linux-kernel - [PATCH net-next 8/8] net: qualcomm: rmnet: avoid unnecessary IPv6 byte-swapping

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Date:   Fri, 11 Jun 2021 14:05:29 -0500
From:   Alex Elder <elder@...aro.org>
To:     subashab@...eaurora.org, stranche@...eaurora.org,
        davem@...emloft.net, kuba@...nel.org
Cc:     bjorn.andersson@...aro.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH net-next 8/8] net: qualcomm: rmnet: avoid unnecessary IPv6 byte-swapping

In the previous patch IPv4 download checksum offload code was
updated to avoid unnecessary byte swapping, based on properties of
the Internet checksum algorithm.  This patch makes comparable
changes to the IPv6 download checksum offload handling.

Signed-off-by: Alex Elder <elder@...aro.org>
---
 .../ethernet/qualcomm/rmnet/rmnet_map_data.c    | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
index 39f198d7595bd..d4d23ab446ef5 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
@@ -123,10 +123,11 @@ rmnet_map_ipv6_dl_csum_trailer(struct sk_buff *skb,
 	struct ipv6hdr *ip6h = (struct ipv6hdr *)skb->data;
 	void *txporthdr = skb->data + sizeof(*ip6h);
 	__sum16 *csum_field, pseudo_csum, csum_temp;
-	u16 csum_value, csum_value_final;
 	__be16 ip6_hdr_csum, addend;
 	__sum16 ip6_payload_csum;
 	__be16 ip_header_csum;
+	u16 csum_value_final;
+	__be16 csum_value;
 	u32 length;
 
 	/* Checksum offload is only supported for UDP and TCP protocols;
@@ -144,21 +145,21 @@ rmnet_map_ipv6_dl_csum_trailer(struct sk_buff *skb,
 	 * of the IP header from the trailer checksum.  We then add the
 	 * checksum computed over the pseudo header.
 	 */
-	csum_value = ~ntohs(csum_trailer->csum_value);
+	csum_value = ~csum_trailer->csum_value;
 	ip_header_csum = (__force __be16)ip_fast_csum(ip6h, sizeof(*ip6h) / 4);
-	ip6_hdr_csum = (__force __be16)~ntohs(ip_header_csum);
+	ip6_hdr_csum = (__force __be16)~ip_header_csum;
 	ip6_payload_csum = csum16_sub((__force __sum16)csum_value,
 				      ip6_hdr_csum);
 
 	length = (ip6h->nexthdr == IPPROTO_UDP) ?
 		 ntohs(((struct udphdr *)txporthdr)->len) :
 		 ntohs(ip6h->payload_len);
-	pseudo_csum = ~(csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
-			     length, ip6h->nexthdr, 0));
-	addend = (__force __be16)ntohs((__force __be16)pseudo_csum);
+	pseudo_csum = ~csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
+				       length, ip6h->nexthdr, 0);
+	addend = (__force __be16)pseudo_csum;
 	pseudo_csum = csum16_add(ip6_payload_csum, addend);
 
-	addend = (__force __be16)ntohs((__force __be16)*csum_field);
+	addend = (__force __be16)*csum_field;
 	csum_temp = ~csum16_sub(pseudo_csum, addend);
 	csum_value_final = (__force u16)csum_temp;
 
@@ -179,7 +180,7 @@ rmnet_map_ipv6_dl_csum_trailer(struct sk_buff *skb,
 		}
 	}
 
-	if (csum_value_final == ntohs((__force __be16)*csum_field)) {
+	if (csum_value_final == (__force u16)*csum_field) {
 		priv->stats.csum_ok++;
 		return 0;
 	} else {
-- 
2.27.0