linux-kernel - [PATCH net-next v5 7/8] TUN & TAP: Methods to determine whether file is TUN/TAP for vhost

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Message-ID: <20250922221553.47802-8-simon.schippers@tu-dortmund.de>
Date: Tue, 23 Sep 2025 00:15:52 +0200
From: Simon Schippers <simon.schippers@...dortmund.de>
To: willemdebruijn.kernel@...il.com, jasowang@...hat.com, mst@...hat.com,
        eperezma@...hat.com, stephen@...workplumber.org, leiyang@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux.dev, kvm@...r.kernel.org
Cc: Simon Schippers <simon.schippers@...dortmund.de>,
        Tim Gebauer <tim.gebauer@...dortmund.de>
Subject: [PATCH net-next v5 7/8] TUN & TAP: Methods to determine whether file is TUN/TAP for vhost_net

Those wrappers are inspired by tun_get_tx_ring/tap_get_tx_ring and replace
those methods.

Co-developed-by: Tim Gebauer <tim.gebauer@...dortmund.de>
Signed-off-by: Tim Gebauer <tim.gebauer@...dortmund.de>
Signed-off-by: Simon Schippers <simon.schippers@...dortmund.de>
---
 drivers/net/tap.c      | 10 +++++-----
 drivers/net/tun.c      | 10 +++++-----
 include/linux/if_tap.h |  5 +++++
 include/linux/if_tun.h |  6 ++++++
 4 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 9720481f6d41..8d3e74330309 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -1277,18 +1277,18 @@ void tap_ring_unconsume(struct file *file, void **batch, int n,
 }
 EXPORT_SYMBOL_GPL(tap_ring_unconsume);
 
-struct ptr_ring *tap_get_ptr_ring(struct file *file)
+bool is_tap_file(struct file *file)
 {
 	struct tap_queue *q;
 
 	if (file->f_op != &tap_fops)
-		return ERR_PTR(-EINVAL);
+		return false;
 	q = file->private_data;
 	if (!q)
-		return ERR_PTR(-EBADFD);
-	return &q->ring;
+		return false;
+	return true;
 }
-EXPORT_SYMBOL_GPL(tap_get_ptr_ring);
+EXPORT_SYMBOL_GPL(is_tap_file);
 
 int tap_queue_resize(struct tap_dev *tap)
 {
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 25b170e903e1..b0193b06fedc 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -3822,18 +3822,18 @@ void tun_ring_unconsume(struct file *file, void **batch, int n,
 }
 EXPORT_SYMBOL_GPL(tun_ring_unconsume);
 
-struct ptr_ring *tun_get_tx_ring(struct file *file)
+bool is_tun_file(struct file *file)
 {
 	struct tun_file *tfile;
 
 	if (file->f_op != &tun_fops)
-		return ERR_PTR(-EINVAL);
+		return false;
 	tfile = file->private_data;
 	if (!tfile)
-		return ERR_PTR(-EBADFD);
-	return &tfile->tx_ring;
+		return false;
+	return true;
 }
-EXPORT_SYMBOL_GPL(tun_get_tx_ring);
+EXPORT_SYMBOL_GPL(is_tun_file);
 
 module_init(tun_init);
 module_exit(tun_cleanup);
diff --git a/include/linux/if_tap.h b/include/linux/if_tap.h
index 0cf8cf200d52..5bbcc8611bf5 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 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 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 bd954bb117e8..869d61898e60 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 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 is_tun_file(struct file *f)
+{
+	return false;
+}
+
 static inline bool tun_is_xdp_frame(void *ptr)
 {
 	return false;
-- 
2.43.0