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SubjectRe: [PATCH v2] xfrm: policy: Fix xfrm policy match
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.

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