Commit db543c1f authored by Rusty Russell's avatar Rusty Russell Committed by David S. Miller
Browse files

net: skb_copy_datagram_from_iovec() 



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: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e3b99556

include/linux/skbuff.h

+4 −0
Original line number Diff line number Diff line
@@ -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);

net/core/datagram.c

+87 −0
Original line number Diff line number Diff line
@@ -339,6 +339,93 @@ fault: 
	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)

CRA Git | Maintained and supported by SUSTech CRA and CCSE