Commit 9d0407bc authored by Alex Elder's avatar Alex Elder Committed by David S. Miller
Browse files

net: qualcomm: rmnet: show that an intermediate sum is zero 



This patch simply demonstrates that a checksum value computed when
verifying an offloaded transport checksum value for both IPv4 and
IPv6 is (normally) 0.  It can be squashed into the next patch.

Signed-off-by: default avatarAlex Elder <elder@linaro.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent bbd45f10

drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c

+9 −0
Original line number Diff line number Diff line
@@ -84,6 +84,11 @@ rmnet_map_ipv4_dl_csum_trailer(struct sk_buff *skb, 
					 ip4h->protocol, 0);

	pseudo_csum = csum16_add(ip_payload_csum, (__force __be16)pseudo_csum);



	/* The trailer checksum *includes* the checksum in the transport

	 * header.  Adding that to the pseudo checksum will yield 0xffff

	 * ("negative 0") if the message arrived intact.

	 */

	WARN_ON((__sum16)~pseudo_csum);

	csum_value_final = ~csum16_sub(pseudo_csum, (__force __be16)*csum_field);



	if (unlikely(!csum_value_final)) {
@@ -150,6 +155,10 @@ rmnet_map_ipv6_dl_csum_trailer(struct sk_buff *skb, 
				       length, ip6h->nexthdr, 0);

	pseudo_csum = csum16_add(ip6_payload_csum, (__force __be16)pseudo_csum);



	/* Adding the payload checksum to the pseudo checksum yields 0xffff

	 * ("negative 0") if the message arrived intact.

	 */

	WARN_ON((__sum16)~pseudo_csum);

	csum_value_final = ~csum16_sub(pseudo_csum, (__force __be16)*csum_field);



	if (unlikely(csum_value_final == 0)) {