* [PATCH net-next V4 1/6] can: use skb hash instead of private variable in headroom
2026-01-28 22:43 [PATCH net-next v4 0/6] move CAN skb headroom content to skb extensions Oliver Hartkopp via B4 Relay
@ 2026-01-28 22:43 ` Oliver Hartkopp via B4 Relay
2026-01-28 22:43 ` [PATCH net-next V4 2/6] can: add CAN skb extension infrastructure Oliver Hartkopp via B4 Relay
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-01-28 22:43 UTC (permalink / raw)
To: netdev, linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde
From: Oliver Hartkopp <socketcan@hartkopp.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: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.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 3ebd4f779b9bdf9d0ce1d1b22b3ccdea2c8e841b..0da615afa04de7c3df16c189ef8c7c1664d1a681 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 5fb8d0e3f9c1d027a2d5cd7c4eec7f2fa0340ed4..5c382ed6175578b0bea0ca172f41ce7e48da0442 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 1abc25a8d144e891c9a54cb8171ec44b25b83602..869ea574a40a194b27081ae5eeed701f91ec69c4 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 770173d8db42813d5c085248d1bcf5fbe717955b..70659987ef4d27fc25aaecf01302306d3f7494d0 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 7eba8ae01a5b1bb06fb745b6e656fa23b3935fd6..8ed60f18c2eaff7053cb2c76e5e4cf1124dd3ac5 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 ce588b85665a05a28aa499e72ce5db32ecb66126..4bb60b8f9b96188a328e77be2fdefcb879da1089 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 ff9c4fd7b4337a0ba8fa6846be4a9da35c232049..1589e8ca634ecc2b59eb0c2a1e48f546fafccbe0 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 8656ab388c83e68b7f779b7bc0ac97a8d0d009e5..d5d3e5320f7ac5fb247756f6413ab448c75447f6 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 12293363413ce6906b068e45d000d188836f6a91..fb4f9c854df04d90ed6bd4601c616ac39bb85ad9 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;
}
@@ -956,11 +956,10 @@ 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
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH net-next V4 2/6] can: add CAN skb extension infrastructure
2026-01-28 22:43 [PATCH net-next v4 0/6] move CAN skb headroom content to skb extensions Oliver Hartkopp via B4 Relay
2026-01-28 22:43 ` [PATCH net-next V4 1/6] can: use skb hash instead of private variable in headroom Oliver Hartkopp via B4 Relay
@ 2026-01-28 22:43 ` Oliver Hartkopp via B4 Relay
2026-01-28 22:43 ` [PATCH net-next V4 3/6] can: move ifindex to CAN skb extensions Oliver Hartkopp via B4 Relay
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-01-28 22:43 UTC (permalink / raw)
To: netdev, linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde
From: Oliver Hartkopp <socketcan@hartkopp.net>
To remove the private CAN bus skb headroom infrastructure 8 bytes need to
be stored in the skb. The skb extensions are a common pattern and an easy
and efficient way to hold private data travelling along with the skb. We
only need the skb_ext_add() and skb_ext_find() functions to allocate and
access CAN specific content as the skb helpers to copy/clone/free skbs
automatically take care of skb extensions and their final removal.
This patch introduces the complete CAN skb extensions infrastructure:
- add struct can_skb_ext in new file include/net/can.h
- add include/net/can.h in MAINTAINERS
- add SKB_EXT_CAN to skbuff.c and skbuff.h
- select SKB_EXTENSIONS in Kconfig when CONFIG_CAN is enabled
- check for existing CAN skb extensions in can_rcv() in af_can.c
- add CAN skb extensions allocation at every skb_alloc() location
- introduce can_skb_ext_add() and can_skb_ext_find() helpers
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
MAINTAINERS | 1 +
drivers/net/can/dev/skb.c | 56 +++++++++++++++++++++++++++++++++++++----------
include/linux/can/skb.h | 17 ++++++++++++++
include/linux/skbuff.h | 3 +++
include/net/can.h | 28 ++++++++++++++++++++++++
net/can/Kconfig | 1 +
net/can/af_can.c | 9 +++++---
net/can/bcm.c | 15 +++++++++++++
net/can/gw.c | 13 +++++++++++
net/can/isotp.c | 24 ++++++++++++++++++++
net/can/j1939/socket.c | 8 +++++++
net/can/j1939/transport.c | 15 +++++++++++++
net/can/raw.c | 8 +++++++
net/core/skbuff.c | 4 ++++
14 files changed, 188 insertions(+), 14 deletions(-)
diff --git a/MAINTAINERS b/MAINTAINERS
index c3df85fd5acdecfad95498918f3ee175ef7994ec..97f276375219eea66c92e086d078e45d28b40d6c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5632,10 +5632,11 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/mkl/linux-can-next.git
F: Documentation/networking/can.rst
F: Documentation/networking/iso15765-2.rst
F: include/linux/can/can-ml.h
F: include/linux/can/core.h
F: include/linux/can/skb.h
+F: include/net/can.h
F: include/net/netns/can.h
F: include/uapi/linux/can.h
F: include/uapi/linux/can/bcm.h
F: include/uapi/linux/can/gw.h
F: include/uapi/linux/can/isotp.h
diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index 0da615afa04de7c3df16c189ef8c7c1664d1a681..c572745565f6d0ff25729039220614ecb117e2b3 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -4,10 +4,11 @@
* Copyright (C) 2008-2009 Wolfgang Grandegger <wg@grandegger.com>
*/
#include <linux/can/dev.h>
#include <linux/module.h>
+#include <net/can.h>
#define MOD_DESC "CAN device driver interface"
MODULE_DESCRIPTION(MOD_DESC);
MODULE_LICENSE("GPL v2");
@@ -205,40 +206,53 @@ static void init_can_skb_reserve(struct sk_buff *skb)
}
struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf)
{
struct sk_buff *skb;
+ struct can_skb_ext *csx;
skb = netdev_alloc_skb(dev, sizeof(struct can_skb_priv) +
sizeof(struct can_frame));
- if (unlikely(!skb)) {
- *cf = NULL;
+ if (unlikely(!skb))
+ goto out_error_cc;
- return NULL;
+ csx = can_skb_ext_add(skb);
+ if (!csx) {
+ kfree_skb(skb);
+ goto out_error_cc;
}
skb->protocol = htons(ETH_P_CAN);
init_can_skb_reserve(skb);
can_skb_prv(skb)->ifindex = dev->ifindex;
*cf = skb_put_zero(skb, sizeof(struct can_frame));
return skb;
+
+out_error_cc:
+ *cf = NULL;
+
+ return NULL;
}
EXPORT_SYMBOL_GPL(alloc_can_skb);
struct sk_buff *alloc_canfd_skb(struct net_device *dev,
struct canfd_frame **cfd)
{
struct sk_buff *skb;
+ struct can_skb_ext *csx;
skb = netdev_alloc_skb(dev, sizeof(struct can_skb_priv) +
sizeof(struct canfd_frame));
- if (unlikely(!skb)) {
- *cfd = NULL;
+ if (unlikely(!skb))
+ goto out_error_fd;
- return NULL;
+ csx = can_skb_ext_add(skb);
+ if (!csx) {
+ kfree_skb(skb);
+ goto out_error_fd;
}
skb->protocol = htons(ETH_P_CANFD);
init_can_skb_reserve(skb);
can_skb_prv(skb)->ifindex = dev->ifindex;
@@ -247,26 +261,38 @@ struct sk_buff *alloc_canfd_skb(struct net_device *dev,
/* set CAN FD flag by default */
(*cfd)->flags = CANFD_FDF;
return skb;
+
+out_error_fd:
+ *cfd = NULL;
+
+ return NULL;
}
EXPORT_SYMBOL_GPL(alloc_canfd_skb);
struct sk_buff *alloc_canxl_skb(struct net_device *dev,
struct canxl_frame **cxl,
unsigned int data_len)
{
struct sk_buff *skb;
+ struct can_skb_ext *csx;
if (data_len < CANXL_MIN_DLEN || data_len > CANXL_MAX_DLEN)
- goto out_error;
+ goto out_error_xl;
skb = netdev_alloc_skb(dev, sizeof(struct can_skb_priv) +
CANXL_HDR_SIZE + data_len);
if (unlikely(!skb))
- goto out_error;
+ goto out_error_xl;
+
+ csx = can_skb_ext_add(skb);
+ if (!csx) {
+ kfree_skb(skb);
+ goto out_error_xl;
+ }
skb->protocol = htons(ETH_P_CANXL);
init_can_skb_reserve(skb);
can_skb_prv(skb)->ifindex = dev->ifindex;
@@ -276,11 +302,11 @@ struct sk_buff *alloc_canxl_skb(struct net_device *dev,
(*cxl)->flags = CANXL_XLF;
(*cxl)->len = data_len;
return skb;
-out_error:
+out_error_xl:
*cxl = NULL;
return NULL;
}
EXPORT_SYMBOL_GPL(alloc_canxl_skb);
@@ -301,17 +327,25 @@ struct sk_buff *alloc_can_err_skb(struct net_device *dev, struct can_frame **cf)
EXPORT_SYMBOL_GPL(alloc_can_err_skb);
/* Check for outgoing skbs that have not been created by the CAN subsystem */
static bool can_skb_headroom_valid(struct net_device *dev, struct sk_buff *skb)
{
+ struct can_skb_ext *csx = can_skb_ext_find(skb);
+
/* af_packet creates a headroom of HH_DATA_MOD bytes which is fine */
if (WARN_ON_ONCE(skb_headroom(skb) < sizeof(struct can_skb_priv)))
return false;
/* af_packet does not apply CAN skb specific settings */
- if (skb->ip_summed == CHECKSUM_NONE) {
- /* init headroom */
+ if (skb->ip_summed == CHECKSUM_NONE || !csx) {
+ /* init CAN skb content */
+ if (!csx) {
+ csx = can_skb_ext_add(skb);
+ if (!csx)
+ return false;
+ }
+
can_skb_prv(skb)->ifindex = dev->ifindex;
skb->ip_summed = CHECKSUM_UNNECESSARY;
/* perform proper loopback on capable devices */
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
index 869ea574a40a194b27081ae5eeed701f91ec69c4..68c0f24e69149707e38d657e821d6cbe129f7d1d 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -12,10 +12,11 @@
#define _CAN_SKB_H
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/can.h>
+#include <net/can.h>
#include <net/sock.h>
void can_flush_echo_skb(struct net_device *dev);
int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
unsigned int idx, unsigned int frame_len);
@@ -66,10 +67,26 @@ static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
static inline void can_skb_reserve(struct sk_buff *skb)
{
skb_reserve(skb, sizeof(struct can_skb_priv));
}
+static inline struct can_skb_ext *can_skb_ext_add(struct sk_buff *skb)
+{
+ struct can_skb_ext *csx = skb_ext_add(skb, SKB_EXT_CAN);
+
+ /* skb_ext_add() returns uninitialized space */
+ if (csx)
+ csx->can_gw_hops = 0;
+
+ return csx;
+}
+
+static inline struct can_skb_ext *can_skb_ext_find(struct sk_buff *skb)
+{
+ return skb_ext_find(skb, SKB_EXT_CAN);
+}
+
static inline void can_skb_set_owner(struct sk_buff *skb, struct sock *sk)
{
/* If the socket has already been closed by user space, the
* refcount may already be 0 (and the socket will be freed
* after the last TX skb has been freed). So only increase
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index e6bfe5d0c5252b2e7540e1fef9317aab83feced2..b5beb28e5730133a2f4f95557fa308e7cc30ef6d 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -4986,10 +4986,13 @@ enum skb_ext_id {
#if IS_ENABLED(CONFIG_MCTP_FLOWS)
SKB_EXT_MCTP,
#endif
#if IS_ENABLED(CONFIG_INET_PSP)
SKB_EXT_PSP,
+#endif
+#if IS_ENABLED(CONFIG_CAN)
+ SKB_EXT_CAN,
#endif
SKB_EXT_NUM, /* must be last */
};
/**
diff --git a/include/net/can.h b/include/net/can.h
new file mode 100644
index 0000000000000000000000000000000000000000..6db9e826f0e05fda2f361e11c58dd6b7378d767c
--- /dev/null
+++ b/include/net/can.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) */
+/*
+ * net/can.h
+ *
+ * Definitions for the CAN network socket buffer extensions
+ *
+ * Copyright (C) 2026 Oliver Hartkopp <socketcan@hartkopp.net>
+ *
+ */
+
+#ifndef _NET_CAN_H
+#define _NET_CAN_H
+
+/**
+ * struct can_skb_ext - skb extensions for CAN specific content
+ * @can_iif: ifindex of the first interface the CAN frame appeared on
+ * @can_framelen: cached echo CAN frame length for bql
+ * @can_gw_hops: can-gw CAN frame time-to-live counter
+ * @can_ext_flags: CAN skb extensions flags
+ */
+struct can_skb_ext {
+ int can_iif;
+ u16 can_framelen;
+ u8 can_gw_hops;
+ u8 can_ext_flags;
+};
+
+#endif /* _NET_CAN_H */
diff --git a/net/can/Kconfig b/net/can/Kconfig
index af64a6f764588cc63862ce285ee47f3245d72d5e..abbb4be7ad2152c66abd2e28dbbd5282ec45d065 100644
--- a/net/can/Kconfig
+++ b/net/can/Kconfig
@@ -3,10 +3,11 @@
# Controller Area Network (CAN) network layer core configuration
#
menuconfig CAN
tristate "CAN bus subsystem support"
+ select SKB_EXTENSIONS
help
Controller Area Network (CAN) is a slow (up to 1Mbit/s) serial
communications protocol. Development of the CAN bus started in
1983 at Robert Bosch GmbH, and the protocol was officially
released in 1986. The CAN bus was originally mainly for automotive,
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 70659987ef4d27fc25aaecf01302306d3f7494d0..22c65a014861600c96078f605309419a96b8c6bd 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -685,11 +685,12 @@ static void can_receive(struct sk_buff *skb, struct net_device *dev)
}
static int can_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
- if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) || !can_is_can_skb(skb))) {
+ if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) ||
+ !can_skb_ext_find(skb) || !can_is_can_skb(skb))) {
pr_warn_once("PF_CAN: dropped non conform CAN skbuff: dev type %d, len %d\n",
dev->type, skb->len);
kfree_skb_reason(skb, SKB_DROP_REASON_CAN_RX_INVALID_FRAME);
return NET_RX_DROP;
@@ -700,11 +701,12 @@ static int can_rcv(struct sk_buff *skb, struct net_device *dev,
}
static int canfd_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
- if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) || !can_is_canfd_skb(skb))) {
+ if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) ||
+ !can_skb_ext_find(skb) || !can_is_canfd_skb(skb))) {
pr_warn_once("PF_CAN: dropped non conform CAN FD skbuff: dev type %d, len %d\n",
dev->type, skb->len);
kfree_skb_reason(skb, SKB_DROP_REASON_CANFD_RX_INVALID_FRAME);
return NET_RX_DROP;
@@ -715,11 +717,12 @@ static int canfd_rcv(struct sk_buff *skb, struct net_device *dev,
}
static int canxl_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
- if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) || !can_is_canxl_skb(skb))) {
+ if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) ||
+ !can_skb_ext_find(skb) || !can_is_canxl_skb(skb))) {
pr_warn_once("PF_CAN: dropped non conform CAN XL skbuff: dev type %d, len %d\n",
dev->type, skb->len);
kfree_skb_reason(skb, SKB_DROP_REASON_CANXL_RX_INVALID_FRAME);
return NET_RX_DROP;
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 8ed60f18c2eaff7053cb2c76e5e4cf1124dd3ac5..38452069dea883a35b86ba2d085d5c37a11a909d 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -57,10 +57,11 @@
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/can/bcm.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
+#include <net/can.h>
#include <net/sock.h>
#include <net/net_namespace.h>
/*
* To send multiple CAN frame content within TX_SETUP or to filter
@@ -289,10 +290,11 @@ static int bcm_proc_show(struct seq_file *m, void *v)
* of the given bcm tx op
*/
static void bcm_can_tx(struct bcm_op *op)
{
struct sk_buff *skb;
+ struct can_skb_ext *csx;
struct net_device *dev;
struct canfd_frame *cf;
int err;
/* no target device? => exit */
@@ -312,10 +314,16 @@ static void bcm_can_tx(struct bcm_op *op)
skb = alloc_skb(op->cfsiz + sizeof(struct can_skb_priv), gfp_any());
if (!skb)
goto out;
+ csx = can_skb_ext_add(skb);
+ if (!csx) {
+ kfree_skb(skb);
+ goto out;
+ }
+
can_skb_reserve(skb);
can_skb_prv(skb)->ifindex = dev->ifindex;
skb_put_data(skb, cf, op->cfsiz);
@@ -1315,10 +1323,11 @@ static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
*/
static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk,
int cfsiz)
{
struct sk_buff *skb;
+ struct can_skb_ext *csx;
struct net_device *dev;
int err;
/* we need a real device to send frames */
if (!ifindex)
@@ -1326,10 +1335,16 @@ static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk,
skb = alloc_skb(cfsiz + sizeof(struct can_skb_priv), GFP_KERNEL);
if (!skb)
return -ENOMEM;
+ csx = can_skb_ext_add(skb);
+ if (!csx) {
+ kfree_skb(skb);
+ return -ENOMEM;
+ }
+
can_skb_reserve(skb);
err = memcpy_from_msg(skb_put(skb, cfsiz), msg, cfsiz);
if (err < 0) {
kfree_skb(skb);
diff --git a/net/can/gw.c b/net/can/gw.c
index 55eccb1c7620c094e04a7525b5d6c2becb96b72c..8894ab5d2087c759135ec21644dcbe31a9e5162f 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -53,10 +53,11 @@
#include <linux/skbuff.h>
#include <linux/can.h>
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/can/gw.h>
+#include <net/can.h>
#include <net/rtnetlink.h>
#include <net/net_namespace.h>
#include <net/sock.h>
#define CAN_GW_NAME "can-gw"
@@ -457,10 +458,11 @@ static void cgw_csum_crc8_neg(struct canfd_frame *cf,
static void can_can_gw_rcv(struct sk_buff *skb, void *data)
{
struct cgw_job *gwj = (struct cgw_job *)data;
struct canfd_frame *cf;
struct sk_buff *nskb;
+ struct can_skb_ext *csx, *ncsx;
struct cf_mod *mod;
int modidx = 0;
/* process strictly Classic CAN or CAN FD frames */
if (gwj->flags & CGW_FLAGS_CAN_FD) {
@@ -469,10 +471,14 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
} else {
if (!can_is_can_skb(skb))
return;
}
+ csx = can_skb_ext_find(skb);
+ if (!csx)
+ return;
+
/* Do not handle CAN frames routed more than 'max_hops' times.
* In general we should never catch this delimiter which is intended
* to cover a misconfiguration protection (e.g. circular CAN routes).
*
* The Controller Area Network controllers only accept CAN frames with
@@ -516,10 +522,17 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
if (!nskb) {
gwj->dropped_frames++;
return;
}
+ ncsx = can_skb_ext_find(nskb);
+ if (!ncsx) {
+ kfree_skb(nskb);
+ gwj->dropped_frames++;
+ return;
+ }
+
/* put the incremented hop counter in the cloned skb */
cgw_hops(nskb) = cgw_hops(skb) + 1;
/* first processing of this CAN frame -> adjust to private hop limit */
if (gwj->limit_hops && cgw_hops(nskb) == 1)
diff --git a/net/can/isotp.c b/net/can/isotp.c
index 4bb60b8f9b96188a328e77be2fdefcb879da1089..c4fb8afde165d28a4b4783f1d1f7fb1b063cd41a 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -67,10 +67,11 @@
#include <linux/can.h>
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/can/isotp.h>
#include <linux/slab.h>
+#include <net/can.h>
#include <net/sock.h>
#include <net/net_namespace.h>
MODULE_DESCRIPTION("PF_CAN ISO 15765-2 transport protocol");
MODULE_LICENSE("Dual BSD/GPL");
@@ -212,18 +213,25 @@ static enum hrtimer_restart isotp_rx_timer_handler(struct hrtimer *hrtimer)
static int isotp_send_fc(struct sock *sk, int ae, u8 flowstatus)
{
struct net_device *dev;
struct sk_buff *nskb;
+ struct can_skb_ext *csx;
struct canfd_frame *ncf;
struct isotp_sock *so = isotp_sk(sk);
int can_send_ret;
nskb = alloc_skb(so->ll.mtu + sizeof(struct can_skb_priv), gfp_any());
if (!nskb)
return 1;
+ csx = can_skb_ext_add(nskb);
+ if (!csx) {
+ kfree_skb(nskb);
+ return 1;
+ }
+
dev = dev_get_by_index(sock_net(sk), so->ifindex);
if (!dev) {
kfree_skb(nskb);
return 1;
}
@@ -760,10 +768,11 @@ static void isotp_fill_dataframe(struct canfd_frame *cf, struct isotp_sock *so,
static void isotp_send_cframe(struct isotp_sock *so)
{
struct sock *sk = &so->sk;
struct sk_buff *skb;
+ struct can_skb_ext *csx;
struct net_device *dev;
struct canfd_frame *cf;
int can_send_ret;
int ae = (so->opt.flags & CAN_ISOTP_EXTEND_ADDR) ? 1 : 0;
@@ -775,10 +784,17 @@ static void isotp_send_cframe(struct isotp_sock *so)
if (!skb) {
dev_put(dev);
return;
}
+ csx = can_skb_ext_add(skb);
+ if (!csx) {
+ kfree_skb(skb);
+ dev_put(dev);
+ return;
+ }
+
can_skb_reserve(skb);
can_skb_prv(skb)->ifindex = dev->ifindex;
cf = (struct canfd_frame *)skb->data;
skb_put_zero(skb, so->ll.mtu);
@@ -936,10 +952,11 @@ static enum hrtimer_restart isotp_txfr_timer_handler(struct hrtimer *hrtimer)
static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
{
struct sock *sk = sock->sk;
struct isotp_sock *so = isotp_sk(sk);
struct sk_buff *skb;
+ struct can_skb_ext *csx;
struct net_device *dev;
struct canfd_frame *cf;
int ae = (so->opt.flags & CAN_ISOTP_EXTEND_ADDR) ? 1 : 0;
int wait_tx_done = (so->opt.flags & CAN_ISOTP_WAIT_TX_DONE) ? 1 : 0;
s64 hrtimer_sec = ISOTP_ECHO_TIMEOUT;
@@ -1003,10 +1020,17 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
if (!skb) {
dev_put(dev);
goto err_out_drop;
}
+ csx = can_skb_ext_add(skb);
+ if (!csx) {
+ kfree_skb(skb);
+ dev_put(dev);
+ goto err_out_drop;
+ }
+
can_skb_reserve(skb);
can_skb_prv(skb)->ifindex = dev->ifindex;
so->tx.len = size;
so->tx.idx = 0;
diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index 1589e8ca634ecc2b59eb0c2a1e48f546fafccbe0..fc28a7677369da821324e6c1e371a449f7a85336 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -15,10 +15,11 @@
#include <linux/can/can-ml.h>
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/errqueue.h>
#include <linux/if_arp.h>
+#include <net/can.h>
#include "j1939-priv.h"
#define J1939_MIN_NAMELEN CAN_REQUIRED_SIZE(struct sockaddr_can, can_addr.j1939)
@@ -882,10 +883,11 @@ static struct sk_buff *j1939_sk_alloc_skb(struct net_device *ndev,
int *errcode)
{
struct j1939_sock *jsk = j1939_sk(sk);
struct j1939_sk_buff_cb *skcb;
struct sk_buff *skb;
+ struct can_skb_ext *csx;
int ret;
skb = sock_alloc_send_skb(sk,
size +
sizeof(struct can_frame) -
@@ -893,10 +895,16 @@ static struct sk_buff *j1939_sk_alloc_skb(struct net_device *ndev,
sizeof(struct can_skb_priv),
msg->msg_flags & MSG_DONTWAIT, &ret);
if (!skb)
goto failure;
+ csx = can_skb_ext_add(skb);
+ if (!csx) {
+ kfree_skb(skb);
+ goto failure;
+ }
+
can_skb_reserve(skb);
can_skb_prv(skb)->ifindex = ndev->ifindex;
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 d5d3e5320f7ac5fb247756f6413ab448c75447f6..0514f3504e39927f7950cfad33a20d6536bca797 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -7,10 +7,11 @@
// Marc Kleine-Budde <kernel@pengutronix.de>
// Copyright (c) 2017-2019 Pengutronix,
// Oleksij Rempel <kernel@pengutronix.de>
#include <linux/can/skb.h>
+#include <net/can.h>
#include "j1939-priv.h"
#define J1939_XTP_TX_RETRY_LIMIT 100
@@ -589,17 +590,24 @@ sk_buff *j1939_tp_tx_dat_new(struct j1939_priv *priv,
const struct j1939_sk_buff_cb *re_skcb,
bool ctl,
bool swap_src_dst)
{
struct sk_buff *skb;
+ struct can_skb_ext *csx;
struct j1939_sk_buff_cb *skcb;
skb = alloc_skb(sizeof(struct can_frame) + sizeof(struct can_skb_priv),
GFP_ATOMIC);
if (unlikely(!skb))
return ERR_PTR(-ENOMEM);
+ csx = can_skb_ext_add(skb);
+ if (!csx) {
+ kfree_skb(skb);
+ return ERR_PTR(-ENOMEM);
+ }
+
skb->dev = priv->ndev;
can_skb_reserve(skb);
can_skb_prv(skb)->ifindex = priv->ndev->ifindex;
/* reserve CAN header */
skb_reserve(skb, offsetof(struct can_frame, data));
@@ -1523,17 +1531,24 @@ static struct
j1939_session *j1939_session_fresh_new(struct j1939_priv *priv,
int size,
const struct j1939_sk_buff_cb *rel_skcb)
{
struct sk_buff *skb;
+ struct can_skb_ext *csx;
struct j1939_sk_buff_cb *skcb;
struct j1939_session *session;
skb = alloc_skb(size + sizeof(struct can_skb_priv), GFP_ATOMIC);
if (unlikely(!skb))
return NULL;
+ csx = can_skb_ext_add(skb);
+ if (!csx) {
+ kfree_skb(skb);
+ return NULL;
+ }
+
skb->dev = priv->ndev;
can_skb_reserve(skb);
can_skb_prv(skb)->ifindex = priv->ndev->ifindex;
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 fb4f9c854df04d90ed6bd4601c616ac39bb85ad9..03438e9bc535eef3cee29188b0d57be9a907a383 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -51,10 +51,11 @@
#include <linux/can.h>
#include <linux/can/can-ml.h>
#include <linux/can/core.h>
#include <linux/can/skb.h>
#include <linux/can/raw.h>
+#include <net/can.h>
#include <net/sock.h>
#include <net/net_namespace.h>
MODULE_DESCRIPTION("PF_CAN raw protocol");
MODULE_LICENSE("Dual BSD/GPL");
@@ -916,10 +917,11 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
{
struct sock *sk = sock->sk;
struct raw_sock *ro = raw_sk(sk);
struct sockcm_cookie sockc;
struct sk_buff *skb;
+ struct can_skb_ext *csx;
struct net_device *dev;
unsigned int txmtu;
int ifindex;
int err = -EINVAL;
@@ -954,10 +956,16 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
skb = sock_alloc_send_skb(sk, size + sizeof(struct can_skb_priv),
msg->msg_flags & MSG_DONTWAIT, &err);
if (!skb)
goto put_dev;
+ csx = can_skb_ext_add(skb);
+ if (!csx) {
+ kfree_skb(skb);
+ goto put_dev;
+ }
+
can_skb_reserve(skb);
can_skb_prv(skb)->ifindex = dev->ifindex;
/* fill the skb before testing for valid CAN frames */
err = memcpy_from_msg(skb_put(skb, size), msg, size);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 4d3920e5b141a02117186c3095f15f4f7a35b1df..648c20e190387b8c66e2a6ff8e265795f81974c7 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -76,10 +76,11 @@
#include <net/ip6_checksum.h>
#include <net/xfrm.h>
#include <net/mpls.h>
#include <net/mptcp.h>
#include <net/mctp.h>
+#include <net/can.h>
#include <net/page_pool/helpers.h>
#include <net/psp/types.h>
#include <net/dropreason.h>
#include <net/xdp_sock.h>
@@ -5137,10 +5138,13 @@ static const u8 skb_ext_type_len[] = {
[SKB_EXT_MCTP] = SKB_EXT_CHUNKSIZEOF(struct mctp_flow),
#endif
#if IS_ENABLED(CONFIG_INET_PSP)
[SKB_EXT_PSP] = SKB_EXT_CHUNKSIZEOF(struct psp_skb_ext),
#endif
+#if IS_ENABLED(CONFIG_CAN)
+ [SKB_EXT_CAN] = SKB_EXT_CHUNKSIZEOF(struct can_skb_ext),
+#endif
};
static __always_inline unsigned int skb_ext_total_length(void)
{
unsigned int l = SKB_EXT_CHUNKSIZEOF(struct skb_ext);
--
2.47.3
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH net-next V4 3/6] can: move ifindex to CAN skb extensions
2026-01-28 22:43 [PATCH net-next v4 0/6] move CAN skb headroom content to skb extensions Oliver Hartkopp via B4 Relay
2026-01-28 22:43 ` [PATCH net-next V4 1/6] can: use skb hash instead of private variable in headroom Oliver Hartkopp via B4 Relay
2026-01-28 22:43 ` [PATCH net-next V4 2/6] can: add CAN skb extension infrastructure Oliver Hartkopp via B4 Relay
@ 2026-01-28 22:43 ` Oliver Hartkopp via B4 Relay
2026-01-28 22:43 ` [PATCH net-next V4 4/6] can: move frame_len " Oliver Hartkopp via B4 Relay
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-01-28 22:43 UTC (permalink / raw)
To: netdev, linux-can; +Cc: Oliver Hartkopp
From: Oliver Hartkopp <socketcan@hartkopp.net>
When routing CAN frames over different CAN interfaces the interface index
skb->iif is overwritten with every single hop. To prevent sending a CAN
frame back to its originating (first) incoming CAN interface another
ifindex variable is needed, which was stored in can_skb_priv::ifindex.
Move the can_skb_priv::ifindex content to can_skb_ext::can_iif.
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
drivers/net/can/dev/skb.c | 9 ++++-----
net/can/bcm.c | 4 ++--
net/can/gw.c | 2 +-
net/can/isotp.c | 6 +++---
net/can/j1939/socket.c | 2 +-
net/can/j1939/transport.c | 4 ++--
net/can/raw.c | 2 +-
7 files changed, 14 insertions(+), 15 deletions(-)
diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index c572745565f6d0ff25729039220614ecb117e2b3..470255fe7367b6ff038e45255abc3ea9eed88704 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -221,11 +221,11 @@ struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf)
goto out_error_cc;
}
skb->protocol = htons(ETH_P_CAN);
init_can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
*cf = skb_put_zero(skb, sizeof(struct can_frame));
return skb;
@@ -253,11 +253,11 @@ struct sk_buff *alloc_canfd_skb(struct net_device *dev,
goto out_error_fd;
}
skb->protocol = htons(ETH_P_CANFD);
init_can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
*cfd = skb_put_zero(skb, sizeof(struct canfd_frame));
/* set CAN FD flag by default */
(*cfd)->flags = CANFD_FDF;
@@ -292,11 +292,11 @@ struct sk_buff *alloc_canxl_skb(struct net_device *dev,
goto out_error_xl;
}
skb->protocol = htons(ETH_P_CANXL);
init_can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
*cxl = skb_put_zero(skb, CANXL_HDR_SIZE + data_len);
/* set CAN XL flag and length information by default */
(*cxl)->flags = CANXL_XLF;
@@ -342,12 +342,11 @@ static bool can_skb_headroom_valid(struct net_device *dev, struct sk_buff *skb)
csx = can_skb_ext_add(skb);
if (!csx)
return false;
}
- can_skb_prv(skb)->ifindex = dev->ifindex;
-
+ csx->can_iif = dev->ifindex;
skb->ip_summed = CHECKSUM_UNNECESSARY;
/* perform proper loopback on capable devices */
if (dev->flags & IFF_ECHO)
skb->pkt_type = PACKET_LOOPBACK;
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 38452069dea883a35b86ba2d085d5c37a11a909d..f102d17e86190b7a46f806870991136c0b416b0d 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -321,11 +321,11 @@ static void bcm_can_tx(struct bcm_op *op)
kfree_skb(skb);
goto out;
}
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
skb_put_data(skb, cf, op->cfsiz);
/* send with loopback */
skb->dev = dev;
@@ -1355,11 +1355,11 @@ static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk,
if (!dev) {
kfree_skb(skb);
return -ENODEV;
}
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
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/gw.c b/net/can/gw.c
index 8894ab5d2087c759135ec21644dcbe31a9e5162f..ad89a1913b3422f77fdf91b5552380282b2db09a 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -503,11 +503,11 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
return;
}
/* is sending the skb back to the incoming interface not allowed? */
if (!(gwj->flags & CGW_FLAGS_CAN_IIF_TX_OK) &&
- can_skb_prv(skb)->ifindex == gwj->dst.dev->ifindex)
+ csx->can_iif == gwj->dst.dev->ifindex)
return;
/* clone the given skb, which has not been done in can_rcv()
*
* When there is at least one modification function activated,
diff --git a/net/can/isotp.c b/net/can/isotp.c
index c4fb8afde165d28a4b4783f1d1f7fb1b063cd41a..01ceb3febbb757d2d727d90f987b9c47dd45973d 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -235,11 +235,11 @@ static int isotp_send_fc(struct sock *sk, int ae, u8 flowstatus)
kfree_skb(nskb);
return 1;
}
can_skb_reserve(nskb);
- can_skb_prv(nskb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
nskb->dev = dev;
can_skb_set_owner(nskb, sk);
ncf = (struct canfd_frame *)nskb->data;
skb_put_zero(nskb, so->ll.mtu);
@@ -792,11 +792,11 @@ static void isotp_send_cframe(struct isotp_sock *so)
dev_put(dev);
return;
}
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
cf = (struct canfd_frame *)skb->data;
skb_put_zero(skb, so->ll.mtu);
/* create consecutive frame */
@@ -1028,11 +1028,11 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
dev_put(dev);
goto err_out_drop;
}
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
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 fc28a7677369da821324e6c1e371a449f7a85336..f03bae79354e1cc7fa8655d92fe9f5b9db2d65bb 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -902,11 +902,11 @@ static struct sk_buff *j1939_sk_alloc_skb(struct net_device *ndev,
kfree_skb(skb);
goto failure;
}
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = ndev->ifindex;
+ csx->can_iif = ndev->ifindex;
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 0514f3504e39927f7950cfad33a20d6536bca797..96e02ad4a726fbc947cbae55687c0d6aa613d50e 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -606,11 +606,11 @@ 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;
+ csx->can_iif = priv->ndev->ifindex;
/* 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));
@@ -1547,11 +1547,11 @@ 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;
+ csx->can_iif = priv->ndev->ifindex;
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 03438e9bc535eef3cee29188b0d57be9a907a383..7c89962ec913396e7948c0f6d2ad80c8f66a8985 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -963,11 +963,11 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
kfree_skb(skb);
goto put_dev;
}
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
/* 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
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH net-next V4 4/6] can: move frame_len to CAN skb extensions
2026-01-28 22:43 [PATCH net-next v4 0/6] move CAN skb headroom content to skb extensions Oliver Hartkopp via B4 Relay
` (2 preceding siblings ...)
2026-01-28 22:43 ` [PATCH net-next V4 3/6] can: move ifindex to CAN skb extensions Oliver Hartkopp via B4 Relay
@ 2026-01-28 22:43 ` Oliver Hartkopp via B4 Relay
2026-01-28 22:43 ` [PATCH net-next V4 5/6] can: remove private CAN skb headroom infrastructure Oliver Hartkopp via B4 Relay
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-01-28 22:43 UTC (permalink / raw)
To: netdev, linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde
From: Oliver Hartkopp <socketcan@hartkopp.net>
The can_skb_priv::frame_len variable is used to cache a previous
calculated CAN frame length to be passed to BQL queueing disciplines.
Move the can_skb_priv::frame_len content to can_skb_ext::can_framelen.
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
drivers/net/can/dev/skb.c | 29 +++++++++++++++++++++--------
1 file changed, 21 insertions(+), 8 deletions(-)
diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index 470255fe7367b6ff038e45255abc3ea9eed88704..408ee49abce145f49c7837ff30809bc3e42f8ab5 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -47,10 +47,11 @@ void can_flush_echo_skb(struct net_device *dev)
*/
int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
unsigned int idx, unsigned int frame_len)
{
struct can_priv *priv = netdev_priv(dev);
+ struct can_skb_ext *csx;
if (idx >= priv->echo_skb_max) {
netdev_err(dev, "%s: BUG! Trying to access can_priv::echo_skb out of bounds (%u/max %u)\n",
__func__, idx, priv->echo_skb_max);
return -EINVAL;
@@ -73,11 +74,13 @@ int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev,
/* make settings for echo to reduce code in irq context */
skb->ip_summed = CHECKSUM_UNNECESSARY;
skb->dev = dev;
/* save frame_len to reuse it when transmission is completed */
- can_skb_prv(skb)->frame_len = frame_len;
+ csx = can_skb_ext_find(skb);
+ if (csx)
+ csx->can_framelen = frame_len;
if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)
skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
skb_tx_timestamp(skb);
@@ -110,20 +113,25 @@ __can_get_echo_skb(struct net_device *dev, unsigned int idx,
if (priv->echo_skb[idx]) {
/* Using "struct canfd_frame::len" for the frame
* length is supported on both CAN and CANFD frames.
*/
struct sk_buff *skb = priv->echo_skb[idx];
- struct can_skb_priv *can_skb_priv = can_skb_prv(skb);
+ struct can_skb_ext *csx;
if (skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS)
skb_tstamp_tx(skb, skb_hwtstamps(skb));
/* get the real payload length for netdev statistics */
*len_ptr = can_skb_get_data_len(skb);
- if (frame_len_ptr)
- *frame_len_ptr = can_skb_priv->frame_len;
+ if (frame_len_ptr) {
+ csx = can_skb_ext_find(skb);
+ if (csx)
+ *frame_len_ptr = csx->can_framelen;
+ else
+ *frame_len_ptr = 0;
+ }
priv->echo_skb[idx] = NULL;
if (skb->pkt_type == PACKET_LOOPBACK) {
skb->pkt_type = PACKET_BROADCAST;
@@ -179,14 +187,19 @@ void can_free_echo_skb(struct net_device *dev, unsigned int idx,
return;
}
if (priv->echo_skb[idx]) {
struct sk_buff *skb = priv->echo_skb[idx];
- struct can_skb_priv *can_skb_priv = can_skb_prv(skb);
-
- if (frame_len_ptr)
- *frame_len_ptr = can_skb_priv->frame_len;
+ struct can_skb_ext *csx;
+
+ if (frame_len_ptr) {
+ csx = can_skb_ext_find(skb);
+ if (csx)
+ *frame_len_ptr = csx->can_framelen;
+ else
+ *frame_len_ptr = 0;
+ }
dev_kfree_skb_any(skb);
priv->echo_skb[idx] = NULL;
}
}
--
2.47.3
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH net-next V4 5/6] can: remove private CAN skb headroom infrastructure
2026-01-28 22:43 [PATCH net-next v4 0/6] move CAN skb headroom content to skb extensions Oliver Hartkopp via B4 Relay
` (3 preceding siblings ...)
2026-01-28 22:43 ` [PATCH net-next V4 4/6] can: move frame_len " Oliver Hartkopp via B4 Relay
@ 2026-01-28 22:43 ` Oliver Hartkopp via B4 Relay
2026-01-28 22:43 ` [PATCH net-next V4 6/6] can: gw: use can_gw_hops instead of sk_buff::csum_start Oliver Hartkopp via B4 Relay
2026-01-29 1:41 ` [PATCH net-next v4 0/6] move CAN skb headroom content to skb extensions Jakub Kicinski
6 siblings, 0 replies; 8+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-01-28 22:43 UTC (permalink / raw)
To: netdev, linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde
From: Oliver Hartkopp <socketcan@hartkopp.net>
This patch removes struct can_skb_priv which was stored at skb->head and
the can_skb_reserve() helper which was used to shift skb->head.
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
drivers/net/can/dev/skb.c | 31 +++++++++----------------------
include/linux/can/skb.h | 31 -------------------------------
net/can/bcm.c | 7 ++-----
net/can/isotp.c | 12 ++++--------
net/can/j1939/socket.c | 4 +---
net/can/j1939/transport.c | 7 ++-----
net/can/raw.c | 5 ++---
7 files changed, 20 insertions(+), 77 deletions(-)
diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index 408ee49abce145f49c7837ff30809bc3e42f8ab5..95fcdc1026f808656551c0253faafafd1018f48c 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -204,40 +204,33 @@ void can_free_echo_skb(struct net_device *dev, unsigned int idx,
}
}
EXPORT_SYMBOL_GPL(can_free_echo_skb);
/* fill common values for CAN sk_buffs */
-static void init_can_skb_reserve(struct sk_buff *skb)
+static void init_can_skb(struct sk_buff *skb)
{
skb->pkt_type = PACKET_BROADCAST;
skb->ip_summed = CHECKSUM_UNNECESSARY;
-
- skb_reset_mac_header(skb);
- skb_reset_network_header(skb);
- skb_reset_transport_header(skb);
-
- can_skb_reserve(skb);
}
struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf)
{
struct sk_buff *skb;
struct can_skb_ext *csx;
- skb = netdev_alloc_skb(dev, sizeof(struct can_skb_priv) +
- sizeof(struct can_frame));
+ skb = netdev_alloc_skb(dev, sizeof(struct can_frame));
if (unlikely(!skb))
goto out_error_cc;
csx = can_skb_ext_add(skb);
if (!csx) {
kfree_skb(skb);
goto out_error_cc;
}
skb->protocol = htons(ETH_P_CAN);
- init_can_skb_reserve(skb);
+ init_can_skb(skb);
csx->can_iif = dev->ifindex;
*cf = skb_put_zero(skb, sizeof(struct can_frame));
return skb;
@@ -253,23 +246,22 @@ struct sk_buff *alloc_canfd_skb(struct net_device *dev,
struct canfd_frame **cfd)
{
struct sk_buff *skb;
struct can_skb_ext *csx;
- skb = netdev_alloc_skb(dev, sizeof(struct can_skb_priv) +
- sizeof(struct canfd_frame));
+ skb = netdev_alloc_skb(dev, sizeof(struct canfd_frame));
if (unlikely(!skb))
goto out_error_fd;
csx = can_skb_ext_add(skb);
if (!csx) {
kfree_skb(skb);
goto out_error_fd;
}
skb->protocol = htons(ETH_P_CANFD);
- init_can_skb_reserve(skb);
+ init_can_skb(skb);
csx->can_iif = dev->ifindex;
*cfd = skb_put_zero(skb, sizeof(struct canfd_frame));
/* set CAN FD flag by default */
@@ -292,23 +284,22 @@ struct sk_buff *alloc_canxl_skb(struct net_device *dev,
struct can_skb_ext *csx;
if (data_len < CANXL_MIN_DLEN || data_len > CANXL_MAX_DLEN)
goto out_error_xl;
- skb = netdev_alloc_skb(dev, sizeof(struct can_skb_priv) +
- CANXL_HDR_SIZE + data_len);
+ skb = netdev_alloc_skb(dev, CANXL_HDR_SIZE + data_len);
if (unlikely(!skb))
goto out_error_xl;
csx = can_skb_ext_add(skb);
if (!csx) {
kfree_skb(skb);
goto out_error_xl;
}
skb->protocol = htons(ETH_P_CANXL);
- init_can_skb_reserve(skb);
+ init_can_skb(skb);
csx->can_iif = dev->ifindex;
*cxl = skb_put_zero(skb, CANXL_HDR_SIZE + data_len);
/* set CAN XL flag and length information by default */
@@ -338,18 +329,14 @@ struct sk_buff *alloc_can_err_skb(struct net_device *dev, struct can_frame **cf)
return skb;
}
EXPORT_SYMBOL_GPL(alloc_can_err_skb);
/* Check for outgoing skbs that have not been created by the CAN subsystem */
-static bool can_skb_headroom_valid(struct net_device *dev, struct sk_buff *skb)
+static bool can_skb_init_valid(struct net_device *dev, struct sk_buff *skb)
{
struct can_skb_ext *csx = can_skb_ext_find(skb);
- /* af_packet creates a headroom of HH_DATA_MOD bytes which is fine */
- if (WARN_ON_ONCE(skb_headroom(skb) < sizeof(struct can_skb_priv)))
- return false;
-
/* af_packet does not apply CAN skb specific settings */
if (skb->ip_summed == CHECKSUM_NONE || !csx) {
/* init CAN skb content */
if (!csx) {
csx = can_skb_ext_add(skb);
@@ -403,11 +390,11 @@ bool can_dropped_invalid_skb(struct net_device *dev, struct sk_buff *skb)
default:
goto inval_skb;
}
- if (!can_skb_headroom_valid(dev, skb))
+ if (!can_skb_init_valid(dev, skb))
goto inval_skb;
return false;
inval_skb:
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
index 68c0f24e69149707e38d657e821d6cbe129f7d1d..a70a0296707115c71e2f228d434cf4d76ffa9c06 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -36,41 +36,10 @@ struct sk_buff *alloc_canxl_skb(struct net_device *dev,
unsigned int data_len);
struct sk_buff *alloc_can_err_skb(struct net_device *dev,
struct can_frame **cf);
bool can_dropped_invalid_skb(struct net_device *dev, struct sk_buff *skb);
-/*
- * The struct can_skb_priv is used to transport additional information along
- * with the stored struct can(fd)_frame that can not be contained in existing
- * struct sk_buff elements.
- * N.B. that this information must not be modified in cloned CAN sk_buffs.
- * To modify the CAN frame content or the struct can_skb_priv content
- * skb_copy() needs to be used instead of skb_clone().
- */
-
-/**
- * struct can_skb_priv - private additional data inside CAN sk_buffs
- * @ifindex: ifindex of the first interface the CAN frame appeared on
- * @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;
- unsigned int frame_len;
- struct can_frame cf[];
-};
-
-static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
-{
- return (struct can_skb_priv *)(skb->head);
-}
-
-static inline void can_skb_reserve(struct sk_buff *skb)
-{
- skb_reserve(skb, sizeof(struct can_skb_priv));
-}
-
static inline struct can_skb_ext *can_skb_ext_add(struct sk_buff *skb)
{
struct can_skb_ext *csx = skb_ext_add(skb, SKB_EXT_CAN);
/* skb_ext_add() returns uninitialized space */
diff --git a/net/can/bcm.c b/net/can/bcm.c
index f102d17e86190b7a46f806870991136c0b416b0d..b7324e9c955b7f03a8f032676bbd89aa8e06bded 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -310,21 +310,20 @@ static void bcm_can_tx(struct bcm_op *op)
if (!dev) {
/* RFC: should this bcm_op remove itself here? */
return;
}
- skb = alloc_skb(op->cfsiz + sizeof(struct can_skb_priv), gfp_any());
+ skb = alloc_skb(op->cfsiz, gfp_any());
if (!skb)
goto out;
csx = can_skb_ext_add(skb);
if (!csx) {
kfree_skb(skb);
goto out;
}
- can_skb_reserve(skb);
csx->can_iif = dev->ifindex;
skb_put_data(skb, cf, op->cfsiz);
/* send with loopback */
@@ -1331,22 +1330,20 @@ static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk,
/* we need a real device to send frames */
if (!ifindex)
return -ENODEV;
- skb = alloc_skb(cfsiz + sizeof(struct can_skb_priv), GFP_KERNEL);
+ skb = alloc_skb(cfsiz, GFP_KERNEL);
if (!skb)
return -ENOMEM;
csx = can_skb_ext_add(skb);
if (!csx) {
kfree_skb(skb);
return -ENOMEM;
}
- can_skb_reserve(skb);
-
err = memcpy_from_msg(skb_put(skb, cfsiz), msg, cfsiz);
if (err < 0) {
kfree_skb(skb);
return err;
}
diff --git a/net/can/isotp.c b/net/can/isotp.c
index 01ceb3febbb757d2d727d90f987b9c47dd45973d..434986cc8fe55e206325da4aa25bef4f5a12e6c7 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -218,11 +218,11 @@ static int isotp_send_fc(struct sock *sk, int ae, u8 flowstatus)
struct can_skb_ext *csx;
struct canfd_frame *ncf;
struct isotp_sock *so = isotp_sk(sk);
int can_send_ret;
- nskb = alloc_skb(so->ll.mtu + sizeof(struct can_skb_priv), gfp_any());
+ nskb = alloc_skb(so->ll.mtu, gfp_any());
if (!nskb)
return 1;
csx = can_skb_ext_add(nskb);
if (!csx) {
@@ -234,13 +234,11 @@ static int isotp_send_fc(struct sock *sk, int ae, u8 flowstatus)
if (!dev) {
kfree_skb(nskb);
return 1;
}
- can_skb_reserve(nskb);
csx->can_iif = dev->ifindex;
-
nskb->dev = dev;
can_skb_set_owner(nskb, sk);
ncf = (struct canfd_frame *)nskb->data;
skb_put_zero(nskb, so->ll.mtu);
@@ -778,11 +776,11 @@ static void isotp_send_cframe(struct isotp_sock *so)
dev = dev_get_by_index(sock_net(sk), so->ifindex);
if (!dev)
return;
- skb = alloc_skb(so->ll.mtu + sizeof(struct can_skb_priv), GFP_ATOMIC);
+ skb = alloc_skb(so->ll.mtu, GFP_ATOMIC);
if (!skb) {
dev_put(dev);
return;
}
@@ -791,11 +789,10 @@ static void isotp_send_cframe(struct isotp_sock *so)
kfree_skb(skb);
dev_put(dev);
return;
}
- can_skb_reserve(skb);
csx->can_iif = dev->ifindex;
cf = (struct canfd_frame *)skb->data;
skb_put_zero(skb, so->ll.mtu);
@@ -1013,12 +1010,12 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
if (!dev) {
err = -ENXIO;
goto err_out_drop;
}
- skb = sock_alloc_send_skb(sk, so->ll.mtu + sizeof(struct can_skb_priv),
- msg->msg_flags & MSG_DONTWAIT, &err);
+ skb = sock_alloc_send_skb(sk, so->ll.mtu, msg->msg_flags & MSG_DONTWAIT,
+ &err);
if (!skb) {
dev_put(dev);
goto err_out_drop;
}
@@ -1027,11 +1024,10 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
kfree_skb(skb);
dev_put(dev);
goto err_out_drop;
}
- can_skb_reserve(skb);
csx->can_iif = dev->ifindex;
so->tx.len = size;
so->tx.idx = 0;
diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index f03bae79354e1cc7fa8655d92fe9f5b9db2d65bb..10014d95c31960cb535d88d50ca22483da2415e5 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -889,23 +889,21 @@ static struct sk_buff *j1939_sk_alloc_skb(struct net_device *ndev,
int ret;
skb = sock_alloc_send_skb(sk,
size +
sizeof(struct can_frame) -
- sizeof(((struct can_frame *)NULL)->data) +
- sizeof(struct can_skb_priv),
+ sizeof(((struct can_frame *)NULL)->data),
msg->msg_flags & MSG_DONTWAIT, &ret);
if (!skb)
goto failure;
csx = can_skb_ext_add(skb);
if (!csx) {
kfree_skb(skb);
goto failure;
}
- can_skb_reserve(skb);
csx->can_iif = ndev->ifindex;
skb_reserve(skb, offsetof(struct can_frame, data));
ret = memcpy_from_msg(skb_put(skb, size), msg, size);
if (ret < 0)
diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
index 96e02ad4a726fbc947cbae55687c0d6aa613d50e..e63cf79af1c4294407f602369e83ec2278a5707b 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -593,23 +593,21 @@ sk_buff *j1939_tp_tx_dat_new(struct j1939_priv *priv,
{
struct sk_buff *skb;
struct can_skb_ext *csx;
struct j1939_sk_buff_cb *skcb;
- skb = alloc_skb(sizeof(struct can_frame) + sizeof(struct can_skb_priv),
- GFP_ATOMIC);
+ skb = alloc_skb(sizeof(struct can_frame), GFP_ATOMIC);
if (unlikely(!skb))
return ERR_PTR(-ENOMEM);
csx = can_skb_ext_add(skb);
if (!csx) {
kfree_skb(skb);
return ERR_PTR(-ENOMEM);
}
skb->dev = priv->ndev;
- can_skb_reserve(skb);
csx->can_iif = priv->ndev->ifindex;
/* 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 */
@@ -1535,22 +1533,21 @@ j1939_session *j1939_session_fresh_new(struct j1939_priv *priv,
struct sk_buff *skb;
struct can_skb_ext *csx;
struct j1939_sk_buff_cb *skcb;
struct j1939_session *session;
- skb = alloc_skb(size + sizeof(struct can_skb_priv), GFP_ATOMIC);
+ skb = alloc_skb(size, GFP_ATOMIC);
if (unlikely(!skb))
return NULL;
csx = can_skb_ext_add(skb);
if (!csx) {
kfree_skb(skb);
return NULL;
}
skb->dev = priv->ndev;
- can_skb_reserve(skb);
csx->can_iif = priv->ndev->ifindex;
skcb = j1939_skb_to_cb(skb);
memcpy(skcb, rel_skcb, sizeof(*skcb));
session = j1939_session_new(priv, skb, size);
diff --git a/net/can/raw.c b/net/can/raw.c
index 7c89962ec913396e7948c0f6d2ad80c8f66a8985..d33ce436018ff3586b572242674d4d31b940c95c 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -951,22 +951,21 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
if (can_cap_enabled(dev, CAN_CAP_RO)) {
err = -EACCES;
goto put_dev;
}
- skb = sock_alloc_send_skb(sk, size + sizeof(struct can_skb_priv),
- msg->msg_flags & MSG_DONTWAIT, &err);
+ skb = sock_alloc_send_skb(sk, size, msg->msg_flags & MSG_DONTWAIT,
+ &err);
if (!skb)
goto put_dev;
csx = can_skb_ext_add(skb);
if (!csx) {
kfree_skb(skb);
goto put_dev;
}
- can_skb_reserve(skb);
csx->can_iif = dev->ifindex;
/* fill the skb before testing for valid CAN frames */
err = memcpy_from_msg(skb_put(skb, size), msg, size);
if (err < 0)
--
2.47.3
^ permalink raw reply related [flat|nested] 8+ messages in thread* [PATCH net-next V4 6/6] can: gw: use can_gw_hops instead of sk_buff::csum_start
2026-01-28 22:43 [PATCH net-next v4 0/6] move CAN skb headroom content to skb extensions Oliver Hartkopp via B4 Relay
` (4 preceding siblings ...)
2026-01-28 22:43 ` [PATCH net-next V4 5/6] can: remove private CAN skb headroom infrastructure Oliver Hartkopp via B4 Relay
@ 2026-01-28 22:43 ` Oliver Hartkopp via B4 Relay
2026-01-29 1:41 ` [PATCH net-next v4 0/6] move CAN skb headroom content to skb extensions Jakub Kicinski
6 siblings, 0 replies; 8+ messages in thread
From: Oliver Hartkopp via B4 Relay @ 2026-01-28 22:43 UTC (permalink / raw)
To: netdev, linux-can; +Cc: Oliver Hartkopp, Marc Kleine-Budde
From: Oliver Hartkopp <socketcan@hartkopp.net>
As CAN skbs don't use IP checksums the skb->csum_start variable was used to
store the can-gw CAN frame time-to-live counter together with
skb->ip_summed set to CHECKSUM_UNNECESSARY.
Remove the 'hack' using the skb->csum_start variable and move the content
to can_skb_ext::can_gw_hops of the CAN skb extensions.
The module parameter 'max_hops' has been reduced to a single byte to fit
can_skb_ext::can_gw_hops as the maximum value to be stored is 6.
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
net/can/gw.c | 23 ++++++-----------------
1 file changed, 6 insertions(+), 17 deletions(-)
diff --git a/net/can/gw.c b/net/can/gw.c
index ad89a1913b3422f77fdf91b5552380282b2db09a..2c134c9e5159d659b83881c51b3814debbc5f9c8 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -69,12 +69,12 @@ MODULE_ALIAS(CAN_GW_NAME);
#define CGW_MIN_HOPS 1
#define CGW_MAX_HOPS 6
#define CGW_DEFAULT_HOPS 1
-static unsigned int max_hops __read_mostly = CGW_DEFAULT_HOPS;
-module_param(max_hops, uint, 0444);
+static unsigned char max_hops __read_mostly = CGW_DEFAULT_HOPS;
+module_param(max_hops, byte, 0444);
MODULE_PARM_DESC(max_hops,
"maximum " CAN_GW_NAME " routing hops for CAN frames "
"(valid values: " __stringify(CGW_MIN_HOPS) "-"
__stringify(CGW_MAX_HOPS) " hops, "
"default: " __stringify(CGW_DEFAULT_HOPS) ")");
@@ -478,23 +478,12 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
return;
/* Do not handle CAN frames routed more than 'max_hops' times.
* In general we should never catch this delimiter which is intended
* to cover a misconfiguration protection (e.g. circular CAN routes).
- *
- * The Controller Area Network controllers only accept CAN frames with
- * correct CRCs - which are not visible in the controller registers.
- * According to skbuff.h documentation the csum_start element for IP
- * checksums is undefined/unused when ip_summed == CHECKSUM_UNNECESSARY.
- * Only CAN skbs can be processed here which already have this property.
*/
-
-#define cgw_hops(skb) ((skb)->csum_start)
-
- BUG_ON(skb->ip_summed != CHECKSUM_UNNECESSARY);
-
- if (cgw_hops(skb) >= max_hops) {
+ if (csx->can_gw_hops >= max_hops) {
/* indicate deleted frames due to misconfiguration */
gwj->deleted_frames++;
return;
}
@@ -530,15 +519,15 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
gwj->dropped_frames++;
return;
}
/* put the incremented hop counter in the cloned skb */
- cgw_hops(nskb) = cgw_hops(skb) + 1;
+ ncsx->can_gw_hops = csx->can_gw_hops + 1;
/* first processing of this CAN frame -> adjust to private hop limit */
- if (gwj->limit_hops && cgw_hops(nskb) == 1)
- cgw_hops(nskb) = max_hops - gwj->limit_hops + 1;
+ if (gwj->limit_hops && ncsx->can_gw_hops == 1)
+ ncsx->can_gw_hops = max_hops - gwj->limit_hops + 1;
nskb->dev = gwj->dst.dev;
/* pointer to modifiable CAN frame */
cf = (struct canfd_frame *)nskb->data;
--
2.47.3
^ permalink raw reply related [flat|nested] 8+ messages in thread* Re: [PATCH net-next v4 0/6] move CAN skb headroom content to skb extensions
2026-01-28 22:43 [PATCH net-next v4 0/6] move CAN skb headroom content to skb extensions Oliver Hartkopp via B4 Relay
` (5 preceding siblings ...)
2026-01-28 22:43 ` [PATCH net-next V4 6/6] can: gw: use can_gw_hops instead of sk_buff::csum_start Oliver Hartkopp via B4 Relay
@ 2026-01-29 1:41 ` Jakub Kicinski
6 siblings, 0 replies; 8+ messages in thread
From: Jakub Kicinski @ 2026-01-29 1:41 UTC (permalink / raw)
To: Oliver Hartkopp via B4 Relay
Cc: socketcan, netdev, linux-can, Marc Kleine-Budde
On Wed, 28 Jan 2026 23:43:39 +0100 Oliver Hartkopp via B4 Relay wrote:
> CAN bus related skbuffs (ETH_P_CAN/ETH_P_CANFD/ETH_P_CANXL) simply contain
> CAN frame structs for CAN CC/FD/XL of skb->len length at skb->data. Those
> CAN skbs do not have network/mac/transport headers nor other such
> references for encapsulated protocols like ethernet/IP protocols.
>
> To store data for CAN specific use-cases all CAN bus related skbuffs are
> created with a 16 byte private skb headroom (struct can_skb_priv). Using
> the skb headroom and accessing skb->head for this private data led to
> several problems in the past likely due to "The struct can_skb_priv
> business is highly unconventional for the networking stack." [1]
>
> This patch set aims to remove the unconventional skb headroom usage for CAN
> bus related skbuffs and use the common skb extensions instead.
If you're targeting netdev trees please comply with our community
guidelines:
https://www.kernel.org/doc/html/next/process/maintainer-netdev.html
--
pv-bot: 24h
^ permalink raw reply [flat|nested] 8+ messages in thread