From: Alex Elder <elder@linaro.org>
To: subashab@codeaurora.org, stranche@codeaurora.org,
davem@davemloft.net, kuba@kernel.org
Cc: bjorn.andersson@linaro.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH net-next 2/8] net: qualcomm: rmnet: rearrange some NOTs
Date: Sat, 12 Jun 2021 09:37:30 -0500 [thread overview]
Message-ID: <20210612143736.3498712-3-elder@linaro.org> (raw)
In-Reply-To: <20210612143736.3498712-1-elder@linaro.org>
With the ones' complement arithmetic, the sum of two negated values
is equal to the negation of the sum of the two original values [1].
Rearrange the calculation ip6_payload_sum using this property.
[1] https://tools.ietf.org/html/rfc1071
Signed-off-by: Alex Elder <elder@linaro.org>
---
drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
index 3e6feef0fd252..1b170e9189d8a 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
@@ -140,8 +140,8 @@ rmnet_map_ipv6_dl_csum_trailer(struct sk_buff *skb,
* checksum computed over the pseudo header.
*/
ip_header_csum = (__force __be16)ip_fast_csum(ip6h, sizeof(*ip6h) / 4);
- ip6_payload_csum = csum16_sub((__force __sum16)~csum_trailer->csum_value,
- ~ip_header_csum);
+ ip6_payload_csum = ~csum16_sub((__force __sum16)csum_trailer->csum_value,
+ ip_header_csum);
length = (ip6h->nexthdr == IPPROTO_UDP) ?
ntohs(((struct udphdr *)txporthdr)->len) :
--
2.27.0
next prev parent reply other threads:[~2021-06-12 14:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-12 14:37 [PATCH net-next 0/8] net: qualcomm: rmnet: MAPv4 download checksum cleanup, part 2 Alex Elder
2021-06-12 14:37 ` [PATCH net-next 1/8] net: qualcomm: rmnet: remove some local variables Alex Elder
2021-06-12 14:37 ` Alex Elder [this message]
2021-06-12 14:37 ` [PATCH net-next 3/8] net: qualcomm: rmnet: show that an intermediate sum is zero Alex Elder
2021-06-12 14:37 ` [PATCH net-next 4/8] net: qualcomm: rmnet: return earlier for bad checksum Alex Elder
2021-06-12 14:37 ` [PATCH net-next 5/8] net: qualcomm: rmnet: remove unneeded code Alex Elder
2021-06-12 14:37 ` [PATCH net-next 6/8] net: qualcomm: rmnet: trailer value is a checksum Alex Elder
2021-06-12 14:37 ` [PATCH net-next 7/8] net: qualcomm: rmnet: drop some unary NOTs Alex Elder
2021-06-12 14:37 ` [PATCH net-next 8/8] net: qualcomm: rmnet: IPv6 payload length is simple Alex Elder
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