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From:   Jeffrey Ji <jeffreyjilinux@gmail.com>
To:     "David S . Miller" <davem@davemloft.net>
Cc:     Brian Vazquez <brianvv@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        David Ahern <dsahern@kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        Antoine Tenart <atenart@kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Alexander Lobakin <alexandr.lobakin@intel.com>,
        Kumar Kartikeya Dwivedi <memxor@gmail.com>,
        Arnd Bergmann <arnd@arndb.de>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, jeffreyji <jeffreyji@google.com>
Subject: [PATCH v2 net-next] net-core: add rx_otherhost_dropped counter
Date:   Thu,  3 Mar 2022 00:30:34 +0000
Message-Id: <20220303003034.1906898-1-jeffreyjilinux@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: jeffreyji <jeffreyji@google.com>

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.)

changelog:

v2: add kdoc comment

Signed-off-by: jeffreyji <jeffreyji@google.com>
---
 include/linux/netdevice.h    | 3 +++
 include/uapi/linux/if_link.h | 5 +++++
 net/core/dev.c               | 2 ++
 net/ipv4/ip_input.c          | 1 +
 net/ipv6/ip6_input.c         | 1 +
 5 files changed, 12 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index c79ee2296296..e4073c38bd77 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1741,6 +1741,8 @@ enum netdev_ml_priv_type {
  *			do not use this in drivers
  *	@rx_nohandler:	nohandler dropped packets by core network on
  *			inactive devices, do not use this in drivers
+ *	@rx_otherhost_dropped:	Dropped packets due to mismatch in packet dest
+ *				MAC address
  *	@carrier_up_count:	Number of times the carrier has been up
  *	@carrier_down_count:	Number of times the carrier has been down
  *
@@ -2025,6 +2027,7 @@ struct net_device {
 	atomic_long_t		rx_dropped;
 	atomic_long_t		tx_dropped;
 	atomic_long_t		rx_nohandler;
+	atomic_long_t		rx_otherhost_dropped;
 
 	/* Stats to monitor link on/off, flapping */
 	atomic_t		carrier_up_count;
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index e315e53125f4..17e74385fca8 100644
--- a/include/uapi/linux/if_link.h
+++ b/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
+ * packet's 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;
 };
 
 /* The struct should be in sync with struct ifmap */
diff --git a/net/core/dev.c b/net/core/dev.c
index 2d6771075720..d039d8fdc16a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10037,6 +10037,8 @@ struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
 	storage->rx_dropped += (unsigned long)atomic_long_read(&dev->rx_dropped);
 	storage->tx_dropped += (unsigned long)atomic_long_read(&dev->tx_dropped);
 	storage->rx_nohandler += (unsigned long)atomic_long_read(&dev->rx_nohandler);
+	storage->rx_otherhost_dropped +=
+		(unsigned long)atomic_long_read(&dev->rx_otherhost_dropped);
 	return storage;
 }
 EXPORT_SYMBOL(dev_get_stats);
diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index d94f9f7e60c3..ef97b0a4c77f 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -450,6 +450,7 @@ 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) {
+		atomic_long_inc(&skb->dev->rx_otherhost_dropped);
 		drop_reason = SKB_DROP_REASON_OTHERHOST;
 		goto drop;
 	}
diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index d4b1e2c5aa76..3f0cbe126d82 100644
--- a/net/ipv6/ip6_input.c
+++ b/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) {
+		atomic_long_inc(&skb->dev->rx_otherhost_dropped);
 		kfree_skb(skb);
 		return NULL;
 	}
-- 
2.35.1.616.g0bdcbb4464-goog