[PATCH net-next 0/2] vsock/test: improve sigpipe test reliability

[PATCH net-next 0/2] vsock/test: improve sigpipe test reliability

[Stefano Garzarella]

Running the tests continuously I noticed that sometimes the sigpipe
test would fail due to a race between the control message of the test
and the vsock transport messages.

While I was at it I also improved the test by checking the errno we
expect.

Stefano Garzarella (2):
  vsock/test: retry send() to avoid occasional failure in sigpipe test
  vsock/test: check also expected errno on sigpipe test

 tools/testing/vsock/vsock_test.c | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

-- 
2.49.0

[PATCH net-next 1/2] vsock/test: retry send() to avoid occasional failure in sigpipe test

[Stefano Garzarella]

From: Stefano Garzarella <sgarzare@redhat.com>

When the other peer calls shutdown(SHUT_RD), there is a chance that
the send() call could occur before the message carrying the close
information arrives over the transport. In such cases, the send()
might still succeed. To avoid this race, let's retry the send() call
a few times, ensuring the test is more reliable.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 tools/testing/vsock/vsock_test.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
index d0f6d253ac72..7de870dee1cf 100644
--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -1064,11 +1064,18 @@ static void test_stream_check_sigpipe(int fd)
 
 	have_sigpipe = 0;
 
-	res = send(fd, "A", 1, 0);
-	if (res != -1) {
-		fprintf(stderr, "expected send(2) failure, got %zi\n", res);
-		exit(EXIT_FAILURE);
-	}
+	/* When the other peer calls shutdown(SHUT_RD), there is a chance that
+	 * the send() call could occur before the message carrying the close
+	 * information arrives over the transport. In such cases, the send()
+	 * might still succeed. To avoid this race, let's retry the send() call
+	 * a few times, ensuring the test is more reliable.
+	 */
+	timeout_begin(TIMEOUT);
+	do {
+		res = send(fd, "A", 1, 0);
+		timeout_check("send");
+	} while (res != -1);
+	timeout_end();
 
 	if (!have_sigpipe) {
 		fprintf(stderr, "SIGPIPE expected\n");
@@ -1077,11 +1084,12 @@ static void test_stream_check_sigpipe(int fd)
 
 	have_sigpipe = 0;
 
-	res = send(fd, "A", 1, MSG_NOSIGNAL);
-	if (res != -1) {
-		fprintf(stderr, "expected send(2) failure, got %zi\n", res);
-		exit(EXIT_FAILURE);
-	}
+	timeout_begin(TIMEOUT);
+	do {
+		res = send(fd, "A", 1, MSG_NOSIGNAL);
+		timeout_check("send");
+	} while (res != -1);
+	timeout_end();
 
 	if (have_sigpipe) {
 		fprintf(stderr, "SIGPIPE not expected\n");
-- 
2.49.0

Re: [PATCH net-next 1/2] vsock/test: retry send() to avoid occasional failure in sigpipe test

[Paolo Abeni]

On 5/8/25 4:20 PM, Stefano Garzarella wrote:
> From: Stefano Garzarella <sgarzare@redhat.com>
> 
> When the other peer calls shutdown(SHUT_RD), there is a chance that
> the send() call could occur before the message carrying the close
> information arrives over the transport. In such cases, the send()
> might still succeed. To avoid this race, let's retry the send() call
> a few times, ensuring the test is more reliable.
> 
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
>  tools/testing/vsock/vsock_test.c | 28 ++++++++++++++++++----------
>  1 file changed, 18 insertions(+), 10 deletions(-)
> 
> diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
> index d0f6d253ac72..7de870dee1cf 100644
> --- a/tools/testing/vsock/vsock_test.c
> +++ b/tools/testing/vsock/vsock_test.c
> @@ -1064,11 +1064,18 @@ static void test_stream_check_sigpipe(int fd)
>  
>  	have_sigpipe = 0;
>  
> -	res = send(fd, "A", 1, 0);
> -	if (res != -1) {
> -		fprintf(stderr, "expected send(2) failure, got %zi\n", res);
> -		exit(EXIT_FAILURE);
> -	}
> +	/* When the other peer calls shutdown(SHUT_RD), there is a chance that
> +	 * the send() call could occur before the message carrying the close
> +	 * information arrives over the transport. In such cases, the send()
> +	 * might still succeed. To avoid this race, let's retry the send() call
> +	 * a few times, ensuring the test is more reliable.
> +	 */
> +	timeout_begin(TIMEOUT);
> +	do {
> +		res = send(fd, "A", 1, 0);
> +		timeout_check("send");
> +	} while (res != -1);

AFAICS the above could spin on send() for up to 10s, I would say
considerably more than 'a few times' ;)

In practice that could cause side effect on the timing of other
concurrent tests (due to one CPU being 100% used for a while).

What if the peer rcvbuf fills-up: will the send fail? That could cause
false-negative.

I *think* it should be better to insert a short sleep in the loop.

/P

Re: [PATCH net-next 1/2] vsock/test: retry send() to avoid occasional failure in sigpipe test

[Stefano Garzarella]

On Tue, May 13, 2025 at 12:37:36PM +0200, Paolo Abeni wrote:
>On 5/8/25 4:20 PM, Stefano Garzarella wrote:
>> From: Stefano Garzarella <sgarzare@redhat.com>
>>
>> When the other peer calls shutdown(SHUT_RD), there is a chance that
>> the send() call could occur before the message carrying the close
>> information arrives over the transport. In such cases, the send()
>> might still succeed. To avoid this race, let's retry the send() call
>> a few times, ensuring the test is more reliable.
>>
>> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
>> ---
>>  tools/testing/vsock/vsock_test.c | 28 ++++++++++++++++++----------
>>  1 file changed, 18 insertions(+), 10 deletions(-)
>>
>> diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
>> index d0f6d253ac72..7de870dee1cf 100644
>> --- a/tools/testing/vsock/vsock_test.c
>> +++ b/tools/testing/vsock/vsock_test.c
>> @@ -1064,11 +1064,18 @@ static void test_stream_check_sigpipe(int fd)
>>
>>  	have_sigpipe = 0;
>>
>> -	res = send(fd, "A", 1, 0);
>> -	if (res != -1) {
>> -		fprintf(stderr, "expected send(2) failure, got %zi\n", res);
>> -		exit(EXIT_FAILURE);
>> -	}
>> +	/* When the other peer calls shutdown(SHUT_RD), there is a chance that
>> +	 * the send() call could occur before the message carrying the close
>> +	 * information arrives over the transport. In such cases, the send()
>> +	 * might still succeed. To avoid this race, let's retry the send() call
>> +	 * a few times, ensuring the test is more reliable.
>> +	 */
>> +	timeout_begin(TIMEOUT);
>> +	do {
>> +		res = send(fd, "A", 1, 0);
>> +		timeout_check("send");
>> +	} while (res != -1);
>
>AFAICS the above could spin on send() for up to 10s, I would say
>considerably more than 'a few times' ;)
>
>In practice that could cause side effect on the timing of other
>concurrent tests (due to one CPU being 100% used for a while).
>
>What if the peer rcvbuf fills-up: will the send fail? That could cause
>false-negative.

Good point!

>
>I *think* it should be better to insert a short sleep in the loop.

Agree, I'll add.

Thanks,
Stefano

[PATCH net-next 2/2] vsock/test: check also expected errno on sigpipe test

[Stefano Garzarella]

From: Stefano Garzarella <sgarzare@redhat.com>

In the sigpipe test, we expect send() to fail, but we do not check if
send() fails with the errno we expect (EPIPE).

Add this check and repeat the send() in case of EINTR as we do in other
tests.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 tools/testing/vsock/vsock_test.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
index 7de870dee1cf..533d9463a297 100644
--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -1074,9 +1074,13 @@ static void test_stream_check_sigpipe(int fd)
 	do {
 		res = send(fd, "A", 1, 0);
 		timeout_check("send");
-	} while (res != -1);
+	} while (res != -1 && errno == EINTR);
 	timeout_end();
 
+	if (errno != EPIPE) {
+		fprintf(stderr, "unexpected send(2) errno %d\n", errno);
+		exit(EXIT_FAILURE);
+	}
 	if (!have_sigpipe) {
 		fprintf(stderr, "SIGPIPE expected\n");
 		exit(EXIT_FAILURE);
@@ -1088,9 +1092,13 @@ static void test_stream_check_sigpipe(int fd)
 	do {
 		res = send(fd, "A", 1, MSG_NOSIGNAL);
 		timeout_check("send");
-	} while (res != -1);
+	} while (res != -1 && errno == EINTR);
 	timeout_end();
 
+	if (errno != EPIPE) {
+		fprintf(stderr, "unexpected send(2) errno %d\n", errno);
+		exit(EXIT_FAILURE);
+	}
 	if (have_sigpipe) {
 		fprintf(stderr, "SIGPIPE not expected\n");
 		exit(EXIT_FAILURE);
-- 
2.49.0

Re: [PATCH net-next 2/2] vsock/test: check also expected errno on sigpipe test

[Paolo Abeni]

On 5/8/25 4:20 PM, Stefano Garzarella wrote:
> diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
> index 7de870dee1cf..533d9463a297 100644
> --- a/tools/testing/vsock/vsock_test.c
> +++ b/tools/testing/vsock/vsock_test.c
> @@ -1074,9 +1074,13 @@ static void test_stream_check_sigpipe(int fd)
>  	do {
>  		res = send(fd, "A", 1, 0);
>  		timeout_check("send");
> -	} while (res != -1);
> +	} while (res != -1 && errno == EINTR);

I'm low on coffee, but should the above condition be:

		res != -1 || errno == EINTR

instead?

Same thing below.

/P

Re: [PATCH net-next 2/2] vsock/test: check also expected errno on sigpipe test

[Stefano Garzarella]

On Tue, May 13, 2025 at 12:41:17PM +0200, Paolo Abeni wrote:
>On 5/8/25 4:20 PM, Stefano Garzarella wrote:
>> diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
>> index 7de870dee1cf..533d9463a297 100644
>> --- a/tools/testing/vsock/vsock_test.c
>> +++ b/tools/testing/vsock/vsock_test.c
>> @@ -1074,9 +1074,13 @@ static void test_stream_check_sigpipe(int fd)
>>  	do {
>>  		res = send(fd, "A", 1, 0);
>>  		timeout_check("send");
>> -	} while (res != -1);
>> +	} while (res != -1 && errno == EINTR);
>
>I'm low on coffee, but should the above condition be:
>
>		res != -1 || errno == EINTR
>
>instead?

Ooops, copy & paste where we waited successful send().

>
>Same thing below.

I'll fix both!

Thanks,
Stefano