hv_netvsc: Add support to set MTU reservation from guest side
When packet encapsulation is in use, the MTU needs to be reduced for
headroom reservation.
The existing code takes the updated MTU value only from the host side.
But vSwitch extensions, such as Open vSwitch, require the flexibility
to change the MTU to different values from within a guest during the
lifecycle of a vNIC, when the encapsulation protocol is changed. The
patch supports this kind of MTU changes.
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index dd45440..26cd14c 100644
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -589,6 +589,7 @@
#define NETVSC_MTU 65536
+#define NETVSC_MTU_MIN 68
#define NETVSC_RECEIVE_BUFFER_SIZE (1024*1024*16) /* 16MB */
#define NETVSC_RECEIVE_BUFFER_SIZE_LEGACY (1024*1024*15) /* 15MB */
diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 358475e..b855ba9 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -743,8 +743,7 @@
if (nvdev->nvsp_version >= NVSP_PROTOCOL_VERSION_2)
limit = NETVSC_MTU - ETH_HLEN;
- /* Hyper-V hosts don't support MTU < ETH_DATA_LEN (1500) */
- if (mtu < ETH_DATA_LEN || mtu > limit)
+ if (mtu < NETVSC_MTU_MIN || 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 236aeb7..2e40417 100644
--- a/drivers/net/hyperv/rndis_filter.c
+++ b/drivers/net/hyperv/rndis_filter.c
@@ -1054,7 +1054,7 @@
ret = rndis_filter_query_device(rndis_device,
RNDIS_OID_GEN_MAXIMUM_FRAME_SIZE,
&mtu, &size);
- if (ret == 0 && size == sizeof(u32))
+ if (ret == 0 && size == sizeof(u32) && mtu < net_device->ndev->mtu)
net_device->ndev->mtu = mtu;
/* Get the mac address */
