skbuff.c

Linux Kernel 2.6.9 for OMAP1710

	}

	copy_skb_header(n, skb);
out:
	return n;
}

/**
 *	pskb_expand_head - reallocate header of &sk_buff
 *	@skb: buffer to reallocate
 *	@nhead: room to add at head
 *	@ntail: room to add at tail
 *	@gfp_mask: allocation priority
 *
 *	Expands (or creates identical copy, if &nhead and &ntail are zero)
 *	header of skb. &sk_buff itself is not changed. &sk_buff MUST have
 *	reference count of 1. Returns zero in the case of success or error,
 *	if expansion failed. In the last case, &sk_buff is not changed.
 *
 *	All the pointers pointing into skb header may change and must be
 *	reloaded after call to this function.
 */

int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, int gfp_mask)
{
	int i;
	u8 *data;
	int size = nhead + (skb->end - skb->head) + ntail;
	long off;

	if (skb_shared(skb))
		BUG();

	size = SKB_DATA_ALIGN(size);

	data = kmalloc(size + sizeof(struct skb_shared_info), gfp_mask);
	if (!data)
		goto nodata;

	/* Copy only real data... and, alas, header. This should be
	 * optimized for the cases when header is void. */
	memcpy(data + nhead, skb->head, skb->tail - skb->head);
	memcpy(data + size, skb->end, sizeof(struct skb_shared_info));

	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
		get_page(skb_shinfo(skb)->frags[i].page);

	if (skb_shinfo(skb)->frag_list)
		skb_clone_fraglist(skb);

	skb_release_data(skb);

	off = (data + nhead) - skb->head;

	skb->head     = data;
	skb->end      = data + size;
	skb->data    += off;
	skb->tail    += off;
	skb->mac.raw += off;
	skb->h.raw   += off;
	skb->nh.raw  += off;
	skb->cloned   = 0;
	atomic_set(&skb_shinfo(skb)->dataref, 1);
	return 0;

nodata:
	return -ENOMEM;
}

/* Make private copy of skb with writable head and some headroom */

struct sk_buff *skb_realloc_headroom(struct sk_buff *skb, unsigned int headroom)
{
	struct sk_buff *skb2;
	int delta = headroom - skb_headroom(skb);

	if (delta <= 0)
		skb2 = pskb_copy(skb, GFP_ATOMIC);
	else {
		skb2 = skb_clone(skb, GFP_ATOMIC);
		if (skb2 && pskb_expand_head(skb2, SKB_DATA_ALIGN(delta), 0,
					     GFP_ATOMIC)) {
			kfree_skb(skb2);
			skb2 = NULL;
		}
	}
	return skb2;
}


/**
 *	skb_copy_expand	-	copy and expand sk_buff
 *	@skb: buffer to copy
 *	@newheadroom: new free bytes at head
 *	@newtailroom: new free bytes at tail
 *	@gfp_mask: allocation priority
 *
 *	Make a copy of both an &sk_buff and its data and while doing so
 *	allocate additional space.
 *
 *	This is used when the caller wishes to modify the data and needs a
 *	private copy of the data to alter as well as more space for new fields.
 *	Returns %NULL on failure or the pointer to the buffer
 *	on success. The returned buffer has a reference count of 1.
 *
 *	You must pass %GFP_ATOMIC as the allocation priority if this function
 *	is called from an interrupt.
 *
 *	BUG ALERT: ip_summed is not copied. Why does this work? Is it used
 *	only by netfilter in the cases when checksum is recalculated? --ANK
 */
struct sk_buff *skb_copy_expand(const struct sk_buff *skb,
				int newheadroom, int newtailroom, int gfp_mask)
{
	/*
	 *	Allocate the copy buffer
	 */
	struct sk_buff *n = alloc_skb(newheadroom + skb->len + newtailroom,
				      gfp_mask);
	int head_copy_len, head_copy_off;

	if (!n)
		return NULL;

	skb_reserve(n, newheadroom);

	/* Set the tail pointer and length */
	skb_put(n, skb->len);

	head_copy_len = skb_headroom(skb);
	head_copy_off = 0;
	if (newheadroom <= head_copy_len)
		head_copy_len = newheadroom;
	else
		head_copy_off = newheadroom - head_copy_len;

	/* Copy the linear header and data. */
	if (skb_copy_bits(skb, -head_copy_len, n->head + head_copy_off,
			  skb->len + head_copy_len))
		BUG();

	copy_skb_header(n, skb);
	skb_shinfo(n)->tso_size = skb_shinfo(skb)->tso_size;
	skb_shinfo(n)->tso_segs = skb_shinfo(skb)->tso_segs;

	return n;
}

/**
 *	skb_pad			-	zero pad the tail of an skb
 *	@skb: buffer to pad
 *	@pad: space to pad
 *
 *	Ensure that a buffer is followed by a padding area that is zero
 *	filled. Used by network drivers which may DMA or transfer data
 *	beyond the buffer end onto the wire.
 *
 *	May return NULL in out of memory cases.
 */
 
struct sk_buff *skb_pad(struct sk_buff *skb, int pad)
{
	struct sk_buff *nskb;
	
	/* If the skbuff is non linear tailroom is always zero.. */
	if (skb_tailroom(skb) >= pad) {
		memset(skb->data+skb->len, 0, pad);
		return skb;
	}
	
	nskb = skb_copy_expand(skb, skb_headroom(skb), skb_tailroom(skb) + pad, GFP_ATOMIC);
	kfree_skb(skb);
	if (nskb)
		memset(nskb->data+nskb->len, 0, pad);
	return nskb;
}	
 
/* Trims skb to length len. It can change skb pointers, if "realloc" is 1.
 * If realloc==0 and trimming is impossible without change of data,
 * it is BUG().
 */

int ___pskb_trim(struct sk_buff *skb, unsigned int len, int realloc)
{
	int offset = skb_headlen(skb);
	int nfrags = skb_shinfo(skb)->nr_frags;
	int i;

	for (i = 0; i < nfrags; i++) {
		int end = offset + skb_shinfo(skb)->frags[i].size;
		if (end > len) {
			if (skb_cloned(skb)) {
				if (!realloc)
					BUG();
				if (pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
					return -ENOMEM;
			}
			if (len <= offset) {
				put_page(skb_shinfo(skb)->frags[i].page);
				skb_shinfo(skb)->nr_frags--;
			} else {
				skb_shinfo(skb)->frags[i].size = len - offset;
			}
		}
		offset = end;
	}

	if (offset < len) {
		skb->data_len -= skb->len - len;
		skb->len       = len;
	} else {
		if (len <= skb_headlen(skb)) {
			skb->len      = len;
			skb->data_len = 0;
			skb->tail     = skb->data + len;
			if (skb_shinfo(skb)->frag_list && !skb_cloned(skb))
				skb_drop_fraglist(skb);
		} else {
			skb->data_len -= skb->len - len;
			skb->len       = len;
		}
	}

	return 0;
}

/**
 *	__pskb_pull_tail - advance tail of skb header
 *	@skb: buffer to reallocate
 *	@delta: number of bytes to advance tail
 *
 *	The function makes a sense only on a fragmented &sk_buff,
 *	it expands header moving its tail forward and copying necessary
 *	data from fragmented part.
 *
 *	&sk_buff MUST have reference count of 1.
 *
 *	Returns %NULL (and &sk_buff does not change) if pull failed
 *	or value of new tail of skb in the case of success.
 *
 *	All the pointers pointing into skb header may change and must be
 *	reloaded after call to this function.
 */

/* Moves tail of skb head forward, copying data from fragmented part,
 * when it is necessary.
 * 1. It may fail due to malloc failure.
 * 2. It may change skb pointers.
 *
 * It is pretty complicated. Luckily, it is called only in exceptional cases.
 */
unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta)
{
	/* If skb has not enough free space at tail, get new one
	 * plus 128 bytes for future expansions. If we have enough
	 * room at tail, reallocate without expansion only if skb is cloned.
	 */
	int i, k, eat = (skb->tail + delta) - skb->end;

	if (eat > 0 || skb_cloned(skb)) {
		if (pskb_expand_head(skb, 0, eat > 0 ? eat + 128 : 0,
				     GFP_ATOMIC))
			return NULL;
	}

	if (skb_copy_bits(skb, skb_headlen(skb), skb->tail, delta))
		BUG();

	/* Optimization: no fragments, no reasons to preestimate
	 * size of pulled pages. Superb.
	 */
	if (!skb_shinfo(skb)->frag_list)
		goto pull_pages;

	/* Estimate size of pulled pages. */
	eat = delta;
	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
		if (skb_shinfo(skb)->frags[i].size >= eat)
			goto pull_pages;
		eat -= skb_shinfo(skb)->frags[i].size;
	}

	/* If we need update frag list, we are in troubles.
	 * Certainly, it possible to add an offset to skb data,
	 * but taking into account that pulling is expected to
	 * be very rare operation, it is worth to fight against
	 * further bloating skb head and crucify ourselves here instead.
	 * Pure masohism, indeed. 8)8)
	 */
	if (eat) {
		struct sk_buff *list = skb_shinfo(skb)->frag_list;
		struct sk_buff *clone = NULL;
		struct sk_buff *insp = NULL;

		do {
			if (!list)
				BUG();

			if (list->len <= eat) {
				/* Eaten as whole. */
				eat -= list->len;
				list = list->next;
				insp = list;
			} else {
				/* Eaten partially. */

				if (skb_shared(list)) {
					/* Sucks! We need to fork list. :-( */
					clone = skb_clone(list, GFP_ATOMIC);
					if (!clone)
						return NULL;
					insp = list->next;
					list = clone;
				} else {
					/* This may be pulled without
					 * problems. */
					insp = list;
				}
				if (!pskb_pull(list, eat)) {
					if (clone)
						kfree_skb(clone);
					return NULL;
				}
				break;
			}
		} while (eat);

		/* Free pulled out fragments. */
		while ((list = skb_shinfo(skb)->frag_list) != insp) {
			skb_shinfo(skb)->frag_list = list->next;
			kfree_skb(list);
		}
		/* And insert new clone at head. */
		if (clone) {
			clone->next = list;
			skb_shinfo(skb)->frag_list = clone;
		}
	}
	/* Success! Now we may commit changes to skb data. */

pull_pages:
	eat = delta;
	k = 0;
	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
		if (skb_shinfo(skb)->frags[i].size <= eat) {
			put_page(skb_shinfo(skb)->frags[i].page);
			eat -= skb_shinfo(skb)->frags[i].size;
		} else {
			skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i];
			if (eat) {
				skb_shinfo(skb)->frags[k].page_offset += eat;
				skb_shinfo(skb)->frags[k].size -= eat;
				eat = 0;
			}
			k++;
		}
	}
	skb_shinfo(skb)->nr_frags = k;

	skb->tail     += delta;
	skb->data_len -= delta;

	return skb->tail;
}

/* Copy some data bits from skb to kernel buffer. */

int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len)
{
	int i, copy;
	int start = skb_headlen(skb);

	if (offset > (int)skb->len - len)
		goto fault;

	/* Copy header. */
	if ((copy = start - offset) > 0) {
		if (copy > len)
			copy = len;
		memcpy(to, skb->data + offset, copy);
		if ((len -= copy) == 0)
			return 0;
		offset += copy;
		to     += copy;
	}

	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
		int end;

		BUG_TRAP(start <= offset + len);

		end = start + skb_shinfo(skb)->frags[i].size;
		if ((copy = end - offset) > 0) {
			u8 *vaddr;

			if (copy > len)
				copy = len;

			vaddr = kmap_skb_frag(&skb_shinfo(skb)->frags[i]);
			memcpy(to,
			       vaddr + skb_shinfo(skb)->frags[i].page_offset+
			       offset - start, copy);
			kunmap_skb_frag(vaddr);

			if ((len -= copy) == 0)
				return 0;
			offset += copy;
			to     += copy;
		}
		start = end;
	}

	if (skb_shinfo(skb)->frag_list) {
		struct sk_buff *list = skb_shinfo(skb)->frag_list;

		for (; list; list = list->next) {
			int end;

			BUG_TRAP(start <= offset + len);

			end = start + list->len;
			if ((copy = end - offset) > 0) {
				if (copy > len)
					copy = len;
				if (skb_copy_bits(list, offset - start,
						  to, copy))
					goto fault;
				if ((len -= copy) == 0)
					return 0;
				offset += copy;
				to     += copy;
			}
			start = end;
		}
	}
	if (!len)
		return 0;

fault:
	return -EFAULT;
}

/* Keep iterating until skb_iter_next returns false. */
void skb_iter_first(const struct sk_buff *skb, struct skb_iter *i)
{
	i->len = skb_headlen(skb);
	i->data = (unsigned char *)skb->data;
	i->nextfrag = 0;
	i->fraglist = NULL;
}

int skb_iter_next(const struct sk_buff *skb, struct skb_iter *i)
{
	/* Unmap previous, if not head fragment. */
	if (i->nextfrag)
		kunmap_skb_frag(i->data);

	if (i->fraglist) {
	fraglist:
		/* We're iterating through fraglist. */
		if (i->nextfrag < skb_shinfo(i->fraglist)->nr_frags) {
			i->data = kmap_skb_frag(&skb_shinfo(i->fraglist)
						->frags[i->nextfrag]);
			i->len = skb_shinfo(i->fraglist)->frags[i->nextfrag]
				.size;
			i->nextfrag++;
			return 1;
		}
		/* Fragments with fragments?  Too hard! */
		BUG_ON(skb_shinfo(i->fraglist)->frag_list);
		i->fraglist = i->fraglist->next;
		if (!i->fraglist)
			goto end;

		i->len = skb_headlen(i->fraglist);
		i->data = i->fraglist->data;
		i->nextfrag = 0;
		return 1;
	}

	if (i->nextfrag < skb_shinfo(skb)->nr_frags) {
		i->data = kmap_skb_frag(&skb_shinfo(skb)->frags[i->nextfrag]);
		i->len = skb_shinfo(skb)->frags[i->nextfrag].size;
		i->nextfrag++;
		return 1;
	}

	i->fraglist = skb_shinfo(skb)->frag_list;
	if (i->fraglist)
		goto fraglist;