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@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
index a05124e..033b8ad 100644 (file)
--- 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