[XFRM]: Support to increment packet dropping statistics.

Signed-off-by: Masahide NAKAMURA <nakam@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c
index 26fa0cb..867484a 100644
--- a/net/xfrm/xfrm_output.c
+++ b/net/xfrm/xfrm_output.c
@@ -69,10 +69,13 @@
 		err = x->type->output(x, skb);
 
 resume:
-		if (err)
+		if (err) {
+			XFRM_INC_STATS(LINUX_MIB_XFRMOUTSTATEPROTOERROR);
 			goto error_nolock;
+		}
 
 		if (!(skb->dst = dst_pop(dst))) {
+			XFRM_INC_STATS(LINUX_MIB_XFRMOUTERROR);
 			err = -EHOSTUNREACH;
 			goto error_nolock;
 		}
@@ -167,6 +170,7 @@
 	if (skb->ip_summed == CHECKSUM_PARTIAL) {
 		err = skb_checksum_help(skb);
 		if (err) {
+			XFRM_INC_STATS(LINUX_MIB_XFRMOUTERROR);
 			kfree_skb(skb);
 			return err;
 		}