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  */
  34 struct can_skb_priv {
  35         int ifindex;
  36         int skbcnt;
  37         struct can_frame cf[0];
  38 };
  39
  40 static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
  41 {
  42         return (struct can_skb_priv *)(skb->head);
  43 }
  44
  45 static inline void can_skb_reserve(struct sk_buff *skb)
  46 {
  47         skb_reserve(skb, sizeof(struct can_skb_priv));
  48 }
  49
  50 static 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  */
  62 static 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 */