netdev - Re: [PATCH net] fib_rules: return 0 directly if an exactly same rule exists when NLM_F

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Message-ID: <20190605032926.GA18865@dhcp-12-139.nay.redhat.com>
Date:   Wed, 5 Jun 2019 11:29:26 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     Lorenzo Colitti <lorenzo@...gle.com>
Cc:     David Ahern <dsahern@...il.com>,
        David Miller <davem@...emloft.net>,
        Yaro Slav <yaro330@...il.com>,
        Thomas Haller <thaller@...hat.com>,
        Alistair Strachan <astrachan@...gle.com>,
        Greg KH <greg@...ah.com>,
        Linux NetDev <netdev@...r.kernel.org>,
        David Ahern <dsa@...ulusnetworks.com>,
        Maciej Żenczykowski <zenczykowski@...il.com>
Subject: Re: [PATCH net] fib_rules: return 0 directly if an exactly same rule
 exists when NLM_F_EXCL not supplied

On Wed, Jun 05, 2019 at 11:25:11AM +0900, Lorenzo Colitti wrote:
> On Wed, Jun 5, 2019 at 11:15 AM Hangbin Liu <liuhangbin@...il.com> wrote:
> > How do you add the rules? with ip cmd it should has NLM_F_EXCL flag and
> > you will get -EEXIST error out.
> 
> The fact that the code worked before this commit implies that it was
> *not* using NLM_F_EXCL. :-)

Yes, that's why you got the issue.

> We rely on being able to add a rule and either have a dup be created
> (in which case we'll remove it later) or have it fail with EEXIST (in
> which case we won't remove it later).

With Maciej said, how about add NLM_F_EXCL flag when you add a new rule.
If it returned EEXIST, which means there is an dup rule, you just do not
remove it later.

Would that fix your issue?

Thanks
Hangbin