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 * @skbcnt: atomic counter to have an unique id together with skb pointer 31 * @cf: align to the following CAN frame at skb->data 32 */ 33 struct can_skb_priv { 34 int ifindex; 35 int skbcnt; 36 struct can_frame cf[0]; 37 }; 38 39 static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb) 40 { 41 return (struct can_skb_priv *)(skb->head); 42 } 43 44 static inline void can_skb_reserve(struct sk_buff *skb) 45 { 46 skb_reserve(skb, sizeof(struct can_skb_priv)); 47 } 48 49 static inline void can_skb_set_owner(struct sk_buff *skb, struct sock *sk) 50 { 51 if (sk) { 52 sock_hold(sk); 53 skb->destructor = sock_efree; 54 skb->sk = sk; 55 } 56 } 57 58 /* 59 * returns an unshared skb owned by the original sock to be echo'ed back 60 */ 61 static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb) 62 { 63 if (skb_shared(skb)) { 64 struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC); 65 66 if (likely(nskb)) { 67 can_skb_set_owner(nskb, skb->sk); 68 consume_skb(skb); 69 return nskb; 70 } else { 71 kfree_skb(skb); 72 return NULL; 73 } 74 } 75 76 /* we can assume to have an unshared skb with proper owner */ 77 return skb; 78 } 79 80 #endif /* !_CAN_SKB_H */ 81