[PATCH net-next 3/8] net: qualcomm: rmnet: show that an intermediate sum is zero
From: Alex Elder <hidden>
Date: 2021-06-12 14:39:07
Also in:
lkml
Subsystem:
networking drivers, qualcomm rmnet driver, the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Subash Abhinov Kasiviswanathan, Sean Tranchetti, Linus Torvalds
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: Alex Elder <redacted> --- drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
index 1b170e9189d8a..51909b8fa8a80 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c@@ -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)) {
--
2.27.0