neigh: restore old behaviour of default parms values

Previously inet devices were only constructed when addresses are added.
Therefore the default neigh parms values they get are the ones at the
time of these operations.

Now that we're creating inet devices earlier, this changes the behaviour
of default neigh parms values in an incompatible way (see bug #8519).

This patch creates a compromise by setting the default values at the
same point as before but only for those that have not been explicitly
set by the user since the inet device's creation.

Introduced by:
commit 8030f544
Author: Herbert Xu <herbert@gondor.apana.org.au>
Date:   Thu Feb 22 01:53:47 2007 +0900

    [IPV4] devinet: Register inetdev earlier.
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/inetdevice.h

@@ -220,6 +220,13 @@ static inline struct in_device *__in_dev_get_rtnl(const struct net_device *dev)
 	return rtnl_dereference(dev->ip_ptr);
 }
 
+static inline struct neigh_parms *__in_dev_arp_parms_get_rcu(const struct net_device *dev)
+{
+	struct in_device *in_dev = __in_dev_get_rcu(dev);
+
+	return in_dev ? in_dev->arp_parms : NULL;
+}
+
 void in_dev_finish_destroy(struct in_device *idev);
 
 static inline void in_dev_put(struct in_device *idev)

include/net/neighbour.h

@@ -21,6 +21,7 @@
 #include <linux/skbuff.h>
 #include <linux/rcupdate.h>
 #include <linux/seq_file.h>
+#include <linux/bitmap.h>
 
 #include <linux/err.h>
 #include <linux/sysctl.h>
@@ -81,16 +82,28 @@ struct neigh_parms {
 
 	int	reachable_time;
 	int	data[NEIGH_VAR_DATA_MAX];
+	DECLARE_BITMAP(data_state, NEIGH_VAR_DATA_MAX);
 };
 
 static inline void neigh_var_set(struct neigh_parms *p, int index, int val)
 {
+	set_bit(index, p->data_state);
 	p->data[index] = val;
 }
 
 #define NEIGH_VAR(p, attr) ((p)->data[NEIGH_VAR_ ## attr])
 #define NEIGH_VAR_SET(p, attr, val) neigh_var_set(p, NEIGH_VAR_ ## attr, val)
 
+static inline void neigh_parms_data_state_setall(struct neigh_parms *p)
+{
+	bitmap_fill(p->data_state, NEIGH_VAR_DATA_MAX);
+}
+
+static inline void neigh_parms_data_state_cleanall(struct neigh_parms *p)
+{
+	bitmap_zero(p->data_state, NEIGH_VAR_DATA_MAX);
+}
+
 struct neigh_statistics {
 	unsigned long allocs;		/* number of allocated neighs */
 	unsigned long destroys;		/* number of destroyed neighs */

net/core/neighbour.c

@@ -38,6 +38,7 @@
 #include <linux/random.h>
 #include <linux/string.h>
 #include <linux/log2.h>
+#include <linux/inetdevice.h>
 
 #define DEBUG
 #define NEIGH_DEBUG 1
@@ -1464,6 +1465,8 @@ struct neigh_parms *neigh_parms_alloc(struct net_device *dev,
 		p->next		= tbl->parms.next;
 		tbl->parms.next = p;
 		write_unlock_bh(&tbl->lock);
+
+		neigh_parms_data_state_cleanall(p);
 	}
 	return p;
 }
@@ -2813,22 +2816,68 @@ static int proc_unres_qlen(struct ctl_table *ctl, int write,
 	return ret;
 }
 
+static struct neigh_parms *neigh_get_dev_parms_rcu(struct net_device *dev,
+						   int family)
+{
+	if (family == AF_INET)
+		return __in_dev_arp_parms_get_rcu(dev);
+	return NULL;
+}
+
+static void neigh_copy_dflt_parms(struct net *net, struct neigh_parms *p,
+				  int index)
+{
+	struct net_device *dev;
+	int family = neigh_parms_family(p);
+
+	rcu_read_lock();
+	for_each_netdev_rcu(net, dev) {
+		struct neigh_parms *dst_p =
+				neigh_get_dev_parms_rcu(dev, family);
+
+		if (dst_p && !test_bit(index, dst_p->data_state))
+			dst_p->data[index] = p->data[index];
+	}
+	rcu_read_unlock();
+}
+
+static void neigh_proc_update(struct ctl_table *ctl, int write)
+{
+	struct net_device *dev = ctl->extra1;
+	struct neigh_parms *p = ctl->extra2;
+	struct net *net = p->net;
+	int index = (int *) ctl->data - p->data;
+
+	if (!write)
+		return;
+
+	set_bit(index, p->data_state);
+	if (!dev) /* NULL dev means this is default value */
+		neigh_copy_dflt_parms(net, p, index);
+}
+
 static int neigh_proc_dointvec_zero_intmax(struct ctl_table *ctl, int write,
 					   void __user *buffer,
 					   size_t *lenp, loff_t *ppos)
 {
 	struct ctl_table tmp = *ctl;
+	int ret;
 
 	tmp.extra1 = &zero;
 	tmp.extra2 = &int_max;
 
-	return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
+	ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
+	neigh_proc_update(ctl, write);
+	return ret;
 }
 
 int neigh_proc_dointvec(struct ctl_table *ctl, int write,
 			void __user *buffer, size_t *lenp, loff_t *ppos)
 {
-	return proc_dointvec(ctl, write, buffer, lenp, ppos);
+	int ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
+
+	neigh_proc_update(ctl, write);
+	return ret;
 }
 EXPORT_SYMBOL(neigh_proc_dointvec);
 
@@ -2836,7 +2885,10 @@ int neigh_proc_dointvec_jiffies(struct ctl_table *ctl, int write,
 				void __user *buffer,
 				size_t *lenp, loff_t *ppos)
 {
-	return proc_dointvec_jiffies(ctl, write, buffer, lenp, ppos);
+	int ret = proc_dointvec_jiffies(ctl, write, buffer, lenp, ppos);
+
+	neigh_proc_update(ctl, write);
+	return ret;
 }
 EXPORT_SYMBOL(neigh_proc_dointvec_jiffies);
 
@@ -2844,14 +2896,20 @@ static int neigh_proc_dointvec_userhz_jiffies(struct ctl_table *ctl, int write,
 					      void __user *buffer,
 					      size_t *lenp, loff_t *ppos)
 {
-	return proc_dointvec_userhz_jiffies(ctl, write, buffer, lenp, ppos);
+	int ret = proc_dointvec_userhz_jiffies(ctl, write, buffer, lenp, ppos);
+
+	neigh_proc_update(ctl, write);
+	return ret;
 }
 
 int neigh_proc_dointvec_ms_jiffies(struct ctl_table *ctl, int write,
 				   void __user *buffer,
 				   size_t *lenp, loff_t *ppos)
 {
-	return proc_dointvec_ms_jiffies(ctl, write, buffer, lenp, ppos);
+	int ret = proc_dointvec_ms_jiffies(ctl, write, buffer, lenp, ppos);
+
+	neigh_proc_update(ctl, write);
+	return ret;
 }
 EXPORT_SYMBOL(neigh_proc_dointvec_ms_jiffies);
 
@@ -2859,7 +2917,10 @@ static int neigh_proc_dointvec_unres_qlen(struct ctl_table *ctl, int write,
 					  void __user *buffer,
 					  size_t *lenp, loff_t *ppos)
 {
-	return proc_unres_qlen(ctl, write, buffer, lenp, ppos);
+	int ret = proc_unres_qlen(ctl, write, buffer, lenp, ppos);
+
+	neigh_proc_update(ctl, write);
+	return ret;
 }
 
 #define NEIGH_PARMS_DATA_OFFSET(index)	\
@@ -2962,6 +3023,7 @@ int neigh_sysctl_register(struct net_device *dev, struct neigh_parms *p,
 	for (i = 0; i < ARRAY_SIZE(t->neigh_vars); i++) {
 		t->neigh_vars[i].data += (long) p;
 		t->neigh_vars[i].extra1 = dev;
+		t->neigh_vars[i].extra2 = p;
 	}
 
 	if (dev) {

net/ipv4/devinet.c

@@ -500,6 +500,7 @@ static int inet_set_ifa(struct net_device *dev, struct in_ifaddr *ifa)
 		return -ENOBUFS;
 	}
 	ipv4_devconf_setall(in_dev);
+	neigh_parms_data_state_setall(in_dev->arp_parms);
 	if (ifa->ifa_dev != in_dev) {
 		WARN_ON(ifa->ifa_dev);
 		in_dev_hold(in_dev);
@@ -747,6 +748,7 @@ static struct in_ifaddr *rtm_to_ifaddr(struct net *net, struct nlmsghdr *nlh,
 		goto errout;
 
 	ipv4_devconf_setall(in_dev);
+	neigh_parms_data_state_setall(in_dev->arp_parms);
 	in_dev_hold(in_dev);
 
 	if (tb[IFA_ADDRESS] == NULL)

net/ipv4/ipmr.c

@@ -425,6 +425,7 @@ struct net_device *ipmr_new_tunnel(struct net *net, struct vifctl *v)
 				goto failure;
 
 			ipv4_devconf_setall(in_dev);
+			neigh_parms_data_state_setall(in_dev->arp_parms);
 			IPV4_DEVCONF(in_dev->cnf, RP_FILTER) = 0;
 
 			if (dev_open(dev))
@@ -517,6 +518,7 @@ static struct net_device *ipmr_reg_vif(struct net *net, struct mr_table *mrt)
 	}
 
 	ipv4_devconf_setall(in_dev);
+	neigh_parms_data_state_setall(in_dev->arp_parms);
 	IPV4_DEVCONF(in_dev->cnf, RP_FILTER) = 0;
 	rcu_read_unlock();