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net: Fix skb->csum update in inet_proto_csum_replace16().

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skb->csum is updated incorrectly, when manipulation for
NF_NAT_MANIP_SRC\DST is done on IPV6 packet.

Fix:
There is no need to update skb->csum in inet_proto_csum_replace16(),
because update in two fields a.) IPv6 src/dst address and b.) L4 header
checksum cancels each other for skb->csum calculation. Whereas
inet_proto_csum_replace4 function needs to update skb->csum, because
update in 3 fields a.) IPv4 src/dst address, b.) IPv4 Header checksum
and c.) L4 header checksum results in same diff as L4 Header checksum
for skb->csum calculation.

[ pablo@netfilter.org: a few comestic documentation edits ]
Signed-off-by: Praveen Chaudhary <pchaudhary@linkedin.com>
Signed-off-by: Zhenggen Xu <zxu@linkedin.com>
Signed-off-by: Andy Stracner <astracner@linkedin.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Praveen Chaudhary
2020-01-23 12:33:28 -08:00
committed by Pablo Neira Ayuso
parent eb014de4fd
commit 189c9b1e94
1 changed files with 17 additions and 3 deletions
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20
net/core/utils.c
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@@ -438,6 +438,23 @@ void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
} }
EXPORT_SYMBOL(inet_proto_csum_replace4); EXPORT_SYMBOL(inet_proto_csum_replace4);
/**
* inet_proto_csum_replace16 - update layer 4 header checksum field
* @sum: Layer 4 header checksum field
* @skb: sk_buff for the packet
* @from: old IPv6 address
* @to: new IPv6 address
* @pseudohdr: True if layer 4 header checksum includes pseudoheader
*
* Update layer 4 header as per the update in IPv6 src/dst address.
*
* There is no need to update skb->csum in this function, because update in two
* fields a.) IPv6 src/dst address and b.) L4 header checksum cancels each other
* for skb->csum calculation. Whereas inet_proto_csum_replace4 function needs to
* update skb->csum, because update in 3 fields a.) IPv4 src/dst address,
* b.) IPv4 Header checksum and c.) L4 header checksum results in same diff as
* L4 Header checksum for skb->csum calculation.
*/
void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb, void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
const __be32 *from, const __be32 *to, const __be32 *from, const __be32 *to,
bool pseudohdr) bool pseudohdr)
@@ -449,9 +466,6 @@ void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
if (skb->ip_summed != CHECKSUM_PARTIAL) { if (skb->ip_summed != CHECKSUM_PARTIAL) {
*sum = csum_fold(csum_partial(diff, sizeof(diff), *sum = csum_fold(csum_partial(diff, sizeof(diff),
~csum_unfold(*sum))); ~csum_unfold(*sum)));
if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr)
skb->csum = ~csum_partial(diff, sizeof(diff),
~skb->csum);
} else if (pseudohdr) } else if (pseudohdr)
*sum = ~csum_fold(csum_partial(diff, sizeof(diff), *sum = ~csum_fold(csum_partial(diff, sizeof(diff),
csum_unfold(*sum))); csum_unfold(*sum)));