rtnetlink: prepare nla_put_iflink() to run under RCU

We want to be able to run rtnl_fill_ifinfo() under RCU protection
instead of RTNL in the future.

This patch prepares dev_get_iflink() and nla_put_iflink()
to run either with RTNL or RCU held.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/infiniband/ulp/ipoib/ipoib_main.c

@@ -1272,10 +1272,10 @@ static int ipoib_get_iflink(const struct net_device *dev)
 
 	/* parent interface */
 	if (!test_bit(IPOIB_FLAG_SUBINTERFACE, &priv->flags))
-		return dev->ifindex;
+		return READ_ONCE(dev->ifindex);
 
 	/* child/vlan interface */
-	return priv->parent->ifindex;
+	return READ_ONCE(priv->parent->ifindex);
 }
 
 static u32 ipoib_addr_hash(struct ipoib_neigh_hash *htbl, u8 *daddr)

drivers/net/can/vxcan.c

@@ -119,7 +119,7 @@ static int vxcan_get_iflink(const struct net_device *dev)
 
 	rcu_read_lock();
 	peer = rcu_dereference(priv->peer);
-	iflink = peer ? peer->ifindex : 0;
+	iflink = peer ? READ_ONCE(peer->ifindex) : 0;
 	rcu_read_unlock();
 
 	return iflink;

drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c

@@ -98,7 +98,7 @@ static int rmnet_vnd_get_iflink(const struct net_device *dev)
 {
 	struct rmnet_priv *priv = netdev_priv(dev);
 
-	return priv->real_dev->ifindex;
+	return READ_ONCE(priv->real_dev->ifindex);
 }
 
 static int rmnet_vnd_init(struct net_device *dev)

drivers/net/ipvlan/ipvlan_main.c

@@ -349,7 +349,7 @@ static int ipvlan_get_iflink(const struct net_device *dev)
 {
 	struct ipvl_dev *ipvlan = netdev_priv(dev);
 
-	return ipvlan->phy_dev->ifindex;
+	return READ_ONCE(ipvlan->phy_dev->ifindex);
 }
 
 static const struct net_device_ops ipvlan_netdev_ops = {

drivers/net/macsec.c

@@ -3753,7 +3753,7 @@ static void macsec_get_stats64(struct net_device *dev,
 
 static int macsec_get_iflink(const struct net_device *dev)
 {
-	return macsec_priv(dev)->real_dev->ifindex;
+	return READ_ONCE(macsec_priv(dev)->real_dev->ifindex);
 }
 
 static const struct net_device_ops macsec_netdev_ops = {

drivers/net/macvlan.c

@@ -1158,7 +1158,7 @@ static int macvlan_dev_get_iflink(const struct net_device *dev)
 {
 	struct macvlan_dev *vlan = netdev_priv(dev);
 
-	return vlan->lowerdev->ifindex;
+	return READ_ONCE(vlan->lowerdev->ifindex);
 }
 
 static const struct ethtool_ops macvlan_ethtool_ops = {

drivers/net/netkit.c

@@ -145,7 +145,7 @@ static int netkit_get_iflink(const struct net_device *dev)
 	rcu_read_lock();
 	peer = rcu_dereference(nk->peer);
 	if (peer)
-		iflink = peer->ifindex;
+		iflink = READ_ONCE(peer->ifindex);
 	rcu_read_unlock();
 	return iflink;
 }

drivers/net/veth.c

@@ -1461,7 +1461,7 @@ static int veth_get_iflink(const struct net_device *dev)
 
 	rcu_read_lock();
 	peer = rcu_dereference(priv->peer);
-	iflink = peer ? peer->ifindex : 0;
+	iflink = peer ? READ_ONCE(peer->ifindex) : 0;
 	rcu_read_unlock();
 
 	return iflink;

drivers/net/wireless/virtual/virt_wifi.c

@@ -453,7 +453,7 @@ static int virt_wifi_net_device_get_iflink(const struct net_device *dev)
 {
 	struct virt_wifi_netdev_priv *priv = netdev_priv(dev);
 
-	return priv->lowerdev->ifindex;
+	return READ_ONCE(priv->lowerdev->ifindex);
 }
 
 static const struct net_device_ops virt_wifi_ops = {

net/8021q/vlan_dev.c

@@ -762,9 +762,9 @@ static void vlan_dev_netpoll_cleanup(struct net_device *dev)
 
 static int vlan_dev_get_iflink(const struct net_device *dev)
 {
-	struct net_device *real_dev = vlan_dev_priv(dev)->real_dev;
+	const struct net_device *real_dev = vlan_dev_priv(dev)->real_dev;
 
-	return real_dev->ifindex;
+	return READ_ONCE(real_dev->ifindex);
 }
 
 static int vlan_dev_fill_forward_path(struct net_device_path_ctx *ctx,

net/core/dev.c

@@ -641,7 +641,7 @@ int dev_get_iflink(const struct net_device *dev)
 	if (dev->netdev_ops && dev->netdev_ops->ndo_get_iflink)
 		return dev->netdev_ops->ndo_get_iflink(dev);
 
-	return dev->ifindex;
+	return READ_ONCE(dev->ifindex);
 }
 EXPORT_SYMBOL(dev_get_iflink);
 

net/core/rtnetlink.c

@@ -1611,10 +1611,10 @@ static int put_master_ifindex(struct sk_buff *skb, struct net_device *dev)
 static int nla_put_iflink(struct sk_buff *skb, const struct net_device *dev,
 			  bool force)
 {
-	int ifindex = dev_get_iflink(dev);
+	int iflink = dev_get_iflink(dev);
 
-	if (force || dev->ifindex != ifindex)
-		return nla_put_u32(skb, IFLA_LINK, ifindex);
+	if (force || READ_ONCE(dev->ifindex) != iflink)
+		return nla_put_u32(skb, IFLA_LINK, iflink);
 
 	return 0;
 }

net/dsa/user.c

@@ -352,7 +352,7 @@ void dsa_user_mii_bus_init(struct dsa_switch *ds)
 /* user device handling ****************************************************/
 static int dsa_user_get_iflink(const struct net_device *dev)
 {
-	return dsa_user_to_conduit(dev)->ifindex;
+	return READ_ONCE(dsa_user_to_conduit(dev)->ifindex);
 }
 
 static int dsa_user_open(struct net_device *dev)

net/ieee802154/6lowpan/core.c

@@ -93,7 +93,7 @@ static int lowpan_neigh_construct(struct net_device *dev, struct neighbour *n)
 
 static int lowpan_get_iflink(const struct net_device *dev)
 {
-	return lowpan_802154_dev(dev)->wdev->ifindex;
+	return READ_ONCE(lowpan_802154_dev(dev)->wdev->ifindex);
 }
 
 static const struct net_device_ops lowpan_netdev_ops = {

net/ipv6/ip6_tunnel.c

@@ -1756,7 +1756,7 @@ int ip6_tnl_get_iflink(const struct net_device *dev)
 {
 	struct ip6_tnl *t = netdev_priv(dev);
 
-	return t->parms.link;
+	return READ_ONCE(t->parms.link);
 }
 EXPORT_SYMBOL(ip6_tnl_get_iflink);
 

net/xfrm/xfrm_interface_core.c

@@ -727,7 +727,7 @@ static int xfrmi_get_iflink(const struct net_device *dev)
 {
 	struct xfrm_if *xi = netdev_priv(dev);
 
-	return xi->p.link;
+	return READ_ONCE(xi->p.link);
 }
 
 static const struct net_device_ops xfrmi_netdev_ops = {