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 * @skbcnt:     atomic counter to have an unique id together with skb pointer
  31 * @cf:         align to the following CAN frame at skb->data
  32 */
  33struct can_skb_priv {
  34        int ifindex;
  35        int skbcnt;
  36        struct can_frame cf[0];
  37};
  38
  39static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
  40{
  41        return (struct can_skb_priv *)(skb->head);
  42}
  43
  44static inline void can_skb_reserve(struct sk_buff *skb)
  45{
  46        skb_reserve(skb, sizeof(struct can_skb_priv));
  47}
  48
  49static 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 */
  61static 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