[PATCH v2] macvtap: Correctly set tap features when IFF_VNET_HDR is disabled.

[Vlad Yasevich <vyasevic@redhat.com>]

When the user turns off IFF_VNET_HDR flag, attempts to change
offload features via TUNSETOFFLOAD do not work.  This could cause
GSO packets to be delivered to the user when the user is
not prepared to handle them.

To solve, allow processing of TUNSETOFFLOAD when IFF_VNET_HDR is
disabled.  Treat any attempt to enable offloads as an error in
this case.
We also need to update the TUN_FEATURES mask to include all checksum
options as the underlying device may have something other then
HW_CSUM set.

Change since v1:
  - Removed the call to update offloads when IFF_VNET_HDR is turned off.
  - Changed the macvtap version of TUN_OFFLOADS to include all checksum
    offloads since the physical nic may have them set.
  - Treat enabling of offloads without vnet_hdr support as error.

Signed-off-by: Vlad Yasevich <vyasevic@redhat.com>
---
 drivers/net/macvtap.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index a98fb0e..3acfc37 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -65,7 +65,7 @@ static struct cdev macvtap_cdev;
 
 static const struct proto_ops macvtap_socket_ops;
 
-#define TUN_OFFLOADS (NETIF_F_HW_CSUM | NETIF_F_TSO_ECN | NETIF_F_TSO | \
+#define TUN_OFFLOADS (NETIF_F_ALL_CSUM | NETIF_F_TSO_ECN | NETIF_F_TSO | \
 		      NETIF_F_TSO6 | NETIF_F_UFO)
 #define RX_OFFLOADS (NETIF_F_GRO | NETIF_F_LRO)
 /*
@@ -1024,6 +1024,12 @@ static int set_offload(struct macvtap_queue *q, unsigned long arg)
 	if (!vlan)
 		return -ENOLINK;
 
+	/* If the user is trying to set offloads while IFF_VNET_HDR is
+	 * off, report it as an error.
+	 */
+	if (!(q->flags & IFF_VNET_HDR) && arg)
+		return -EINVAL;
+
 	features = vlan->dev->features;
 
 	if (arg & TUN_F_CSUM) {
@@ -1155,10 +1161,6 @@ static long macvtap_ioctl(struct file *file, unsigned int cmd,
 			    TUN_F_TSO_ECN | TUN_F_UFO))
 			return -EINVAL;
 
-		/* TODO: only accept frames with the features that
-			 got enabled for forwarded frames */
-		if (!(q->flags & IFF_VNET_HDR))
-			return  -EINVAL;
 		rtnl_lock();
 		ret = set_offload(q, arg);
 		rtnl_unlock();
-- 
1.8.1.4