Re: [net-next PATCH v5 0/6] XDP for virtio_net

On Thu, Dec 08, 2016 at 12:46:07PM -0800, John Fastabend wrote:

Fair enough but disabling LRO to handle the case where you "might" get
a DDOS will hurt normal good traffic.

the xdp_pass path is not optimized right now. so even without VMs
we need some work to do. lro or not-lro is imo secondary.

quoted

I frankly don't see a use case where you'd want to steer a packet
all the way into VM just to drop them there?

VM to VM traffic is my use case. And in that model we need XDP at the
virtio or vhost layer in case of malicious/broke/untrusted VM. I have
some vhost patches under development for when net-next opens up again.

excellent. looking forward to vhost patches.

quoted

Without XDP_TX it's too crippled. adjust_head() won't be possible,

Just a nit but any reason not to support adjust_head and then XDP_PASS.
I don't have a use case in mind but also see no reason to preclude it.

adjust_head and xdp_pass needs to be supported. No doubt.
the use case is metadata passing between xdp and upper layers.

In summary:

I think its worth investigating getting LRO working but agree we can't
sacrifice any of the existing features or complicate the code to do it.
If the result of investigating is it can't be done then that is how it
is.

agree

Requiring XDP drivers to support all features is fine for me I can make
the virtio queue scheme a bit more flexible. Michael might have some
opinion on this though.

I say right now all the features are pretty much must have,
but in the future we will become selective.
Like zero-copy a page from dma into user space probably doesn't
make sense to do for virtio.
Multi-port TX from virtio into phys netdev doesn't make sense either.

This series shouldn't be blocked by any of the above.

completely agree.
since we abandoned e1000+xdp patches, the virtio+xdp is the only
thing on the table that allows us to do convenient development
and testing of xdp programs.
We've talked about a repository of blessed xdp programs.
They all would need to be routinely and automatically tested.
So virtio+xdp is a must have feature to me.