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[NET]: Zerocopy sequential reading of skb data

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Implements sequential reading for both linear and non-linear
skb data at zerocopy cost. The data is returned in chunks of
arbitary length, therefore random access is not possible.

Usage:
	from	 := 0
	to	 := 128
	state	 := undef
	data	 := undef
	len	 := undef
	consumed := 0

	skb_prepare_seq_read(skb, from, to, &state)
	while (len = skb_seq_read(consumed, &data, &state)) != 0 do
		/* do something with 'data' of length 'len' */
		if abort then
			/* abort read if we don't wait for
			 * skb_seq_read() to return 0 */
			skb_abort_seq_read(&state)
			return
		endif
		/* not necessary to consume all of 'len' */
		consumed += len
	done

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Thomas Graf
2005-06-23 20:59:51 -07:00
committed by David S. Miller
parent 6408f79cce
commit 677e90eda3
2 changed files with 135 additions and 0 deletions
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18
include/linux/skbuff.h
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@ -321,6 +321,24 @@ extern void skb_over_panic(struct sk_buff *skb, int len,
extern void skb_under_panic(struct sk_buff *skb, int len,
void *here);
struct skb_seq_state
{
__u32 lower_offset;
__u32 upper_offset;
__u32 frag_idx;
__u32 stepped_offset;
struct sk_buff *root_skb;
struct sk_buff *cur_skb;
__u8 *frag_data;
};
extern void skb_prepare_seq_read(struct sk_buff *skb,
unsigned int from, unsigned int to,
struct skb_seq_state *st);
extern unsigned int skb_seq_read(unsigned int consumed, const u8 **data,
struct skb_seq_state *st);
extern void skb_abort_seq_read(struct skb_seq_state *st);
/* Internal */
#define skb_shinfo(SKB) ((struct skb_shared_info *)((SKB)->end))