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can: add private data space for CAN sk_buffs

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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>
This commit is contained in:
Oliver Hartkopp
2013-01-17 18:43:39 +01:00
committed by Marc Kleine-Budde
parent e2d5f2c7d6
commit 156c2bb9f8
5 changed files with 64 additions and 7 deletions
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include/linux/can/skb.h
+35
View File
@@ -0,0 +1,35 @@
/*
* linux/can/skb.h
*
* Definitions for the CAN network socket buffer
*
* Copyright (C) 2012 Oliver Hartkopp <socketcan@hartkopp.net>
*
*/
#ifndef CAN_SKB_H
#define CAN_SKB_H
#include <linux/types.h>
#include <linux/can.h>
/*
* 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
* @cf: align to the following CAN frame at skb->data
*/
struct can_skb_priv {
int ifindex;
struct can_frame cf[0];
};
#endif /* CAN_SKB_H */