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macvtap/tun: cross-endian support for little-endian hosts

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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>
This commit is contained in:
Greg Kurz
2015-04-24 14:50:36 +02:00
committed by Michael S. Tsirkin
parent 2751c9882b
commit 8b8e658b16
4 changed files with 134 additions and 2 deletions
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6
include/uapi/linux/if_tun.h
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@@ -50,6 +50,12 @@
#define TUNGETFILTER _IOR('T', 219, struct sock_fprog)
#define TUNSETVNETLE _IOW('T', 220, int)
#define TUNGETVNETLE _IOR('T', 221, int)
/* The TUNSETVNETBE and TUNGETVNETBE ioctls are for cross-endian support on
* little-endian hosts. Not all kernel configurations support them, but all
* configurations that support SET also support GET.
*/
#define TUNSETVNETBE _IOW('T', 222, int)
#define TUNGETVNETBE _IOR('T', 223, int)
/* TUNSETIFF ifr flags */
#define IFF_TUN 0x0001