netdev - Re: [PATCH net] net: fib_rules: Fix fib_rules_ops->compare implementations to support exact match

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Message-ID: <c9e417f5-1d55-7443-cad6-e08f76755ab8@cumulusnetworks.com>
Date:   Tue, 3 Oct 2017 21:40:19 -0700
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Eyal Birger <eyal.birger@...il.com>,
        David Miller <davem@...emloft.net>
Cc:     shmulik@...f.io, "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        mateusz.bajorski@...ia.com, tgraf@...g.ch,
        Shmulik Ladkani <shmulik.ladkani@...il.com>
Subject: Re: [PATCH net] net: fib_rules: Fix fib_rules_ops->compare
 implementations to support exact match

On 10/3/17 8:58 PM, Eyal Birger wrote:
> Hi David,
> 
> On Wed, Oct 4, 2017 at 12:54 AM, David Miller <davem@...emloft.net> wrote:
>> From: Shmulik Ladkani <shmulik@...f.io>
>> Date: Sat, 30 Sep 2017 11:59:09 +0300
>>
>>> This leads to inconsistencies, depending on order of operations, e.g.:
>>
>> I don't see any inconsistency.  When you insert using NLM_F_EXCL the
>> insertion fails if any existing rule matches or overlaps in any way
>> with the keys in the new rule.
>>
>> Sorry I'm not going to apply this.
> 
> The inconsistency we saw is that 0.0.0.0/0 is treated differently compared to
> all other subnets - for which overlaps are not disallowed - e.g. this succeeds:
> 
> # ip ru add from 10.0.0.0/8 iif eth2 pref 33 table 33
> # ip ru add from 0.0.0.0/1 iif eth2 pref 33 table 33
> # ip ru add from 128.0.0.0/1 iif eth2 pref 33 table 33
> 
> Though being functionally equivalent to adding from=0.0.0.0/0.
> 
> So our understanding was that 'different subnet==different rule', similar to the
> route addition behavior with NLM_F_EXCL.
>

I agree with DaveM ... your "non-working" sequence has a specific entry
followed by a global, match all entry.