include/linux/can/skb.h

   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
  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 */