linux-kernel - [PATCH net-next,v2] hyperv: Add processing of MTU reduced by the host

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Message-Id: <1415830064-1440-1-git-send-email-haiyangz@microsoft.com>
Date:	Wed, 12 Nov 2014 14:07:44 -0800
From:	Haiyang Zhang <haiyangz@...rosoft.com>
To:	davem@...emloft.net, netdev@...r.kernel.org
Cc:	haiyangz@...rosoft.com, kys@...rosoft.com, olaf@...fle.de,
	jasowang@...hat.com, linux-kernel@...r.kernel.org,
	driverdev-devel@...uxdriverproject.org
Subject: [PATCH net-next,v2] hyperv: Add processing of MTU reduced by the host

If the host uses packet encapsulation feature, the MTU may be reduced by the
host due to headroom reservation for encapsulation. This patch handles this
new MTU value.

Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.com>
---
 drivers/net/hyperv/netvsc.c       |    3 ++-
 drivers/net/hyperv/netvsc_drv.c   |    5 +++--
 drivers/net/hyperv/rndis_filter.c |    9 +++++++++
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 7d76c95..6b46311 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -440,7 +440,8 @@ static int negotiate_nvsp_ver(struct hv_device *device,
 	/* NVSPv2 only: Send NDIS config */
 	memset(init_packet, 0, sizeof(struct nvsp_message));
 	init_packet->hdr.msg_type = NVSP_MSG2_TYPE_SEND_NDIS_CONFIG;
-	init_packet->msg.v2_msg.send_ndis_config.mtu = net_device->ndev->mtu;
+	init_packet->msg.v2_msg.send_ndis_config.mtu = net_device->ndev->mtu +
+						       ETH_HLEN;
 	init_packet->msg.v2_msg.send_ndis_config.capability.ieee8021q = 1;
 
 	ret = vmbus_sendpacket(device->channel, init_packet,
diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 3295e4e..15d82ed 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -699,9 +699,10 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 		return -ENODEV;
 
 	if (nvdev->nvsp_version >= NVSP_PROTOCOL_VERSION_2)
-		limit = NETVSC_MTU;
+		limit = NETVSC_MTU - ETH_HLEN;
 
-	if (mtu < 68 || mtu > limit)
+	/* Hyper-V hosts don't support MTU < ETH_DATA_LEN (1500) */
+	if (mtu < ETH_DATA_LEN || mtu > limit)
 		return -EINVAL;
 
 	nvdev->start_remove = true;
diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
index ccce6f2..7b2c5d1 100644
--- a/drivers/net/hyperv/rndis_filter.c
+++ b/drivers/net/hyperv/rndis_filter.c
@@ -998,6 +998,7 @@ int rndis_filter_device_add(struct hv_device *dev,
 	int t;
 	struct ndis_recv_scale_cap rsscap;
 	u32 rsscap_size = sizeof(struct ndis_recv_scale_cap);
+	u32 mtu, size;
 
 	rndis_device = get_rndis_device();
 	if (!rndis_device)
@@ -1029,6 +1030,14 @@ int rndis_filter_device_add(struct hv_device *dev,
 		return ret;
 	}
 
+	/* Get the MTU from the host */
+	size = sizeof(u32);
+	ret = rndis_filter_query_device(rndis_device,
+					RNDIS_OID_GEN_MAXIMUM_FRAME_SIZE,
+					&mtu, &size);
+	if (ret == 0 && size == sizeof(u32))
+		net_device->ndev->mtu = mtu;
+
 	/* Get the mac address */
 	ret = rndis_filter_query_device_mac(rndis_device);
 	if (ret != 0) {
-- 
1.7.1

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