net-core: rx_otherhost_dropped to core_stats

Increment rx_otherhost_dropped counter when packet dropped due to
mismatched dest MAC addr.

An example when this drop can occur is when manually crafting raw
packets that will be consumed by a user space application via a tap
device. For testing purposes local traffic was generated using trafgen
for the client and netcat to start a server

Tested: Created 2 netns, sent 1 packet using trafgen from 1 to the other
with "{eth(daddr=$INCORRECT_MAC...}", verified that iproute2 showed the
counter was incremented. (Also had to modify iproute2 to show the stat,
additional patch for that coming next.)

Signed-off-by: Jeffrey Ji <jeffreyji@google.com>
Reviewed-by: Brian Vazquez <brianvv@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20220406172600.1141083-1-jeffreyjilinux@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/netdevice.h

@@ -203,6 +203,7 @@ struct net_device_core_stats {
 	local_t		rx_dropped;
 	local_t		tx_dropped;
 	local_t		rx_nohandler;
+	local_t		rx_otherhost_dropped;
 } __aligned(4 * sizeof(local_t));
 
 #include <linux/cache.h>
@@ -3837,6 +3838,7 @@ static inline void dev_core_stats_##FIELD##_inc(struct net_device *dev)		\
 DEV_CORE_STATS_INC(rx_dropped)
 DEV_CORE_STATS_INC(tx_dropped)
 DEV_CORE_STATS_INC(rx_nohandler)
+DEV_CORE_STATS_INC(rx_otherhost_dropped)
 
 static __always_inline int ____dev_forward_skb(struct net_device *dev,
 					       struct sk_buff *skb,

include/uapi/linux/if_link.h

@@ -211,6 +211,9 @@ struct rtnl_link_stats {
  * @rx_nohandler: Number of packets received on the interface
  *   but dropped by the networking stack because the device is
  *   not designated to receive packets (e.g. backup link in a bond).
+ *
+ * @rx_otherhost_dropped: Number of packets dropped due to mismatch
+ *   in destination MAC address.
  */
 struct rtnl_link_stats64 {
 	__u64	rx_packets;
@@ -243,6 +246,8 @@ struct rtnl_link_stats64 {
 	__u64	rx_compressed;
 	__u64	tx_compressed;
 	__u64	rx_nohandler;
+
+	__u64	rx_otherhost_dropped;
 };
 
 /* Subset of link stats useful for in-HW collection. Meaning of the fields is as

net/core/dev.c

@@ -10358,6 +10358,7 @@ struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
 			storage->rx_dropped += local_read(&core_stats->rx_dropped);
 			storage->tx_dropped += local_read(&core_stats->tx_dropped);
 			storage->rx_nohandler += local_read(&core_stats->rx_nohandler);
+			storage->rx_otherhost_dropped += local_read(&core_stats->rx_otherhost_dropped);
 		}
 	}
 	return storage;

net/ipv4/ip_input.c

@@ -451,6 +451,7 @@ static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net)
 	 * that it receives, do not try to analyse it.
 	 */
 	if (skb->pkt_type == PACKET_OTHERHOST) {
+		dev_core_stats_rx_otherhost_dropped_inc(skb->dev);
 		drop_reason = SKB_DROP_REASON_OTHERHOST;
 		goto drop;
 	}

net/ipv6/ip6_input.c

@@ -150,6 +150,7 @@ static struct sk_buff *ip6_rcv_core(struct sk_buff *skb, struct net_device *dev,
 	struct inet6_dev *idev;
 
 	if (skb->pkt_type == PACKET_OTHERHOST) {
+		dev_core_stats_rx_otherhost_dropped_inc(skb->dev);
 		kfree_skb(skb);
 		return NULL;
 	}