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net: qualcomm: rmnet: remove unneeded code

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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>
This commit is contained in:
Alex Elder
2021-06-12 09:37:33 -05:00
committed by David S. Miller
parent fab01a6f3a
commit 698aa6c46b
1 changed files with 14 additions and 61 deletions
Download Patch File Download Diff File Expand all files Collapse all files

75
drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
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@@ -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