->netns_local = true;
+	failover_dev->netns_immutable = true;
 
 	failover_dev->hw_features = FAILOVER_VLAN_FEATURES |
 				    NETIF_F_HW_VLAN_CTAG_TX |

@@ -2203,7 +2203,7 @@ static void team_setup(struct net_device *dev)
 	dev->lltx = true;
 
 	/* Don't allow team devices to change network namespaces. */
-	dev->netns_local = true;
+	dev->netns_immutable = true;
 
 	dev->features |= NETIF_F_GRO;
 

@@ -1617,7 +1617,7 @@ static void vrf_setup(struct net_device *dev)
 	dev->lltx = true;
 
 	/* don't allow vrf devices to change network namespaces. */
-	dev->netns_local = true;
+	dev->netns_immutable = true;
 
 	/* does not make sense for a VLAN to be added to a vrf device */
 	dev->features   |= NETIF_F_VLAN_CHALLENGED;

@@ -1994,7 +1994,7 @@ enum netdev_reg_state {
  *			regardless of source, even if those aren't
  *			HWTSTAMP_SOURCE_NETDEV
  *	@change_proto_down: device supports setting carrier via IFLA_PROTO_DOWN
- *	@netns_local: interface can't change network namespaces
+ *	@netns_immutable: interface can't change network namespaces
  *	@fcoe_mtu:	device supports maximum FCoE MTU, 2158 bytes
  *
  *	@net_notifier_list:	List of per-net netdev notifier block

@@ -2400,7 +2400,7 @@ struct net_device {
 	/* priv_flags_slow, ungrouped to save space */
 	unsigned long		see_all_hwtstamp_requests:1;
 	unsigned long		change_proto_down:1;
-	unsigned long		netns_local:1;
+	unsigned long		netns_immutable:1;
 	unsigned long		fcoe_mtu:1;
 
 	struct list_head	net_notifier_list;

@@ -1037,7 +1037,7 @@ static void batadv_softif_init_early(struct net_device *dev)
 	dev->features |= NETIF_F_HW_VLAN_CTAG_FILTER;
 	dev->priv_flags |= IFF_NO_QUEUE;
 	dev->lltx = true;
-	dev->netns_local = true;
+	dev->netns_immutable = true;
 
 	/* can't call min_mtu, because the needed variables
 	 * have not been initialized yet

@@ -488,7 +488,7 @@ void br_dev_setup(struct net_device *dev)
 	SET_NETDEV_DEVTYPE(dev, &br_type);
 	dev->priv_flags = IFF_EBRIDGE | IFF_NO_QUEUE;
 	dev->lltx = true;
-	dev->netns_local = true;
+	dev->netns_immutable = true;
 
 	dev->features = COMMON_FEATURES | NETIF_F_HW_VLAN_CTAG_TX |
 			NETIF_F_HW_VLAN_STAG_TX;

@@ -12023,7 +12023,7 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 
 	/* Don't allow namespace local devices to be moved. */
 	err = -EINVAL;
-	if (dev->netns_local)
+	if (dev->netns_immutable)
 		goto out;
 
 	/* Ensure the device has been registered */

@@ -12405,7 +12405,7 @@ static void __net_exit default_device_exit_net(struct net *net)
 		char fb_name[IFNAMSIZ];
 
 		/* Ignore unmoveable devices (i.e. loopback) */
-		if (dev->netns_local)
+		if (dev->netns_immutable)
 			continue;
 
 		/* Leave virtual devices for the generic cleanup */

@@ -643,7 +643,7 @@ void hsr_dev_setup(struct net_device *dev)
 	/* Not sure about this. Taken from bridge code. netdevice.h says
 	 * it means "Does not change network namespaces".
 	 */
-	dev->netns_local = true;
+	dev->netns_immutable = true;
 
 	dev->needs_free_netdev = true;
 

@@ -116,7 +116,7 @@ static void lowpan_setup(struct net_device *ldev)
 	ldev->netdev_ops	= &lowpan_netdev_ops;
 	ldev->header_ops	= &lowpan_header_ops;
 	ldev->needs_free_netdev	= true;
-	ldev->netns_local	= true;
+	ldev->netns_immutable	= true;
 }
 
 static int lowpan_validate(struct nlattr *tb[], struct nlattr *data[],

@@ -226,11 +226,11 @@ int cfg802154_switch_netns(struct cfg802154_registered_device *rdev,
 	list_for_each_entry(wpan_dev, &rdev->wpan_dev_list, list) {
 		if (!wpan_dev->netdev)
 			continue;
-		wpan_dev->netdev->netns_local = false;
+		wpan_dev->netdev->netns_immutable = false;
 		err = dev_change_net_namespace(wpan_dev->netdev, net, "wpan%d");
 		if (err)
 			break;
-		wpan_dev->netdev->netns_local = true;
+		wpan_dev->netdev->netns_immutable = true;
 	}
 
 	if (err) {

@@ -242,11 +242,11 @@ int cfg802154_switch_netns(struct cfg802154_registered_device *rdev,
 						     list) {
 			if (!wpan_dev->netdev)
 				continue;
-			wpan_dev->netdev->netns_local = false;
+			wpan_dev->netdev->netns_immutable = false;
 			err = dev_change_net_namespace(wpan_dev->netdev, net,
 						       "wpan%d");
 			WARN_ON(err);
-			wpan_dev->netdev->netns_local = true;
+			wpan_dev->netdev->netns_immutable = true;
 		}
 
 		return err;

@@ -291,7 +291,7 @@ static int cfg802154_netdev_notifier_call(struct notifier_block *nb,
 	switch (state) {
 		/* TODO NETDEV_DEVTYPE */
 	case NETDEV_REGISTER:
-		dev->netns_local = true;
+		dev->netns_immutable = true;
 		wpan_dev->identifier = ++rdev->wpan_dev_id;
 		list_add_rcu(&wpan_dev->list, &rdev->wpan_dev_list);
 		rdev->devlist_generation++;

@@ -1162,7 +1162,7 @@ int ip_tunnel_init_net(struct net *net, unsigned int ip_tnl_net_id,
 	 * Allowing to move it to another netns is clearly unsafe.
 	 */
 	if (!IS_ERR(itn->fb_tunnel_dev)) {
-		itn->fb_tunnel_dev->netns_local = true;
+		itn->fb_tunnel_dev->netns_immutable = true;
 		itn->fb_tunnel_dev->mtu = ip_tunnel_bind_dev(itn->fb_tunnel_dev);
 		ip_tunnel_add(itn, netdev_priv(itn->fb_tunnel_dev));
 		itn->type = itn->fb_tunnel_dev->type;

@@ -563,7 +563,7 @@ static void reg_vif_setup(struct net_device *dev)
 	dev->flags		= IFF_NOARP;
 	dev->netdev_ops		= &reg_vif_netdev_ops;
 	dev->needs_free_netdev	= true;
-	dev->netns_local	= true;
+	dev->netns_immutable	= true;
 }
 
 static struct net_device *ipmr_reg_vif(struct net *net, struct mr_table *mrt)

@@ -1621,7 +1621,7 @@ static int __net_init ip6gre_init_net(struct net *net)
 	/* FB netdevice is special: we have one, and only one per netns.
 	 * Allowing to move it to another netns is clearly unsafe.
 	 */
-	ign->fb_tunnel_dev->netns_local = true;
+	ign->fb_tunnel_dev->netns_immutable = true;
 
 	ip6gre_fb_tunnel_init(ign->fb_tunnel_dev);
 	ign->fb_tunnel_dev->rtnl_link_ops = &ip6gre_link_ops;

@@ -2261,7 +2261,7 @@ static int __net_init ip6_tnl_init_net(struct net *net)
 	/* FB netdevice is special: we have one, and only one per netns.
 	 * Allowing to move it to another netns is clearly unsafe.
 	 */
-	ip6n->fb_tnl_dev->netns_local = true;
+	ip6n->fb_tnl_dev->netns_immutable = true;
 
 	err = ip6_fb_tnl_dev_init(ip6n->fb_tnl_dev);
 	if (err < 0)

@@ -668,7 +668,7 @@ static void reg_vif_setup(struct net_device *dev)
 	dev->flags		= IFF_NOARP;
 	dev->netdev_ops		= &reg_vif_netdev_ops;
 	dev->needs_free_netdev	= true;
-	dev->netns_local	= true;
+	dev->netns_immutable	= true;
 }
 
 static struct net_device *ip6mr_reg_vif(struct net *net, struct mr_table *mrt)

@@ -1856,7 +1856,7 @@ static int __net_init sit_init_net(struct net *net)
 	/* FB netdevice is special: we have one, and only one per netns.
 	 * Allowing to move it to another netns is clearly unsafe.
 	 */
-	sitn->fb_tunnel_dev->netns_local = true;
+	sitn->fb_tunnel_dev->netns_immutable = true;
 
 	err = register_netdev(sitn->fb_tunnel_dev);
 	if (err)

@@ -149,7 +149,7 @@ static struct vport *internal_dev_create(const struct vport_parms *parms)
 
 	/* Restrict bridge port to current netns. */
 	if (vport->port_no == OVSP_LOCAL)
-		vport->dev->netns_local = true;
+		vport->dev->netns_immutable = true;
 
 	rtnl_lock();
 	err = register_netdevice(vport->dev);

@@ -162,11 +162,11 @@ int cfg80211_switch_netns(struct cfg80211_registered_device *rdev,
 	list_for_each_entry(wdev, &rdev->wiphy.wdev_list, list) {
 		if (!wdev->netdev)
 			continue;
-		wdev->netdev->netns_local = false;
+		wdev->netdev->netns_immutable = false;
 		err = dev_change_net_namespace(wdev->netdev, net, "wlan%d");
 		if (err)
 			break;
-		wdev->netdev->netns_local = true;
+		wdev->netdev->netns_immutable = true;
 	}
 
 	if (err) {

@@ -178,11 +178,11 @@ int cfg80211_switch_netns(struct cfg80211_registered_device *rdev,
 						     list) {
 			if (!wdev->netdev)
 				continue;
-			wdev->netdev->netns_local = false;
+			wdev->netdev->netns_immutable = false;
 			err = dev_change_net_namespace(wdev->netdev, net,
 							"wlan%d");
 			WARN_ON(err);
-			wdev->netdev->netns_local = true;
+			wdev->netdev->netns_immutable = true;
 		}
 
 		return err;

@@ -1513,7 +1513,7 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
 		SET_NETDEV_DEVTYPE(dev, &wiphy_type);
 		wdev->netdev = dev;
 		/* can only change netns with wiphy */
-		dev->netns_local = true;
+		dev->netns_immutable = true;
 
 		cfg80211_init_wdev(wdev);
 		break;

@@ -6,7 +6,7 @@ to easily create and test complex environments.
 
 Unfortunately, these namespaces can not be used with actual switching
 ASICs, as their ports can not be migrated to other network namespaces
-(dev->netns_local) and most of them probably do not support the
+(dev->netns_immutable) and most of them probably do not support the
 L1-separation provided by namespaces.
 
 However, a similar kind of flexibility can be achieved by using VRFs and