Add tun_is_tun_file() and tap_is_tap_file() helper functions to check if
a file is a TUN or TAP file, which will be utilized by vhost-net.

Co-developed-by: Tim Gebauer <tim.gebauer@tu-dortmund.de>
Signed-off-by: Tim Gebauer <tim.gebauer@tu-dortmund.de>
Co-developed by: Jon Kohler <jon@nutanix.com>
Signed-off-by: Jon Kohler <jon@nutanix.com>
Signed-off-by: Simon Schippers <simon.schippers@tu-dortmund.de>
---
 drivers/net/tap.c      | 13 +++++++++++++
 drivers/net/tun.c      | 13 +++++++++++++
 include/linux/if_tap.h |  5 +++++
 include/linux/if_tun.h |  6 ++++++
 4 files changed, 37 insertions(+)

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 0069e2f177f4..56b8fe376e4a 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -1283,6 +1283,19 @@ struct ptr_ring *tap_get_ptr_ring(struct file *file)
 }
 EXPORT_SYMBOL_GPL(tap_get_ptr_ring);
 
+bool tap_is_tap_file(struct file *file)
+{
+	struct tap_queue *q;
+
+	if (file->f_op != &tap_fops)
+		return false;
+	q = file->private_data;
+	if (!q)
+		return false;
+	return true;
+}
+EXPORT_SYMBOL_GPL(tap_is_tap_file);
+
 int tap_queue_resize(struct tap_dev *tap)
 {
 	struct net_device *dev = tap->dev;
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index bf109440d2c7..dc2d267d30d7 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -3860,6 +3860,19 @@ struct ptr_ring *tun_get_tx_ring(struct file *file)
 }
 EXPORT_SYMBOL_GPL(tun_get_tx_ring);
 
+bool tun_is_tun_file(struct file *file)
+{
+	struct tun_file *tfile;
+
+	if (file->f_op != &tun_fops)
+		return false;
+	tfile = file->private_data;
+	if (!tfile)
+		return false;
+	return true;
+}
+EXPORT_SYMBOL_GPL(tun_is_tun_file);
+
 module_init(tun_init);
 module_exit(tun_cleanup);
 MODULE_DESCRIPTION(DRV_DESCRIPTION);
diff --git a/include/linux/if_tap.h b/include/linux/if_tap.h
index 28326a69745a..14194342b784 100644
--- a/include/linux/if_tap.h
+++ b/include/linux/if_tap.h
@@ -14,6 +14,7 @@ struct ptr_ring *tap_get_ptr_ring(struct file *file);
 int tap_ring_consume_batched(struct file *file, void **array, int n);
 void tap_ring_unconsume(struct file *file, void **batch, int n,
 			void (*destroy)(void *));
+bool tap_is_tap_file(struct file *file);
 #else
 #include <linux/err.h>
 #include <linux/errno.h>
@@ -32,6 +33,10 @@ static inline int tap_ring_consume_batched(struct file *f,
 }
 static inline void tap_ring_unconsume(struct file *file, void **batch,
 				      int n, void (*destroy)(void *)) {}
+static inline bool tap_is_tap_file(struct file *f)
+{
+	return false;
+}
 #endif /* CONFIG_TAP */
 
 /*
diff --git a/include/linux/if_tun.h b/include/linux/if_tun.h
index 1274c6b34eb6..0910c6dbac20 100644
--- a/include/linux/if_tun.h
+++ b/include/linux/if_tun.h
@@ -25,6 +25,7 @@ struct ptr_ring *tun_get_tx_ring(struct file *file);
 int tun_ring_consume_batched(struct file *file, void **array, int n);
 void tun_ring_unconsume(struct file *file, void **batch, int n,
 			void (*destroy)(void *));
+bool tun_is_tun_file(struct file *file);
 
 static inline bool tun_is_xdp_frame(void *ptr)
 {
@@ -67,6 +68,11 @@ static inline int tun_ring_consume_batched(struct file *file,
 static inline void tun_ring_unconsume(struct file *file, void **batch,
 				      int n, void (*destroy)(void *)) {}
 
+static inline bool tun_is_tun_file(struct file *f)
+{
+	return false;
+}
+
 static inline bool tun_is_xdp_frame(void *ptr)
 {
 	return false;
-- 
2.43.0