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>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/net/checksum.h b/include/net/checksum.h
index 8f59ca50477c..15f33fde826e 100644
--- a/include/net/checksum.h
+++ b/include/net/checksum.h
@@ -79,6 +79,12 @@ csum_block_add(__wsum csum, __wsum csum2, int offset)
 }
 
 static inline __wsum
+csum_block_add_ext(__wsum csum, __wsum csum2, int offset, int len)
+{
+        return csum_block_add(csum, csum2, offset);
+}
+
+static inline __wsum
 csum_block_sub(__wsum csum, __wsum csum2, int offset)
 {
         u32 sum = (__force u32)csum2;