Commit 0a1ec07a authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by David S. Miller
Browse files

net: skb_copy_datagram_const_iovec() 



There's an skb_copy_datagram_iovec() to copy out of a paged skb,
but it modifies the iovec, and does not support starting
at an offset in the destination. We want both 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 avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0cededf3

include/linux/skbuff.h

+5 −0
Original line number Diff line number Diff line
@@ -1717,6 +1717,11 @@ extern int skb_copy_datagram_from_iovec(struct sk_buff *skb, 
						    int offset,

						    struct iovec *from,

						    int len);

extern int	       skb_copy_datagram_const_iovec(const struct sk_buff *from,

						     int offset,

						     const struct iovec *to,

						     int to_offset,

						     int size);

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);

include/linux/socket.h

+2 −0
Original line number Diff line number Diff line
@@ -318,6 +318,8 @@ extern int csum_partial_copy_fromiovecend(unsigned char *kdata, 


extern int verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr *address, int mode);

extern int memcpy_toiovec(struct iovec *v, unsigned char *kdata, int len);

extern int memcpy_toiovecend(const struct iovec *v, unsigned char *kdata,

			     int offset, int len);

extern int move_addr_to_user(struct sockaddr *kaddr, int klen, void __user *uaddr, int __user *ulen);

extern int move_addr_to_kernel(void __user *uaddr, int ulen, struct sockaddr *kaddr);

extern int put_cmsg(struct msghdr*, int level, int type, int len, void *data);

net/core/datagram.c

+92 −0
Original line number Diff line number Diff line
@@ -338,6 +338,98 @@ fault: 
	return -EFAULT;

}



/**

 *	skb_copy_datagram_const_iovec - Copy a datagram to an iovec.

 *	@skb: buffer to copy

 *	@offset: offset in the buffer to start copying from

 *	@to: io vector to copy to

 *	@to_offset: offset in the io vector to start copying to

 *	@len: amount of data to copy from buffer to iovec

 *

 *	Returns 0 or -EFAULT.

 *	Note: the iovec is not modified during the copy.

 */

int skb_copy_datagram_const_iovec(const struct sk_buff *skb, int offset,

				  const struct iovec *to, int to_offset,

				  int len)

{

	int start = skb_headlen(skb);

	int i, copy = start - offset;



	/* Copy header. */

	if (copy > 0) {

		if (copy > len)

			copy = len;

		if (memcpy_toiovecend(to, skb->data + offset, to_offset, copy))

			goto fault;

		if ((len -= copy) == 0)

			return 0;

		offset += copy;

		to_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_toiovecend(to, vaddr + frag->page_offset +

						offset - start, to_offset, copy);

			kunmap(page);

			if (err)

				goto fault;

			if (!(len -= copy))

				return 0;

			offset += copy;

			to_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_const_iovec(list,

							    offset - start,

							    to, to_offset,

							    copy))

					goto fault;

				if ((len -= copy) == 0)

					return 0;

				offset += copy;

				to_offset += copy;

			}

			start = end;

		}

	}

	if (!len)

		return 0;



fault:

	return -EFAULT;

}

EXPORT_SYMBOL(skb_copy_datagram_const_iovec);



/**

 *	skb_copy_datagram_from_iovec - Copy a datagram from an iovec.

 *	@skb: buffer to copy

net/core/iovec.c

+26 −0
Original line number Diff line number Diff line
@@ -97,6 +97,31 @@ int memcpy_toiovec(struct iovec *iov, unsigned char *kdata, int len) 
	return 0;

}



/*

 *	Copy kernel to iovec. Returns -EFAULT on error.

 */



int memcpy_toiovecend(const struct iovec *iov, unsigned char *kdata,

		      int offset, int len)

{

	int copy;

	for (; len > 0; ++iov) {

		/* Skip over the finished iovecs */

		if (unlikely(offset >= iov->iov_len)) {

			offset -= iov->iov_len;

			continue;

		}

		copy = min_t(unsigned int, iov->iov_len - offset, len);

		offset = 0;

		if (copy_to_user(iov->iov_base, kdata, copy))

			return -EFAULT;

		kdata += copy;

		len -= copy;

	}



	return 0;

}



/*

 *	Copy iovec to kernel. Returns -EFAULT on error.

 *
@@ -236,3 +261,4 @@ EXPORT_SYMBOL(csum_partial_copy_fromiovecend); 
EXPORT_SYMBOL(memcpy_fromiovec);

EXPORT_SYMBOL(memcpy_fromiovecend);

EXPORT_SYMBOL(memcpy_toiovec);

EXPORT_SYMBOL(memcpy_toiovecend);

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