1 /* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) */
2 /*
3 * linux/can/skb.h
4 *
5 * Definitions for the CAN network socket buffer
6 *
7 * Copyright (C) 2012 Oliver Hartkopp <socketcan@hartkopp.net>
8 *
9 */
10
11 #ifndef _CAN_SKB_H
12 #define _CAN_SKB_H
13
14 #include <linux/types.h>
15 #include <linux/skbuff.h>
16 #include <linux/can.h>
17 #include <net/sock.h>
18
19 /*
20 * The struct can_skb_priv is used to transport additional information along
21 * with the stored struct can(fd)_frame that can not be contained in existing
22 * struct sk_buff elements.
23 * N.B. that this information must not be modified in cloned CAN sk_buffs.
24 * To modify the CAN frame content or the struct can_skb_priv content
25 * skb_copy() needs to be used instead of skb_clone().
26 */
27
28 /**
29 * struct can_skb_priv - private additional data inside CAN sk_buffs
30 * @ifindex: ifindex of the first interface the CAN frame appeared on
31 * @skbcnt: atomic counter to have an unique id together with skb pointer
32 * @cf: align to the following CAN frame at skb->data
33 */
34 struct can_skb_priv {
35 int ifindex;
36 int skbcnt;
37 struct can_frame cf[0];
38 };
39
40 static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
41 {
42 return (struct can_skb_priv *)(skb->head);
43 }
44
45 static inline void can_skb_reserve(struct sk_buff *skb)
46 {
47 skb_reserve(skb, sizeof(struct can_skb_priv));
48 }
49
50 static inline void can_skb_set_owner(struct sk_buff *skb, struct sock *sk)
51 {
52 if (sk) {
53 sock_hold(sk);
54 skb->destructor = sock_efree;
55 skb->sk = sk;
56 }
57 }
58
59 /*
60 * returns an unshared skb owned by the original sock to be echo'ed back
61 */
62 static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb)
63 {
64 if (skb_shared(skb)) {
65 struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
66
67 if (likely(nskb)) {
68 can_skb_set_owner(nskb, skb->sk);
69 consume_skb(skb);
70 return nskb;
71 } else {
72 kfree_skb(skb);
73 return NULL;
74 }
75 }
76
77 /* we can assume to have an unshared skb with proper owner */
78 return skb;
79 }
80
81 #endif /* !_CAN_SKB_H */