Re: [PATCH] Work around dhclient brokenness

Chris Wedgwood
2008-08-19T03:26:54Z

On Tue, Aug 19, 2008 at 10:45:20AM +1000, Rusty Russell wrote:

> For those not following closely: We already have a method for the
> guest to accept or reject features. Our problem is that the guest
> is already accepting the CSUM feature: but one critical userspace
> app (dhcp-client) can't actually handle it due to a bug.

Can't we just get dhcp-client client fixed upstream and let the
distro's update in a couple of months?

> The proposal is to add another mechanism, whereby the host doesn't
> advertise CSUM, but advertises a new CSUM2 feature. The driver
> doesn't accept this by default: then guest userspace says "hey, I
> *really can* handle CSUM". This would have to be done dby resetting
> the device in the ethtool callback (that's how we renegotiate
> features). And guests need a special virtio hack in their init
> scripts.

If guest can have modified scripts for virtio and what not, they can
have a fixed dhcp-client.

> This leaves the small number of current users without CSUM (and
> hence GSO etc). Yet they might not use dhcp with bridging anyway.

I think for now that's fine, it's a performance hit that people can
tweak away explicitly without having to add something like a CSUM2
feature.