/*
   * linux/net/sunrpc/socklib.c
   *
   * Common socket helper routines for RPC client and server
   *
   * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
   */

  #include <linux/compiler.h>
  #include <linux/netdevice.h>
  #include <linux/skbuff.h>

  #include <linux/types.h>
  #include <linux/pagemap.h>
  #include <linux/udp.h>
  #include <linux/sunrpc/xdr.h>
  
  
  /**

   * xdr_skb_read_bits - copy some data bits from skb to internal buffer

   * @desc: sk_buff copy helper
   * @to: copy destination
   * @len: number of bytes to copy
   *
   * Possibly called several times to iterate over an sk_buff and copy
   * data out of it.
   */

  size_t xdr_skb_read_bits(struct xdr_skb_reader *desc, void *to, size_t len)

  {
  	if (len > desc->count)
  		len = desc->count;

  	if (unlikely(skb_copy_bits(desc->skb, desc->offset, to, len)))

  		return 0;
  	desc->count -= len;
  	desc->offset += len;
  	return len;
  }
  
  /**

   * xdr_skb_read_and_csum_bits - copy and checksum from skb to buffer

   * @desc: sk_buff copy helper
   * @to: copy destination
   * @len: number of bytes to copy
   *
   * Same as skb_read_bits, but calculate a checksum at the same time.
   */

  static size_t xdr_skb_read_and_csum_bits(struct xdr_skb_reader *desc, void *to, size_t len)

  {

  	unsigned int pos;
  	__wsum csum2;

  
  	if (len > desc->count)
  		len = desc->count;
  	pos = desc->offset;
  	csum2 = skb_copy_and_csum_bits(desc->skb, pos, to, len, 0);
  	desc->csum = csum_block_add(desc->csum, csum2, pos);
  	desc->count -= len;
  	desc->offset += len;
  	return len;
  }
  
  /**
   * xdr_partial_copy_from_skb - copy data out of an skb
   * @xdr: target XDR buffer
   * @base: starting offset
   * @desc: sk_buff copy helper
   * @copy_actor: virtual method for copying data
   *
   */

  ssize_t xdr_partial_copy_from_skb(struct xdr_buf *xdr, unsigned int base, struct xdr_skb_reader *desc, xdr_skb_read_actor copy_actor)

  {
  	struct page	**ppage = xdr->pages;
  	unsigned int	len, pglen = xdr->page_len;
  	ssize_t		copied = 0;
  	int		ret;
  
  	len = xdr->head[0].iov_len;
  	if (base < len) {
  		len -= base;
  		ret = copy_actor(desc, (char *)xdr->head[0].iov_base + base, len);
  		copied += ret;
  		if (ret != len || !desc->count)
  			goto out;
  		base = 0;
  	} else
  		base -= len;
  
  	if (unlikely(pglen == 0))
  		goto copy_tail;
  	if (unlikely(base >= pglen)) {
  		base -= pglen;
  		goto copy_tail;
  	}
  	if (base || xdr->page_base) {
  		pglen -= base;
  		base += xdr->page_base;
  		ppage += base >> PAGE_CACHE_SHIFT;
  		base &= ~PAGE_CACHE_MASK;
  	}
  	do {
  		char *kaddr;
  
  		/* ACL likes to be lazy in allocating pages - ACLs
  		 * are small by default but can get huge. */
  		if (unlikely(*ppage == NULL)) {
  			*ppage = alloc_page(GFP_ATOMIC);
  			if (unlikely(*ppage == NULL)) {
  				if (copied == 0)
  					copied = -ENOMEM;
  				goto out;
  			}
  		}
  
  		len = PAGE_CACHE_SIZE;
  		kaddr = kmap_atomic(*ppage, KM_SKB_SUNRPC_DATA);
  		if (base) {
  			len -= base;
  			if (pglen < len)
  				len = pglen;
  			ret = copy_actor(desc, kaddr + base, len);
  			base = 0;
  		} else {
  			if (pglen < len)
  				len = pglen;
  			ret = copy_actor(desc, kaddr, len);
  		}
  		flush_dcache_page(*ppage);
  		kunmap_atomic(kaddr, KM_SKB_SUNRPC_DATA);
  		copied += ret;
  		if (ret != len || !desc->count)
  			goto out;
  		ppage++;
  	} while ((pglen -= len) != 0);
  copy_tail:
  	len = xdr->tail[0].iov_len;
  	if (base < len)
  		copied += copy_actor(desc, (char *)xdr->tail[0].iov_base + base, len - base);
  out:
  	return copied;
  }
  
  /**
   * csum_partial_copy_to_xdr - checksum and copy data
   * @xdr: target XDR buffer
   * @skb: source skb
   *
   * We have set things up such that we perform the checksum of the UDP
   * packet in parallel with the copies into the RPC client iovec.  -DaveM
   */
  int csum_partial_copy_to_xdr(struct xdr_buf *xdr, struct sk_buff *skb)
  {

  	struct xdr_skb_reader	desc;

  
  	desc.skb = skb;
  	desc.offset = sizeof(struct udphdr);
  	desc.count = skb->len - desc.offset;

  	if (skb_csum_unnecessary(skb))

  		goto no_checksum;
  
  	desc.csum = csum_partial(skb->data, desc.offset, skb->csum);

  	if (xdr_partial_copy_from_skb(xdr, 0, &desc, xdr_skb_read_and_csum_bits) < 0)

  		return -1;
  	if (desc.offset != skb->len) {

  		__wsum csum2;

  		csum2 = skb_checksum(skb, desc.offset, skb->len - desc.offset, 0);
  		desc.csum = csum_block_add(desc.csum, csum2, desc.offset);
  	}
  	if (desc.count)
  		return -1;

  	if (csum_fold(desc.csum))

  		return -1;

  	if (unlikely(skb->ip_summed == CHECKSUM_COMPLETE))

  		netdev_rx_csum_fault(skb->dev);

  	return 0;
  no_checksum:

  	if (xdr_partial_copy_from_skb(xdr, 0, &desc, xdr_skb_read_bits) < 0)

  		return -1;
  	if (desc.count)
  		return -1;
  	return 0;
  }