netdev - [PATCH 1/2] bpf: bpf_csum_diff: fold the checksum before returning the value

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Message-Id: <1562838037-1884-2-git-send-email-p.pisati@gmail.com>
Date:   Thu, 11 Jul 2019 11:40:36 +0200
From:   Paolo Pisati <p.pisati@...il.com>
To:     --to=Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        "David S . Miller" <davem@...emloft.net>,
        Shuah Khan <shuah@...nel.org>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jiong Wang <jiong.wang@...ronome.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] bpf: bpf_csum_diff: fold the checksum before returning the value

From: Paolo Pisati <paolo.pisati@...onical.com>

With this change, bpf_csum_diff behave homogeneously among different
checksum calculation code / csum_partial() (tested on x86-64, arm64 and
arm).

Signed-off-by: Paolo Pisati <paolo.pisati@...onical.com>
---
 net/core/filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index f615e42cf4ef..8db7f58f1ea1 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1990,7 +1990,7 @@ BPF_CALL_5(bpf_csum_diff, __be32 *, from, u32, from_size,
 	for (i = 0; i <   to_size / sizeof(__be32); i++, j++)
 		sp->diff[j] = to[i];
 
-	return csum_partial(sp->diff, diff_size, seed);
+	return csum_fold(csum_partial(sp->diff, diff_size, seed));
 }
 
 static const struct bpf_func_proto bpf_csum_diff_proto = {
-- 
2.17.1