Commit 698aa6c4 authored by Alex Elder's avatar Alex Elder Committed by David S. Miller
Browse files

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: default avatarAlex Elder <elder@linaro.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fab01a6f

drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c

+14 −61
Original line number Diff line number Diff line
@@ -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;

	}

}



#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;

	}

}

#endif