net: skb_checksum: allow custom update/combine for walking skb
Currently, skb_checksum walks over 1) linearized, 2) frags[], and
3) frag_list data and calculats the one's complement, a 32 bit
result suitable for feeding into itself or csum_tcpudp_magic(),
but unsuitable for SCTP as we're calculating CRC32c there.
Hence, in order to not re-implement the very same function in
SCTP (and maybe other protocols) over and over again, use an
update() + combine() callback internally to allow for walking
over the skb with different algorithms.
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 0ab32fa..31aab53 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1928,9 +1928,8 @@
EXPORT_SYMBOL(skb_store_bits);
/* Checksum skb data. */
-
-__wsum skb_checksum(const struct sk_buff *skb, int offset,
- int len, __wsum csum)
+__wsum __skb_checksum(const struct sk_buff *skb, int offset, int len,
+ __wsum csum, const struct skb_checksum_ops *ops)
{
int start = skb_headlen(skb);
int i, copy = start - offset;
@@ -1941,7 +1940,7 @@
if (copy > 0) {
if (copy > len)
copy = len;
- csum = csum_partial(skb->data + offset, copy, csum);
+ csum = ops->update(skb->data + offset, copy, csum);
if ((len -= copy) == 0)
return csum;
offset += copy;
@@ -1962,10 +1961,10 @@
if (copy > len)
copy = len;
vaddr = kmap_atomic(skb_frag_page(frag));
- csum2 = csum_partial(vaddr + frag->page_offset +
- offset - start, copy, 0);
+ csum2 = ops->update(vaddr + frag->page_offset +
+ offset - start, copy, 0);
kunmap_atomic(vaddr);
- csum = csum_block_add(csum, csum2, pos);
+ csum = ops->combine(csum, csum2, pos, copy);
if (!(len -= copy))
return csum;
offset += copy;
@@ -1984,9 +1983,9 @@
__wsum csum2;
if (copy > len)
copy = len;
- csum2 = skb_checksum(frag_iter, offset - start,
- copy, 0);
- csum = csum_block_add(csum, csum2, pos);
+ csum2 = __skb_checksum(frag_iter, offset - start,
+ copy, 0, ops);
+ csum = ops->combine(csum, csum2, pos, copy);
if ((len -= copy) == 0)
return csum;
offset += copy;
@@ -1998,6 +1997,18 @@
return csum;
}
+EXPORT_SYMBOL(__skb_checksum);
+
+__wsum skb_checksum(const struct sk_buff *skb, int offset,
+ int len, __wsum csum)
+{
+ const struct skb_checksum_ops ops = {
+ .update = csum_partial,
+ .combine = csum_block_add_ext,
+ };
+
+ return __skb_checksum(skb, offset, len, csum, &ops);
+}
EXPORT_SYMBOL(skb_checksum);
/* Both of above in one bottle. */