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>

5 files changed, 13 insertions, 8 deletions

diff --git a/include/linux/gen_stats.h b/include/linux/gen_stats.h
index 0ffa41df0ee..710e901085d 100644
--- a/include/linux/gen_stats.h
+++ b/include/linux/gen_stats.h
@@ -22,6 +22,11 @@ struct gnet_stats_basic
 {
         __u64   bytes;
         __u32   packets;
+};
+struct gnet_stats_basic_packed
+{
+        __u64   bytes;
+        __u32   packets;
 } __attribute__ ((packed));
 
 /**
diff --git a/include/net/act_api.h b/include/net/act_api.h
index 565eed8fe49..c05fd717c58 100644
--- a/include/net/act_api.h
+++ b/include/net/act_api.h
@@ -16,7 +16,7 @@ struct tcf_common {
         u32                             tcfc_capab;
         int                             tcfc_action;
         struct tcf_t                    tcfc_tm;
-        struct gnet_stats_basic         tcfc_bstats;
+        struct gnet_stats_basic_packed  tcfc_bstats;
         struct gnet_stats_queue         tcfc_qstats;
         struct gnet_stats_rate_est      tcfc_rate_est;
         spinlock_t                      tcfc_lock;
diff --git a/include/net/gen_stats.h b/include/net/gen_stats.h
index d136b5240ef..c1488553e34 100644
--- a/include/net/gen_stats.h
+++ b/include/net/gen_stats.h
@@ -28,7 +28,7 @@ extern int gnet_stats_start_copy_compat(struct sk_buff *skb, int type,
                                         spinlock_t *lock, struct gnet_dump *d);
 
 extern int gnet_stats_copy_basic(struct gnet_dump *d,
-                                 struct gnet_stats_basic *b);
+                                 struct gnet_stats_basic_packed *b);
 extern int gnet_stats_copy_rate_est(struct gnet_dump *d,
                                     struct gnet_stats_rate_est *r);
 extern int gnet_stats_copy_queue(struct gnet_dump *d,
@@ -37,14 +37,14 @@ extern int gnet_stats_copy_app(struct gnet_dump *d, void *st, int len);
 
 extern int gnet_stats_finish_copy(struct gnet_dump *d);
 
-extern int gen_new_estimator(struct gnet_stats_basic *bstats,
+extern int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
                              struct gnet_stats_rate_est *rate_est,
                              spinlock_t *stats_lock, struct nlattr *opt);
-extern void gen_kill_estimator(struct gnet_stats_basic *bstats,
+extern void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
                                struct gnet_stats_rate_est *rate_est);
-extern int gen_replace_estimator(struct gnet_stats_basic *bstats,
+extern int gen_replace_estimator(struct gnet_stats_basic_packed *bstats,
                                  struct gnet_stats_rate_est *rate_est,
                                  spinlock_t *stats_lock, struct nlattr *opt);
-extern bool gen_estimator_active(const struct gnet_stats_basic *bstats,
+extern bool gen_estimator_active(const struct gnet_stats_basic_packed *bstats,
                                  const struct gnet_stats_rate_est *rate_est);
 #endif
diff --git a/include/net/netfilter/xt_rateest.h b/include/net/netfilter/xt_rateest.h
index 65d594dffbf..ddbf37e1961 100644
--- a/include/net/netfilter/xt_rateest.h
+++ b/include/net/netfilter/xt_rateest.h
@@ -8,7 +8,7 @@ struct xt_rateest {
         spinlock_t                      lock;
         struct gnet_estimator           params;
         struct gnet_stats_rate_est      rstats;
-        struct gnet_stats_basic         bstats;
+        struct gnet_stats_basic_packed  bstats;
 };
 
 extern struct xt_rateest *xt_rateest_lookup(const char *name);
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 964ffa0d881..5482e9582f5 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -72,7 +72,7 @@ struct Qdisc
          */
         unsigned long           state;
         struct sk_buff_head     q;
-        struct gnet_stats_basic bstats;
+        struct gnet_stats_basic_packed bstats;
         struct gnet_stats_queue qstats;
 };