Re: [net-next PATCH v3 00/17] Future-proof tunnel offload handlers

[Hannes Frederic Sowa <hannes@redhat.com>]

On 21.06.2016 11:42, Tom Herbert wrote:
>> > There is also some argument to be had for theory versus application.
>> > Arguably it is the customers that are leading to some of the dirty
>> > hacks as I think vendors are building NICs based on customer use cases
>> > versus following any specifications.  In most data centers the tunnel
>> > underlays will be deployed throughout the network and UDP will likely
>> > be blocked for anything that isn't being used explicitly for
>> > tunneling.  As such we seem to be seeing a lot of NICs that are only
>> > supporting one port for things like this instead of designing them to
>> > handle whatever we can throw at them.
>> >
> Actually, I don't believe that's true. It is not typical to deploy
> firewalls within a data center fabric, and nor do we restrict
> applications from binding to any UDP ports and they can pretty much
> transmit to any port on any host without cost using an unconnected UDP
> socket. I think it's more likely that NIC (and switch vendors) simply
> assumed that port numbers can be treated as global values. That's
> expedient and at small scale we can probably get away with it, but at
> large scale this will eventually bite someone.

I do have access to relatively normal expensive switches that can
basically be used to realize a scenario like the one Alex described. No
firewalls necessary. If you can guarantee that your customers never have
access to your hypervisors or container management namespace, this is
actually a pretty solid assumption.

Bye,
Hannes