l2tp: report rx cookie discards in netlink get

When an L2TPv3 session receives a data frame with an incorrect cookie
l2tp_core logs a warning message and bumps a stats counter to reflect
the fact that the packet has been dropped.

However, the stats counter in question is missing from the l2tp_netlink
get message for tunnel and session instances.

Include the statistic in the netlink get response.

Signed-off-by: Tom Parkin <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/uapi/linux/l2tp.h

···
 	L2TP_ATTR_RX_OOS_PACKETS,	/* u64 */
 	L2TP_ATTR_RX_ERRORS,		/* u64 */
 	L2TP_ATTR_STATS_PAD,
+	L2TP_ATTR_RX_COOKIE_DISCARDS,	/* u64 */
 	__L2TP_ATTR_STATS_MAX,
 };
 

net/l2tp/l2tp_netlink.c

···
 	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_SEQ_DISCARDS,
 			      atomic_long_read(&tunnel->stats.rx_seq_discards),
 			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_COOKIE_DISCARDS,
+			      atomic_long_read(&tunnel->stats.rx_cookie_discards),
+			      L2TP_ATTR_STATS_PAD) ||
 	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_OOS_PACKETS,
 			      atomic_long_read(&tunnel->stats.rx_oos_packets),
 			      L2TP_ATTR_STATS_PAD) ||
···
 			      L2TP_ATTR_STATS_PAD) ||
 	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_SEQ_DISCARDS,
 			      atomic_long_read(&session->stats.rx_seq_discards),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_COOKIE_DISCARDS,
+			      atomic_long_read(&session->stats.rx_cookie_discards),
 			      L2TP_ATTR_STATS_PAD) ||
 	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_OOS_PACKETS,
 			      atomic_long_read(&session->stats.rx_oos_packets),