Re: [PATCH bpf-next] selftests/bpf: Remove "&>" usage in the selftests

[Martin KaFai Lau <martin.lau@linux.dev>]

On 1/26/24 6:50 PM, Martin KaFai Lau wrote:
> diff --git a/tools/testing/selftests/bpf/prog_tests/lwt_redirect.c b/tools/testing/selftests/bpf/prog_tests/lwt_redirect.c
> index 59b38569f310..beeb3ac1c361 100644
> --- a/tools/testing/selftests/bpf/prog_tests/lwt_redirect.c
> +++ b/tools/testing/selftests/bpf/prog_tests/lwt_redirect.c
> @@ -85,7 +85,7 @@ static void ping_dev(const char *dev, bool is_ingress)
>   		snprintf(ip, sizeof(ip), "20.0.0.%d", link_index);
>   
>   	/* We won't get a reply. Don't fail here */
> -	SYS_NOFAIL("ping %s -c1 -W1 -s %d >/dev/null 2>&1",
> +	SYS_NOFAIL("ping %s -c1 -W1 -s %d",
>   		   ip, ICMP_PAYLOAD_SIZE);
>   }

The "lwt_redirect/lwt_redirect_normal" is flaky now in s390.
I don't see how this change affected it other than
moving the ">/dev/null 2>&1" part to SYS_NOFAIL.

====
Error: #142/1 lwt_redirect/lwt_redirect_normal
test_lwt_redirect_run:PASS:netns_create 0 nsec
open_netns:PASS:malloc token 0 nsec
open_netns:PASS:open /proc/self/ns/net 0 nsec
open_netns:PASS:open netns fd 0 nsec
open_netns:PASS:setns 0 nsec
test_lwt_redirect_run:PASS:setns 0 nsec
open_tuntap:PASS:open(/dev/net/tun) 0 nsec
open_tuntap:PASS:ioctl(TUNSETIFF) 0 nsec
open_tuntap:PASS:fcntl(O_NONBLOCK) 0 nsec
setup_redirect_target:PASS:open_tuntap 0 nsec
setup_redirect_target:PASS:if_nametoindex 0 nsec
setup_redirect_target:PASS:ip link add link_err type dummy 0 nsec
setup_redirect_target:PASS:ip link set lo up 0 nsec
setup_redirect_target:PASS:ip addr add dev lo 10.0.0.1/32 0 nsec
setup_redirect_target:PASS:ip link set link_err up 0 nsec
setup_redirect_target:PASS:ip link set tap0 up 0 nsec
setup_redirect_target:PASS:ip route add 10.0.0.0/24 dev link_err encap bpf xmit obj test_lwt_redirect.bpf.o sec redir_ingress 0 nsec
setup_redirect_target:PASS:ip route add 20.0.0.0/24 dev link_err encap bpf xmit obj test_lwt_redirect.bpf.o sec redir_egress 0 nsec
test_lwt_redirect_normal:PASS:setup_redirect_target 0 nsec
ping_dev:PASS:if_nametoindex 0 nsec
send_and_capture_test_packets:FAIL:wait_for_epacket unexpected wait_for_epacket: actual 0 != expected 1
(/tmp/work/bpf/bpf/tools/testing/selftests/bpf/prog_tests/lwt_redirect.c:175: errno: Success) test_lwt_redirect_normal egress test fails
====

May be the timeout is too short...

static void send_and_capture_test_packets(const char *test_name, int tap_fd,
					const char *target_dev, bool need_mac)
{
	int psock = -1;
	struct timeval timeo = {
		.tv_sec = 0,
		.tv_usec = 250000,
	};

	/* ... */
}

[ ... ]

> diff --git a/tools/testing/selftests/bpf/test_progs.h b/tools/testing/selftests/bpf/test_progs.h
> index 2f9f6f250f17..80df51244886 100644
> --- a/tools/testing/selftests/bpf/test_progs.h
> +++ b/tools/testing/selftests/bpf/test_progs.h
> @@ -385,10 +385,15 @@ int test__join_cgroup(const char *path);
>   			goto goto_label;				\
>   	})
>   
> +#define ALL_TO_DEV_NULL " >/dev/null 2>&1"
> +
>   #define SYS_NOFAIL(fmt, ...)						\
>   	({								\
>   		char cmd[1024];						\
> -		snprintf(cmd, sizeof(cmd), fmt, ##__VA_ARGS__);		\
> +		int n;							\
> +		n = snprintf(cmd, sizeof(cmd), fmt, ##__VA_ARGS__);	\
> +		if (n < sizeof(cmd) && sizeof(cmd) - n >= sizeof(ALL_TO_DEV_NULL)) \
> +			strcat(cmd, ALL_TO_DEV_NULL);			\
>   		system(cmd);						\
>   	})