netdev - [PATCH net-next 6/7] can: add drop reasons in the receive path of AF

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Message-ID: <20250610094933.1593081-7-mkl@pengutronix.de>
Date: Tue, 10 Jun 2025 11:46:21 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	kuba@...nel.org,
	linux-can@...r.kernel.org,
	kernel@...gutronix.de,
	Davide Caratti <dcaratti@...hat.com>,
	Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH net-next 6/7] can: add drop reasons in the receive path of AF_CAN

From: Davide Caratti <dcaratti@...hat.com>

Besides the existing pr_warn_once(), use skb drop reasons in case AF_CAN
layer drops non-conformant CAN{,FD,XL} frames, or conformant frames
received by "wrong" devices, so that it's possible to debug (and count)
such events using existing tracepoints:

| # perf record -e skb:kfree_skb -aR -- ./drv/canfdtest -v -g -l 1 vcan0
| # perf script
| [...]
| canfdtest  1123 [000]  3893.271264: skb:kfree_skb: skbaddr=0xffff975703c9f700 rx_sk=(nil) protocol=12 location=can_rcv+0x4b  reason: CAN_RX_INVALID_FRAME

Signed-off-by: Davide Caratti <dcaratti@...hat.com>
Link: https://patch.msgid.link/20250604160605.1005704-2-dcaratti@redhat.com
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 include/net/dropreason-core.h | 18 ++++++++++++++++++
 net/can/af_can.c              |  6 +++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index bcf9d7467e1a..b9e78290269e 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -121,6 +121,9 @@
 	FN(ARP_PVLAN_DISABLE)		\
 	FN(MAC_IEEE_MAC_CONTROL)	\
 	FN(BRIDGE_INGRESS_STP_STATE)	\
+	FN(CAN_RX_INVALID_FRAME)	\
+	FN(CANFD_RX_INVALID_FRAME)	\
+	FN(CANXL_RX_INVALID_FRAME)	\
 	FNe(MAX)
 
 /**
@@ -573,6 +576,21 @@ enum skb_drop_reason {
 	 * ingress bridge port does not allow frames to be forwarded.
 	 */
 	SKB_DROP_REASON_BRIDGE_INGRESS_STP_STATE,
+	/**
+	 * @SKB_DROP_REASON_CAN_RX_INVALID_FRAME: received
+	 * non conform CAN frame (or device is unable to receive CAN frames)
+	 */
+	SKB_DROP_REASON_CAN_RX_INVALID_FRAME,
+	/**
+	 * @SKB_DROP_REASON_CANFD_RX_INVALID_FRAME: received
+	 * non conform CAN-FD frame (or device is unable to receive CAN frames)
+	 */
+	SKB_DROP_REASON_CANFD_RX_INVALID_FRAME,
+	/**
+	 * @SKB_DROP_REASON_CANXL_RX_INVALID_FRAME: received
+	 * non conform CAN-XL frame (or device is unable to receive CAN frames)
+	 */
+	SKB_DROP_REASON_CANXL_RX_INVALID_FRAME,
 	/**
 	 * @SKB_DROP_REASON_MAX: the maximum of core drop reasons, which
 	 * shouldn't be used as a real 'reason' - only for tracing code gen
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 4aab7033c933..b2387a46794a 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -683,7 +683,7 @@ static int can_rcv(struct sk_buff *skb, struct net_device *dev,
 		pr_warn_once("PF_CAN: dropped non conform CAN skbuff: dev type %d, len %d\n",
 			     dev->type, skb->len);
 
-		kfree_skb(skb);
+		kfree_skb_reason(skb, SKB_DROP_REASON_CAN_RX_INVALID_FRAME);
 		return NET_RX_DROP;
 	}
 
@@ -698,7 +698,7 @@ static int canfd_rcv(struct sk_buff *skb, struct net_device *dev,
 		pr_warn_once("PF_CAN: dropped non conform CAN FD skbuff: dev type %d, len %d\n",
 			     dev->type, skb->len);
 
-		kfree_skb(skb);
+		kfree_skb_reason(skb, SKB_DROP_REASON_CANFD_RX_INVALID_FRAME);
 		return NET_RX_DROP;
 	}
 
@@ -713,7 +713,7 @@ static int canxl_rcv(struct sk_buff *skb, struct net_device *dev,
 		pr_warn_once("PF_CAN: dropped non conform CAN XL skbuff: dev type %d, len %d\n",
 			     dev->type, skb->len);
 
-		kfree_skb(skb);
+		kfree_skb_reason(skb, SKB_DROP_REASON_CANXL_RX_INVALID_FRAME);
 		return NET_RX_DROP;
 	}
 
-- 
2.47.2