net: fix 64 bit counters on 32 bit arches

There is a small possibility that a reader gets incorrect values on 32
bit arches. SNMP applications could catch incorrect counters when a
32bit high part is changed by another stats consumer/provider.

One way to solve this is to add a rtnl_link_stats64 param to all
ndo_get_stats64() methods, and also add such a parameter to
dev_get_stats().

Rule is that we are not allowed to use dev->stats64 as a temporary
storage for 64bit stats, but a caller provided area (usually on stack)

Old drivers (only providing get_stats() method) need no changes.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 4 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 4d27368674db..60de65316fdb 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -666,7 +666,8 @@ struct netdev_rx_queue {
  *      Callback uses when the transmitter has not made any progress
  *      for dev->watchdog ticks.
  *
- * struct rtnl_link_stats64* (*ndo_get_stats64)(struct net_device *dev);
+ * struct rtnl_link_stats64* (*ndo_get_stats64)(struct net_device *dev
+ *                      struct rtnl_link_stats64 *storage);
  * struct net_device_stats* (*ndo_get_stats)(struct net_device *dev);
  *      Called when a user wants to get the network device usage
  *      statistics. Drivers must do one of the following:
@@ -733,7 +734,8 @@ struct net_device_ops {
                                                    struct neigh_parms *);
         void                    (*ndo_tx_timeout) (struct net_device *dev);
 
-        struct rtnl_link_stats64* (*ndo_get_stats64)(struct net_device *dev);
+        struct rtnl_link_stats64* (*ndo_get_stats64)(struct net_device *dev,
+                                                     struct rtnl_link_stats64 *storage);
         struct net_device_stats* (*ndo_get_stats)(struct net_device *dev);
 
         void                    (*ndo_vlan_rx_register)(struct net_device *dev,
@@ -2139,8 +2141,10 @@ extern void		netdev_features_change(struct net_device *dev);
 /* Load a device via the kmod */
 extern void             dev_load(struct net *net, const char *name);
 extern void             dev_mcast_init(void);
-extern const struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev);
-extern void             dev_txq_stats_fold(const struct net_device *dev, struct net_device_stats *stats);
+extern const struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
+                                                     struct rtnl_link_stats64 *storage);
+extern void             dev_txq_stats_fold(const struct net_device *dev,
+                                           struct net_device_stats *stats);
 
 extern int              netdev_max_backlog;
 extern int              netdev_tstamp_prequeue;