ipv6: prepare inet6_fill_ifinfo() for RCU protection

We want to use RCU protection instead of RTNL
for inet6_fill_ifinfo().
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -4354,8 +4354,10 @@ static inline bool netif_testing(const struct net_device *dev)
  */
 static inline bool netif_oper_up(const struct net_device *dev)
 {
-	return (dev->operstate == IF_OPER_UP ||
-		dev->operstate == IF_OPER_UNKNOWN /* backward compat */);
+	unsigned int operstate = READ_ONCE(dev->operstate);
+
+	return	operstate == IF_OPER_UP ||
+		operstate == IF_OPER_UNKNOWN /* backward compat */;
 }
 
 /**

net/core/dev.c

@@ -8632,12 +8632,12 @@ unsigned int dev_get_flags(const struct net_device *dev)
 {
 	unsigned int flags;
 
-	flags = (dev->flags & ~(IFF_PROMISC |
+	flags = (READ_ONCE(dev->flags) & ~(IFF_PROMISC |
 				IFF_ALLMULTI |
 				IFF_RUNNING |
 				IFF_LOWER_UP |
 				IFF_DORMANT)) |
-		(dev->gflags & (IFF_PROMISC |
+		(READ_ONCE(dev->gflags) & (IFF_PROMISC |
 				IFF_ALLMULTI));
 
 	if (netif_running(dev)) {

net/ipv6/addrconf.c

@@ -6062,6 +6062,7 @@ static int inet6_fill_ifinfo(struct sk_buff *skb, struct inet6_dev *idev,
 	struct net_device *dev = idev->dev;
 	struct ifinfomsg *hdr;
 	struct nlmsghdr *nlh;
+	int ifindex, iflink;
 	void *protoinfo;
 
 	nlh = nlmsg_put(skb, portid, seq, event, sizeof(*hdr), flags);
@@ -6072,16 +6073,18 @@ static int inet6_fill_ifinfo(struct sk_buff *skb, struct inet6_dev *idev,
 	hdr->ifi_family = AF_INET6;
 	hdr->__ifi_pad = 0;
 	hdr->ifi_type = dev->type;
-	hdr->ifi_index = dev->ifindex;
+	ifindex = READ_ONCE(dev->ifindex);
+	hdr->ifi_index = ifindex;
 	hdr->ifi_flags = dev_get_flags(dev);
 	hdr->ifi_change = 0;
 
+	iflink = dev_get_iflink(dev);
 	if (nla_put_string(skb, IFLA_IFNAME, dev->name) ||
 	    (dev->addr_len &&
 	     nla_put(skb, IFLA_ADDRESS, dev->addr_len, dev->dev_addr)) ||
-	    nla_put_u32(skb, IFLA_MTU, dev->mtu) ||
-	    (dev->ifindex != dev_get_iflink(dev) &&
-	     nla_put_u32(skb, IFLA_LINK, dev_get_iflink(dev))) ||
+	    nla_put_u32(skb, IFLA_MTU, READ_ONCE(dev->mtu)) ||
+	    (ifindex != iflink &&
+	     nla_put_u32(skb, IFLA_LINK, iflink)) ||
 	    nla_put_u8(skb, IFLA_OPERSTATE,
 		       netif_running(dev) ? READ_ONCE(dev->operstate) : IF_OPER_DOWN))
 		goto nla_put_failure;