can: add private data space for CAN sk_buffs
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.
can_skb_priv is located in the skb headroom, which does not touch the existing
CAN sk_buff usage with skb->data and skb->len, so that even out-of-tree
CAN drivers can be used without changes.
Btw. out-of-tree CAN drivers without can_skb_priv in the sk_buff headroom
would not support features based on can_skb_priv.
The can_skb_priv->ifindex contains the first interface where the CAN frame
appeared on the local host. Unfortunately skb->skb_iif can not be used as this
value is overwritten in every netif_receive_skb() call.
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c
index adc3708..e79a8d1 100644
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -55,6 +55,7 @@
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/can.h>
+#include <linux/can/skb.h>
static __initconst const char banner[] =
KERN_INFO "slcan: serial line CAN interface driver\n";
@@ -184,7 +185,8 @@
cf.data[i] |= tmp;
}
- skb = dev_alloc_skb(sizeof(struct can_frame));
+ skb = dev_alloc_skb(sizeof(struct can_frame) +
+ sizeof(struct can_skb_priv));
if (!skb)
return;
@@ -192,6 +194,10 @@
skb->protocol = htons(ETH_P_CAN);
skb->pkt_type = PACKET_BROADCAST;
skb->ip_summed = CHECKSUM_UNNECESSARY;
+
+ skb_reserve(skb, sizeof(struct can_skb_priv));
+ ((struct can_skb_priv *)(skb->head))->ifindex = sl->dev->ifindex;
+
memcpy(skb_put(skb, sizeof(struct can_frame)),
&cf, sizeof(struct can_frame));
netif_rx_ni(skb);