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net: skb_copy_datagram_from_iovec()

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There's an skb_copy_datagram_iovec() to copy out of a paged skb, but
nothing the other way around (because we don't do that).

We want to allocate big skbs in tun.c, so let's add the function.
It's a carbon copy of skb_copy_datagram_iovec() with enough changes to
be annoying.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Rusty Russell 2008-08-15 15:13:53 -07:00 committed by David S. Miller
parent e3b9955697
commit db543c1f97
2 changed files with 91 additions and 0 deletions
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4
include/linux/skbuff.h
View file

@ -1452,6 +1452,10 @@ extern int skb_copy_datagram_iovec(const struct sk_buff *from,
extern int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
int hlen,
struct iovec *iov);
extern int skb_copy_datagram_from_iovec(struct sk_buff *skb,
int offset,
struct iovec *from,
int len);
extern void skb_free_datagram(struct sock *sk, struct sk_buff *skb);
extern int skb_kill_datagram(struct sock *sk, struct sk_buff *skb,
unsigned int flags);

87
net/core/datagram.c
View file

@ -339,6 +339,93 @@ int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset,
return -EFAULT;
}
/**
* skb_copy_datagram_from_iovec - Copy a datagram from an iovec.
* @skb: buffer to copy
* @offset: offset in the buffer to start copying to
* @from: io vector to copy to
* @len: amount of data to copy to buffer from iovec
*
* Returns 0 or -EFAULT.
* Note: the iovec is modified during the copy.
*/
int skb_copy_datagram_from_iovec(struct sk_buff *skb, int offset,
struct iovec *from, int len)
{
int start = skb_headlen(skb);
int i, copy = start - offset;
/* Copy header. */
if (copy > 0) {
if (copy > len)
copy = len;
if (memcpy_fromiovec(skb->data + offset, from, copy))
goto fault;
if ((len -= copy) == 0)
return 0;
offset += copy;
}
/* Copy paged appendix. Hmm... why does this look so complicated? */
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
int end;
WARN_ON(start > offset + len);
end = start + skb_shinfo(skb)->frags[i].size;
if ((copy = end - offset) > 0) {
int err;
u8 *vaddr;
skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
struct page *page = frag->page;
if (copy > len)
copy = len;
vaddr = kmap(page);
err = memcpy_fromiovec(vaddr + frag->page_offset +
offset - start, from, copy);
kunmap(page);
if (err)
goto fault;
if (!(len -= copy))
return 0;
offset += 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;
WARN_ON(start > offset + len);
end = start + list->len;
if ((copy = end - offset) > 0) {
if (copy > len)
copy = len;
if (skb_copy_datagram_from_iovec(list,
offset - start,
from, copy))
goto fault;
if ((len -= copy) == 0)
return 0;
offset += copy;
}
start = end;
}
}
if (!len)
return 0;
fault:
return -EFAULT;
}
EXPORT_SYMBOL(skb_copy_datagram_from_iovec);
static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
u8 __user *to, int len,
__wsum *csump)