v4.19.13 snapshot.
diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h
new file mode 100644
index 0000000..b3379a9
--- /dev/null
+++ b/include/linux/can/skb.h
@@ -0,0 +1,81 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * linux/can/skb.h
+ *
+ * Definitions for the CAN network socket buffer
+ *
+ * Copyright (C) 2012 Oliver Hartkopp <socketcan@hartkopp.net>
+ *
+ */
+
+#ifndef _CAN_SKB_H
+#define _CAN_SKB_H
+
+#include <linux/types.h>
+#include <linux/skbuff.h>
+#include <linux/can.h>
+#include <net/sock.h>
+
+/*
+ * The struct can_skb_priv is used to transport additional information along
+ * with the stored struct can(fd)_frame that can not be contained in existing
+ * struct sk_buff elements.
+ * N.B. that this information must not be modified in cloned CAN sk_buffs.
+ * To modify the CAN frame content or the struct can_skb_priv content
+ * skb_copy() needs to be used instead of skb_clone().
+ */
+
+/**
+ * struct can_skb_priv - private additional data inside CAN sk_buffs
+ * @ifindex: ifindex of the first interface the CAN frame appeared on
+ * @skbcnt: atomic counter to have an unique id together with skb pointer
+ * @cf: align to the following CAN frame at skb->data
+ */
+struct can_skb_priv {
+ int ifindex;
+ int skbcnt;
+ struct can_frame cf[0];
+};
+
+static inline struct can_skb_priv *can_skb_prv(struct sk_buff *skb)
+{
+ return (struct can_skb_priv *)(skb->head);
+}
+
+static inline void can_skb_reserve(struct sk_buff *skb)
+{
+ skb_reserve(skb, sizeof(struct can_skb_priv));
+}
+
+static inline void can_skb_set_owner(struct sk_buff *skb, struct sock *sk)
+{
+ if (sk) {
+ sock_hold(sk);
+ skb->destructor = sock_efree;
+ skb->sk = sk;
+ }
+}
+
+/*
+ * returns an unshared skb owned by the original sock to be echo'ed back
+ */
+static inline struct sk_buff *can_create_echo_skb(struct sk_buff *skb)
+{
+ if (skb_shared(skb)) {
+ struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
+
+ if (likely(nskb)) {
+ can_skb_set_owner(nskb, skb->sk);
+ consume_skb(skb);
+ return nskb;
+ } else {
+ kfree_skb(skb);
+ return NULL;
+ }
+ }
+
+ /* we can assume to have an unshared skb with proper owner */
+ return skb;
+}
+
+#endif /* !_CAN_SKB_H */