1/*
2 * linux/can/skb.h
3 *
4 * Definitions for the CAN network socket buffer
5 *
6 * Copyright (C) 2012 Oliver Hartkopp <socketcan@hartkopp.net>
7 *
8 */
9
10#ifndef _CAN_SKB_H
11#define _CAN_SKB_H
12
13#include <linux/types.h>
14#include <linux/skbuff.h>
15#include <linux/can.h>
16#include <net/sock.h>
17
18/*
19 * The struct can_skb_priv is used to transport additional information along
20 * with the stored struct can(fd)_frame that can not be contained in existing
21 * struct sk_buff elements.
22 * N.B. that this information must not be modified in cloned CAN sk_buffs.
23 * To modify the CAN frame content or the struct can_skb_priv content
24 * skb_copy() needs to be used instead of skb_clone().
25 */
26
27/**
28 * struct can_skb_priv - private additional data inside CAN sk_buffs
29 * @ifindex:	ifindex of the first interface the CAN frame appeared on
30 * @skbcnt:	atomic counter to have an unique id together with skb pointer
31 * @cf:		align to the following CAN frame at skb->data
32 */
33struct can_skb_priv {
34	int ifindex;
35	int skbcnt;
36	struct can_frame cf[0];
37};
38
39static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
40{
41	return (struct can_skb_priv *)(skb->head);
42}
43
44static inline void can_skb_reserve(struct sk_buff *skb)
45{
46	skb_reserve(skb, sizeof(struct can_skb_priv));
47}
48
49static inline void can_skb_set_owner(struct sk_buff *skb, struct sock *sk)
50{
51	if (sk) {
52		sock_hold(sk);
53		skb->destructor = sock_efree;
54		skb->sk = sk;
55	}
56}
57
58/*
59 * returns an unshared skb owned by the original sock to be echo'ed back
60 */
61static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb)
62{
63	if (skb_shared(skb)) {
64		struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
65
66		if (likely(nskb)) {
67			can_skb_set_owner(nskb, skb->sk);
68			consume_skb(skb);
69			return nskb;
70		} else {
71			kfree_skb(skb);
72			return NULL;
73		}
74	}
75
76	/* we can assume to have an unshared skb with proper owner */
77	return skb;
78}
79
80#endif /* !_CAN_SKB_H */
81