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

Hi David,

On Wed, Oct 4, 2017 at 12:54 AM, David Miller [off-list ref] wrote:

From: Shmulik Ladkani <redacted>
Date: Sat, 30 Sep 2017 11:59:09 +0300

quoted

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.

Best regards,
Eyal.