[PATCH] [netfilter]: Fix skb->csum calculation when netfilter manipulation for NF_NAT_MANIP_SRC\DST is done on IPV6 packet.

[Praveen Chaudhary <praveen5582@gmail.com>]

Update skb->csum, when netfilter code updates IPV6 SRC\DST address in IPV6 HEADER due to iptable rule.

Signed-off-by: Praveen Chaudhary <pchaudhary@linkedin.com>
Signed-off-by: Zhenggen Xu <zxu@linkedin.com>
Signed-off-by: Andy Stracner <astracner@linkedin.com>
---
 include/net/checksum.h       |  2 ++
 net/core/utils.c             | 13 +++++++++++++
 net/netfilter/nf_nat_proto.c |  2 ++
 3 files changed, 17 insertions(+)

diff --git a/include/net/checksum.h b/include/net/checksum.h
index 97bf488..d7d28b7 100644
--- a/include/net/checksum.h
+++ b/include/net/checksum.h
@@ -145,6 +145,8 @@ void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
 void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
 			       const __be32 *from, const __be32 *to,
 			       bool pseudohdr);
+void inet_proto_skb_csum_replace16(struct sk_buff *skb,
+			       const __be32 *from, const __be32 *to);
 void inet_proto_csum_replace_by_diff(__sum16 *sum, struct sk_buff *skb,
 				     __wsum diff, bool pseudohdr);
 
diff --git a/net/core/utils.c b/net/core/utils.c
index 6b6e51d..ab3284b 100644
--- a/net/core/utils.c
+++ b/net/core/utils.c
@@ -458,6 +458,19 @@ void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
 }
 EXPORT_SYMBOL(inet_proto_csum_replace16);
 
+void inet_proto_skb_csum_replace16(struct sk_buff *skb,
+			       const __be32 *from, const __be32 *to)
+{
+	__be32 diff[] = {
+		~from[0], ~from[1], ~from[2], ~from[3],
+		to[0], to[1], to[2], to[3],
+	};
+	if (skb->ip_summed == CHECKSUM_COMPLETE)
+		skb->csum = csum_partial(diff, sizeof(diff),
+				  skb->csum);
+}
+EXPORT_SYMBOL(inet_proto_skb_csum_replace16);
+
 void inet_proto_csum_replace_by_diff(__sum16 *sum, struct sk_buff *skb,
 				     __wsum diff, bool pseudohdr)
 {
diff --git a/net/netfilter/nf_nat_proto.c b/net/netfilter/nf_nat_proto.c
index 0a59c14..de94590 100644
--- a/net/netfilter/nf_nat_proto.c
+++ b/net/netfilter/nf_nat_proto.c
@@ -467,6 +467,8 @@ static void nf_nat_ipv6_csum_update(struct sk_buff *skb,
 	}
 	inet_proto_csum_replace16(check, skb, oldip->s6_addr32,
 				  newip->s6_addr32, true);
+	inet_proto_skb_csum_replace16(skb, oldip->s6_addr32,
+				  newip->s6_addr32);
 #endif
 }
 
-- 
2.7.4