net: restore gnet_stats_basic to previous definition

In 5e140dfc1fe87eae27846f193086724806b33c7d "net: reorder struct Qdisc
for better SMP performance" the definition of struct gnet_stats_basic
changed incompatibly, as copies of this struct are shipped to
userland via netlink.

Restoring old behavior is not welcome, for performance reason.

Fix is to use a private structure for kernel, and
teach gnet_stats_copy_basic() to convert from kernel to user land,
using legacy structure (struct gnet_stats_basic)

Based on a report and initial patch from Michael Spang.

Reported-by: Michael Spang <mspang@csclub.uwaterloo.ca>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 3 deletions

diff --git a/net/core/gen_stats.c b/net/core/gen_stats.c
index c3d0ffeac243..8569310268ab 100644
--- a/net/core/gen_stats.c
+++ b/net/core/gen_stats.c
@@ -106,16 +106,21 @@ gnet_stats_start_copy(struct sk_buff *skb, int type, spinlock_t *lock,
  * if the room in the socket buffer was not sufficient.
  */
 int
-gnet_stats_copy_basic(struct gnet_dump *d, struct gnet_stats_basic *b)
+gnet_stats_copy_basic(struct gnet_dump *d, struct gnet_stats_basic_packed *b)
 {
         if (d->compat_tc_stats) {
                 d->tc_stats.bytes = b->bytes;
                 d->tc_stats.packets = b->packets;
         }
 
-        if (d->tail)
-                return gnet_stats_copy(d, TCA_STATS_BASIC, b, sizeof(*b));
+        if (d->tail) {
+                struct gnet_stats_basic sb;
 
+                memset(&sb, 0, sizeof(sb));
+                sb.bytes = b->bytes;
+                sb.packets = b->packets;
+                return gnet_stats_copy(d, TCA_STATS_BASIC, &sb, sizeof(sb));
+        }
         return 0;
 }