On Tue. 2 Aug. 2022 at 04:02, Oliver Hartkopp <socketcan@xxxxxxxxxxxx> wrote:
> To simplify the testing in user space all struct canfd_frame's provided by
> the CAN subsystem of the Linux kernel now have the CANFD_FDF flag set in
> canfd_frame::flags.
>
> NB: Handcrafted ETH_P_CANFD frames introduced via PF_PACKET socket might
> not set this bit correctly. During the check for sufficient headroom in
> PF_PACKET sk_buffs the uninitialized CAN sk_buff data structures are filled.
> In the case of a CAN FD frame the CANFD_FDF flag is set accordingly.
>
> As the CAN frame content is already zero initialized in alloc_canfd_skb()
> the obsolete initialization of cf->flags in the CTU CAN FD driver has been
> removed as it would overwrite the already set CANFD_FDF flag.
>
> Signed-off-by: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
> ---
> drivers/net/can/ctucanfd/ctucanfd_base.c | 1 -
> drivers/net/can/dev/skb.c | 11 +++++++++++
> include/uapi/linux/can.h | 4 ++--
> net/can/af_can.c | 5 +++++
> 4 files changed, 18 insertions(+), 3 deletions(-)
Would it be relevant to also set the flag when the skb is cloned?
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
index 182749e858b3..24de0bb7092e 100644
--- a/include/linux/can/skb.h
+++ b/include/linux/can/skb.h
@@ -85,6 +85,7 @@ static inline void can_skb_set_owner(struct sk_buff
*skb, struct sock *sk)
static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb)
{
struct sk_buff *nskb;
+ struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
nskb = skb_clone(skb, GFP_ATOMIC);
if (unlikely(!nskb)) {
@@ -92,6 +93,9 @@ static inline struct sk_buff
*can_create_echo_skb(struct sk_buff *skb)
return NULL;
}
+ if (can_is_canfd_skb(skb))
+ cfd->flags |= CANFD_FDF;
+
can_skb_set_owner(nskb, skb->sk);
consume_skb(skb);
return nskb;
> diff --git a/drivers/net/can/ctucanfd/ctucanfd_base.c b/drivers/net/can/ctucanfd/ctucanfd_base.c
> index 3c18d028bd8c..c4026712ab7d 100644
> --- a/drivers/net/can/ctucanfd/ctucanfd_base.c
> +++ b/drivers/net/can/ctucanfd/ctucanfd_base.c
> @@ -655,11 +655,10 @@ static void ctucan_read_rx_frame(struct ctucan_priv *priv, struct canfd_frame *c
> cf->can_id = (idw & CAN_EFF_MASK) | CAN_EFF_FLAG;
> else
> cf->can_id = (idw >> 18) & CAN_SFF_MASK;
>
> /* BRS, ESI, RTR Flags */
> - cf->flags = 0;
> if (FIELD_GET(REG_FRAME_FORMAT_W_FDF, ffw)) {
> if (FIELD_GET(REG_FRAME_FORMAT_W_BRS, ffw))
> cf->flags |= CANFD_BRS;
> if (FIELD_GET(REG_FRAME_FORMAT_W_ESI_RSV, ffw))
> cf->flags |= CANFD_ESI;
> diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
> index b896e1ce3b47..adb413bdd734 100644
> --- a/drivers/net/can/dev/skb.c
> +++ b/drivers/net/can/dev/skb.c
> @@ -242,10 +242,13 @@ struct sk_buff *alloc_canfd_skb(struct net_device *dev,
> can_skb_prv(skb)->ifindex = dev->ifindex;
> can_skb_prv(skb)->skbcnt = 0;
>
> *cfd = skb_put_zero(skb, sizeof(struct canfd_frame));
>
> + /* set CAN FD flag by default */
> + (*cfd)->flags = CANFD_FDF;
> +
> return skb;
> }
> EXPORT_SYMBOL_GPL(alloc_canfd_skb);
>
> struct sk_buff *alloc_can_err_skb(struct net_device *dev, struct can_frame **cf)
> @@ -285,10 +288,18 @@ static bool can_skb_headroom_valid(struct net_device *dev, struct sk_buff *skb)
> skb->pkt_type = PACKET_HOST;
>
> skb_reset_mac_header(skb);
> skb_reset_network_header(skb);
> skb_reset_transport_header(skb);
> +
> + /* set CANFD_FDF flag for CAN FD frames */
> + if (can_is_canfd_skb(skb)) {
> + struct canfd_frame *cfd;
> +
> + cfd = (struct canfd_frame *)skb->data;
> + cfd->flags |= CANFD_FDF;
> + }
> }
>
> return true;
> }
>
> diff --git a/include/uapi/linux/can.h b/include/uapi/linux/can.h
> index 90801ada2bbe..7b23eeeb3273 100644
> --- a/include/uapi/linux/can.h
> +++ b/include/uapi/linux/can.h
> @@ -139,12 +139,12 @@ struct can_frame {
> * The struct can_frame and struct canfd_frame intentionally share the same
> * layout to be able to write CAN frame content into a CAN FD frame structure.
> * When this is done the former differentiation via CAN_MTU / CANFD_MTU gets
> * lost. CANFD_FDF allows programmers to mark CAN FD frames in the case of
> * using struct canfd_frame for mixed CAN / CAN FD content (dual use).
> - * N.B. the Kernel APIs do NOT provide mixed CAN / CAN FD content inside of
> - * struct canfd_frame therefore the CANFD_FDF flag is disregarded by Linux.
> + * Since the introduction of CAN XL the CANFD_FDF flag is set in all CAN FD
> + * frame structures provided by the CAN subsystem of the Linux kernel.
> */
> #define CANFD_BRS 0x01 /* bit rate switch (second bitrate for payload data) */
> #define CANFD_ESI 0x02 /* error state indicator of the transmitting node */
> #define CANFD_FDF 0x04 /* mark CAN FD for dual use of struct canfd_frame */
>
> diff --git a/net/can/af_can.c b/net/can/af_can.c
> index afa6c2151bc4..072a6a5c9dd1 100644
> --- a/net/can/af_can.c
> +++ b/net/can/af_can.c
> @@ -203,11 +203,16 @@ int can_send(struct sk_buff *skb, int loop)
> int err = -EINVAL;
>
> if (can_is_can_skb(skb)) {
> skb->protocol = htons(ETH_P_CAN);
> } else if (can_is_canfd_skb(skb)) {
> + struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
> +
> skb->protocol = htons(ETH_P_CANFD);
> +
> + /* set CAN FD flag for CAN FD frames by default */
> + cfd->flags |= CANFD_FDF;
> } else {
> goto inval_skb;
> }
>
> /* Make sure the CAN frame can pass the selected CAN netdevice. */
Once all the malloc and clone functions set the flag, is there still a
route that would reach the can_send() without setting the CANFD_FDF
flag? If the answer is supposedly no, maybe it is better to remove the
check (or maybe replace it with a debug message to identify missed use
cases).
Yours sincerely,
Vincent Mailhol
