* [can-next v2 1/5] can: use skb hash instead of private variable in headroom
2026-01-17 13:28 [can-next v2 0/5] can: remove private skb headroom infrastructure Oliver Hartkopp
@ 2026-01-17 13:28 ` Oliver Hartkopp
2026-01-17 13:28 ` [can-next v2 2/5] can: move can_iif from private headroom to struct sk_buff Oliver Hartkopp
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Oliver Hartkopp @ 2026-01-17 13:28 UTC (permalink / raw)
To: linux-can, Marc Kleine-Budde, Jakub Kicinski, Paolo Abeni
Cc: Vincent Mailhol, netdev, Eric Dumazet, Simon Horman,
Oleksij Rempel, davem, Oliver Hartkopp
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. The skb->hash is a value used for RPS to identify skbs.
We use it as intended.
Patch 1/5 to remove the private CAN bus skb headroom infrastructure.
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
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 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 12293363413c..6ebc6abb5987 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] 6+ messages in thread* [can-next v2 2/5] can: move can_iif from private headroom to struct sk_buff
2026-01-17 13:28 [can-next v2 0/5] can: remove private skb headroom infrastructure Oliver Hartkopp
2026-01-17 13:28 ` [can-next v2 1/5] can: use skb hash instead of private variable in headroom Oliver Hartkopp
@ 2026-01-17 13:28 ` Oliver Hartkopp
2026-01-17 13:28 ` [can-next v2 3/5] can: move frame length " Oliver Hartkopp
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Oliver Hartkopp @ 2026-01-17 13:28 UTC (permalink / raw)
To: linux-can, Marc Kleine-Budde, Jakub Kicinski, Paolo Abeni
Cc: Vincent Mailhol, netdev, Eric Dumazet, Simon Horman,
Oleksij Rempel, davem, Oliver Hartkopp
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.
can_iif is the first variable moved into the formerly unused space in CAN
skbs (the inner protocol space for ethernet/IP encapsulation).
The skb->encapsulation flag remains false in CAN skbs so that the
ethernet/IP encapsulation (tunnel) data is tagged as unused/invalid in the
case the skb is accidentally routed to non-CAN targets (netdev/netlayer).
To make sure the CAN skb was not crafted e.g. by PF_PACKET or it was
modified by other networking components, the received CAN skb is checked
in can_rcv for skb->encapsulation to be false.
Patch 2/5 to remove the private CAN bus skb headroom infrastructure.
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
drivers/net/can/dev/skb.c | 8 ++++----
include/linux/can/skb.h | 2 --
include/linux/skbuff.h | 23 +++++++++++++++++------
net/can/af_can.c | 21 ++++++++++++---------
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 +-
10 files changed, 43 insertions(+), 31 deletions(-)
diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index 0da615afa04d..b54474687aaa 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -216,11 +216,11 @@ struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf)
return NULL;
}
skb->protocol = htons(ETH_P_CAN);
init_can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ skb->can_iif = dev->ifindex;
*cf = skb_put_zero(skb, sizeof(struct can_frame));
return skb;
}
@@ -239,11 +239,11 @@ struct sk_buff *alloc_canfd_skb(struct net_device *dev,
return NULL;
}
skb->protocol = htons(ETH_P_CANFD);
init_can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ skb->can_iif = dev->ifindex;
*cfd = skb_put_zero(skb, sizeof(struct canfd_frame));
/* set CAN FD flag by default */
(*cfd)->flags = CANFD_FDF;
@@ -266,11 +266,11 @@ struct sk_buff *alloc_canxl_skb(struct net_device *dev,
if (unlikely(!skb))
goto out_error;
skb->protocol = htons(ETH_P_CANXL);
init_can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ skb->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;
@@ -308,11 +308,11 @@ static bool can_skb_headroom_valid(struct net_device *dev, struct sk_buff *skb)
return false;
/* af_packet does not apply CAN skb specific settings */
if (skb->ip_summed == CHECKSUM_NONE) {
/* init headroom */
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ skb->can_iif = dev->ifindex;
skb->ip_summed = CHECKSUM_UNNECESSARY;
/* perform proper loopback on capable devices */
if (dev->flags & IFF_ECHO)
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
index 869ea574a40a..679ea4c851ac 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -46,16 +46,14 @@ bool can_dropped_invalid_skb(struct net_device *dev, struct sk_buff *skb);
* 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)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 86737076101d..ab415de74466 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -861,10 +861,11 @@ enum skb_tstamp_type {
* @reserved_tailroom: (aka @mark) number of bytes of free space available
* at the tail of an sk_buff
* @vlan_all: vlan fields (proto & tci)
* @vlan_proto: vlan encapsulation protocol
* @vlan_tci: vlan tag control information
+ * @can_iif: ifindex of the first interface the CAN frame appeared on
* @inner_protocol: Protocol (encapsulation)
* @inner_ipproto: (aka @inner_protocol) stores ipproto when
* skb->inner_protocol_type == ENCAP_TYPE_IPPROTO;
* @inner_transport_header: Inner transport layer header (encapsulation)
* @inner_network_header: Network layer header (encapsulation)
@@ -1067,17 +1068,27 @@ struct sk_buff {
__u32 mark;
__u32 reserved_tailroom;
};
union {
- __be16 inner_protocol;
- __u8 inner_ipproto;
- };
+ /* inner protocol data for eth/ip encapsulation */
+ struct {
+ union {
+ __be16 inner_protocol;
+ __u8 inner_ipproto;
+ };
- __u16 inner_transport_header;
- __u16 inner_network_header;
- __u16 inner_mac_header;
+ __u16 inner_transport_header;
+ __u16 inner_network_header;
+ __u16 inner_mac_header;
+ };
+
+ /* space for protocols without protocol/header encapsulation */
+ struct {
+ int can_iif;
+ };
+ };
__be16 protocol;
__u16 transport_header;
__u16 network_header;
__u16 mac_header;
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 70659987ef4d..37be7e4921c8 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -685,13 +685,14 @@ 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))) {
- pr_warn_once("PF_CAN: dropped non conform CAN skbuff: dev type %d, len %d\n",
- dev->type, skb->len);
+ if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) ||
+ !can_is_can_skb(skb) || skb->encapsulation)) {
+ pr_warn_once("PF_CAN: dropped non conform CAN skbuff: dev type %d, len %d, encap %d\n",
+ dev->type, skb->len, skb->encapsulation);
kfree_skb_reason(skb, SKB_DROP_REASON_CAN_RX_INVALID_FRAME);
return NET_RX_DROP;
}
@@ -700,13 +701,14 @@ 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))) {
- pr_warn_once("PF_CAN: dropped non conform CAN FD skbuff: dev type %d, len %d\n",
- dev->type, skb->len);
+ if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) ||
+ !can_is_canfd_skb(skb) || skb->encapsulation)) {
+ pr_warn_once("PF_CAN: dropped non conform CAN FD skbuff: dev type %d, len %d, encap %d\n",
+ dev->type, skb->len, skb->encapsulation);
kfree_skb_reason(skb, SKB_DROP_REASON_CANFD_RX_INVALID_FRAME);
return NET_RX_DROP;
}
@@ -715,13 +717,14 @@ 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))) {
- pr_warn_once("PF_CAN: dropped non conform CAN XL skbuff: dev type %d, len %d\n",
- dev->type, skb->len);
+ if (unlikely(dev->type != ARPHRD_CAN || !can_get_ml_priv(dev) ||
+ !can_is_canxl_skb(skb) || skb->encapsulation)) {
+ pr_warn_once("PF_CAN: dropped non conform CAN XL skbuff: dev type %d, len %d, encap %d\n",
+ dev->type, skb->len, skb->encapsulation);
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 8ed60f18c2ea..a8867e7b77d2 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -313,11 +313,11 @@ 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;
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ skb->can_iif = dev->ifindex;
skb_put_data(skb, cf, op->cfsiz);
/* send with loopback */
skb->dev = dev;
@@ -1340,11 +1340,11 @@ 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;
+ skb->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 55eccb1c7620..74d771a3540c 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -497,11 +497,11 @@ 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)
+ skb->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 4bb60b8f9b96..e7623e5736ca 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -227,11 +227,11 @@ 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;
+ nskb->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);
@@ -776,11 +776,11 @@ static void isotp_send_cframe(struct isotp_sock *so)
dev_put(dev);
return;
}
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ skb->can_iif = dev->ifindex;
cf = (struct canfd_frame *)skb->data;
skb_put_zero(skb, so->ll.mtu);
/* create consecutive frame */
@@ -1004,11 +1004,11 @@ 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;
+ skb->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 1589e8ca634e..d2642d86b4a9 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -894,11 +894,11 @@ static struct sk_buff *j1939_sk_alloc_skb(struct net_device *ndev,
msg->msg_flags & MSG_DONTWAIT, &ret);
if (!skb)
goto failure;
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = ndev->ifindex;
+ skb->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 d4be13422f50..8a767b75194f 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -598,11 +598,11 @@ sk_buff *j1939_tp_tx_dat_new(struct j1939_priv *priv,
if (unlikely(!skb))
return ERR_PTR(-ENOMEM);
skb->dev = priv->ndev;
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = priv->ndev->ifindex;
+ skb->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));
@@ -1532,11 +1532,11 @@ j1939_session *j1939_session_fresh_new(struct j1939_priv *priv,
if (unlikely(!skb))
return NULL;
skb->dev = priv->ndev;
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = priv->ndev->ifindex;
+ skb->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 6ebc6abb5987..b3198e423954 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -955,11 +955,11 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
msg->msg_flags & MSG_DONTWAIT, &err);
if (!skb)
goto put_dev;
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ skb->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] 6+ messages in thread* [can-next v2 3/5] can: move frame length from private headroom to struct sk_buff
2026-01-17 13:28 [can-next v2 0/5] can: remove private skb headroom infrastructure Oliver Hartkopp
2026-01-17 13:28 ` [can-next v2 1/5] can: use skb hash instead of private variable in headroom Oliver Hartkopp
2026-01-17 13:28 ` [can-next v2 2/5] can: move can_iif from private headroom to struct sk_buff Oliver Hartkopp
@ 2026-01-17 13:28 ` Oliver Hartkopp
2026-01-17 13:28 ` [can-next v2 4/5] can: remove private skb headroom infrastructure Oliver Hartkopp
2026-01-17 13:28 ` [can-next v2 5/5] can: gw: use new can_gw_hops variable instead of re-using csum_start Oliver Hartkopp
4 siblings, 0 replies; 6+ messages in thread
From: Oliver Hartkopp @ 2026-01-17 13:28 UTC (permalink / raw)
To: linux-can, Marc Kleine-Budde, Jakub Kicinski, Paolo Abeni
Cc: Vincent Mailhol, netdev, Eric Dumazet, Simon Horman,
Oleksij Rempel, davem, Oliver Hartkopp
The can_skb_priv::frame_len variable is used to cache a previous
calculated CAN frame length to be passed to BQL queueing disciplines.
To maintain a compilable migration step the frame_len value in struct
can_skb_priv is only renamed but not removed.
Patch 3/5 to remove the private CAN bus skb headroom infrastructure.
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
drivers/net/can/dev/skb.c | 8 +++-----
include/linux/can/skb.h | 3 +--
include/linux/skbuff.h | 2 ++
3 files changed, 6 insertions(+), 7 deletions(-)
diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index b54474687aaa..ffd71ad0252a 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -72,11 +72,11 @@ 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;
+ skb->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);
@@ -109,20 +109,19 @@ __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);
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;
+ *frame_len_ptr = skb->can_framelen;
priv->echo_skb[idx] = NULL;
if (skb->pkt_type == PACKET_LOOPBACK) {
skb->pkt_type = PACKET_BROADCAST;
@@ -178,14 +177,13 @@ 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;
+ *frame_len_ptr = skb->can_framelen;
dev_kfree_skb_any(skb);
priv->echo_skb[idx] = NULL;
}
}
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
index 679ea4c851ac..eba9557e2c1e 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -46,15 +46,14 @@ bool can_dropped_invalid_skb(struct net_device *dev, struct sk_buff *skb);
* skb_copy() needs to be used instead of skb_clone().
*/
/**
* struct can_skb_priv - private additional data inside CAN sk_buffs
- * @frame_len: length of CAN frame in data link layer
* @cf: align to the following CAN frame at skb->data
*/
struct can_skb_priv {
- unsigned int frame_len;
+ unsigned int frame_len_to_be_removed;
struct can_frame cf[];
};
static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
{
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index ab415de74466..eccd0b3898a0 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -862,10 +862,11 @@ enum skb_tstamp_type {
* at the tail of an sk_buff
* @vlan_all: vlan fields (proto & tci)
* @vlan_proto: vlan encapsulation protocol
* @vlan_tci: vlan tag control information
* @can_iif: ifindex of the first interface the CAN frame appeared on
+ * @can_framelen: cached echo CAN frame length for bql
* @inner_protocol: Protocol (encapsulation)
* @inner_ipproto: (aka @inner_protocol) stores ipproto when
* skb->inner_protocol_type == ENCAP_TYPE_IPPROTO;
* @inner_transport_header: Inner transport layer header (encapsulation)
* @inner_network_header: Network layer header (encapsulation)
@@ -1083,10 +1084,11 @@ struct sk_buff {
};
/* space for protocols without protocol/header encapsulation */
struct {
int can_iif;
+ __u16 can_framelen;
};
};
__be16 protocol;
__u16 transport_header;
--
2.47.3
^ permalink raw reply related [flat|nested] 6+ messages in thread* [can-next v2 4/5] can: remove private skb headroom infrastructure
2026-01-17 13:28 [can-next v2 0/5] can: remove private skb headroom infrastructure Oliver Hartkopp
` (2 preceding siblings ...)
2026-01-17 13:28 ` [can-next v2 3/5] can: move frame length " Oliver Hartkopp
@ 2026-01-17 13:28 ` Oliver Hartkopp
2026-01-17 13:28 ` [can-next v2 5/5] can: gw: use new can_gw_hops variable instead of re-using csum_start Oliver Hartkopp
4 siblings, 0 replies; 6+ messages in thread
From: Oliver Hartkopp @ 2026-01-17 13:28 UTC (permalink / raw)
To: linux-can, Marc Kleine-Budde, Jakub Kicinski, Paolo Abeni
Cc: Vincent Mailhol, netdev, Eric Dumazet, Simon Horman,
Oleksij Rempel, davem, Oliver Hartkopp
This patch removes the now-empty private CAN skb headroom infrastructure.
Patch 4/5 to remove the private CAN bus skb headroom infrastructure.
Tested-by: Oleksij Rempel <o.rempel@pengutronix.de> # for j1939
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de> # for j1939
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
drivers/net/can/dev/skb.c | 27 +++++++++++----------------
include/linux/can/skb.h | 28 ----------------------------
net/can/bcm.c | 7 ++-----
net/can/isotp.c | 9 +++------
net/can/j1939/socket.c | 4 +---
net/can/j1939/transport.c | 7 ++-----
net/can/raw.c | 5 ++---
7 files changed, 21 insertions(+), 66 deletions(-)
diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index ffd71ad0252a..2445f6c9f9d4 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -188,36 +188,33 @@ 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;
- 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)) {
*cf = NULL;
return NULL;
}
skb->protocol = htons(ETH_P_CAN);
- init_can_skb_reserve(skb);
+ init_can_skb(skb);
skb->can_iif = dev->ifindex;
*cf = skb_put_zero(skb, sizeof(struct can_frame));
return skb;
@@ -227,20 +224,19 @@ EXPORT_SYMBOL_GPL(alloc_can_skb);
struct sk_buff *alloc_canfd_skb(struct net_device *dev,
struct canfd_frame **cfd)
{
struct sk_buff *skb;
- 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)) {
*cfd = NULL;
return NULL;
}
skb->protocol = htons(ETH_P_CANFD);
- init_can_skb_reserve(skb);
+ init_can_skb(skb);
skb->can_iif = dev->ifindex;
*cfd = skb_put_zero(skb, sizeof(struct canfd_frame));
/* set CAN FD flag by default */
@@ -257,17 +253,16 @@ struct sk_buff *alloc_canxl_skb(struct net_device *dev,
struct sk_buff *skb;
if (data_len < CANXL_MIN_DLEN || data_len > CANXL_MAX_DLEN)
goto out_error;
- 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;
skb->protocol = htons(ETH_P_CANXL);
- init_can_skb_reserve(skb);
+ init_can_skb(skb);
skb->can_iif = dev->ifindex;
*cxl = skb_put_zero(skb, CANXL_HDR_SIZE + data_len);
/* set CAN XL flag and length information by default */
@@ -297,14 +292,14 @@ 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)
{
- /* 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)))
+ /* skb with inner protocols do not contain CAN content */
+ if (skb->encapsulation)
return false;
/* af_packet does not apply CAN skb specific settings */
if (skb->ip_summed == CHECKSUM_NONE) {
/* init headroom */
@@ -355,11 +350,11 @@ 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 eba9557e2c1e..c5d617a0f9be 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -35,38 +35,10 @@ 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
- * @cf: align to the following CAN frame at skb->data
- */
-struct can_skb_priv {
- unsigned int frame_len_to_be_removed;
- 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 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/net/can/bcm.c b/net/can/bcm.c
index a8867e7b77d2..99dac9af2b86 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -308,15 +308,14 @@ 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;
- can_skb_reserve(skb);
skb->can_iif = dev->ifindex;
skb_put_data(skb, cf, op->cfsiz);
/* send with loopback */
@@ -1322,16 +1321,14 @@ 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;
- 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 e7623e5736ca..3486d558b3c0 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -216,21 +216,20 @@ static int isotp_send_fc(struct sock *sk, int ae, u8 flowstatus)
struct sk_buff *nskb;
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;
dev = dev_get_by_index(sock_net(sk), so->ifindex);
if (!dev) {
kfree_skb(nskb);
return 1;
}
- can_skb_reserve(nskb);
nskb->can_iif = dev->ifindex;
nskb->dev = dev;
can_skb_set_owner(nskb, sk);
ncf = (struct canfd_frame *)nskb->data;
@@ -769,17 +768,16 @@ 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;
}
- can_skb_reserve(skb);
skb->can_iif = dev->ifindex;
cf = (struct canfd_frame *)skb->data;
skb_put_zero(skb, so->ll.mtu);
@@ -996,18 +994,17 @@ 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),
+ skb = sock_alloc_send_skb(sk, so->ll.mtu,
msg->msg_flags & MSG_DONTWAIT, &err);
if (!skb) {
dev_put(dev);
goto err_out_drop;
}
- can_skb_reserve(skb);
skb->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 d2642d86b4a9..f7d0b3c4aeb4 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -887,17 +887,15 @@ 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;
- can_skb_reserve(skb);
skb->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 8a767b75194f..53308755a0c2 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -591,17 +591,15 @@ sk_buff *j1939_tp_tx_dat_new(struct j1939_priv *priv,
bool swap_src_dst)
{
struct sk_buff *skb;
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);
skb->dev = priv->ndev;
- can_skb_reserve(skb);
skb->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 */
@@ -1526,16 +1524,15 @@ j1939_session *j1939_session_fresh_new(struct j1939_priv *priv,
{
struct sk_buff *skb;
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;
skb->dev = priv->ndev;
- can_skb_reserve(skb);
skb->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 b3198e423954..01ef08523030 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -949,16 +949,15 @@ 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;
- can_skb_reserve(skb);
skb->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] 6+ messages in thread* [can-next v2 5/5] can: gw: use new can_gw_hops variable instead of re-using csum_start
2026-01-17 13:28 [can-next v2 0/5] can: remove private skb headroom infrastructure Oliver Hartkopp
` (3 preceding siblings ...)
2026-01-17 13:28 ` [can-next v2 4/5] can: remove private skb headroom infrastructure Oliver Hartkopp
@ 2026-01-17 13:28 ` Oliver Hartkopp
4 siblings, 0 replies; 6+ messages in thread
From: Oliver Hartkopp @ 2026-01-17 13:28 UTC (permalink / raw)
To: linux-can, Marc Kleine-Budde, Jakub Kicinski, Paolo Abeni
Cc: Vincent Mailhol, netdev, Eric Dumazet, Simon Horman,
Oleksij Rempel, davem, Oliver Hartkopp
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.
As we still have 16 bit left in the inner protocol space for ethernet/IP
encapsulation the time-to-live counter is moved there to remove the 'hack'
using the skb->csum_start variable. This patch solves the problem that the
CAN information was scattered in different places in the skb.
Patch 5/5 to remove the private CAN bus skb headroom infrastructure.
Tested-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
include/linux/skbuff.h | 2 ++
net/can/gw.c | 23 ++++++-----------------
2 files changed, 8 insertions(+), 17 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index eccd0b3898a0..7ef0b8e24a30 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -863,10 +863,11 @@ enum skb_tstamp_type {
* @vlan_all: vlan fields (proto & tci)
* @vlan_proto: vlan encapsulation protocol
* @vlan_tci: vlan tag control information
* @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
* @inner_protocol: Protocol (encapsulation)
* @inner_ipproto: (aka @inner_protocol) stores ipproto when
* skb->inner_protocol_type == ENCAP_TYPE_IPPROTO;
* @inner_transport_header: Inner transport layer header (encapsulation)
* @inner_network_header: Network layer header (encapsulation)
@@ -1085,10 +1086,11 @@ struct sk_buff {
/* space for protocols without protocol/header encapsulation */
struct {
int can_iif;
__u16 can_framelen;
+ __u16 can_gw_hops;
};
};
__be16 protocol;
__u16 transport_header;
diff --git a/net/can/gw.c b/net/can/gw.c
index 74d771a3540c..fca0566963a2 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -68,12 +68,12 @@ 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 short max_hops __read_mostly = CGW_DEFAULT_HOPS;
+module_param(max_hops, ushort, 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) ")");
@@ -472,23 +472,12 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
}
/* 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 (skb->can_gw_hops >= max_hops) {
/* indicate deleted frames due to misconfiguration */
gwj->deleted_frames++;
return;
}
@@ -517,15 +506,15 @@ 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;
+ nskb->can_gw_hops = skb->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 && nskb->can_gw_hops == 1)
+ nskb->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
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