[LTP] [PATCH] syscalls/ioctl03: add IFF_BACKPRESSURE flag

Avinesh Kumar avinesh.kumar@suse.com
Wed Sep 2 15:40:18 CEST 2026


From: Avinesh Kumar <avinesh.kumar@suse.com>

Kernel commit 485e38995cc3 ("tun/tap: add IFF_BACKPRESSURE flag")
introduced a new TUNSETIFF flag, and d00c7369ef24 ("tun/tap &
vhost-net: stop tail-drop when IFF_BACKPRESSURE is set") added it
to TUN_FEATURES. TUNGETFEATURES now reports bit 0x80 on kernels
that support it, which ioctl03 does not recognize and reports as:

  ioctl03.c:90: TFAIL: (UNKNOWN 0x80)

Add IFF_BACKPRESSURE to the known flags table.

Signed-off-by: Avinesh Kumar <avinesh.kumar@suse.com>
---
 testcases/kernel/syscalls/ioctl/ioctl03.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/testcases/kernel/syscalls/ioctl/ioctl03.c b/testcases/kernel/syscalls/ioctl/ioctl03.c
index 8a868a98e605..1f538016344c 100644
--- a/testcases/kernel/syscalls/ioctl/ioctl03.c
+++ b/testcases/kernel/syscalls/ioctl/ioctl03.c
@@ -44,6 +44,10 @@
 #define IFF_NO_CARRIER	0x0040
 #endif
 
+#ifndef IFF_BACKPRESSURE
+#define IFF_BACKPRESSURE	0x0080
+#endif
+
 static struct {
 	unsigned int flag;
 	const char *name;
@@ -56,7 +60,8 @@ static struct {
 	{IFF_MULTI_QUEUE, "MULTI_QUEUE"},
 	{IFF_NAPI, "IFF_NAPI"},
 	{IFF_NAPI_FRAGS, "IFF_NAPI_FRAGS"},
-	{IFF_NO_CARRIER, "IFF_NO_CARRIER"}
+	{IFF_NO_CARRIER, "IFF_NO_CARRIER"},
+	{IFF_BACKPRESSURE, "IFF_BACKPRESSURE"}
 };
 
 static void verify_features(void)
-- 
2.55.0



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