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[]; 38 }; 39 can_skb_prv(struct sk_buff * skb)40static 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)45static 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)50static inline void can_skb_set_owner(struct sk_buff *skb, struct sock *sk) 51 { 52 /* If the socket has already been closed by user space, the 53 * refcount may already be 0 (and the socket will be freed 54 * after the last TX skb has been freed). So only increase 55 * socket refcount if the refcount is > 0. 56 */ 57 if (sk && refcount_inc_not_zero(&sk->sk_refcnt)) { 58 skb->destructor = sock_efree; 59 skb->sk = sk; 60 } 61 } 62 63 /* 64 * returns an unshared skb owned by the original sock to be echo'ed back 65 */ can_create_echo_skb(struct sk_buff * skb)66static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb) 67 { 68 struct sk_buff *nskb; 69 70 nskb = skb_clone(skb, GFP_ATOMIC); 71 if (unlikely(!nskb)) { 72 kfree_skb(skb); 73 return NULL; 74 } 75 76 can_skb_set_owner(nskb, skb->sk); 77 consume_skb(skb); 78 return nskb; 79 } 80 81 #endif /* !_CAN_SKB_H */ 82