net/caif/cfpkt_skbuff.c - kernel/msm-4.19 - Gitiles

 /*
  * Copyright (C) ST-Ericsson AB 2010
  * Author:	Sjur Brendeland/sjur.brandeland@stericsson.com
  * License terms: GNU General Public License (GPL) version 2
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__

 #include <linux/string.h>
 #include <linux/skbuff.h>
 #include <linux/hardirq.h>
 #include <net/caif/cfpkt.h>

 #define PKT_PREFIX  48
 #define PKT_POSTFIX 2
 #define PKT_LEN_WHEN_EXTENDING 128
 #define PKT_ERROR(pkt, errmsg)		   \
 do {					   \
 	cfpkt_priv(pkt)->erronous = true;  \
 	skb_reset_tail_pointer(&pkt->skb); \
 	pr_warn(errmsg);		   \
 } while (0)

 struct cfpktq {
 	struct sk_buff_head head;
 	atomic_t count;
 	/* Lock protects count updates */
 	spinlock_t lock;
 };

 /*
  * net/caif/ is generic and does not
  * understand SKB, so we do this typecast
  */
 struct cfpkt {
 	struct sk_buff skb;
 };

 /* Private data inside SKB */
 struct cfpkt_priv_data {
 	struct dev_info dev_info;
 	bool erronous;
 };

 static inline struct cfpkt_priv_data *cfpkt_priv(struct cfpkt *pkt)
 {
 	return (struct cfpkt_priv_data *) pkt->skb.cb;
 }

 static inline bool is_erronous(struct cfpkt *pkt)
 {
 	return cfpkt_priv(pkt)->erronous;
 }

 static inline struct sk_buff *pkt_to_skb(struct cfpkt *pkt)
 {
 	return &pkt->skb;
 }

 static inline struct cfpkt *skb_to_pkt(struct sk_buff *skb)
 {
 	return (struct cfpkt *) skb;
 }


 struct cfpkt *cfpkt_fromnative(enum caif_direction dir, void *nativepkt)
 {
 	struct cfpkt *pkt = skb_to_pkt(nativepkt);
 	cfpkt_priv(pkt)->erronous = false;
 	return pkt;
 }
 EXPORT_SYMBOL(cfpkt_fromnative);

 void *cfpkt_tonative(struct cfpkt *pkt)
 {
 	return (void *) pkt;
 }
 EXPORT_SYMBOL(cfpkt_tonative);

 static struct cfpkt *cfpkt_create_pfx(u16 len, u16 pfx)
 {
 	struct sk_buff *skb;

 	if (likely(in_interrupt()))
 		skb = alloc_skb(len + pfx, GFP_ATOMIC);
 	else
 		skb = alloc_skb(len + pfx, GFP_KERNEL);

 	if (unlikely(skb == NULL))
 		return NULL;

 	skb_reserve(skb, pfx);
 	return skb_to_pkt(skb);
 }

 inline struct cfpkt *cfpkt_create(u16 len)
 {
 	return cfpkt_create_pfx(len + PKT_POSTFIX, PKT_PREFIX);
 }
 EXPORT_SYMBOL(cfpkt_create);

 void cfpkt_destroy(struct cfpkt *pkt)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);
 	kfree_skb(skb);
 }
 EXPORT_SYMBOL(cfpkt_destroy);

 inline bool cfpkt_more(struct cfpkt *pkt)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);
 	return skb->len > 0;
 }
 EXPORT_SYMBOL(cfpkt_more);

 int cfpkt_peek_head(struct cfpkt *pkt, void *data, u16 len)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);
 	if (skb_headlen(skb) >= len) {
 		memcpy(data, skb->data, len);
 		return 0;
 	}
 	return !cfpkt_extr_head(pkt, data, len) &&
 	    !cfpkt_add_head(pkt, data, len);
 }
 EXPORT_SYMBOL(cfpkt_peek_head);

 int cfpkt_extr_head(struct cfpkt *pkt, void *data, u16 len)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);
 	u8 *from;
 	if (unlikely(is_erronous(pkt)))
 		return -EPROTO;

 	if (unlikely(len > skb->len)) {
 		PKT_ERROR(pkt, "read beyond end of packet\n");
 		return -EPROTO;
 	}

 	if (unlikely(len > skb_headlen(skb))) {
 		if (unlikely(skb_linearize(skb) != 0)) {
 			PKT_ERROR(pkt, "linearize failed\n");
 			return -EPROTO;
 		}
 	}
 	from = skb_pull(skb, len);
 	from -= len;
 	memcpy(data, from, len);
 	return 0;
 }
 EXPORT_SYMBOL(cfpkt_extr_head);

 int cfpkt_extr_trail(struct cfpkt *pkt, void *dta, u16 len)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);
 	u8 *data = dta;
 	u8 *from;
 	if (unlikely(is_erronous(pkt)))
 		return -EPROTO;

 	if (unlikely(skb_linearize(skb) != 0)) {
 		PKT_ERROR(pkt, "linearize failed\n");
 		return -EPROTO;
 	}
 	if (unlikely(skb->data + len > skb_tail_pointer(skb))) {
 		PKT_ERROR(pkt, "read beyond end of packet\n");
 		return -EPROTO;
 	}
 	from = skb_tail_pointer(skb) - len;
 	skb_trim(skb, skb->len - len);
 	memcpy(data, from, len);
 	return 0;
 }
 EXPORT_SYMBOL(cfpkt_extr_trail);

 int cfpkt_pad_trail(struct cfpkt *pkt, u16 len)
 {
 	return cfpkt_add_body(pkt, NULL, len);
 }
 EXPORT_SYMBOL(cfpkt_pad_trail);

 int cfpkt_add_body(struct cfpkt *pkt, const void *data, u16 len)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);
 	struct sk_buff *lastskb;
 	u8 *to;
 	u16 addlen = 0;


 	if (unlikely(is_erronous(pkt)))
 		return -EPROTO;

 	lastskb = skb;

 	/* Check whether we need to add space at the tail */
 	if (unlikely(skb_tailroom(skb) < len)) {
 		if (likely(len < PKT_LEN_WHEN_EXTENDING))
 			addlen = PKT_LEN_WHEN_EXTENDING;
 		else
 			addlen = len;
 	}

 	/* Check whether we need to change the SKB before writing to the tail */
 	if (unlikely((addlen > 0) || skb_cloned(skb) || skb_shared(skb))) {

 		/* Make sure data is writable */
 		if (unlikely(skb_cow_data(skb, addlen, &lastskb) < 0)) {
 			PKT_ERROR(pkt, "cow failed\n");
 			return -EPROTO;
 		}
 		/*
 		 * Is the SKB non-linear after skb_cow_data()? If so, we are
 		 * going to add data to the last SKB, so we need to adjust
 		 * lengths of the top SKB.
 		 */
 		if (lastskb != skb) {
 			pr_warn("Packet is non-linear\n");
 			skb->len += len;
 			skb->data_len += len;
 		}
 	}

 	/* All set to put the last SKB and optionally write data there. */
 	to = skb_put(lastskb, len);
 	if (likely(data))
 		memcpy(to, data, len);
 	return 0;
 }
 EXPORT_SYMBOL(cfpkt_add_body);

 inline int cfpkt_addbdy(struct cfpkt *pkt, u8 data)
 {
 	return cfpkt_add_body(pkt, &data, 1);
 }
 EXPORT_SYMBOL(cfpkt_addbdy);

 int cfpkt_add_head(struct cfpkt *pkt, const void *data2, u16 len)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);
 	struct sk_buff *lastskb;
 	u8 *to;
 	const u8 *data = data2;
 	int ret;
 	if (unlikely(is_erronous(pkt)))
 		return -EPROTO;
 	if (unlikely(skb_headroom(skb) < len)) {
 		PKT_ERROR(pkt, "no headroom\n");
 		return -EPROTO;
 	}

 	/* Make sure data is writable */
 	ret = skb_cow_data(skb, 0, &lastskb);
 	if (unlikely(ret < 0)) {
 		PKT_ERROR(pkt, "cow failed\n");
 		return ret;
 	}

 	to = skb_push(skb, len);
 	memcpy(to, data, len);
 	return 0;
 }
 EXPORT_SYMBOL(cfpkt_add_head);

 inline int cfpkt_add_trail(struct cfpkt *pkt, const void *data, u16 len)
 {
 	return cfpkt_add_body(pkt, data, len);
 }
 EXPORT_SYMBOL(cfpkt_add_trail);

 inline u16 cfpkt_getlen(struct cfpkt *pkt)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);
 	return skb->len;
 }
 EXPORT_SYMBOL(cfpkt_getlen);

 inline u16 cfpkt_iterate(struct cfpkt *pkt,
 			    u16 (*iter_func)(u16, void *, u16),
 			    u16 data)
 {
 	/*
 	 * Don't care about the performance hit of linearizing,
 	 * Checksum should not be used on high-speed interfaces anyway.
 	 */
 	if (unlikely(is_erronous(pkt)))
 		return -EPROTO;
 	if (unlikely(skb_linearize(&pkt->skb) != 0)) {
 		PKT_ERROR(pkt, "linearize failed\n");
 		return -EPROTO;
 	}
 	return iter_func(data, pkt->skb.data, cfpkt_getlen(pkt));
 }
 EXPORT_SYMBOL(cfpkt_iterate);

 int cfpkt_setlen(struct cfpkt *pkt, u16 len)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);


 	if (unlikely(is_erronous(pkt)))
 		return -EPROTO;

 	if (likely(len <= skb->len)) {
 		if (unlikely(skb->data_len))
 			___pskb_trim(skb, len);
 		else
 			skb_trim(skb, len);

 			return cfpkt_getlen(pkt);
 	}

 	/* Need to expand SKB */
 	if (unlikely(!cfpkt_pad_trail(pkt, len - skb->len)))
 		PKT_ERROR(pkt, "skb_pad_trail failed\n");

 	return cfpkt_getlen(pkt);
 }
 EXPORT_SYMBOL(cfpkt_setlen);

 struct cfpkt *cfpkt_append(struct cfpkt *dstpkt,
 			     struct cfpkt *addpkt,
 			     u16 expectlen)
 {
 	struct sk_buff *dst = pkt_to_skb(dstpkt);
 	struct sk_buff *add = pkt_to_skb(addpkt);
 	u16 addlen = skb_headlen(add);
 	u16 neededtailspace;
 	struct sk_buff *tmp;
 	u16 dstlen;
 	u16 createlen;
 	if (unlikely(is_erronous(dstpkt) || is_erronous(addpkt))) {
 		return dstpkt;
 	}
 	if (expectlen > addlen)
 		neededtailspace = expectlen;
 	else
 		neededtailspace = addlen;

 	if (dst->tail + neededtailspace > dst->end) {
 		/* Create a dumplicate of 'dst' with more tail space */
 		struct cfpkt *tmppkt;
 		dstlen = skb_headlen(dst);
 		createlen = dstlen + neededtailspace;
 		tmppkt = cfpkt_create(createlen + PKT_PREFIX + PKT_POSTFIX);
 		if (tmppkt == NULL)
 			return NULL;
 		tmp = pkt_to_skb(tmppkt);
 		skb_set_tail_pointer(tmp, dstlen);
 		tmp->len = dstlen;
 		memcpy(tmp->data, dst->data, dstlen);
 		cfpkt_destroy(dstpkt);
 		dst = tmp;
 	}
 	memcpy(skb_tail_pointer(dst), add->data, skb_headlen(add));
 	cfpkt_destroy(addpkt);
 	dst->tail += addlen;
 	dst->len += addlen;
 	return skb_to_pkt(dst);
 }
 EXPORT_SYMBOL(cfpkt_append);

 struct cfpkt *cfpkt_split(struct cfpkt *pkt, u16 pos)
 {
 	struct sk_buff *skb2;
 	struct sk_buff *skb = pkt_to_skb(pkt);
 	struct cfpkt *tmppkt;
 	u8 *split = skb->data + pos;
 	u16 len2nd = skb_tail_pointer(skb) - split;

 	if (unlikely(is_erronous(pkt)))
 		return NULL;

 	if (skb->data + pos > skb_tail_pointer(skb)) {
 		PKT_ERROR(pkt, "trying to split beyond end of packet\n");
 		return NULL;
 	}

 	/* Create a new packet for the second part of the data */
 	tmppkt = cfpkt_create_pfx(len2nd + PKT_PREFIX + PKT_POSTFIX,
 				  PKT_PREFIX);
 	if (tmppkt == NULL)
 		return NULL;
 	skb2 = pkt_to_skb(tmppkt);


 	if (skb2 == NULL)
 		return NULL;

 	/* Reduce the length of the original packet */
 	skb_set_tail_pointer(skb, pos);
 	skb->len = pos;

 	memcpy(skb2->data, split, len2nd);
 	skb2->tail += len2nd;
 	skb2->len += len2nd;
 	return skb_to_pkt(skb2);
 }
 EXPORT_SYMBOL(cfpkt_split);

 bool cfpkt_erroneous(struct cfpkt *pkt)
 {
 	return cfpkt_priv(pkt)->erronous;
 }
 EXPORT_SYMBOL(cfpkt_erroneous);


 struct caif_payload_info *cfpkt_info(struct cfpkt *pkt)
 {
 	return (struct caif_payload_info *)&pkt_to_skb(pkt)->cb;
 }
 EXPORT_SYMBOL(cfpkt_info);
	/*
	* Copyright (C) ST-Ericsson AB 2010
	* Author: Sjur Brendeland/sjur.brandeland@stericsson.com
	* License terms: GNU General Public License (GPL) version 2
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__

	#include <linux/string.h>
	#include <linux/skbuff.h>
	#include <linux/hardirq.h>
	#include <net/caif/cfpkt.h>

	#define PKT_PREFIX 48
	#define PKT_POSTFIX 2
	#define PKT_LEN_WHEN_EXTENDING 128
	#define PKT_ERROR(pkt, errmsg) \
	do { \
	cfpkt_priv(pkt)->erronous = true; \
	skb_reset_tail_pointer(&pkt->skb); \
	pr_warn(errmsg); \
	} while (0)

	struct cfpktq {
	struct sk_buff_head head;
	atomic_t count;
	/* Lock protects count updates */
	spinlock_t lock;
	};

	/*
	* net/caif/ is generic and does not
	* understand SKB, so we do this typecast
	*/
	struct cfpkt {
	struct sk_buff skb;
	};

	/* Private data inside SKB */
	struct cfpkt_priv_data {
	struct dev_info dev_info;
	bool erronous;
	};

	static inline struct cfpkt_priv_data cfpkt_priv(struct cfpkt pkt)
	{
	return (struct cfpkt_priv_data *) pkt->skb.cb;
	}

	static inline bool is_erronous(struct cfpkt *pkt)
	{
	return cfpkt_priv(pkt)->erronous;
	}

	static inline struct sk_buff pkt_to_skb(struct cfpkt pkt)
	{
	return &pkt->skb;
	}

	static inline struct cfpkt skb_to_pkt(struct sk_buff skb)
	{
	return (struct cfpkt *) skb;
	}


	struct cfpkt cfpkt_fromnative(enum caif_direction dir, void nativepkt)
	{
	struct cfpkt *pkt = skb_to_pkt(nativepkt);
	cfpkt_priv(pkt)->erronous = false;
	return pkt;
	}
	EXPORT_SYMBOL(cfpkt_fromnative);

	void cfpkt_tonative(struct cfpkt pkt)
	{
	return (void *) pkt;
	}
	EXPORT_SYMBOL(cfpkt_tonative);

	static struct cfpkt *cfpkt_create_pfx(u16 len, u16 pfx)
	{
	struct sk_buff *skb;

	if (likely(in_interrupt()))
	skb = alloc_skb(len + pfx, GFP_ATOMIC);
	else
	skb = alloc_skb(len + pfx, GFP_KERNEL);

	if (unlikely(skb == NULL))
	return NULL;

	skb_reserve(skb, pfx);
	return skb_to_pkt(skb);
	}

	inline struct cfpkt *cfpkt_create(u16 len)
	{
	return cfpkt_create_pfx(len + PKT_POSTFIX, PKT_PREFIX);
	}
	EXPORT_SYMBOL(cfpkt_create);

	void cfpkt_destroy(struct cfpkt *pkt)
	{
	struct sk_buff *skb = pkt_to_skb(pkt);
	kfree_skb(skb);
	}
	EXPORT_SYMBOL(cfpkt_destroy);

	inline bool cfpkt_more(struct cfpkt *pkt)
	{
	struct sk_buff *skb = pkt_to_skb(pkt);
	return skb->len > 0;
	}
	EXPORT_SYMBOL(cfpkt_more);

	int cfpkt_peek_head(struct cfpkt pkt, void data, u16 len)
	{
	struct sk_buff *skb = pkt_to_skb(pkt);
	if (skb_headlen(skb) >= len) {
	memcpy(data, skb->data, len);
	return 0;
	}
	return !cfpkt_extr_head(pkt, data, len) &&
	!cfpkt_add_head(pkt, data, len);
	}
	EXPORT_SYMBOL(cfpkt_peek_head);

	int cfpkt_extr_head(struct cfpkt pkt, void data, u16 len)
	{
	struct sk_buff *skb = pkt_to_skb(pkt);
	u8 *from;
	if (unlikely(is_erronous(pkt)))
	return -EPROTO;

	if (unlikely(len > skb->len)) {
	PKT_ERROR(pkt, "read beyond end of packet\n");
	return -EPROTO;
	}

	if (unlikely(len > skb_headlen(skb))) {
	if (unlikely(skb_linearize(skb) != 0)) {
	PKT_ERROR(pkt, "linearize failed\n");
	return -EPROTO;
	}
	}
	from = skb_pull(skb, len);
	from -= len;
	memcpy(data, from, len);
	return 0;
	}
	EXPORT_SYMBOL(cfpkt_extr_head);

	int cfpkt_extr_trail(struct cfpkt pkt, void dta, u16 len)
	{
	struct sk_buff *skb = pkt_to_skb(pkt);
	u8 *data = dta;
	u8 *from;
	if (unlikely(is_erronous(pkt)))
	return -EPROTO;

	if (unlikely(skb_linearize(skb) != 0)) {
	PKT_ERROR(pkt, "linearize failed\n");
	return -EPROTO;
	}
	if (unlikely(skb->data + len > skb_tail_pointer(skb))) {
	PKT_ERROR(pkt, "read beyond end of packet\n");
	return -EPROTO;
	}
	from = skb_tail_pointer(skb) - len;
	skb_trim(skb, skb->len - len);
	memcpy(data, from, len);
	return 0;
	}
	EXPORT_SYMBOL(cfpkt_extr_trail);

	int cfpkt_pad_trail(struct cfpkt *pkt, u16 len)
	{
	return cfpkt_add_body(pkt, NULL, len);
	}
	EXPORT_SYMBOL(cfpkt_pad_trail);

	int cfpkt_add_body(struct cfpkt pkt, const void data, u16 len)
	{
	struct sk_buff *skb = pkt_to_skb(pkt);
	struct sk_buff *lastskb;
	u8 *to;
	u16 addlen = 0;


	if (unlikely(is_erronous(pkt)))
	return -EPROTO;

	lastskb = skb;

	/* Check whether we need to add space at the tail */
	if (unlikely(skb_tailroom(skb) < len)) {
	if (likely(len < PKT_LEN_WHEN_EXTENDING))
	addlen = PKT_LEN_WHEN_EXTENDING;
	else
	addlen = len;
	}

	/* Check whether we need to change the SKB before writing to the tail */
	if (unlikely((addlen > 0) \|\| skb_cloned(skb) \|\| skb_shared(skb))) {

	/* Make sure data is writable */
	if (unlikely(skb_cow_data(skb, addlen, &lastskb) < 0)) {
	PKT_ERROR(pkt, "cow failed\n");
	return -EPROTO;
	}
	/*
	* Is the SKB non-linear after skb_cow_data()? If so, we are
	* going to add data to the last SKB, so we need to adjust
	* lengths of the top SKB.
	*/
	if (lastskb != skb) {
	pr_warn("Packet is non-linear\n");
	skb->len += len;
	skb->data_len += len;
	}
	}

	/* All set to put the last SKB and optionally write data there. */
	to = skb_put(lastskb, len);
	if (likely(data))
	memcpy(to, data, len);
	return 0;
	}
	EXPORT_SYMBOL(cfpkt_add_body);

	inline int cfpkt_addbdy(struct cfpkt *pkt, u8 data)
	{
	return cfpkt_add_body(pkt, &data, 1);
	}
	EXPORT_SYMBOL(cfpkt_addbdy);

	int cfpkt_add_head(struct cfpkt pkt, const void data2, u16 len)
	{
	struct sk_buff *skb = pkt_to_skb(pkt);
	struct sk_buff *lastskb;
	u8 *to;
	const u8 *data = data2;
	int ret;
	if (unlikely(is_erronous(pkt)))
	return -EPROTO;
	if (unlikely(skb_headroom(skb) < len)) {
	PKT_ERROR(pkt, "no headroom\n");
	return -EPROTO;
	}

	/* Make sure data is writable */
	ret = skb_cow_data(skb, 0, &lastskb);
	if (unlikely(ret < 0)) {
	PKT_ERROR(pkt, "cow failed\n");
	return ret;
	}

	to = skb_push(skb, len);
	memcpy(to, data, len);
	return 0;
	}
	EXPORT_SYMBOL(cfpkt_add_head);

	inline int cfpkt_add_trail(struct cfpkt pkt, const void data, u16 len)
	{
	return cfpkt_add_body(pkt, data, len);
	}
	EXPORT_SYMBOL(cfpkt_add_trail);

	inline u16 cfpkt_getlen(struct cfpkt *pkt)
	{
	struct sk_buff *skb = pkt_to_skb(pkt);
	return skb->len;
	}
	EXPORT_SYMBOL(cfpkt_getlen);

	inline u16 cfpkt_iterate(struct cfpkt *pkt,
	u16 (iter_func)(u16, void , u16),
	u16 data)
	{
	/*
	* Don't care about the performance hit of linearizing,
	* Checksum should not be used on high-speed interfaces anyway.
	*/
	if (unlikely(is_erronous(pkt)))
	return -EPROTO;
	if (unlikely(skb_linearize(&pkt->skb) != 0)) {
	PKT_ERROR(pkt, "linearize failed\n");
	return -EPROTO;
	}
	return iter_func(data, pkt->skb.data, cfpkt_getlen(pkt));
	}
	EXPORT_SYMBOL(cfpkt_iterate);

	int cfpkt_setlen(struct cfpkt *pkt, u16 len)
	{
	struct sk_buff *skb = pkt_to_skb(pkt);


	if (unlikely(is_erronous(pkt)))
	return -EPROTO;

	if (likely(len <= skb->len)) {
	if (unlikely(skb->data_len))
	___pskb_trim(skb, len);
	else
	skb_trim(skb, len);

	return cfpkt_getlen(pkt);
	}

	/* Need to expand SKB */
	if (unlikely(!cfpkt_pad_trail(pkt, len - skb->len)))
	PKT_ERROR(pkt, "skb_pad_trail failed\n");

	return cfpkt_getlen(pkt);
	}
	EXPORT_SYMBOL(cfpkt_setlen);

	struct cfpkt cfpkt_append(struct cfpkt dstpkt,
	struct cfpkt *addpkt,
	u16 expectlen)
	{
	struct sk_buff *dst = pkt_to_skb(dstpkt);
	struct sk_buff *add = pkt_to_skb(addpkt);
	u16 addlen = skb_headlen(add);
	u16 neededtailspace;
	struct sk_buff *tmp;
	u16 dstlen;
	u16 createlen;
	if (unlikely(is_erronous(dstpkt) \|\| is_erronous(addpkt))) {
	return dstpkt;
	}
	if (expectlen > addlen)
	neededtailspace = expectlen;
	else
	neededtailspace = addlen;

	if (dst->tail + neededtailspace > dst->end) {
	/* Create a dumplicate of 'dst' with more tail space */
	struct cfpkt *tmppkt;
	dstlen = skb_headlen(dst);
	createlen = dstlen + neededtailspace;
	tmppkt = cfpkt_create(createlen + PKT_PREFIX + PKT_POSTFIX);
	if (tmppkt == NULL)
	return NULL;
	tmp = pkt_to_skb(tmppkt);
	skb_set_tail_pointer(tmp, dstlen);
	tmp->len = dstlen;
	memcpy(tmp->data, dst->data, dstlen);
	cfpkt_destroy(dstpkt);
	dst = tmp;
	}
	memcpy(skb_tail_pointer(dst), add->data, skb_headlen(add));
	cfpkt_destroy(addpkt);
	dst->tail += addlen;
	dst->len += addlen;
	return skb_to_pkt(dst);
	}
	EXPORT_SYMBOL(cfpkt_append);

	struct cfpkt cfpkt_split(struct cfpkt pkt, u16 pos)
	{
	struct sk_buff *skb2;
	struct sk_buff *skb = pkt_to_skb(pkt);
	struct cfpkt *tmppkt;
	u8 *split = skb->data + pos;
	u16 len2nd = skb_tail_pointer(skb) - split;

	if (unlikely(is_erronous(pkt)))
	return NULL;

	if (skb->data + pos > skb_tail_pointer(skb)) {
	PKT_ERROR(pkt, "trying to split beyond end of packet\n");
	return NULL;
	}

	/* Create a new packet for the second part of the data */
	tmppkt = cfpkt_create_pfx(len2nd + PKT_PREFIX + PKT_POSTFIX,
	PKT_PREFIX);
	if (tmppkt == NULL)
	return NULL;
	skb2 = pkt_to_skb(tmppkt);


	if (skb2 == NULL)
	return NULL;

	/* Reduce the length of the original packet */
	skb_set_tail_pointer(skb, pos);
	skb->len = pos;

	memcpy(skb2->data, split, len2nd);
	skb2->tail += len2nd;
	skb2->len += len2nd;
	return skb_to_pkt(skb2);
	}
	EXPORT_SYMBOL(cfpkt_split);

	bool cfpkt_erroneous(struct cfpkt *pkt)
	{
	return cfpkt_priv(pkt)->erronous;
	}
	EXPORT_SYMBOL(cfpkt_erroneous);


	struct caif_payload_info cfpkt_info(struct cfpkt pkt)
	{
	return (struct caif_payload_info *)&pkt_to_skb(pkt)->cb;
	}
	EXPORT_SYMBOL(cfpkt_info);