can: use skb hash instead of private variable in headroom

The can_skb_priv::skbcnt variable is used to identify CAN skbs in the RX
path analogue to the skb->hash.

As the skb hash is not filled in CAN skbs move the private skbcnt value to
skb->hash and set skb->sw_hash accordingly. The skb->hash is a value used
for RPS to identify skbs. Use it as intended.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20260201-can_skb_ext-v8-1-3635d790fe8b@hartkopp.net
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

6 files changed, 14 insertions, 15 deletions

diff --git a/net/can/af_can.c b/net/can/af_can.c
index 770173d8db42..70659987ef4d 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -641,6 +641,16 @@ static int can_rcv_filter(struct can_dev_rcv_lists *dev_rcv_lists, struct sk_buf
 	return matches;
 }
 
+void can_set_skb_uid(struct sk_buff *skb)
+{
+	/* create non-zero unique skb identifier together with *skb */
+	while (!(skb->hash))
+		skb->hash = atomic_inc_return(&skbcounter);
+
+	skb->sw_hash = 1;
+}
+EXPORT_SYMBOL(can_set_skb_uid);
+
 static void can_receive(struct sk_buff *skb, struct net_device *dev)
 {
 	struct can_dev_rcv_lists *dev_rcv_lists;
@@ -652,9 +662,7 @@ static void can_receive(struct sk_buff *skb, struct net_device *dev)
 	atomic_long_inc(&pkg_stats->rx_frames);
 	atomic_long_inc(&pkg_stats->rx_frames_delta);
 
-	/* create non-zero unique skb identifier together with *skb */
-	while (!(can_skb_prv(skb)->skbcnt))
-		can_skb_prv(skb)->skbcnt = atomic_inc_return(&skbcounter);
+	can_set_skb_uid(skb);
 
 	rcu_read_lock();
 
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 7eba8ae01a5b..8ed60f18c2ea 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -316,7 +316,6 @@ static void bcm_can_tx(struct bcm_op *op)
 
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 
 	skb_put_data(skb, cf, op->cfsiz);
 
@@ -1344,7 +1343,6 @@ static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk,
 	}
 
 	can_skb_prv(skb)->ifindex = dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 	skb->dev = dev;
 	can_skb_set_owner(skb, sk);
 	err = can_send(skb, 1); /* send with loopback */
diff --git a/net/can/isotp.c b/net/can/isotp.c
index ce588b85665a..4bb60b8f9b96 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -230,7 +230,6 @@ static int isotp_send_fc(struct sock *sk, int ae, u8 flowstatus)
 
 	can_skb_reserve(nskb);
 	can_skb_prv(nskb)->ifindex = dev->ifindex;
-	can_skb_prv(nskb)->skbcnt = 0;
 
 	nskb->dev = dev;
 	can_skb_set_owner(nskb, sk);
@@ -780,7 +779,6 @@ static void isotp_send_cframe(struct isotp_sock *so)
 
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 
 	cf = (struct canfd_frame *)skb->data;
 	skb_put_zero(skb, so->ll.mtu);
@@ -1009,7 +1007,6 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
 
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 
 	so->tx.len = size;
 	so->tx.idx = 0;
diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index ff9c4fd7b433..1589e8ca634e 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -897,7 +897,6 @@ static struct sk_buff *j1939_sk_alloc_skb(struct net_device *ndev,
 
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = ndev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 	skb_reserve(skb, offsetof(struct can_frame, data));
 
 	ret = memcpy_from_msg(skb_put(skb, size), msg, size);
diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
index 8656ab388c83..d5d3e5320f7a 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -601,7 +601,6 @@ sk_buff *j1939_tp_tx_dat_new(struct j1939_priv *priv,
 	skb->dev = priv->ndev;
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = priv->ndev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 	/* reserve CAN header */
 	skb_reserve(skb, offsetof(struct can_frame, data));
 
@@ -1536,7 +1535,6 @@ j1939_session *j1939_session_fresh_new(struct j1939_priv *priv,
 	skb->dev = priv->ndev;
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = priv->ndev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 	skcb = j1939_skb_to_cb(skb);
 	memcpy(skcb, rel_skcb, sizeof(*skcb));
 
diff --git a/net/can/raw.c b/net/can/raw.c
index 12293363413c..fb4f9c854df0 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -76,7 +76,7 @@ MODULE_ALIAS("can-proto-1");
 
 struct uniqframe {
 	const struct sk_buff *skb;
-	int skbcnt;
+	u32 hash;
 	unsigned int join_rx_count;
 };
 
@@ -164,7 +164,7 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
 
 	/* eliminate multiple filter matches for the same skb */
 	if (this_cpu_ptr(ro->uniq)->skb == oskb &&
-	    this_cpu_ptr(ro->uniq)->skbcnt == can_skb_prv(oskb)->skbcnt) {
+	    this_cpu_ptr(ro->uniq)->hash == oskb->hash) {
 		if (!ro->join_filters)
 			return;
 
@@ -174,7 +174,7 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
 			return;
 	} else {
 		this_cpu_ptr(ro->uniq)->skb = oskb;
-		this_cpu_ptr(ro->uniq)->skbcnt = can_skb_prv(oskb)->skbcnt;
+		this_cpu_ptr(ro->uniq)->hash = oskb->hash;
 		this_cpu_ptr(ro->uniq)->join_rx_count = 1;
 		/* drop first frame to check all enabled filters? */
 		if (ro->join_filters && ro->count > 1)
@@ -958,7 +958,6 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
 
 	can_skb_reserve(skb);
 	can_skb_prv(skb)->ifindex = dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
 
 	/* fill the skb before testing for valid CAN frames */
 	err = memcpy_from_msg(skb_put(skb, size), msg, size);