net/caif/cfpkt_skbuff.c - kernel/common - Git at Google

 /*
  * Copyright (C) ST-Ericsson AB 2010
  * Author:	Sjur Brendeland/[email protected]
  * License terms: GNU General Public License (GPL) version 2
  */

 #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_warning("CAIF: " 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;
 };

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

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

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

 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, "cfpkt_extr_head read beyond end of packet\n");
 		return -EPROTO;
 	}

 	if (unlikely(len > skb_headlen(skb))) {
 		if (unlikely(skb_linearize(skb) != 0)) {
 			PKT_ERROR(pkt, "cfpkt_extr_head 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, "cfpkt_extr_trail linearize failed\n");
 		return -EPROTO;
 	}
 	if (unlikely(skb->data + len > skb_tail_pointer(skb))) {
 		PKT_ERROR(pkt, "cfpkt_extr_trail 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, "cfpkt_add_body: 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_warning("CAIF: %s(): Packet is non-linear\n",
 				   __func__);
 			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, "cfpkt_add_head: no headroom\n");
 		return -EPROTO;
 	}

 	/* Make sure data is writable */
 	ret = skb_cow_data(skb, 0, &lastskb);
 	if (unlikely(ret < 0)) {
 		PKT_ERROR(pkt, "cfpkt_add_head: 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, "cfpkt_iterate: 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, "cfpkt_setlen: skb_pad_trail failed\n");

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

 struct cfpkt *cfpkt_create_uplink(const unsigned char *data, unsigned int len)
 {
 	struct cfpkt *pkt = cfpkt_create_pfx(len + PKT_POSTFIX, PKT_PREFIX);
 	if (!pkt)
 		return NULL;
 	if (unlikely(data != NULL))
 		cfpkt_add_body(pkt, data, len);
 	return pkt;
 }
 EXPORT_SYMBOL(cfpkt_create_uplink);

 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,
 			  "cfpkt_split: trying to split beyond end of packet");
 		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);

 char *cfpkt_log_pkt(struct cfpkt *pkt, char *buf, int buflen)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);
 	char *p = buf;
 	int i;

 	/*
 	 * Sanity check buffer length, it needs to be at least as large as
 	 * the header info: ~=50+ bytes
 	 */
 	if (buflen < 50)
 		return NULL;

 	snprintf(buf, buflen, "%s: pkt:%p len:%ld(%ld+%ld) {%ld,%ld} data: [",
 		is_erronous(pkt) ? "ERRONOUS-SKB" :
 		 (skb->data_len != 0 ? "COMPLEX-SKB" : "SKB"),
 		 skb,
 		 (long) skb->len,
 		 (long) (skb_tail_pointer(skb) - skb->data),
 		 (long) skb->data_len,
 		 (long) (skb->data - skb->head),
 		 (long) (skb_tail_pointer(skb) - skb->head));
 	p = buf + strlen(buf);

 	for (i = 0; i < skb_tail_pointer(skb) - skb->data && i < 300; i++) {
 		if (p > buf + buflen - 10) {
 			sprintf(p, "...");
 			p = buf + strlen(buf);
 			break;
 		}
 		sprintf(p, "%02x,", skb->data[i]);
 		p = buf + strlen(buf);
 	}
 	sprintf(p, "]\n");
 	return buf;
 }
 EXPORT_SYMBOL(cfpkt_log_pkt);

 int cfpkt_raw_append(struct cfpkt *pkt, void **buf, unsigned int buflen)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);
 	struct sk_buff *lastskb;

 	caif_assert(buf != NULL);
 	if (unlikely(is_erronous(pkt)))
 		return -EPROTO;
 	/* Make sure SKB is writable */
 	if (unlikely(skb_cow_data(skb, 0, &lastskb) < 0)) {
 		PKT_ERROR(pkt, "cfpkt_raw_append: skb_cow_data failed\n");
 		return -EPROTO;
 	}

 	if (unlikely(skb_linearize(skb) != 0)) {
 		PKT_ERROR(pkt, "cfpkt_raw_append: linearize failed\n");
 		return -EPROTO;
 	}

 	if (unlikely(skb_tailroom(skb) < buflen)) {
 		PKT_ERROR(pkt, "cfpkt_raw_append: buffer too short - failed\n");
 		return -EPROTO;
 	}

 	*buf = skb_put(skb, buflen);
 	return 1;
 }
 EXPORT_SYMBOL(cfpkt_raw_append);

 int cfpkt_raw_extract(struct cfpkt *pkt, void **buf, unsigned int buflen)
 {
 	struct sk_buff *skb = pkt_to_skb(pkt);

 	caif_assert(buf != NULL);
 	if (unlikely(is_erronous(pkt)))
 		return -EPROTO;

 	if (unlikely(buflen > skb->len)) {
 		PKT_ERROR(pkt, "cfpkt_raw_extract: buflen too large "
 				"- failed\n");
 		return -EPROTO;
 	}

 	if (unlikely(buflen > skb_headlen(skb))) {
 		if (unlikely(skb_linearize(skb) != 0)) {
 			PKT_ERROR(pkt, "cfpkt_raw_extract: linearize failed\n");
 			return -EPROTO;
 		}
 	}

 	*buf = skb->data;
 	skb_pull(skb, buflen);

 	return 1;
 }
 EXPORT_SYMBOL(cfpkt_raw_extract);

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

 struct cfpktq *cfpktq_create(void)
 {
 	struct cfpktq *q = kmalloc(sizeof(struct cfpktq), GFP_ATOMIC);
 	if (!q)
 		return NULL;
 	skb_queue_head_init(&q->head);
 	atomic_set(&q->count, 0);
 	spin_lock_init(&q->lock);
 	return q;
 }
 EXPORT_SYMBOL(cfpktq_create);

 void cfpkt_queue(struct cfpktq *pktq, struct cfpkt *pkt, unsigned short prio)
 {
 	atomic_inc(&pktq->count);
 	spin_lock(&pktq->lock);
 	skb_queue_tail(&pktq->head, pkt_to_skb(pkt));
 	spin_unlock(&pktq->lock);

 }
 EXPORT_SYMBOL(cfpkt_queue);

 struct cfpkt *cfpkt_qpeek(struct cfpktq *pktq)
 {
 	struct cfpkt *tmp;
 	spin_lock(&pktq->lock);
 	tmp = skb_to_pkt(skb_peek(&pktq->head));
 	spin_unlock(&pktq->lock);
 	return tmp;
 }
 EXPORT_SYMBOL(cfpkt_qpeek);

 struct cfpkt *cfpkt_dequeue(struct cfpktq *pktq)
 {
 	struct cfpkt *pkt;
 	spin_lock(&pktq->lock);
 	pkt = skb_to_pkt(skb_dequeue(&pktq->head));
 	if (pkt) {
 		atomic_dec(&pktq->count);
 		caif_assert(atomic_read(&pktq->count) >= 0);
 	}
 	spin_unlock(&pktq->lock);
 	return pkt;
 }
 EXPORT_SYMBOL(cfpkt_dequeue);

 int cfpkt_qcount(struct cfpktq *pktq)
 {
 	return atomic_read(&pktq->count);
 }
 EXPORT_SYMBOL(cfpkt_qcount);

 struct cfpkt *cfpkt_clone_release(struct cfpkt *pkt)
 {
 	struct cfpkt *clone;
 	clone  = skb_to_pkt(skb_clone(pkt_to_skb(pkt), GFP_ATOMIC));
 	/* Free original packet. */
 	cfpkt_destroy(pkt);
 	if (!clone)
 		return NULL;
 	return clone;
 }
 EXPORT_SYMBOL(cfpkt_clone_release);

 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/[email protected]
	* License terms: GNU General Public License (GPL) version 2
	*/

	#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_warning("CAIF: " 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;
	};

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

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

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

	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, "cfpkt_extr_head read beyond end of packet\n");
	return -EPROTO;
	}

	if (unlikely(len > skb_headlen(skb))) {
	if (unlikely(skb_linearize(skb) != 0)) {
	PKT_ERROR(pkt, "cfpkt_extr_head 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, "cfpkt_extr_trail linearize failed\n");
	return -EPROTO;
	}
	if (unlikely(skb->data + len > skb_tail_pointer(skb))) {
	PKT_ERROR(pkt, "cfpkt_extr_trail 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, "cfpkt_add_body: 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_warning("CAIF: %s(): Packet is non-linear\n",
	__func__);
	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, "cfpkt_add_head: no headroom\n");
	return -EPROTO;
	}

	/* Make sure data is writable */
	ret = skb_cow_data(skb, 0, &lastskb);
	if (unlikely(ret < 0)) {
	PKT_ERROR(pkt, "cfpkt_add_head: 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, "cfpkt_iterate: 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, "cfpkt_setlen: skb_pad_trail failed\n");

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

	struct cfpkt cfpkt_create_uplink(const unsigned char data, unsigned int len)
	{
	struct cfpkt *pkt = cfpkt_create_pfx(len + PKT_POSTFIX, PKT_PREFIX);
	if (!pkt)
	return NULL;
	if (unlikely(data != NULL))
	cfpkt_add_body(pkt, data, len);
	return pkt;
	}
	EXPORT_SYMBOL(cfpkt_create_uplink);

	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,
	"cfpkt_split: trying to split beyond end of packet");
	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);

	char cfpkt_log_pkt(struct cfpkt pkt, char *buf, int buflen)
	{
	struct sk_buff *skb = pkt_to_skb(pkt);
	char *p = buf;
	int i;

	/*
	* Sanity check buffer length, it needs to be at least as large as
	* the header info: ~=50+ bytes
	*/
	if (buflen < 50)
	return NULL;

	snprintf(buf, buflen, "%s: pkt:%p len:%ld(%ld+%ld) {%ld,%ld} data: [",
	is_erronous(pkt) ? "ERRONOUS-SKB" :
	(skb->data_len != 0 ? "COMPLEX-SKB" : "SKB"),
	skb,
	(long) skb->len,
	(long) (skb_tail_pointer(skb) - skb->data),
	(long) skb->data_len,
	(long) (skb->data - skb->head),
	(long) (skb_tail_pointer(skb) - skb->head));
	p = buf + strlen(buf);

	for (i = 0; i < skb_tail_pointer(skb) - skb->data && i < 300; i++) {
	if (p > buf + buflen - 10) {
	sprintf(p, "...");
	p = buf + strlen(buf);
	break;
	}
	sprintf(p, "%02x,", skb->data[i]);
	p = buf + strlen(buf);
	}
	sprintf(p, "]\n");
	return buf;
	}
	EXPORT_SYMBOL(cfpkt_log_pkt);

	int cfpkt_raw_append(struct cfpkt pkt, void *buf, unsigned int buflen)
	{
	struct sk_buff *skb = pkt_to_skb(pkt);
	struct sk_buff *lastskb;

	caif_assert(buf != NULL);
	if (unlikely(is_erronous(pkt)))
	return -EPROTO;
	/* Make sure SKB is writable */
	if (unlikely(skb_cow_data(skb, 0, &lastskb) < 0)) {
	PKT_ERROR(pkt, "cfpkt_raw_append: skb_cow_data failed\n");
	return -EPROTO;
	}

	if (unlikely(skb_linearize(skb) != 0)) {
	PKT_ERROR(pkt, "cfpkt_raw_append: linearize failed\n");
	return -EPROTO;
	}

	if (unlikely(skb_tailroom(skb) < buflen)) {
	PKT_ERROR(pkt, "cfpkt_raw_append: buffer too short - failed\n");
	return -EPROTO;
	}

	*buf = skb_put(skb, buflen);
	return 1;
	}
	EXPORT_SYMBOL(cfpkt_raw_append);

	int cfpkt_raw_extract(struct cfpkt pkt, void *buf, unsigned int buflen)
	{
	struct sk_buff *skb = pkt_to_skb(pkt);

	caif_assert(buf != NULL);
	if (unlikely(is_erronous(pkt)))
	return -EPROTO;

	if (unlikely(buflen > skb->len)) {
	PKT_ERROR(pkt, "cfpkt_raw_extract: buflen too large "
	"- failed\n");
	return -EPROTO;
	}

	if (unlikely(buflen > skb_headlen(skb))) {
	if (unlikely(skb_linearize(skb) != 0)) {
	PKT_ERROR(pkt, "cfpkt_raw_extract: linearize failed\n");
	return -EPROTO;
	}
	}

	*buf = skb->data;
	skb_pull(skb, buflen);

	return 1;
	}
	EXPORT_SYMBOL(cfpkt_raw_extract);

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

	struct cfpktq *cfpktq_create(void)
	{
	struct cfpktq *q = kmalloc(sizeof(struct cfpktq), GFP_ATOMIC);
	if (!q)
	return NULL;
	skb_queue_head_init(&q->head);
	atomic_set(&q->count, 0);
	spin_lock_init(&q->lock);
	return q;
	}
	EXPORT_SYMBOL(cfpktq_create);

	void cfpkt_queue(struct cfpktq pktq, struct cfpkt pkt, unsigned short prio)
	{
	atomic_inc(&pktq->count);
	spin_lock(&pktq->lock);
	skb_queue_tail(&pktq->head, pkt_to_skb(pkt));
	spin_unlock(&pktq->lock);

	}
	EXPORT_SYMBOL(cfpkt_queue);

	struct cfpkt cfpkt_qpeek(struct cfpktq pktq)
	{
	struct cfpkt *tmp;
	spin_lock(&pktq->lock);
	tmp = skb_to_pkt(skb_peek(&pktq->head));
	spin_unlock(&pktq->lock);
	return tmp;
	}
	EXPORT_SYMBOL(cfpkt_qpeek);

	struct cfpkt cfpkt_dequeue(struct cfpktq pktq)
	{
	struct cfpkt *pkt;
	spin_lock(&pktq->lock);
	pkt = skb_to_pkt(skb_dequeue(&pktq->head));
	if (pkt) {
	atomic_dec(&pktq->count);
	caif_assert(atomic_read(&pktq->count) >= 0);
	}
	spin_unlock(&pktq->lock);
	return pkt;
	}
	EXPORT_SYMBOL(cfpkt_dequeue);

	int cfpkt_qcount(struct cfpktq *pktq)
	{
	return atomic_read(&pktq->count);
	}
	EXPORT_SYMBOL(cfpkt_qcount);

	struct cfpkt cfpkt_clone_release(struct cfpkt pkt)
	{
	struct cfpkt *clone;
	clone = skb_to_pkt(skb_clone(pkt_to_skb(pkt), GFP_ATOMIC));
	/* Free original packet. */
	cfpkt_destroy(pkt);
	if (!clone)
	return NULL;
	return clone;
	}
	EXPORT_SYMBOL(cfpkt_clone_release);

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