net/core: relax BUILD_BUG_ON in netdev_stats_to_stats64
The netdev_stats_to_stats64 function copies the deprecated
net_device_stats format stats into rtnl_link_stats64 for legacy support
purposes, but with the BUILD_BUG_ON as it was, it wasn't possible to
extend rtnl_link_stats64 without also extending net_device_stats. Relax
the BUILD_BUG_ON to only require that rtnl_link_stats64 is larger, and
zero out all the stat counters that aren't present in net_device_stats.
CC: Eric Dumazet <edumazet@google.com>
CC: netdev@vger.kernel.org
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index 8cba3d8..65863e5 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7253,24 +7253,31 @@
}
}
-/* Convert net_device_stats to rtnl_link_stats64. They have the same
- * fields in the same order, with only the type differing.
+/* Convert net_device_stats to rtnl_link_stats64. rtnl_link_stats64 has
+ * all the same fields in the same order as net_device_stats, with only
+ * the type differing, but rtnl_link_stats64 may have additional fields
+ * at the end for newer counters.
*/
void netdev_stats_to_stats64(struct rtnl_link_stats64 *stats64,
const struct net_device_stats *netdev_stats)
{
#if BITS_PER_LONG == 64
- BUILD_BUG_ON(sizeof(*stats64) != sizeof(*netdev_stats));
+ BUILD_BUG_ON(sizeof(*stats64) < sizeof(*netdev_stats));
memcpy(stats64, netdev_stats, sizeof(*stats64));
+ /* zero out counters that only exist in rtnl_link_stats64 */
+ memset((char *)stats64 + sizeof(*netdev_stats), 0,
+ sizeof(*stats64) - sizeof(*netdev_stats));
#else
- size_t i, n = sizeof(*stats64) / sizeof(u64);
+ size_t i, n = sizeof(*netdev_stats) / sizeof(unsigned long);
const unsigned long *src = (const unsigned long *)netdev_stats;
u64 *dst = (u64 *)stats64;
- BUILD_BUG_ON(sizeof(*netdev_stats) / sizeof(unsigned long) !=
- sizeof(*stats64) / sizeof(u64));
+ BUILD_BUG_ON(n > sizeof(*stats64) / sizeof(u64));
for (i = 0; i < n; i++)
dst[i] = src[i];
+ /* zero out counters that only exist in rtnl_link_stats64 */
+ memset((char *)stats64 + n * sizeof(u64), 0,
+ sizeof(*stats64) - n * sizeof(u64));
#endif
}
EXPORT_SYMBOL(netdev_stats_to_stats64);