ipv4: fix wildcard search with inet_confirm_addr()

Help of this function says: "in_dev: only on this interface, 0=any interface",
but since commit 39a6d06300 ("[NETNS]: Process inet_confirm_addr in the
correct namespace."), the code supposes that it will never be NULL. This
function is never called with in_dev == NULL, but it's exported and may be used
by an external module.

Because this patch restore the ability to call inet_confirm_addr() with in_dev
== NULL, I partially revert the above commit, as suggested by Julian.

CC: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Reviewed-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bonding.h

@@ -394,8 +394,8 @@ static inline __be32 bond_confirm_addr(struct net_device *dev, __be32 dst, __be3
 	in_dev = __in_dev_get_rcu(dev);
 
 	if (in_dev)
-		addr = inet_confirm_addr(in_dev, dst, local, RT_SCOPE_HOST);
-
+		addr = inet_confirm_addr(dev_net(dev), in_dev, dst, local,
+					 RT_SCOPE_HOST);
 	rcu_read_unlock();
 	return addr;
 }

include/linux/inetdevice.h

@@ -164,11 +164,10 @@ int devinet_ioctl(struct net *net, unsigned int cmd, void __user *);
 void devinet_init(void);
 struct in_device *inetdev_by_index(struct net *, int);
 __be32 inet_select_addr(const struct net_device *dev, __be32 dst, int scope);
-__be32 inet_confirm_addr(struct in_device *in_dev, __be32 dst, __be32 local,
-			 int scope);
+__be32 inet_confirm_addr(struct net *net, struct in_device *in_dev, __be32 dst,
+			 __be32 local, int scope);
 struct in_ifaddr *inet_ifa_byprefix(struct in_device *in_dev, __be32 prefix,
 				    __be32 mask);
-
 static __inline__ int inet_ifa_match(__be32 addr, struct in_ifaddr *ifa)
 {
 	return !((addr^ifa->ifa_address)&ifa->ifa_mask);

net/ipv4/arp.c

@@ -381,6 +381,7 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
 
 static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)
 {
+	struct net *net = dev_net(in_dev->dev);
 	int scope;
 
 	switch (IN_DEV_ARP_IGNORE(in_dev)) {
@@ -399,6 +400,7 @@ static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)
 	case 3:	/* Do not reply for scope host addresses */
 		sip = 0;
 		scope = RT_SCOPE_LINK;
+		in_dev = NULL;
 		break;
 	case 4:	/* Reserved */
 	case 5:
@@ -410,7 +412,7 @@ static int arp_ignore(struct in_device *in_dev, __be32 sip, __be32 tip)
 	default:
 		return 0;
 	}
-	return !inet_confirm_addr(in_dev, sip, tip, scope);
+	return !inet_confirm_addr(net, in_dev, sip, tip, scope);
 }
 
 static int arp_filter(__be32 sip, __be32 tip, struct net_device *dev)

net/ipv4/devinet.c

@@ -1240,22 +1240,21 @@ static __be32 confirm_addr_indev(struct in_device *in_dev, __be32 dst,
 
 /*
  * Confirm that local IP address exists using wildcards:
- * - in_dev: only on this interface, 0=any interface
+ * - net: netns to check, cannot be NULL
+ * - in_dev: only on this interface, NULL=any interface
  * - dst: only in the same subnet as dst, 0=any dst
  * - local: address, 0=autoselect the local address
  * - scope: maximum allowed scope value for the local address
  */
-__be32 inet_confirm_addr(struct in_device *in_dev,
+__be32 inet_confirm_addr(struct net *net, struct in_device *in_dev,
 			 __be32 dst, __be32 local, int scope)
 {
 	__be32 addr = 0;
 	struct net_device *dev;
-	struct net *net;
 
-	if (scope != RT_SCOPE_LINK)
+	if (in_dev != NULL)
 		return confirm_addr_indev(in_dev, dst, local, scope);
 
-	net = dev_net(in_dev->dev);
 	rcu_read_lock();
 	for_each_netdev_rcu(net, dev) {
 		in_dev = __in_dev_get_rcu(dev);