Willem de Bruijn wrote:

Akihiko Odaki wrote:

quoted

Decouple vnet-related functions from tun_struct so that we can reuse
them for tap in the future.

Signed-off-by: Akihiko Odaki <redacted>
---
 drivers/net/tun.c | 53 +++++++++++++++++++++++++++--------------------------
 1 file changed, 27 insertions(+), 26 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index ec56ac865848..add09dfdada5 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c

@@ -298,16 +298,16 @@ static bool tun_napi_frags_enabled(const struct tun_file *tfile)
 	return tfile->napi_frags_enabled;
 }
 
-static inline bool tun_legacy_is_little_endian(struct tun_struct *tun)
+static inline bool tun_legacy_is_little_endian(unsigned int flags)
 {
 	return !(IS_ENABLED(CONFIG_TUN_VNET_CROSS_LE) &&
-		 (tun->flags & TUN_VNET_BE)) &&
+		 (flags & TUN_VNET_BE)) &&
 		virtio_legacy_is_little_endian();
 }
 
-static long tun_get_vnet_be(struct tun_struct *tun, int __user *argp)
+static long tun_get_vnet_be(unsigned int flags, int __user *argp)
 {
-	int be = !!(tun->flags & TUN_VNET_BE);
+	int be = !!(flags & TUN_VNET_BE);
 
 	if (!IS_ENABLED(CONFIG_TUN_VNET_CROSS_LE))
 		return -EINVAL;

@@ -318,7 +318,7 @@ static long tun_get_vnet_be(struct tun_struct *tun, int __user *argp)
 	return 0;
 }
 
-static long tun_set_vnet_be(struct tun_struct *tun, int __user *argp)
+static long tun_set_vnet_be(unsigned int *flags, int __user *argp)
 {
 	int be;
 

@@ -329,27 +329,26 @@ static long tun_set_vnet_be(struct tun_struct *tun, int __user *argp)
 		return -EFAULT;
 
 	if (be)
-		tun->flags |= TUN_VNET_BE;
+		*flags |= TUN_VNET_BE;
 	else
-		tun->flags &= ~TUN_VNET_BE;
+		*flags &= ~TUN_VNET_BE;
 
 	return 0;
 }
 
-static inline bool tun_is_little_endian(struct tun_struct *tun)
+static inline bool tun_is_little_endian(unsigned int flags)
 {
-	return tun->flags & TUN_VNET_LE ||
-		tun_legacy_is_little_endian(tun);
+	return flags & TUN_VNET_LE || tun_legacy_is_little_endian(flags);
 }
 
-static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)
+static inline u16 tun16_to_cpu(unsigned int flags, __virtio16 val)
 {
-	return __virtio16_to_cpu(tun_is_little_endian(tun), val);
+	return __virtio16_to_cpu(tun_is_little_endian(flags), val);
 }
 
-static inline __virtio16 cpu_to_tun16(struct tun_struct *tun, u16 val)
+static inline __virtio16 cpu_to_tun16(unsigned int flags, u16 val)
 {
-	return __cpu_to_virtio16(tun_is_little_endian(tun), val);
+	return __cpu_to_virtio16(tun_is_little_endian(flags), val);
 }
 
 static inline u32 tun_hashfn(u32 rxhash)

@@ -1764,6 +1763,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 
 	if (tun->flags & IFF_VNET_HDR) {
 		int vnet_hdr_sz = READ_ONCE(tun->vnet_hdr_sz);
+		int flags = tun->flags;

Here and elsewhere: instead of passing around and repeatedly parsing
flags, have a variable is_little_endian (or is_le)?

I guess this will not work everywhere, because endianness is not a
boolean flag.. Code checks both TUN_VNET_LE and TUN_VNET_BE.