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From: Praveen Chaudhary <praveen5582@gmail.com>
To: davem@davemloft.net, fw@strlen.de, kadlec@netfilter.org,
	pablo@netfilter.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Cc: Zhenggen Xu <zxu@linkedin.com>, Andy Stracner <astracner@linkedin.com>
Subject: [PATCH] [netfilter]: Fix skb->csum calculation when netfilter manipulation for NF_NAT_MANIP_SRC\DST is done on IPV6 packet.
Date: Mon, 28 Oct 2019 15:27:55 -0700	[thread overview]
Message-ID: <1572301675-5403-2-git-send-email-pchaudhary@linkedin.com> (raw)
In-Reply-To: <1572301675-5403-1-git-send-email-pchaudhary@linkedin.com>

No need to update skb->csum in function inet_proto_csum_replace16(),
even if skb->ip_summed == CHECKSUM_COMPLETE, because change in L4
header checksum field and change in IPV6 header cancels each other
for skb->csum calculation.

Signed-off-by: Praveen Chaudhary <pchaudhary@linkedin.com>
Signed-off-by: Zhenggen Xu <zxu@linkedin.com>
Signed-off-by: Andy Stracner <astracner@linkedin.com>
---
Changes in V2.
1.) Updating diff as per email discussion with Florian Westphal.
    Since inet_proto_csum_replace16() does incorrect calculation
    for skb->csum in all cases.
2.) Change in Commmit logs.
---
---
 net/core/utils.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/core/utils.c b/net/core/utils.c
index 6b6e51d..cec9924 100644
--- a/net/core/utils.c
+++ b/net/core/utils.c
@@ -438,6 +438,12 @@ void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
 }
 EXPORT_SYMBOL(inet_proto_csum_replace4);
 
+/**
+ * No need to update skb->csum in this function, even if
+ * skb->ip_summed == CHECKSUM_COMPLETE, because change in
+ * L4 header checksum field and change in IPV6 header
+ * cancels each other for skb->csum calculation.
+ */
 void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
 			       const __be32 *from, const __be32 *to,
 			       bool pseudohdr)
@@ -449,9 +455,6 @@ void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
 	if (skb->ip_summed != CHECKSUM_PARTIAL) {
 		*sum = csum_fold(csum_partial(diff, sizeof(diff),
 				 ~csum_unfold(*sum)));
-		if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr)
-			skb->csum = ~csum_partial(diff, sizeof(diff),
-						  ~skb->csum);
 	} else if (pseudohdr)
 		*sum = ~csum_fold(csum_partial(diff, sizeof(diff),
 				  csum_unfold(*sum)));
-- 
2.7.4


  reply	other threads:[~2019-10-28 22:28 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-28 22:27 [PATCH] [netfilter]: Fix skb->csum calculation when netfilter manipulation for NF_NAT_MANIP_SRC\DST is done on IPV6 packet Praveen Chaudhary
2019-10-28 22:27 ` Praveen Chaudhary [this message]
2019-10-29 16:09   ` Florian Westphal
  -- strict thread matches above, loose matches on Subject: below --
2019-10-23 19:02 [PATCH] " Praveen Chaudhary
2019-10-23 19:02 ` [PATCH] [netfilter]: " Praveen Chaudhary
2019-10-23 19:33   ` Florian Westphal
     [not found]     ` <CAJ_cd4qHM3kqz24Uywpyyz0mPz7axiNZk0Q385ROd4O8XZ11fA@mail.gmail.com>
2019-10-24  1:12       ` Florian Westphal

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