1 /* SPDX-License-Identifier: GPL-2.0 */
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 
can_skb_prv(struct sk_buff * skb)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 
can_skb_reserve(struct sk_buff * skb)45 static inline void can_skb_reserve(struct sk_buff *skb)
46 {
47 	skb_reserve(skb, sizeof(struct can_skb_priv));
48 }
49 
can_skb_set_owner(struct sk_buff * skb,struct sock * sk)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  */
can_create_echo_skb(struct sk_buff * skb)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 */
82