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-rw-r--r--net/core/skbuff.c117
1 files changed, 117 insertions, 0 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 6d68c03bc051..d285f2f7e812 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1500,6 +1500,120 @@ void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len)
1500 skb_split_no_header(skb, skb1, len, pos); 1500 skb_split_no_header(skb, skb1, len, pos);
1501} 1501}
1502 1502
1503/**
1504 * skb_prepare_seq_read - Prepare a sequential read of skb data
1505 * @skb: the buffer to read
1506 * @from: lower offset of data to be read
1507 * @to: upper offset of data to be read
1508 * @st: state variable
1509 *
1510 * Initializes the specified state variable. Must be called before
1511 * invoking skb_seq_read() for the first time.
1512 */
1513void skb_prepare_seq_read(struct sk_buff *skb, unsigned int from,
1514 unsigned int to, struct skb_seq_state *st)
1515{
1516 st->lower_offset = from;
1517 st->upper_offset = to;
1518 st->root_skb = st->cur_skb = skb;
1519 st->frag_idx = st->stepped_offset = 0;
1520 st->frag_data = NULL;
1521}
1522
1523/**
1524 * skb_seq_read - Sequentially read skb data
1525 * @consumed: number of bytes consumed by the caller so far
1526 * @data: destination pointer for data to be returned
1527 * @st: state variable
1528 *
1529 * Reads a block of skb data at &consumed relative to the
1530 * lower offset specified to skb_prepare_seq_read(). Assigns
1531 * the head of the data block to &data and returns the length
1532 * of the block or 0 if the end of the skb data or the upper
1533 * offset has been reached.
1534 *
1535 * The caller is not required to consume all of the data
1536 * returned, i.e. &consumed is typically set to the number
1537 * of bytes already consumed and the next call to
1538 * skb_seq_read() will return the remaining part of the block.
1539 *
1540 * Note: The size of each block of data returned can be arbitary,
1541 * this limitation is the cost for zerocopy seqeuental
1542 * reads of potentially non linear data.
1543 *
1544 * Note: Fragment lists within fragments are not implemented
1545 * at the moment, state->root_skb could be replaced with
1546 * a stack for this purpose.
1547 */
1548unsigned int skb_seq_read(unsigned int consumed, const u8 **data,
1549 struct skb_seq_state *st)
1550{
1551 unsigned int block_limit, abs_offset = consumed + st->lower_offset;
1552 skb_frag_t *frag;
1553
1554 if (unlikely(abs_offset >= st->upper_offset))
1555 return 0;
1556
1557next_skb:
1558 block_limit = skb_headlen(st->cur_skb);
1559
1560 if (abs_offset < block_limit) {
1561 *data = st->cur_skb->data + abs_offset;
1562 return block_limit - abs_offset;
1563 }
1564
1565 if (st->frag_idx == 0 && !st->frag_data)
1566 st->stepped_offset += skb_headlen(st->cur_skb);
1567
1568 while (st->frag_idx < skb_shinfo(st->cur_skb)->nr_frags) {
1569 frag = &skb_shinfo(st->cur_skb)->frags[st->frag_idx];
1570 block_limit = frag->size + st->stepped_offset;
1571
1572 if (abs_offset < block_limit) {
1573 if (!st->frag_data)
1574 st->frag_data = kmap_skb_frag(frag);
1575
1576 *data = (u8 *) st->frag_data + frag->page_offset +
1577 (abs_offset - st->stepped_offset);
1578
1579 return block_limit - abs_offset;
1580 }
1581
1582 if (st->frag_data) {
1583 kunmap_skb_frag(st->frag_data);
1584 st->frag_data = NULL;
1585 }
1586
1587 st->frag_idx++;
1588 st->stepped_offset += frag->size;
1589 }
1590
1591 if (st->cur_skb->next) {
1592 st->cur_skb = st->cur_skb->next;
1593 st->frag_idx = 0;
1594 goto next_skb;
1595 } else if (st->root_skb == st->cur_skb &&
1596 skb_shinfo(st->root_skb)->frag_list) {
1597 st->cur_skb = skb_shinfo(st->root_skb)->frag_list;
1598 goto next_skb;
1599 }
1600
1601 return 0;
1602}
1603
1604/**
1605 * skb_abort_seq_read - Abort a sequential read of skb data
1606 * @st: state variable
1607 *
1608 * Must be called if skb_seq_read() was not called until it
1609 * returned 0.
1610 */
1611void skb_abort_seq_read(struct skb_seq_state *st)
1612{
1613 if (st->frag_data)
1614 kunmap_skb_frag(st->frag_data);
1615}
1616
1503void __init skb_init(void) 1617void __init skb_init(void)
1504{ 1618{
1505 skbuff_head_cache = kmem_cache_create("skbuff_head_cache", 1619 skbuff_head_cache = kmem_cache_create("skbuff_head_cache",
@@ -1538,3 +1652,6 @@ EXPORT_SYMBOL(skb_queue_tail);
1538EXPORT_SYMBOL(skb_unlink); 1652EXPORT_SYMBOL(skb_unlink);
1539EXPORT_SYMBOL(skb_append); 1653EXPORT_SYMBOL(skb_append);
1540EXPORT_SYMBOL(skb_split); 1654EXPORT_SYMBOL(skb_split);
1655EXPORT_SYMBOL(skb_prepare_seq_read);
1656EXPORT_SYMBOL(skb_seq_read);
1657EXPORT_SYMBOL(skb_abort_seq_read);