macvtap/tun: cross-endian support for little-endian hosts
The VNET_LE flag was introduced to fix accesses to virtio 1.0 headers
that are always little-endian. It can also be used to handle the special
case of a legacy little-endian device implemented by a big-endian host.
Let's add a flag and ioctls for big-endian devices as well. If both flags
are set, little-endian wins.
Since this is isn't a common usecase, the feature is controlled by a kernel
config option (not set by default).
Both macvtap and tun are covered by this patch since they share the same
API with userland.
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index df51d60..71ac0ec 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -244,6 +244,20 @@
If you don't know what to use this for, you don't need it.
+config TUN_VNET_CROSS_LE
+ bool "Support for cross-endian vnet headers on little-endian kernels"
+ default n
+ ---help---
+ This option allows TUN/TAP and MACVTAP device drivers in a
+ little-endian kernel to parse vnet headers that come from a
+ big-endian legacy virtio device.
+
+ Userspace programs can control the feature using the TUNSETVNETBE
+ and TUNGETVNETBE ioctls.
+
+ Unless you have a little-endian system hosting a big-endian virtual
+ machine with a legacy virtio NIC, you should say N.
+
config VETH
tristate "Virtual ethernet pair device"
---help---