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@hetzner-cloud.de Reviewed-by: Willem de Bruijn willemb@google.com --- 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);