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 0ffa41d..710e901 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 565eed8..c05fd71 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 d136b52..c148855 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 65d594d..ddbf37e 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 964ffa0..5482e95 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;
 };