RE: [PATCH net,1/1] hyperv: Add support for setting MAC from within guests

-----Original Message-----
From: Ben Hutchings [mailto:bhutchings@solarflare.com]
Sent: Friday, July 06, 2012 8:19 PM
To: Haiyang Zhang
Cc: davem@davemloft.net; netdev@vger.kernel.org; KY Srinivasan;
olaf@aepfle.de; linux-kernel@vger.kernel.org;
devel@linuxdriverproject.org
Subject: Re: [PATCH net,1/1] hyperv: Add support for setting MAC from
within guests

On Fri, 2012-07-06 at 14:25 -0700, Haiyang Zhang wrote:

quoted

This adds support for setting synthetic NIC MAC address from within

Linux

quoted

guests. Before using this feature, the option "spoofing of MAC

address"

quoted

should be enabled at the Hyper-V manager / Settings of the synthetic
NIC.

[...]

quoted

+int rndis_filter_set_device_mac(struct hv_device *hdev, char *mac)
+{

[...]

quoted

+	t = wait_for_completion_timeout(&request->wait_event, 5*HZ);
+	if (t == 0) {
+		netdev_err(ndev, "timeout before we got a set

response...\n");

quoted

+		/*
+		 * can't put_rndis_request, since we may still receive a
+		 * send-completion.
+		 */
+		return -EBUSY;
+	} else {
+		set_complete = &request->response_msg.msg.set_complete;
+		if (set_complete->status != RNDIS_STATUS_SUCCESS)
+			ret = -EINVAL;

[...]

Is there a specific error code that indicates the hypervisor is
configured not to allow MAC address changes?  If so, shouldn't that be
translated to return EPERM rather than EINVAL?

I have check the return code, 0xc000000d, which is returned both when MAC
spoofing is not enabled or the parameter contains other errors. So we can't
tell if it permission error or not. I will re-submit this patch still
using EINVAL.

Thanks,
- Haiyang