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SubjectRe: [PATCH v2,net-next 1/2] ip_gre: fix parsing gre header in ipgre_err
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> On 2018年9月14日, at 下午8:44, Edward Cree <ecree@solarflare.com> wrote:
>
> On 13/09/18 18:58, David Miller wrote:
>> From: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
>> Date: Wed, 12 Sep 2018 17:21:21 +0800
>>
>>> @@ -86,7 +86,7 @@ int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
>>>
>>> options = (__be32 *)(greh + 1);
>>> if (greh->flags & GRE_CSUM) {
>>> - if (skb_checksum_simple_validate(skb)) {
>>> + if (csum_err && skb_checksum_simple_validate(skb)) {
>>> *csum_err = true;
>>> return -EINVAL;
>>> }
>> You want to ignore csum errors, but you do not want to elide the side
>> effects of the skb_checksum_simple_validate() call which are to set
>> skb->csum_valid and skb->csum.
>>
>> Therefore, the skb_checksum_simple_validate() call still needs to be
>> performed. We just wont return -EINVAL in the NULL csum_err case.
>
> How about just reversing the order of the AND?
>
> if (skb_checksum_simple_validate(skb) && csum_err) {
> *csum_err = true;
> return -EINVAL;
> }
>
>

It looks good to me, thanks!

But skb_checksum_try_convert only need to be called after the checksum is
validated, so I suggested a better solution as following:

89 if (!skb_checksum_simple_validate(skb)) {
90 skb_checksum_try_convert(skb, IPPROTO_GRE, 0,
91 null_compute_pseudo);
92 } else if (csum_err) {
93 *csum_err = true;
94 return -EINVAL;
95 }






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