LXR linux/include/linux/can/skb.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   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 */
  34struct can_skb_priv {
  35        int ifindex;
  36        int skbcnt;
  37        struct can_frame cf[0];
  38};
  39
  40static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
  41{
  42        return (struct can_skb_priv *)(skb->head);
  43}
  44
  45static inline void can_skb_reserve(struct sk_buff *skb)
  46{
  47        skb_reserve(skb, sizeof(struct can_skb_priv));
  48}
  49
  50static inline void can_skb_set_owner(struct sk_buff *skb, struct sock *sk)
  51{
  52        if (sk) {
  53                sock_hold(sk);
  54                skb->destructor = sock_efree;
  55                skb->sk = sk;
  56        }
  57}
  58
  59/*
  60 * returns an unshared skb owned by the original sock to be echo'ed back
  61 */
  62static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb)
  63{
  64        if (skb_shared(skb)) {
  65                struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
  66
  67                if (likely(nskb)) {
  68                        can_skb_set_owner(nskb, skb->sk);
  69                        consume_skb(skb);
  70                        return nskb;
  71                } else {
  72                        kfree_skb(skb);
  73                        return NULL;
  74                }
  75        }
  76
  77        /* we can assume to have an unshared skb with proper owner */
  78        return skb;
  79}
  80
  81#endif /* !_CAN_SKB_H */
  82