netdev - Re: fib_frontend: Add network specific broadcasts, when it takes a sense

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Date:   Mon, 12 Dec 2016 17:52:04 +0100
From:   Hannes Frederic Sowa <hannes@...essinduktion.org>
To:     Brandon Philips <brandon.philips@...eos.com>,
        Jiri Benc <jbenc@...hat.com>
Cc:     netdev@...r.kernel.org, Tom Denham <tom@...era.io>,
        Aaron Levy <aaron.levy@...eos.com>,
        Brad Ison <bison@...eos.com>
Subject: Re: fib_frontend: Add network specific broadcasts, when it takes a
 sense

On 12.12.2016 15:44, Brandon Philips wrote:
> On Mon, Dec 12, 2016 at 9:30 AM, Jiri Benc <jbenc@...hat.com> wrote:
>> On Fri, 9 Dec 2016 15:41:52 -0800, Brandon Philips wrote:
>>> The issue we have: when creating the VXLAN interface and assigning it
>>> an address we see a broadcast route being added by the Kernel. For
>>> example if we have 10.4.0.0/16 a broadcast route to 10.4.0.0 is
>>> created. This route is unwanted because we assign 10.4.0.0 to one of
>>> our VXLAN interfaces.
>>
>> Are you saying you're trying to assign the IP address 10.4.0.0/16 as a
>> unicast address to an interface? Then you'll run into way more problems
>> than the one you're describing. You can't have host part of the IP
>> address consisting of all zeros (or all ones). Just don't do it. Choose
>> a valid IP address instead.
> 
> Yes, this is what we are doing; it is because of an upstream, to us,
> address assignment so I will figure it out upstream.
> 
> Regardless, it is hard to find an RFC that says "simply don't do this
> because _____". The closest I could find was RFC 922 after sending
> this which says:
> 
> "There is probably no reason for such addresses to appear anywhere but
> as the source address of an ICMP Information".

Alternatively you can renumber the network to use /32 and add the
unicast routes for your /16 yourself.

Bye,
Hannes