On Tue, Jun 29, 2010 at 12:36:47AM -0700, David Miller wrote:
From: "Michael S. Tsirkin"<mst@xxxxxxxxxx>Yes, and I think it was a mistake to add the hack there. This is what
Date: Mon, 28 Jun 2010 13:08:07 +0300
Userspace virtio server has the following hackYikes, this is awful too.
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
The interface to return the relevant information was added
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@xxxxxxxxxx>
Nothing in the kernel should be mucking around with procotol packets
like this by default. In particular, what the heck does port 67 mean?
Locally I can use it for whatever I want for my own purposes, I don't
have to follow the conventions for service ports as specified by the
But I can't have the packet checksum state be left alone for port 67
traffic on a box using virtio because you have this hack there.
And yes it's broken on machines using the qemu thing, but at least the
hack there is restricted to userspace.
prevented applications from using the new interface in the 3 years
since it was first introduced.