/*
* linux/can/skb.h
*
* Definitions for the CAN network socket buffer
*
* Copyright (C) 2012 Oliver Hartkopp <[email protected]>
*
*/

#ifndef CAN_SKB_H
#define CAN_SKB_H

#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/can.h>
#include <net/sock.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];
};

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_destructor(struct sk_buff *skb)
{
sock_put(skb->sk);
}

static inline void can_skb_set_owner(struct sk_buff *skb, struct sock *sk)
{
if (sk) {
sock_hold(sk);
skb->destructor = can_skb_destructor;
skb->sk = sk;
}
}

/*
* returns an unshared skb owned by the original sock to be echo'ed back
*/
static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb)
{
if (skb_shared(skb)) {
struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);

if (likely(nskb)) {
can_skb_set_owner(nskb, skb->sk);
consume_skb(skb);
return nskb;
} else {
kfree_skb(skb);
return NULL;
}
}

/* we can assume to have an unshared skb with proper owner */
return skb;
}

#endif /* CAN_SKB_H */