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Message-Id: <20210612143736.3498712-6-elder@linaro.org>
Date: Sat, 12 Jun 2021 09:37:33 -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 5/8] net: qualcomm: rmnet: remove unneeded code
The previous patch makes rmnet_map_ipv4_dl_csum_trailer() return
early with an error if it is determined that the computed checksum
for the IP payload does not match what was expected.
If the computed checksum *does* match the expected value, the IP
payload (i.e., the transport message), can be considered good.
There is no need to do any further processing of the message.
This means a big block of code is unnecessary for validating the
transport checksum value, and can be removed.
Make comparable changes in rmnet_map_ipv6_dl_csum_trailer().
Signed-off-by: Alex Elder <elder@...aro.org>
---
.../ethernet/qualcomm/rmnet/rmnet_map_data.c | 75 ++++---------------
1 file changed, 14 insertions(+), 61 deletions(-)
diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
index a05124eb8602e..033b8ad3d7356 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
@@ -37,7 +37,6 @@ rmnet_map_ipv4_dl_csum_trailer(struct sk_buff *skb,
void *txporthdr = skb->data + ip4h->ihl * 4;
__sum16 *csum_field, pseudo_csum;
__sum16 ip_payload_csum;
- __sum16 csum_value_final;
/* Computing the checksum over just the IPv4 header--including its
* checksum field--should yield 0. If it doesn't, the IP header
@@ -93,37 +92,15 @@ rmnet_map_ipv4_dl_csum_trailer(struct sk_buff *skb,
pseudo_csum = ~csum_tcpudp_magic(ip4h->saddr, ip4h->daddr,
ntohs(ip4h->tot_len) - ip4h->ihl * 4,
ip4h->protocol, 0);
- pseudo_csum = csum16_add(ip_payload_csum, (__force __be16)pseudo_csum);
/* The cast is required to ensure only the low 16 bits are examined */
- if ((__sum16)~pseudo_csum) {
+ if (ip_payload_csum != (__sum16)~pseudo_csum) {
priv->stats.csum_validation_failed++;
return -EINVAL;
}
- csum_value_final = ~csum16_sub(pseudo_csum, (__force __be16)*csum_field);
- if (unlikely(!csum_value_final)) {
- switch (ip4h->protocol) {
- case IPPROTO_UDP:
- /* RFC 768 - DL4 1's complement rule for UDP csum 0 */
- csum_value_final = ~csum_value_final;
- break;
-
- case IPPROTO_TCP:
- /* DL4 Non-RFC compliant TCP checksum found */
- if (*csum_field == (__force __sum16)0xFFFF)
- csum_value_final = ~csum_value_final;
- break;
- }
- }
-
- if (csum_value_final == *csum_field) {
- priv->stats.csum_ok++;
- return 0;
- } else {
- priv->stats.csum_validation_failed++;
- return -EINVAL;
- }
+ priv->stats.csum_ok++;
+ return 0;
}
#if IS_ENABLED(CONFIG_IPV6)
@@ -137,7 +114,6 @@ rmnet_map_ipv6_dl_csum_trailer(struct sk_buff *skb,
__sum16 *csum_field, pseudo_csum;
__sum16 ip6_payload_csum;
__be16 ip_header_csum;
- __sum16 csum_value_final;
u32 length;
/* Checksum offload is only supported for UDP and TCP protocols;
@@ -154,11 +130,6 @@ rmnet_map_ipv6_dl_csum_trailer(struct sk_buff *skb,
* transport checksum from this, we first subract the contribution
* of the IP header from the trailer checksum. We then add the
* checksum computed over the pseudo header.
- *
- * It's sufficient to compare the IP payload checksum with the
- * negated pseudo checksum to determine whether the packet
- * checksum was good. (See further explanation in comments
- * in rmnet_map_ipv4_dl_csum_trailer()).
*/
ip_header_csum = (__force __be16)ip_fast_csum(ip6h, sizeof(*ip6h) / 4);
ip6_payload_csum = ~csum16_sub((__force __sum16)csum_trailer->csum_value,
@@ -169,40 +140,22 @@ rmnet_map_ipv6_dl_csum_trailer(struct sk_buff *skb,
ntohs(ip6h->payload_len);
pseudo_csum = ~csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
length, ip6h->nexthdr, 0);
- pseudo_csum = csum16_add(ip6_payload_csum, (__force __be16)pseudo_csum);
- /* The cast is required to ensure only the low 16 bits are examined */
- if ((__sum16)~pseudo_csum) {
+ /* It's sufficient to compare the IP payload checksum with the
+ * negated pseudo checksum to determine whether the packet
+ * checksum was good. (See further explanation in comments
+ * in rmnet_map_ipv4_dl_csum_trailer()).
+ *
+ * The cast is required to ensure only the low 16 bits are
+ * examined.
+ */
+ if (ip6_payload_csum != (__sum16)~pseudo_csum) {
priv->stats.csum_validation_failed++;
return -EINVAL;
}
- csum_value_final = ~csum16_sub(pseudo_csum, (__force __be16)*csum_field);
-
- if (unlikely(csum_value_final == 0)) {
- switch (ip6h->nexthdr) {
- case IPPROTO_UDP:
- /* RFC 2460 section 8.1
- * DL6 One's complement rule for UDP checksum 0
- */
- csum_value_final = ~csum_value_final;
- break;
-
- case IPPROTO_TCP:
- /* DL6 Non-RFC compliant TCP checksum found */
- if (*csum_field == (__force __sum16)0xFFFF)
- csum_value_final = ~csum_value_final;
- break;
- }
- }
-
- if (csum_value_final == *csum_field) {
- priv->stats.csum_ok++;
- return 0;
- } else {
- priv->stats.csum_validation_failed++;
- return -EINVAL;
- }
+ priv->stats.csum_ok++;
+ return 0;
}
#endif
--
2.27.0
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