So far the creation of the TX echo skb was optional and can be controlled by the local sender of a CAN frame. It turns out that the TX echo CAN skb can be piggybacked to carry information in the driver from the TX- to the TX-complete handler. Several drivers already use the return value of can_get_echo_skb() (which is the length of the data field in the CAN frame) for their number of transferred bytes statistics. The statistics are not working if CAN echo skbs are disabled. Another use case is to calculate and set the CAN frame length on the wire, which is needed for BQL support in both the TX and TX-completion handler. For now in can_put_echo_skb(), which is called from the TX handler, the skb carrying the CAN frame is discarded if no TX echo is requested, leading to the above illustrated problems. This patch changes the can_put_echo_skb() function, so that the echo skb is always generated. If the sender requests no echo, the echo skb is consumed in __can_get_echo_skb() without being passed into the RX handler of the networking stack, but the CAN data length and CAN frame length information is properly returned. Link: https://lore.kernel.org/r/20210309211904.3348700-1-mkl@xxxxxxxxxxxxxx Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> --- drivers/net/can/dev/skb.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c index 6a64fe410987..22b0472a5fad 100644 --- a/drivers/net/can/dev/skb.c +++ b/drivers/net/can/dev/skb.c @@ -45,7 +45,7 @@ int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev, BUG_ON(idx >= priv->echo_skb_max); /* check flag whether this packet has to be looped back */ - if (!(dev->flags & IFF_ECHO) || skb->pkt_type != PACKET_LOOPBACK || + if (!(dev->flags & IFF_ECHO) || (skb->protocol != htons(ETH_P_CAN) && skb->protocol != htons(ETH_P_CANFD))) { kfree_skb(skb); @@ -58,7 +58,6 @@ int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev, return -ENOMEM; /* make settings for echo to reduce code in irq context */ - skb->pkt_type = PACKET_BROADCAST; skb->ip_summed = CHECKSUM_UNNECESSARY; skb->dev = dev; @@ -111,6 +110,13 @@ __can_get_echo_skb(struct net_device *dev, unsigned int idx, u8 *len_ptr, priv->echo_skb[idx] = NULL; + if (skb->pkt_type == PACKET_LOOPBACK) { + skb->pkt_type = PACKET_BROADCAST; + } else { + dev_consume_skb_any(skb); + return NULL; + } + return skb; } -- 2.30.2
