linux-kernel - Re: [PATCHv2] vhost-net: add dhclient work-around from userspace

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Message-ID: <20100628153028.GA1452@redhat.com>
Date:	Mon, 28 Jun 2010 18:30:28 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	kvm@...r.kernel.org, virtualization@...ts.osdl.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	ykaul@...hat.com, markmc@...hat.com
Subject: Re: [PATCHv2] vhost-net: add dhclient work-around from userspace

On Mon, Jun 28, 2010 at 01:08:07PM +0300, Michael S. Tsirkin wrote:
> Userspace virtio server has the following hack
> so guests rely on it, and we have to replicate it, too:
> 
> Use port number to detect incoming IPv4 DHCP response packets,
> and fill in the checksum for these.
> 
> The issue we are solving is that on linux guests, some apps
> that use recvmsg with AF_PACKET sockets, don't know how to
> handle CHECKSUM_PARTIAL;
> The interface to return the relevant information was added
> in 8dc4194474159660d7f37c495e3fc3f10d0db8cc,
> and older userspace does not use it.
> One important user of recvmsg with AF_PACKET is dhclient,
> so we add a work-around just for DHCP.
> 
> Don't bother applying the hack to IPv6 as userspace virtio does not
> have a work-around for that - let's hope guests will do the right
> thing wrt IPv6.
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>

Tested-by: Laine Stump <laine@...hat.com>

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