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/tun.c b/drivers/net/tun.c
index b210139..cb376b2d 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -111,6 +111,7 @@
#define TUN_FASYNC IFF_ATTACH_QUEUE
/* High bits in flags field are unused. */
#define TUN_VNET_LE 0x80000000
+#define TUN_VNET_BE 0x40000000
#define TUN_FEATURES (IFF_NO_PI | IFF_ONE_QUEUE | IFF_VNET_HDR | \
IFF_MULTI_QUEUE)
@@ -206,10 +207,58 @@
u32 flow_count;
};
+#ifdef CONFIG_TUN_VNET_CROSS_LE
+static inline bool tun_legacy_is_little_endian(struct tun_struct *tun)
+{
+ return tun->flags & TUN_VNET_BE ? false :
+ virtio_legacy_is_little_endian();
+}
+
+static long tun_get_vnet_be(struct tun_struct *tun, int __user *argp)
+{
+ int be = !!(tun->flags & TUN_VNET_BE);
+
+ if (put_user(be, argp))
+ return -EFAULT;
+
+ return 0;
+}
+
+static long tun_set_vnet_be(struct tun_struct *tun, int __user *argp)
+{
+ int be;
+
+ if (get_user(be, argp))
+ return -EFAULT;
+
+ if (be)
+ tun->flags |= TUN_VNET_BE;
+ else
+ tun->flags &= ~TUN_VNET_BE;
+
+ return 0;
+}
+#else
+static inline bool tun_legacy_is_little_endian(struct tun_struct *tun)
+{
+ return virtio_legacy_is_little_endian();
+}
+
+static long tun_get_vnet_be(struct tun_struct *tun, int __user *argp)
+{
+ return -EINVAL;
+}
+
+static long tun_set_vnet_be(struct tun_struct *tun, int __user *argp)
+{
+ return -EINVAL;
+}
+#endif /* CONFIG_TUN_VNET_CROSS_LE */
+
static inline bool tun_is_little_endian(struct tun_struct *tun)
{
return tun->flags & TUN_VNET_LE ||
- virtio_legacy_is_little_endian();
+ tun_legacy_is_little_endian(tun);
}
static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
@@ -2062,6 +2111,14 @@
tun->flags &= ~TUN_VNET_LE;
break;
+ case TUNGETVNETBE:
+ ret = tun_get_vnet_be(tun, argp);
+ break;
+
+ case TUNSETVNETBE:
+ ret = tun_set_vnet_be(tun, argp);
+ break;
+
case TUNATTACHFILTER:
/* Can be set only for TAPs */
ret = -EINVAL;