lkml.org 
[lkml]   [2021]   [Jun]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH net-next 3/8] net: qualcomm: rmnet: show that an intermediate sum is zero
Date
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 <elder@linaro.org>
---
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
\
 
 \ /
  Last update: 2021-06-12 16:40    [W:0.065 / U:0.176 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site