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SubjectRe: [PATCH v2] xfrm: policy: Fix xfrm policy match
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On 2020/5/23 17:02, Xin Long wrote:
> On Fri, May 22, 2020 at 8:39 PM Yuehaibing <yuehaibing@huawei.com> wrote:
>>
>> On 2020/5/22 13:49, Xin Long wrote:
>>> On Fri, May 22, 2020 at 9:45 AM Yuehaibing <yuehaibing@huawei.com> wrote:
>>>>
>>>> On 2020/5/21 14:49, Xin Long wrote:
>>>>> On Tue, May 19, 2020 at 4:53 PM Steffen Klassert
>>>>> <steffen.klassert@secunet.com> wrote:
>>>>>>
>>>>>> On Fri, May 15, 2020 at 04:39:57PM +0800, Yuehaibing wrote:
>>>>>>>
>>>>>>> Friendly ping...
>>>>>>>
>>>>>>> Any plan for this issue?
>>>>>>
>>>>>> There was still no consensus between you and Xin on how
>>>>>> to fix this issue. Once this happens, I consider applying
>>>>>> a fix.
>>>>>>
>>>>> Sorry, Yuehaibing, I can't really accept to do: (A->mark.m & A->mark.v)
>>>>> I'm thinking to change to:
>>>>>
>>>>> static bool xfrm_policy_mark_match(struct xfrm_policy *policy,
>>>>> struct xfrm_policy *pol)
>>>>> {
>>>>> - u32 mark = policy->mark.v & policy->mark.m;
>>>>> -
>>>>> - if (policy->mark.v == pol->mark.v && policy->mark.m == pol->mark.m)
>>>>> - return true;
>>>>> -
>>>>> - if ((mark & pol->mark.m) == pol->mark.v &&
>>>>> - policy->priority == pol->priority)
>>>>> + if (policy->mark.v == pol->mark.v &&
>>>>> + (policy->mark.m == pol->mark.m ||
>>>>> + policy->priority == pol->priority))
>>>>> return true;
>>>>>
>>>>> return false;
>>>>>
>>>>> which means we consider (the same value and mask) or
>>>>> (the same value and priority) as the same one. This will
>>>>> cover both problems.
>>>>
>>>> policy A (mark.v = 0x1011, mark.m = 0x1011, priority = 1)
>>>> policy B (mark.v = 0x1001, mark.m = 0x1001, priority = 1)
>>> I'd think these are 2 different policies.
>>>
>>>>
>>>> when fl->flowi_mark == 0x12341011, in xfrm_policy_match() do check like this:
>>>>
>>>> (fl->flowi_mark & pol->mark.m) != pol->mark.v
>>>>
>>>> 0x12341011 & 0x1011 == 0x00001011
>>>> 0x12341011 & 0x1001 == 0x00001001
>>>>
>>>> This also match different policy depends on the order of policy inserting.
>>> Yes, this may happen when a user adds 2 policies like that.
>>> But I think this's a problem that the user doesn't configure it well,
>>> 'priority' should be set.
>>> and this can not be avoided, also such as:
>>>
>>> policy A (mark.v = 0xff00, mark.m = 0x1000, priority = 1)
>>> policy B (mark.v = 0x00ff, mark.m = 0x0011, priority = 1)
>>>
>>> try with 0x12341011
>>>
>>> So just be it, let users decide.
>>
>> Ok, this make sense.
> Thanks Yuehaibing, it's good we're on the same page now.
>
> Just realized the patch I created above won't work for the case:
>
> policy A (mark.v = 0x10, mark.m = 0, priority = 1)
> policy B (mark.v = 0x1, mark.m = 0, priority = 2)
> policy C (mark.v = 0x10, mark.m = 0, priority = 2)
>
> when policy C is being added, the warning still occurs.

Do you means this:

policy A (mark.v = 0x10, mark.m = 0, priority = 1)
policy B (mark.v = 0x10, mark.m = 1, priority = 2)
policy C (mark.v = 0x10, mark.m = 0, priority = 2)

>
> So I will just check value and priority:
> - u32 mark = policy->mark.v & policy->mark.m;
> -
> - if (policy->mark.v == pol->mark.v && policy->mark.m == pol->mark.m)
> - return true;
> -
> - if ((mark & pol->mark.m) == pol->mark.v &&
> + if (policy->mark.v == pol->mark.v &&
> policy->priority == pol->priority)
> return true;
>
> This allows two policies like this exist:
>
> policy A (mark.v = 0x10, mark.m = 0, priority = 1)
> policy C (mark.v = 0x10, mark.m = 0, priority = 2)
>
> But I don't think it's a problem.

Agreed.
>
> .
>

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