netdev - [PATCH bpf-next v2 6/6] selftests/bpf: fix file descriptor assertion in open

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Message-ID: <20250217172308.3291739-7-marcus.wichelmann@hetzner-cloud.de>
Date: Mon, 17 Feb 2025 17:23:08 +0000
From: Marcus Wichelmann <marcus.wichelmann@...zner-cloud.de>
To: netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Cc: willemdebruijn.kernel@...il.com,
	jasowang@...hat.com,
	andrew+netdev@...n.ch,
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	marcus.wichelmann@...zner-cloud.de
Subject: [PATCH bpf-next v2 6/6] selftests/bpf: fix file descriptor assertion in open_tuntap helper

The open_tuntap helper function uses open() to get a file descriptor for
/dev/net/tun.

The open(2) manpage writes this about its return value:

  On success, open(), openat(), and creat() return the new file
  descriptor (a nonnegative integer).  On error, -1 is returned and
  errno is set to indicate the error.

This means that the fd > 0 assertion in the open_tuntap helper is
incorrect and should rather check for fd >= 0.

When running the BPF selftests locally, this incorrect assertion was not
an issue, but the BPF kernel-patches CI failed because of this:

  open_tuntap:FAIL:open(/dev/net/tun) unexpected open(/dev/net/tun):
  actual 0 <= expected 0

Signed-off-by: Marcus Wichelmann <marcus.wichelmann@...zner-cloud.de>
---
 tools/testing/selftests/bpf/network_helpers.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c
index e1cfa1b37754..9b59bfd5d912 100644
--- a/tools/testing/selftests/bpf/network_helpers.c
+++ b/tools/testing/selftests/bpf/network_helpers.c
@@ -571,7 +571,7 @@ int open_tuntap(const char *dev_name, bool need_mac)
 	struct ifreq ifr;
 	int fd = open("/dev/net/tun", O_RDWR);
 
-	if (!ASSERT_GT(fd, 0, "open(/dev/net/tun)"))
+	if (!ASSERT_GE(fd, 0, "open(/dev/net/tun)"))
 		return -1;
 
 	ifr.ifr_flags = IFF_NO_PI | (need_mac ? IFF_TAP : IFF_TUN);
-- 
2.43.0