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Message-ID: <20260112150908.5815-2-socketcan@hartkopp.net>
Date: Mon, 12 Jan 2026 16:09:04 +0100
From: Oliver Hartkopp <socketcan@...tkopp.net>
To: linux-can@...r.kernel.org,
Marc Kleine-Budde <mkl@...gutronix.de>,
Jakub Kicinski <kuba@...nel.org>
Cc: Vincent Mailhol <mailhol@...nel.org>,
netdev@...r.kernel.org,
Paolo Abeni <pabeni@...hat.com>,
Eric Dumazet <edumazet@...gle.com>,
Simon Horman <horms@...nel.org>,
davem@...emloft.net,
Oliver Hartkopp <socketcan@...tkopp.net>
Subject: [can-next 1/5] 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
we can move the private skbcnt value to skb->hash and set skb->sw_hash
accordingly.
Patch 1/5 to remove the private CAN bus skb headroom infrastructure.
Signed-off-by: Oliver Hartkopp <socketcan@...tkopp.net>
---
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
@@ -200,11 +200,10 @@ static void init_can_skb_reserve(struct sk_buff *skb)
skb_reset_mac_header(skb);
skb_reset_network_header(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)
{
struct sk_buff *skb;
@@ -310,11 +309,10 @@ static bool can_skb_headroom_valid(struct net_device *dev, struct sk_buff *skb)
/* af_packet does not apply CAN skb specific settings */
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;
/* perform proper loopback on capable devices */
if (dev->flags & IFF_ECHO)
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
@@ -56,8 +56,9 @@ extern void can_rx_unregister(struct net *net, struct net_device *dev,
canid_t can_id, canid_t mask,
void (*func)(struct sk_buff *, void *),
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
@@ -47,17 +47,15 @@ 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[];
};
static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
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
@@ -639,10 +639,20 @@ 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;
struct net *net = dev_net(dev);
struct can_pkg_stats *pkg_stats = net->can.pkg_stats;
@@ -650,13 +660,11 @@ static void can_receive(struct sk_buff *skb, struct net_device *dev)
/* update statistics */
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();
/* deliver the packet to sockets listening on all devices */
matches = can_rcv_filter(net->can.rx_alldev_list, skb);
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
@@ -314,11 +314,10 @@ static void bcm_can_tx(struct bcm_op *op)
if (!skb)
goto out;
can_skb_reserve(skb);
can_skb_prv(skb)->ifindex = dev->ifindex;
- can_skb_prv(skb)->skbcnt = 0;
skb_put_data(skb, cf, op->cfsiz);
/* send with loopback */
skb->dev = dev;
@@ -1342,11 +1341,10 @@ static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk,
kfree_skb(skb);
return -ENODEV;
}
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 */
dev_put(dev);
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
@@ -228,11 +228,10 @@ static int isotp_send_fc(struct sock *sk, int ae, u8 flowstatus)
return 1;
}
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);
ncf = (struct canfd_frame *)nskb->data;
skb_put_zero(nskb, so->ll.mtu);
@@ -778,11 +777,10 @@ static void isotp_send_cframe(struct isotp_sock *so)
return;
}
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);
/* create consecutive frame */
@@ -1007,11 +1005,10 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
goto err_out_drop;
}
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;
cf = (struct canfd_frame *)skb->data;
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
@@ -895,11 +895,10 @@ static struct sk_buff *j1939_sk_alloc_skb(struct net_device *ndev,
if (!skb)
goto failure;
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);
if (ret < 0)
goto free_skb;
diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
index 613a911dda10..d4be13422f50 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -599,11 +599,10 @@ sk_buff *j1939_tp_tx_dat_new(struct j1939_priv *priv,
return ERR_PTR(-ENOMEM);
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));
/* skb->cb must be large enough to hold a j1939_sk_buff_cb structure */
BUILD_BUG_ON(sizeof(skb->cb) < sizeof(*re_skcb));
@@ -1534,11 +1533,10 @@ j1939_session *j1939_session_fresh_new(struct j1939_priv *priv,
return NULL;
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));
session = j1939_session_new(priv, skb, size);
if (!session) {
diff --git a/net/can/raw.c b/net/can/raw.c
index d66036da6753..d276eb92ea81 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -74,11 +74,11 @@ MODULE_ALIAS("can-proto-1");
* storing the single filter in dfilter, to avoid using dynamic memory.
*/
struct uniqframe {
const struct sk_buff *skb;
- int skbcnt;
+ __u32 hash;
unsigned int join_rx_count;
};
struct raw_sock {
struct sock sk;
@@ -162,21 +162,21 @@ 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;
this_cpu_inc(ro->uniq->join_rx_count);
/* drop frame until all enabled filters matched */
if (this_cpu_ptr(ro->uniq)->join_rx_count < ro->count)
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)
return;
}
@@ -954,11 +954,10 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
if (!skb)
goto put_dev;
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);
if (err < 0)
goto free_skb;
--
2.47.3
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