netdev - Re: [PATCH v2] fib_rules: match rules based on suppress

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Date:   Tue, 26 Jun 2018 07:51:38 -0700
From:   Roopa Prabhu <roopa@...ulusnetworks.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v2] fib_rules: match rules based on suppress_* properties too

On Mon, Jun 25, 2018 at 4:39 PM, Jason A. Donenfeld <Jason@...c4.com> wrote:
> Two rules with different values of suppress_prefix or suppress_ifgroup
> are not the same. This fixes an -EEXIST when running:
>
>    $ ip -4 rule add table main suppress_prefixlength 0
>
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
> Fixes: f9d4b0c1e969 ("fib_rules: move common handling of newrule delrule msgs into fib_nl2rule")
> ---
> This adds the new condition you mentioned. I'm not sure what you make of
> DaveM's remark about this not being in the original code, but here is
> nonetheless the requested change.

I just saw DaveM's comment and agree the new rule_find is different
but that was intentional and it merged
the finding of the rule in the newlink and dellink paths. I did port
each of the conditions from previous rule_exists
to new rule_find, but forgot to add the new keys which now became
necessary. I replied with details on your
other bug report thread. Also pasting that response here:

So the previous rule_exists code did not check for attribute matches correctly.
It would ignore a rule at the first non-existent attribute mis-match.
And rule_find will always
be called with a valid key.
eg in your case, it would
return at pref mismatch...and never match an existing rule.

$ip -4 rule add table main suppress_prefixlength 0
$ip -4 rule add table main suppress_prefixlength 0
$ip -4 rule add table main suppress_prefixlength 0

$ip rule show
0:      from all lookup local
32763:  from all lookup main suppress_prefixlength 0
32764:  from all lookup main suppress_prefixlength 0
32765:  from all lookup main suppress_prefixlength 0
32766:  from all lookup main
32767:  from all lookup default

With your patch, you should get proper EXISTS check
$ ip -4 rule add table main suppress_prefixlength 0
$ ip -4 rule add table main suppress_prefixlength 0

RTNETLINK answers: File exists

Dave, pls let me know if this is acceptable. If not
I can easily restore the previous rule_exists func. Will also submit a
patch to cover this in self-tests.

thanks.

>
>  net/core/fib_rules.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
> index 126ffc5bc630..bc8425d81022 100644
> --- a/net/core/fib_rules.c
> +++ b/net/core/fib_rules.c
> @@ -416,6 +416,14 @@ static struct fib_rule *rule_find(struct fib_rules_ops *ops,
>                 if (rule->mark && r->mark != rule->mark)
>                         continue;
>
> +               if (rule->suppress_ifgroup != -1 &&
> +                   r->suppress_ifgroup != rule->suppress_ifgroup)
> +                       continue;
> +
> +               if (rule->suppress_prefixlen != -1 &&
> +                   r->suppress_prefixlen != rule->suppress_prefixlen)
> +                       continue;
> +
>                 if (rule->mark_mask && r->mark_mask != rule->mark_mask)
>                         continue;
>
> --