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Message-Id: <20260128-can-skb-ext-v2-1-fe64aa152c8a@pengutronix.de>
Date: Wed, 28 Jan 2026 10:28:53 +0100
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Marc Kleine-Budde <mkl@...gutronix.de>,
Vincent Mailhol <mailhol@...nel.org>,
Oliver Hartkopp <socketcan@...tkopp.net>,
Robin van der Gracht <robin@...tonic.nl>,
Oleksij Rempel <o.rempel@...gutronix.de>, kernel@...gutronix.de,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Simon Horman <horms@...nel.org>
Cc: linux-can@...r.kernel.org, linux-kernel@...r.kernel.org,
netdev@...r.kernel.org
Subject: [PATCH can-next v2 1/6] can: use skb hash instead of private
variable in headroom
From: Oliver Hartkopp <socketcan@...tkopp.net>
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: Oliver Hartkopp <socketcan@...tkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
drivers/net/can/dev/skb.c | 2 --
include/linux/can/core.h | 1 +
include/linux/can/skb.h | 2 --
net/can/af_can.c | 14 +++++++++++---
net/can/bcm.c | 2 --
net/can/isotp.c | 3 ---
net/can/j1939/socket.c | 1 -
net/can/j1939/transport.c | 2 --
net/can/raw.c | 7 +++----
9 files changed, 15 insertions(+), 19 deletions(-)
diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index 3ebd4f779b9b..0da615afa04d 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -202,7 +202,6 @@ static void init_can_skb_reserve(struct sk_buff *skb)
skb_reset_transport_header(skb);
can_skb_reserve(skb);
- can_skb_prv(skb)->skbcnt = 0;
}
struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf)
@@ -312,7 +311,6 @@ static bool can_skb_headroom_valid(struct net_device *dev, struct sk_buff *skb)
if (skb->ip_summed == CHECKSUM_NONE) {
/* init headroom */
can_skb_prv(skb)->ifindex = dev->ifindex;
- can_skb_prv(skb)->skbcnt = 0;
skb->ip_summed = CHECKSUM_UNNECESSARY;
diff --git a/include/linux/can/core.h b/include/linux/can/core.h
index 5fb8d0e3f9c1..5c382ed61755 100644
--- a/include/linux/can/core.h
+++ b/include/linux/can/core.h
@@ -58,6 +58,7 @@ extern void can_rx_unregister(struct net *net, struct net_device *dev,
void *data);
extern int can_send(struct sk_buff *skb, int loop);
+extern void can_set_skb_uid(struct sk_buff *skb);
void can_sock_destruct(struct sock *sk);
#endif /* !_CAN_CORE_H */
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
index 1abc25a8d144..869ea574a40a 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -49,13 +49,11 @@ bool can_dropped_invalid_skb(struct net_device *dev, struct sk_buff *skb);
/**
* struct can_skb_priv - private additional data inside CAN sk_buffs
* @ifindex: ifindex of the first interface the CAN frame appeared on
- * @skbcnt: atomic counter to have an unique id together with skb pointer
* @frame_len: length of CAN frame in data link layer
* @cf: align to the following CAN frame at skb->data
*/
struct can_skb_priv {
int ifindex;
- int skbcnt;
unsigned int frame_len;
struct can_frame cf[];
};
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);
--
2.51.0
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