skbuff.h

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/**
 *	__skb_dequeue - remove from the head of the queue
 *	@list: list to dequeue from
 *
 *	Remove the head of the list. This function does not take any locks
 *	so must be used with appropriate locks held only. The head item is
 *	returned or %NULL if the list is empty.
 */

static inline struct sk_buff *__skb_dequeue(struct sk_buff_head *list)
{
	struct sk_buff *next, *prev, *result;

	prev = (struct sk_buff *) list;
	next = prev->next;
	result = NULL;
	if (next != prev) {
		result = next;
		next = next->next;
		list->qlen--;
		next->prev = prev;
		prev->next = next;
		result->next = NULL;
		result->prev = NULL;
		result->list = NULL;
	}
	return result;
}

/**
 *	skb_dequeue - remove from the head of the queue
 *	@list: list to dequeue from
 *
 *	Remove the head of the list. The list lock is taken so the function
 *	may be used safely with other locking list functions. The head item is
 *	returned or %NULL if the list is empty.
 */

static inline struct sk_buff *skb_dequeue(struct sk_buff_head *list)
{
	long flags;
	struct sk_buff *result;

	spin_lock_irqsave(&list->lock, flags);
	result = __skb_dequeue(list);
	spin_unlock_irqrestore(&list->lock, flags);
	return result;
}

/*
 *	Insert a packet on a list.
 */

static inline void __skb_insert(struct sk_buff *newsk,
	struct sk_buff * prev, struct sk_buff *next,
	struct sk_buff_head * list)
{
	newsk->next = next;
	newsk->prev = prev;
	next->prev = newsk;
	prev->next = newsk;
	newsk->list = list;
	list->qlen++;
}

/**
 *	skb_insert	-	insert a buffer
 *	@old: buffer to insert before
 *	@newsk: buffer to insert
 *
 *	Place a packet before a given packet in a list. The list locks are taken
 *	and this function is atomic with respect to other list locked calls
 *	A buffer cannot be placed on two lists at the same time.
 */

static inline void skb_insert(struct sk_buff *old, struct sk_buff *newsk)
{
	unsigned long flags;

	spin_lock_irqsave(&old->list->lock, flags);
	__skb_insert(newsk, old->prev, old, old->list);
	spin_unlock_irqrestore(&old->list->lock, flags);
}

/*
 *	Place a packet after a given packet in a list.
 */

static inline void __skb_append(struct sk_buff *old, struct sk_buff *newsk)
{
	__skb_insert(newsk, old, old->next, old->list);
}

/**
 *	skb_append	-	append a buffer
 *	@old: buffer to insert after
 *	@newsk: buffer to insert
 *
 *	Place a packet after a given packet in a list. The list locks are taken
 *	and this function is atomic with respect to other list locked calls.
 *	A buffer cannot be placed on two lists at the same time.
 */


static inline void skb_append(struct sk_buff *old, struct sk_buff *newsk)
{
	unsigned long flags;

	spin_lock_irqsave(&old->list->lock, flags);
	__skb_append(old, newsk);
	spin_unlock_irqrestore(&old->list->lock, flags);
}

/*
 * remove sk_buff from list. _Must_ be called atomically, and with
 * the list known..
 */
 
static inline void __skb_unlink(struct sk_buff *skb, struct sk_buff_head *list)
{
	struct sk_buff * next, * prev;

	list->qlen--;
	next = skb->next;
	prev = skb->prev;
	skb->next = NULL;
	skb->prev = NULL;
	skb->list = NULL;
	next->prev = prev;
	prev->next = next;
}

/**
 *	skb_unlink	-	remove a buffer from a list
 *	@skb: buffer to remove
 *
 *	Place a packet after a given packet in a list. The list locks are taken
 *	and this function is atomic with respect to other list locked calls
 *	
 *	Works even without knowing the list it is sitting on, which can be 
 *	handy at times. It also means that THE LIST MUST EXIST when you 
 *	unlink. Thus a list must have its contents unlinked before it is
 *	destroyed.
 */

static inline void skb_unlink(struct sk_buff *skb)
{
	struct sk_buff_head *list = skb->list;

	if(list) {
		unsigned long flags;

		spin_lock_irqsave(&list->lock, flags);
		if(skb->list == list)
			__skb_unlink(skb, skb->list);
		spin_unlock_irqrestore(&list->lock, flags);
	}
}

/* XXX: more streamlined implementation */

/**
 *	__skb_dequeue_tail - remove from the tail of the queue
 *	@list: list to dequeue from
 *
 *	Remove the tail of the list. This function does not take any locks
 *	so must be used with appropriate locks held only. The tail item is
 *	returned or %NULL if the list is empty.
 */

static inline struct sk_buff *__skb_dequeue_tail(struct sk_buff_head *list)
{
	struct sk_buff *skb = skb_peek_tail(list); 
	if (skb)
		__skb_unlink(skb, list);
	return skb;
}

/**
 *	skb_dequeue - remove from the head of the queue
 *	@list: list to dequeue from
 *
 *	Remove the head of the list. The list lock is taken so the function
 *	may be used safely with other locking list functions. The tail item is
 *	returned or %NULL if the list is empty.
 */

static inline struct sk_buff *skb_dequeue_tail(struct sk_buff_head *list)
{
	long flags;
	struct sk_buff *result;

	spin_lock_irqsave(&list->lock, flags);
	result = __skb_dequeue_tail(list);
	spin_unlock_irqrestore(&list->lock, flags);
	return result;
}

/*
 *	Add data to an sk_buff
 */
 
static inline unsigned char *__skb_put(struct sk_buff *skb, unsigned int len)
{
	unsigned char *tmp=skb->tail;
	skb->tail+=len;
	skb->len+=len;
	return tmp;
}

/**
 *	skb_put - add data to a buffer
 *	@skb: buffer to use 
 *	@len: amount of data to add
 *
 *	This function extends the used data area of the buffer. If this would
 *	exceed the total buffer size the kernel will panic. A pointer to the
 *	first byte of the extra data is returned.
 */
 
static inline unsigned char *skb_put(struct sk_buff *skb, unsigned int len)
{
	unsigned char *tmp=skb->tail;
	skb->tail+=len;
	skb->len+=len;
	if(skb->tail>skb->end) {
		skb_over_panic(skb, len, current_text_addr());
	}
	return tmp;
}

static inline unsigned char *__skb_push(struct sk_buff *skb, unsigned int len)
{
	skb->data-=len;
	skb->len+=len;
	return skb->data;
}

/**
 *	skb_push - add data to the start of a buffer
 *	@skb: buffer to use 
 *	@len: amount of data to add
 *
 *	This function extends the used data area of the buffer at the buffer
 *	start. If this would exceed the total buffer headroom the kernel will
 *	panic. A pointer to the first byte of the extra data is returned.
 */

static inline unsigned char *skb_push(struct sk_buff *skb, unsigned int len)
{
	skb->data-=len;
	skb->len+=len;
	if(skb->data<skb->head) {
		skb_under_panic(skb, len, current_text_addr());
	}
	return skb->data;
}

static inline char *__skb_pull(struct sk_buff *skb, unsigned int len)
{
	skb->len-=len;
	return 	skb->data+=len;
}

/**
 *	skb_pull - remove data from the start of a buffer
 *	@skb: buffer to use 
 *	@len: amount of data to remove
 *
 *	This function removes data from the start of a buffer, returning
 *	the memory to the headroom. A pointer to the next data in the buffer
 *	is returned. Once the data has been pulled future pushes will overwrite
 *	the old data.
 */

static inline unsigned char * skb_pull(struct sk_buff *skb, unsigned int len)
{	
	if (len > skb->len)
		return NULL;
	return __skb_pull(skb,len);
}

/**
 *	skb_headroom - bytes at buffer head
 *	@skb: buffer to check
 *
 *	Return the number of bytes of free space at the head of an &sk_buff.
 */
 
static inline int skb_headroom(const struct sk_buff *skb)
{
	return skb->data-skb->head;
}

/**
 *	skb_tailroom - bytes at buffer end
 *	@skb: buffer to check
 *
 *	Return the number of bytes of free space at the tail of an sk_buff
 */

static inline int skb_tailroom(const struct sk_buff *skb)
{
	return skb->end-skb->tail;
}

/**
 *	skb_reserve - adjust headroom
 *	@skb: buffer to alter
 *	@len: bytes to move
 *
 *	Increase the headroom of an empty &sk_buff by reducing the tail
 *	room. This is only allowed for an empty buffer.
 */

static inline void skb_reserve(struct sk_buff *skb, unsigned int len)
{
	skb->data+=len;
	skb->tail+=len;
}


static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
{
	skb->len = len;
	skb->tail = skb->data+len;
}

/**
 *	skb_trim - remove end from a buffer
 *	@skb: buffer to alter
 *	@len: new length
 *
 *	Cut the length of a buffer down by removing data from the tail. If
 *	the buffer is already under the length specified it is not modified.
 */

static inline void skb_trim(struct sk_buff *skb, unsigned int len)
{
	if (skb->len > len) {
		__skb_trim(skb, len);
	}
}

/**
 *	skb_orphan - orphan a buffer
 *	@skb: buffer to orphan
 *
 *	If a buffer currently has an owner then we call the owner's
 *	destructor function and make the @skb unowned. The buffer continues
 *	to exist but is no longer charged to its former owner.
 */


static inline void skb_orphan(struct sk_buff *skb)
{
	if (skb->destructor)
		skb->destructor(skb);
	skb->destructor = NULL;
	skb->sk = NULL;
}

/**
 *	skb_purge - empty a list
 *	@list: list to empty
 *
 *	Delete all buffers on an &sk_buff list. Each buffer is removed from
 *	the list and one reference dropped. This function takes the list
 *	lock and is atomic with respect to other list locking functions.
 */


static inline void skb_queue_purge(struct sk_buff_head *list)
{
	struct sk_buff *skb;
	while ((skb=skb_dequeue(list))!=NULL)
		kfree_skb(skb);
}

/**
 *	__skb_purge - empty a list
 *	@list: list to empty
 *
 *	Delete all buffers on an &sk_buff list. Each buffer is removed from
 *	the list and one reference dropped. This function does not take the
 *	list lock and the caller must hold the relevant locks to use it.
 */


static inline void __skb_queue_purge(struct sk_buff_head *list)
{
	struct sk_buff *skb;
	while ((skb=__skb_dequeue(list))!=NULL)
		kfree_skb(skb);
}

/**
 *	dev_alloc_skb - allocate an skbuff for sending
 *	@length: length to allocate
 *
 *	Allocate a new &sk_buff and assign it a usage count of one. The
 *	buffer has unspecified headroom built in. Users should allocate
 *	the headroom they think they need without accounting for the
 *	built in space. The built in space is used for optimisations.
 *
 *	%NULL is returned in there is no free memory. Although this function
 *	allocates memory it can be called from an interrupt.
 */
 
static inline struct sk_buff *dev_alloc_skb(unsigned int length)
{
	struct sk_buff *skb;

	skb = alloc_skb(length+16, GFP_ATOMIC);
	if (skb)
		skb_reserve(skb,16);
	return skb;
}

/**
 *	skb_cow - copy a buffer if need be
 *	@skb: buffer to copy
 *	@headroom: needed headroom
 *
 *	If the buffer passed lacks sufficient headroom or is a clone then
 *	it is copied and the additional headroom made available. If there
 *	is no free memory %NULL is returned. The new buffer is returned if
 *	a copy was made (and the old one dropped a reference). The existing
 *	buffer is returned otherwise.
 *
 *	This function primarily exists to avoid making two copies when making
 *	a writable copy of a buffer and then growing the headroom.
 */
 

static inline struct sk_buff *
skb_cow(struct sk_buff *skb, unsigned int headroom)
{
	headroom = (headroom+15)&~15;

	if ((unsigned)skb_headroom(skb) < headroom || skb_cloned(skb)) {
		struct sk_buff *skb2 = skb_realloc_headroom(skb, headroom);
		kfree_skb(skb);
		skb = skb2;
	}
	return skb;
}

#define skb_queue_walk(queue, skb) \
		for (skb = (queue)->next;			\
		     (skb != (struct sk_buff *)(queue));	\
		     skb=skb->next)


extern struct sk_buff *		skb_recv_datagram(struct sock *sk,unsigned flags,int noblock, int *err);
extern unsigned int		datagram_poll(struct file *file, struct socket *sock, struct poll_table_struct *wait);
extern int			skb_copy_datagram(struct sk_buff *from, int offset, char *to,int size);
extern int			skb_copy_datagram_iovec(struct sk_buff *from, int offset, struct iovec *to,int size);
extern void			skb_free_datagram(struct sock * sk, struct sk_buff *skb);

extern void skb_init(void);
extern void skb_add_mtu(int mtu);

#ifdef CONFIG_NETFILTER
static inline void
nf_conntrack_put(struct nf_ct_info *nfct)
{
	if (nfct && atomic_dec_and_test(&nfct->master->use))
		nfct->master->destroy(nfct->master);
}
static inline void
nf_conntrack_get(struct nf_ct_info *nfct)
{
	if (nfct)
		atomic_inc(&nfct->master->use);
}
#endif

#endif	/* __KERNEL__ */
#endif	/* _LINUX_SKBUFF_H */