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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 * @cf: align to the following CAN frame at skb->data
31 */
32struct can_skb_priv {
33 int ifindex;
34 struct can_frame cf[0];
35};
36
37static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
38{
39 return (struct can_skb_priv *)(skb->head);
40}
41
42static inline void can_skb_reserve(struct sk_buff *skb)
43{
44 skb_reserve(skb, sizeof(struct can_skb_priv));
45}
46
47static inline void can_skb_set_owner(struct sk_buff *skb, struct sock *sk)
48{
49 if (sk) {
50 sock_hold(sk);
51 skb->destructor = sock_efree;
52 skb->sk = sk;
53 }
54}
55
56/*
57 * returns an unshared skb owned by the original sock to be echo'ed back
58 */
59static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb)
60{
61 if (skb_shared(skb)) {
62 struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
63
64 if (likely(nskb)) {
65 can_skb_set_owner(nskb, skb->sk);
66 consume_skb(skb);
67 return nskb;
68 } else {
69 kfree_skb(skb);
70 return NULL;
71 }
72 }
73
74 /* we can assume to have an unshared skb with proper owner */
75 return skb;
76}
77
78#endif /* !_CAN_SKB_H */