[LTP] [PATCH 1/2] testcases: netns: Check TUN support enabled

[Mylène Josserand]

In case TUN support is not enabled, the test will fail while
performing the "ip" command with following error:
   open: No such file or directory
   netns_netlink    1  TBROK  :  netns_netlink.c:143: system() failed

As the system() call is not setting errno, we are not able to know
if the error is produced by a mis-configuration or not.

Because of that, this commit adds a check during the setup function to see
if the device "/dev/net/tun" is available or not. It is the file
that "ip tuntap add mode tap" command is looking for (and fails with
the "open" error).

Signed-off-by: Mylène Josserand <mylene.josserand@bootlin.com>
---
 testcases/kernel/containers/netns/netns_netlink.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/testcases/kernel/containers/netns/netns_netlink.c b/testcases/kernel/containers/netns/netns_netlink.c
index 47e8235d6..077ec5dab 100644
--- a/testcases/kernel/containers/netns/netns_netlink.c
+++ b/testcases/kernel/containers/netns/netns_netlink.c
@@ -57,6 +57,15 @@ static void cleanup(void)
 
 static void setup(void)
 {
+	/* Check that the TUN support is available */
+	int netfd = open("/dev/net/tun", O_RDWR);
+	if (netfd == -1) {
+		if (errno == ENODEV || errno == ENOENT)
+			tst_brkm(TCONF, NULL, "TUN support is missing?");
+
+		tst_brkm(TBROK | TERRNO, NULL, "opening /dev/net/tun failed");
+	}
+
 	tst_require_root();
 	check_iproute(IP_TUNTAP_MIN_VER);
 	check_netns();
-- 
2.11.0