netdev - Re: [RFC v3 3/3] vxlan: handle underlay VRF changes

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Date:   Wed, 21 Nov 2018 18:48:07 -0700
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Alexis Bauvin <abauvin@...leway.com>,
        Roopa Prabhu <roopa@...ulusnetworks.com>
Cc:     netdev <netdev@...r.kernel.org>, akherbouche@...leway.com
Subject: Re: [RFC v3 3/3] vxlan: handle underlay VRF changes

On 11/21/18 5:54 PM, Alexis Bauvin wrote:
>>> There is one issue I can see with SO_REUSEPORT (if my understanding of it is
>>> correct). From what I understood, enabling this option will balance incoming
>>> connections (for TCP) / dgrams (for UDP) based on a 4-tuple hash (sip, dip,
>>> sport, dport) between sockets listening on the same port.
>>
>> AFAIK there is no balancing done. There is an order to which socket is
>> selected - and it includes the VRF device if relevant.
> 
> Maybe balance was not the correct word, "route" may be more appropriate. Still you
> understood me, thanks for the details!
> 
> Yet, the "if relevant" part is interesting. Does enabling the
> net.ipv4.udp_l3mdev_accept sysctl counts as making vrfs not releavant? In that case,
> both sockets are treated equally, right?

If udp_l3mdev_accept is disabled the default VRF is treated like a  real
VRF as opposed to no VRF (Vyatta's changes), meaning the scope of the
socket is just the VRF (or just the default VRF).

If udp_l3mdev_accept is enabled it allows an unbound UDP socket to work
across all VRFs.

Gives user's options for how to deploy their s/w especially when it
comes to all of the existing software that is has no idea about VRFs.