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 */ 32 struct can_skb_priv { 33 int ifindex; 34 struct can_frame cf[0]; 35 }; 36 can_skb_prv(struct sk_buff * skb)37static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb) 38 { 39 return (struct can_skb_priv *)(skb->head); 40 } 41 can_skb_reserve(struct sk_buff * skb)42static inline void can_skb_reserve(struct sk_buff *skb) 43 { 44 skb_reserve(skb, sizeof(struct can_skb_priv)); 45 } 46 can_skb_destructor(struct sk_buff * skb)47static inline void can_skb_destructor(struct sk_buff *skb) 48 { 49 sock_put(skb->sk); 50 } 51 can_skb_set_owner(struct sk_buff * skb,struct sock * sk)52static inline void can_skb_set_owner(struct sk_buff *skb, struct sock *sk) 53 { 54 if (sk) { 55 sock_hold(sk); 56 skb->destructor = can_skb_destructor; 57 skb->sk = sk; 58 } 59 } 60 61 /* 62 * returns an unshared skb owned by the original sock to be echo'ed back 63 */ can_create_echo_skb(struct sk_buff * skb)64static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb) 65 { 66 if (skb_shared(skb)) { 67 struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC); 68 69 if (likely(nskb)) { 70 can_skb_set_owner(nskb, skb->sk); 71 consume_skb(skb); 72 return nskb; 73 } else { 74 kfree_skb(skb); 75 return NULL; 76 } 77 } 78 79 /* we can assume to have an unshared skb with proper owner */ 80 return skb; 81 } 82 83 #endif /* !_CAN_SKB_H */ 84