LXR linux/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 */
  32struct can_skb_priv {
  33        int ifindex;
  34        struct can_frame cf[0];
  35};
  36
  37static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
  38{
  39        return (struct can_skb_priv *)(skb->head);
  40}
  41
  42static inline void can_skb_reserve(struct sk_buff *skb)
  43{
  44        skb_reserve(skb, sizeof(struct can_skb_priv));
  45}
  46
  47static 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 */
  59static 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