1 /* 2 * linux/can/skb.h 3 * 4 * Definitions for the CAN network socket buffer 5 * 6 * Copyright (C) 2012 Oliver Hartkopp <[email protected]> 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 37 static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb) 38 { 39 return (struct can_skb_priv *)(skb->head); 40 } 41 42 static inline void can_skb_reserve(struct sk_buff *skb) 43 { 44 skb_reserve(skb, sizeof(struct can_skb_priv)); 45 } 46 47 static 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 */ 59 static 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 */ 79