[PATCH v2] selftests: af_unix: Add tests for ECONNRESET and EOF semantics

[PATCH v2] selftests: af_unix: Add tests for ECONNRESET and EOF semantics

[Sunday Adelodun]

Add selftests to verify and document Linux’s intended behaviour for
UNIX domain sockets (SOCK_STREAM and SOCK_DGRAM) when a peer closes.
The tests cover:

  1. EOF returned when a SOCK_STREAM peer closes normally.
  2. ECONNRESET returned when a SOCK_STREAM peer closes with unread data.
  3. SOCK_DGRAM sockets not returning ECONNRESET on peer close.

This follows up on review feedback suggesting a selftest to clarify
Linux’s semantics.

Suggested-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Sunday Adelodun <adelodunolaoluwa@yahoo.com>
---
Changelog:

Changes made from v1:

- Patch prefix updated to selftest: af_unix:.

- All mentions of “UNIX” changed to AF_UNIX.

- Removed BSD references from comments.

- Shared setup refactored using FIXTURE_VARIANT().

- Cleanup moved to FIXTURE_TEARDOWN() to always run.

- Tests consolidated to reduce duplication: EOF, ECONNRESET, SOCK_DGRAM peer close.

- Corrected ASSERT usage and initialization style.

- Makefile updated for new directory af_unix.

 tools/testing/selftests/net/af_unix/Makefile  |   1 +
 .../selftests/net/af_unix/unix_connreset.c    | 161 ++++++++++++++++++
 2 files changed, 162 insertions(+)
 create mode 100644 tools/testing/selftests/net/af_unix/unix_connreset.c

diff --git a/tools/testing/selftests/net/af_unix/Makefile b/tools/testing/selftests/net/af_unix/Makefile
index de805cbbdf69..5826a8372451 100644
--- a/tools/testing/selftests/net/af_unix/Makefile
+++ b/tools/testing/selftests/net/af_unix/Makefile
@@ -7,6 +7,7 @@ TEST_GEN_PROGS := \
 	scm_pidfd \
 	scm_rights \
 	unix_connect \
+	unix_connreset \
 # end of TEST_GEN_PROGS
 
 include ../../lib.mk
diff --git a/tools/testing/selftests/net/af_unix/unix_connreset.c b/tools/testing/selftests/net/af_unix/unix_connreset.c
new file mode 100644
index 000000000000..c65ec997d77d
--- /dev/null
+++ b/tools/testing/selftests/net/af_unix/unix_connreset.c
@@ -0,0 +1,161 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Selftest for AF_UNIX socket close and ECONNRESET behaviour.
+ *
+ * This test verifies that:
+ *  1. SOCK_STREAM sockets return EOF when peer closes normally.
+ *  2. SOCK_STREAM sockets return ECONNRESET if peer closes with unread data.
+ *  3. SOCK_DGRAM sockets do not return ECONNRESET when peer closes.
+ *
+ * These tests document the intended Linux behaviour.
+ *
+ */
+
+#define _GNU_SOURCE
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include "../../kselftest_harness.h"
+
+#define SOCK_PATH "/tmp/af_unix_connreset.sock"
+
+static void remove_socket_file(void)
+{
+	unlink(SOCK_PATH);
+}
+
+FIXTURE(unix_sock)
+{
+	int server;
+	int client;
+	int child;
+};
+
+FIXTURE_VARIANT(unix_sock)
+{
+	int socket_type;
+	const char *name;
+};
+
+/* Define variants: stream and datagram */
+FIXTURE_VARIANT_ADD(unix_sock, stream) {
+	.socket_type = SOCK_STREAM,
+	.name = "SOCK_STREAM",
+};
+
+FIXTURE_VARIANT_ADD(unix_sock, dgram) {
+	.socket_type = SOCK_DGRAM,
+	.name = "SOCK_DGRAM",
+};
+
+FIXTURE_SETUP(unix_sock)
+{
+	struct sockaddr_un addr = {};
+	int err;
+
+	addr.sun_family = AF_UNIX;
+	strcpy(addr.sun_path, SOCK_PATH);
+
+	self->server = socket(AF_UNIX, variant->socket_type, 0);
+	ASSERT_LT(-1, self->server);
+
+	err = bind(self->server, (struct sockaddr *)&addr, sizeof(addr));
+	ASSERT_EQ(0, err);
+
+	if (variant->socket_type == SOCK_STREAM) {
+		err = listen(self->server, 1);
+		ASSERT_EQ(0, err);
+
+		self->client = socket(AF_UNIX, SOCK_STREAM, 0);
+		ASSERT_LT(-1, self->client);
+
+		err = connect(self->client, (struct sockaddr *)&addr, sizeof(addr));
+		ASSERT_EQ(0, err);
+
+		self->child = accept(self->server, NULL, NULL);
+		ASSERT_LT(-1, self->child);
+	} else {
+		/* Datagram: bind and connect only */
+		self->client = socket(AF_UNIX, SOCK_DGRAM | SOCK_NONBLOCK, 0);
+		ASSERT_LT(-1, self->client);
+
+		err = connect(self->client, (struct sockaddr *)&addr, sizeof(addr));
+		ASSERT_EQ(0, err);
+	}
+}
+
+FIXTURE_TEARDOWN(unix_sock)
+{
+	if (variant->socket_type == SOCK_STREAM)
+		close(self->child);
+
+	close(self->client);
+	close(self->server);
+	remove_socket_file();
+}
+
+/* Test 1: peer closes normally */
+TEST_F(unix_sock, eof)
+{
+	char buf[16] = {};
+	ssize_t n;
+
+	if (variant->socket_type != SOCK_STREAM)
+		SKIP(return, "This test only applies to SOCK_STREAM");
+
+	/* Peer closes normally */
+	close(self->child);
+
+	n = recv(self->client, buf, sizeof(buf), 0);
+	TH_LOG("%s: recv=%zd errno=%d (%s)", variant->name, n, errno, strerror(errno));
+	if (n == -1)
+		ASSERT_EQ(ECONNRESET, errno);
+
+	if (n != -1)
+		ASSERT_EQ(0, n);
+}
+
+/* Test 2: peer closes with unread data */
+TEST_F(unix_sock, reset_unread)
+{
+	char buf[16] = {};
+	ssize_t n;
+
+	if (variant->socket_type != SOCK_STREAM)
+		SKIP(return, "This test only applies to SOCK_STREAM");
+
+	/* Send data that will remain unread by client */
+	send(self->client, "hello", 5, 0);
+	close(self->child);
+
+	n = recv(self->client, buf, sizeof(buf), 0);
+	TH_LOG("%s: recv=%zd errno=%d (%s)", variant->name, n, errno, strerror(errno));
+	ASSERT_EQ(-1, n);
+	ASSERT_EQ(ECONNRESET, errno);
+}
+
+/* Test 3: SOCK_DGRAM peer close */
+TEST_F(unix_sock, dgram_reset)
+{
+	char buf[16] = {};
+	ssize_t n;
+
+	if (variant->socket_type != SOCK_DGRAM)
+		SKIP(return, "This test only applies to SOCK_DGRAM");
+
+	send(self->client, "hello", 5, 0);
+	close(self->server);
+
+	n = recv(self->client, buf, sizeof(buf), 0);
+	TH_LOG("%s: recv=%zd errno=%d (%s)", variant->name, n, errno, strerror(errno));
+	/* Expect EAGAIN because there is no datagram and peer is closed. */
+	ASSERT_EQ(-1, n);
+	ASSERT_EQ(EAGAIN, errno);
+}
+
+TEST_HARNESS_MAIN
+
-- 
2.43.0

Re: [PATCH v2] selftests: af_unix: Add tests for ECONNRESET and EOF semantics

[Kuniyuki Iwashima]

On Sat, Oct 25, 2025 at 12:03 PM Sunday Adelodun
<adelodunolaoluwa@yahoo.com> wrote:
>
> Add selftests to verify and document Linux’s intended behaviour for
> UNIX domain sockets (SOCK_STREAM and SOCK_DGRAM) when a peer closes.
> The tests cover:
>
>   1. EOF returned when a SOCK_STREAM peer closes normally.
>   2. ECONNRESET returned when a SOCK_STREAM peer closes with unread data.
>   3. SOCK_DGRAM sockets not returning ECONNRESET on peer close.
>
> This follows up on review feedback suggesting a selftest to clarify
> Linux’s semantics.
>
> Suggested-by: Kuniyuki Iwashima <kuniyu@google.com>
> Signed-off-by: Sunday Adelodun <adelodunolaoluwa@yahoo.com>
> ---
> Changelog:
>
> Changes made from v1:
>
> - Patch prefix updated to selftest: af_unix:.
>
> - All mentions of “UNIX” changed to AF_UNIX.
>
> - Removed BSD references from comments.
>
> - Shared setup refactored using FIXTURE_VARIANT().
>
> - Cleanup moved to FIXTURE_TEARDOWN() to always run.
>
> - Tests consolidated to reduce duplication: EOF, ECONNRESET, SOCK_DGRAM peer close.
>
> - Corrected ASSERT usage and initialization style.
>
> - Makefile updated for new directory af_unix.
>
>  tools/testing/selftests/net/af_unix/Makefile  |   1 +
>  .../selftests/net/af_unix/unix_connreset.c    | 161 ++++++++++++++++++
>  2 files changed, 162 insertions(+)
>  create mode 100644 tools/testing/selftests/net/af_unix/unix_connreset.c
>
> diff --git a/tools/testing/selftests/net/af_unix/Makefile b/tools/testing/selftests/net/af_unix/Makefile
> index de805cbbdf69..5826a8372451 100644
> --- a/tools/testing/selftests/net/af_unix/Makefile
> +++ b/tools/testing/selftests/net/af_unix/Makefile
> @@ -7,6 +7,7 @@ TEST_GEN_PROGS := \
>         scm_pidfd \
>         scm_rights \
>         unix_connect \
> +       unix_connreset \
>  # end of TEST_GEN_PROGS
>
>  include ../../lib.mk
> diff --git a/tools/testing/selftests/net/af_unix/unix_connreset.c b/tools/testing/selftests/net/af_unix/unix_connreset.c
> new file mode 100644
> index 000000000000..c65ec997d77d
> --- /dev/null
> +++ b/tools/testing/selftests/net/af_unix/unix_connreset.c
> @@ -0,0 +1,161 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Selftest for AF_UNIX socket close and ECONNRESET behaviour.
> + *
> + * This test verifies that:
> + *  1. SOCK_STREAM sockets return EOF when peer closes normally.
> + *  2. SOCK_STREAM sockets return ECONNRESET if peer closes with unread data.
> + *  3. SOCK_DGRAM sockets do not return ECONNRESET when peer closes.
> + *
> + * These tests document the intended Linux behaviour.
> + *
> + */
> +
> +#define _GNU_SOURCE
> +#include <stdlib.h>
> +#include <string.h>
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <errno.h>
> +#include <sys/socket.h>
> +#include <sys/un.h>
> +#include "../../kselftest_harness.h"
> +
> +#define SOCK_PATH "/tmp/af_unix_connreset.sock"
> +
> +static void remove_socket_file(void)
> +{
> +       unlink(SOCK_PATH);
> +}
> +
> +FIXTURE(unix_sock)
> +{
> +       int server;
> +       int client;
> +       int child;
> +};
> +
> +FIXTURE_VARIANT(unix_sock)
> +{
> +       int socket_type;
> +       const char *name;
> +};
> +
> +/* Define variants: stream and datagram */
> +FIXTURE_VARIANT_ADD(unix_sock, stream) {
> +       .socket_type = SOCK_STREAM,
> +       .name = "SOCK_STREAM",
> +};
> +
> +FIXTURE_VARIANT_ADD(unix_sock, dgram) {
> +       .socket_type = SOCK_DGRAM,
> +       .name = "SOCK_DGRAM",
> +};

Let's add coverage for SOCK_SEQPACKET,
which needs listen() / connect() but other semantics
are similar to SOCK_DGRAM.


> +
> +FIXTURE_SETUP(unix_sock)
> +{
> +       struct sockaddr_un addr = {};
> +       int err;
> +
> +       addr.sun_family = AF_UNIX;
> +       strcpy(addr.sun_path, SOCK_PATH);
> +
> +       self->server = socket(AF_UNIX, variant->socket_type, 0);
> +       ASSERT_LT(-1, self->server);
> +
> +       err = bind(self->server, (struct sockaddr *)&addr, sizeof(addr));
> +       ASSERT_EQ(0, err);
> +
> +       if (variant->socket_type == SOCK_STREAM) {
> +               err = listen(self->server, 1);
> +               ASSERT_EQ(0, err);
> +
> +               self->client = socket(AF_UNIX, SOCK_STREAM, 0);
> +               ASSERT_LT(-1, self->client);
> +
> +               err = connect(self->client, (struct sockaddr *)&addr, sizeof(addr));
> +               ASSERT_EQ(0, err);
> +
> +               self->child = accept(self->server, NULL, NULL);
> +               ASSERT_LT(-1, self->child);
> +       } else {
> +               /* Datagram: bind and connect only */
> +               self->client = socket(AF_UNIX, SOCK_DGRAM | SOCK_NONBLOCK, 0);
> +               ASSERT_LT(-1, self->client);
> +
> +               err = connect(self->client, (struct sockaddr *)&addr, sizeof(addr));
> +               ASSERT_EQ(0, err);
> +       }
> +}
> +
> +FIXTURE_TEARDOWN(unix_sock)
> +{
> +       if (variant->socket_type == SOCK_STREAM)
> +               close(self->child);
> +
> +       close(self->client);
> +       close(self->server);
> +       remove_socket_file();
> +}
> +
> +/* Test 1: peer closes normally */
> +TEST_F(unix_sock, eof)
> +{
> +       char buf[16] = {};
> +       ssize_t n;
> +
> +       if (variant->socket_type != SOCK_STREAM)
> +               SKIP(return, "This test only applies to SOCK_STREAM");

Instead of skipping, let's define final ASSERT() results
for each type.

Same for other 2 tests.


> +
> +       /* Peer closes normally */
> +       close(self->child);
> +
> +       n = recv(self->client, buf, sizeof(buf), 0);
> +       TH_LOG("%s: recv=%zd errno=%d (%s)", variant->name, n, errno, strerror(errno));
> +       if (n == -1)
> +               ASSERT_EQ(ECONNRESET, errno);

... otherwise, we don't see an error here

> +
> +       if (n != -1)
> +               ASSERT_EQ(0, n);

and this can be checked unconditionally.


> +}
> +
> +/* Test 2: peer closes with unread data */
> +TEST_F(unix_sock, reset_unread)
> +{
> +       char buf[16] = {};
> +       ssize_t n;
> +
> +       if (variant->socket_type != SOCK_STREAM)
> +               SKIP(return, "This test only applies to SOCK_STREAM");
> +
> +       /* Send data that will remain unread by client */
> +       send(self->client, "hello", 5, 0);
> +       close(self->child);
> +
> +       n = recv(self->client, buf, sizeof(buf), 0);
> +       TH_LOG("%s: recv=%zd errno=%d (%s)", variant->name, n, errno, strerror(errno));
> +       ASSERT_EQ(-1, n);
> +       ASSERT_EQ(ECONNRESET, errno);
> +}
> +
> +/* Test 3: SOCK_DGRAM peer close */
> +TEST_F(unix_sock, dgram_reset)
> +{
> +       char buf[16] = {};
> +       ssize_t n;
> +
> +       if (variant->socket_type != SOCK_DGRAM)
> +               SKIP(return, "This test only applies to SOCK_DGRAM");
> +
> +       send(self->client, "hello", 5, 0);
> +       close(self->server);
> +
> +       n = recv(self->client, buf, sizeof(buf), 0);
> +       TH_LOG("%s: recv=%zd errno=%d (%s)", variant->name, n, errno, strerror(errno));
> +       /* Expect EAGAIN because there is no datagram and peer is closed. */
> +       ASSERT_EQ(-1, n);
> +       ASSERT_EQ(EAGAIN, errno);
> +}
> +
> +TEST_HARNESS_MAIN
> +
> --
> 2.43.0
>

Re: [PATCH v2] selftests: af_unix: Add tests for ECONNRESET and EOF semantics

[Sunday Adelodun]

On 10/28/25 19:28, Kuniyuki Iwashima wrote:
> On Sat, Oct 25, 2025 at 12:03 PM Sunday Adelodun
> <adelodunolaoluwa@yahoo.com> wrote:
>> Add selftests to verify and document Linux’s intended behaviour for
>> UNIX domain sockets (SOCK_STREAM and SOCK_DGRAM) when a peer closes.
>> The tests cover:
>>
>>    1. EOF returned when a SOCK_STREAM peer closes normally.
>>    2. ECONNRESET returned when a SOCK_STREAM peer closes with unread data.
>>    3. SOCK_DGRAM sockets not returning ECONNRESET on peer close.
>>
>> This follows up on review feedback suggesting a selftest to clarify
>> Linux’s semantics.
>>
>> Suggested-by: Kuniyuki Iwashima <kuniyu@google.com>
>> Signed-off-by: Sunday Adelodun <adelodunolaoluwa@yahoo.com>
>> ---
>> Changelog:
>>
>> Changes made from v1:
>>
>> - Patch prefix updated to selftest: af_unix:.
>>
>> - All mentions of “UNIX” changed to AF_UNIX.
>>
>> - Removed BSD references from comments.
>>
>> - Shared setup refactored using FIXTURE_VARIANT().
>>
>> - Cleanup moved to FIXTURE_TEARDOWN() to always run.
>>
>> - Tests consolidated to reduce duplication: EOF, ECONNRESET, SOCK_DGRAM peer close.
>>
>> - Corrected ASSERT usage and initialization style.
>>
>> - Makefile updated for new directory af_unix.
>>
>>   tools/testing/selftests/net/af_unix/Makefile  |   1 +
>>   .../selftests/net/af_unix/unix_connreset.c    | 161 ++++++++++++++++++
>>   2 files changed, 162 insertions(+)
>>   create mode 100644 tools/testing/selftests/net/af_unix/unix_connreset.c
>>
>> diff --git a/tools/testing/selftests/net/af_unix/Makefile b/tools/testing/selftests/net/af_unix/Makefile
>> index de805cbbdf69..5826a8372451 100644
>> --- a/tools/testing/selftests/net/af_unix/Makefile
>> +++ b/tools/testing/selftests/net/af_unix/Makefile
>> @@ -7,6 +7,7 @@ TEST_GEN_PROGS := \
>>          scm_pidfd \
>>          scm_rights \
>>          unix_connect \
>> +       unix_connreset \
>>   # end of TEST_GEN_PROGS
>>
>>   include ../../lib.mk
>> diff --git a/tools/testing/selftests/net/af_unix/unix_connreset.c b/tools/testing/selftests/net/af_unix/unix_connreset.c
>> new file mode 100644
>> index 000000000000..c65ec997d77d
>> --- /dev/null
>> +++ b/tools/testing/selftests/net/af_unix/unix_connreset.c
>> @@ -0,0 +1,161 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Selftest for AF_UNIX socket close and ECONNRESET behaviour.
>> + *
>> + * This test verifies that:
>> + *  1. SOCK_STREAM sockets return EOF when peer closes normally.
>> + *  2. SOCK_STREAM sockets return ECONNRESET if peer closes with unread data.
>> + *  3. SOCK_DGRAM sockets do not return ECONNRESET when peer closes.
>> + *
>> + * These tests document the intended Linux behaviour.
>> + *
>> + */
>> +
>> +#define _GNU_SOURCE
>> +#include <stdlib.h>
>> +#include <string.h>
>> +#include <fcntl.h>
>> +#include <unistd.h>
>> +#include <errno.h>
>> +#include <sys/socket.h>
>> +#include <sys/un.h>
>> +#include "../../kselftest_harness.h"
>> +
>> +#define SOCK_PATH "/tmp/af_unix_connreset.sock"
>> +
>> +static void remove_socket_file(void)
>> +{
>> +       unlink(SOCK_PATH);
>> +}
>> +
>> +FIXTURE(unix_sock)
>> +{
>> +       int server;
>> +       int client;
>> +       int child;
>> +};
>> +
>> +FIXTURE_VARIANT(unix_sock)
>> +{
>> +       int socket_type;
>> +       const char *name;
>> +};
>> +
>> +/* Define variants: stream and datagram */
>> +FIXTURE_VARIANT_ADD(unix_sock, stream) {
>> +       .socket_type = SOCK_STREAM,
>> +       .name = "SOCK_STREAM",
>> +};
>> +
>> +FIXTURE_VARIANT_ADD(unix_sock, dgram) {
>> +       .socket_type = SOCK_DGRAM,
>> +       .name = "SOCK_DGRAM",
>> +};
> Let's add coverage for SOCK_SEQPACKET,
> which needs listen() / connect() but other semantics
> are similar to SOCK_DGRAM.

I will add it through:
if (variant->socket_type == SOCK_STREAM ||
		variant->socket_type == SOCK_SEQPACKET)
  

in both the setup and teardown fixtures with a little bit of modification

where necessary (especially in the setup fixture).

And also the fixture_variant_add macro.

>> +
>> +FIXTURE_SETUP(unix_sock)
>> +{
>> +       struct sockaddr_un addr = {};
>> +       int err;
>> +
>> +       addr.sun_family = AF_UNIX;
>> +       strcpy(addr.sun_path, SOCK_PATH);
>> +
>> +       self->server = socket(AF_UNIX, variant->socket_type, 0);
>> +       ASSERT_LT(-1, self->server);
>> +
>> +       err = bind(self->server, (struct sockaddr *)&addr, sizeof(addr));
>> +       ASSERT_EQ(0, err);
>> +
>> +       if (variant->socket_type == SOCK_STREAM) {
>> +               err = listen(self->server, 1);
>> +               ASSERT_EQ(0, err);
>> +
>> +               self->client = socket(AF_UNIX, SOCK_STREAM, 0);
>> +               ASSERT_LT(-1, self->client);
>> +
>> +               err = connect(self->client, (struct sockaddr *)&addr, sizeof(addr));
>> +               ASSERT_EQ(0, err);
>> +
>> +               self->child = accept(self->server, NULL, NULL);
>> +               ASSERT_LT(-1, self->child);
>> +       } else {
>> +               /* Datagram: bind and connect only */
>> +               self->client = socket(AF_UNIX, SOCK_DGRAM | SOCK_NONBLOCK, 0);
>> +               ASSERT_LT(-1, self->client);
>> +
>> +               err = connect(self->client, (struct sockaddr *)&addr, sizeof(addr));
>> +               ASSERT_EQ(0, err);
>> +       }
>> +}
>> +
>> +FIXTURE_TEARDOWN(unix_sock)
>> +{
>> +       if (variant->socket_type == SOCK_STREAM)
>> +               close(self->child);
>> +
>> +       close(self->client);
>> +       close(self->server);
>> +       remove_socket_file();
>> +}
>> +
>> +/* Test 1: peer closes normally */
>> +TEST_F(unix_sock, eof)
>> +{
>> +       char buf[16] = {};
>> +       ssize_t n;
>> +
>> +       if (variant->socket_type != SOCK_STREAM)
>> +               SKIP(return, "This test only applies to SOCK_STREAM");
> Instead of skipping, let's define final ASSERT() results
> for each type.
>
> Same for other 2 tests.

can I use a switch statement in all the tests? say, for example

test1:

...

switch (variant->socket_type) {

case SOCK_STREAM:

case SOCK_SEQPACKET:

         ASSERT_EQ(0, n);

case SOCK_DGRAM:

         ASSERT(-1, n);

         ASSERT_EQ(EAGAIN, errno);

         break;

}

...

test2:

...

switch (variant->socket_type) {

case SOCK_STREAM:

case SOCK_SEQPACKET:

         ASSERT_EQ(-1, n);

         ASSERT_EQ(ECONNRESET, errno);

         break;

case SOCK_DGRAM:

         ASSERT(-1, n);

         ASSERT_EQ(EAGAIN, errno);

         break;

}
...

test 3:

...

switch (variant->socket_type) {

case SOCK_STREAM:

case SOCK_SEQPACKET:

         ASSERT_EQ(-1, n);

         ASSERT_EQ(ECONNRESET, errno);

         break;

case SOCK_DGRAM:

         ASSERT(-1, n);

         ASSERT_EQ(EAGAIN, errno);

         break;

}

...

if not these, could you kindly shed more light to what you meant

>
>
>> +
>> +       /* Peer closes normally */
>> +       close(self->child);
>> +
>> +       n = recv(self->client, buf, sizeof(buf), 0);
>> +       TH_LOG("%s: recv=%zd errno=%d (%s)", variant->name, n, errno, strerror(errno));
>> +       if (n == -1)
>> +               ASSERT_EQ(ECONNRESET, errno);
> ... otherwise, we don't see an error here
>
>> +
>> +       if (n != -1)
>> +               ASSERT_EQ(0, n);
> and this can be checked unconditionally.
did you mean I should remove the if (n != -1) ASSERT_EQ(0, n); part?

>
>> +}
>> +
>> +/* Test 2: peer closes with unread data */
>> +TEST_F(unix_sock, reset_unread)
>> +{
>> +       char buf[16] = {};
>> +       ssize_t n;
>> +
>> +       if (variant->socket_type != SOCK_STREAM)
>> +               SKIP(return, "This test only applies to SOCK_STREAM");
>> +
>> +       /* Send data that will remain unread by client */
>> +       send(self->client, "hello", 5, 0);
>> +       close(self->child);
>> +
>> +       n = recv(self->client, buf, sizeof(buf), 0);
>> +       TH_LOG("%s: recv=%zd errno=%d (%s)", variant->name, n, errno, strerror(errno));
>> +       ASSERT_EQ(-1, n);
>> +       ASSERT_EQ(ECONNRESET, errno);
>> +}
>> +
>> +/* Test 3: SOCK_DGRAM peer close */
>> +TEST_F(unix_sock, dgram_reset)
>> +{
>> +       char buf[16] = {};
>> +       ssize_t n;
>> +
>> +       if (variant->socket_type != SOCK_DGRAM)
>> +               SKIP(return, "This test only applies to SOCK_DGRAM");
>> +
>> +       send(self->client, "hello", 5, 0);
>> +       close(self->server);
>> +
>> +       n = recv(self->client, buf, sizeof(buf), 0);
>> +       TH_LOG("%s: recv=%zd errno=%d (%s)", variant->name, n, errno, strerror(errno));
>> +       /* Expect EAGAIN because there is no datagram and peer is closed. */
>> +       ASSERT_EQ(-1, n);
>> +       ASSERT_EQ(EAGAIN, errno);
>> +}
>> +
>> +TEST_HARNESS_MAIN
>> +
>> --
>> 2.43.0
>>
Thank you very much for the review and comments.

I will send v3 after you review the questions/clarifications I asked in 
my previous reply.
Apologies for the delay in responding.

Thanks again for the guidance and patience, really appreciate it.

Re: [PATCH v2] selftests: af_unix: Add tests for ECONNRESET and EOF semantics

[Kuniyuki Iwashima]

On Thu, Oct 30, 2025 at 6:45 AM Sunday Adelodun
<adelodunolaoluwa@yahoo.com> wrote:
>
> On 10/28/25 19:28, Kuniyuki Iwashima wrote:
> > On Sat, Oct 25, 2025 at 12:03 PM Sunday Adelodun
> > <adelodunolaoluwa@yahoo.com> wrote:
> >> Add selftests to verify and document Linux’s intended behaviour for
> >> UNIX domain sockets (SOCK_STREAM and SOCK_DGRAM) when a peer closes.
> >> The tests cover:
> >>
> >>    1. EOF returned when a SOCK_STREAM peer closes normally.
> >>    2. ECONNRESET returned when a SOCK_STREAM peer closes with unread data.
> >>    3. SOCK_DGRAM sockets not returning ECONNRESET on peer close.
> >>
> >> This follows up on review feedback suggesting a selftest to clarify
> >> Linux’s semantics.
> >>
> >> Suggested-by: Kuniyuki Iwashima <kuniyu@google.com>
> >> Signed-off-by: Sunday Adelodun <adelodunolaoluwa@yahoo.com>
> >> ---
> >> Changelog:
> >>
> >> Changes made from v1:
> >>
> >> - Patch prefix updated to selftest: af_unix:.
> >>
> >> - All mentions of “UNIX” changed to AF_UNIX.
> >>
> >> - Removed BSD references from comments.
> >>
> >> - Shared setup refactored using FIXTURE_VARIANT().
> >>
> >> - Cleanup moved to FIXTURE_TEARDOWN() to always run.
> >>
> >> - Tests consolidated to reduce duplication: EOF, ECONNRESET, SOCK_DGRAM peer close.
> >>
> >> - Corrected ASSERT usage and initialization style.
> >>
> >> - Makefile updated for new directory af_unix.
> >>
> >>   tools/testing/selftests/net/af_unix/Makefile  |   1 +
> >>   .../selftests/net/af_unix/unix_connreset.c    | 161 ++++++++++++++++++
> >>   2 files changed, 162 insertions(+)
> >>   create mode 100644 tools/testing/selftests/net/af_unix/unix_connreset.c
> >>
> >> diff --git a/tools/testing/selftests/net/af_unix/Makefile b/tools/testing/selftests/net/af_unix/Makefile
> >> index de805cbbdf69..5826a8372451 100644
> >> --- a/tools/testing/selftests/net/af_unix/Makefile
> >> +++ b/tools/testing/selftests/net/af_unix/Makefile
> >> @@ -7,6 +7,7 @@ TEST_GEN_PROGS := \
> >>          scm_pidfd \
> >>          scm_rights \
> >>          unix_connect \
> >> +       unix_connreset \
> >>   # end of TEST_GEN_PROGS
> >>
> >>   include ../../lib.mk
> >> diff --git a/tools/testing/selftests/net/af_unix/unix_connreset.c b/tools/testing/selftests/net/af_unix/unix_connreset.c
> >> new file mode 100644
> >> index 000000000000..c65ec997d77d
> >> --- /dev/null
> >> +++ b/tools/testing/selftests/net/af_unix/unix_connreset.c
> >> @@ -0,0 +1,161 @@
> >> +// SPDX-License-Identifier: GPL-2.0
> >> +/*
> >> + * Selftest for AF_UNIX socket close and ECONNRESET behaviour.
> >> + *
> >> + * This test verifies that:
> >> + *  1. SOCK_STREAM sockets return EOF when peer closes normally.
> >> + *  2. SOCK_STREAM sockets return ECONNRESET if peer closes with unread data.
> >> + *  3. SOCK_DGRAM sockets do not return ECONNRESET when peer closes.
> >> + *
> >> + * These tests document the intended Linux behaviour.
> >> + *
> >> + */
> >> +
> >> +#define _GNU_SOURCE
> >> +#include <stdlib.h>
> >> +#include <string.h>
> >> +#include <fcntl.h>
> >> +#include <unistd.h>
> >> +#include <errno.h>
> >> +#include <sys/socket.h>
> >> +#include <sys/un.h>
> >> +#include "../../kselftest_harness.h"
> >> +
> >> +#define SOCK_PATH "/tmp/af_unix_connreset.sock"
> >> +
> >> +static void remove_socket_file(void)
> >> +{
> >> +       unlink(SOCK_PATH);
> >> +}
> >> +
> >> +FIXTURE(unix_sock)
> >> +{
> >> +       int server;
> >> +       int client;
> >> +       int child;
> >> +};
> >> +
> >> +FIXTURE_VARIANT(unix_sock)
> >> +{
> >> +       int socket_type;
> >> +       const char *name;
> >> +};
> >> +
> >> +/* Define variants: stream and datagram */
> >> +FIXTURE_VARIANT_ADD(unix_sock, stream) {
> >> +       .socket_type = SOCK_STREAM,
> >> +       .name = "SOCK_STREAM",
> >> +};
> >> +
> >> +FIXTURE_VARIANT_ADD(unix_sock, dgram) {
> >> +       .socket_type = SOCK_DGRAM,
> >> +       .name = "SOCK_DGRAM",
> >> +};
> > Let's add coverage for SOCK_SEQPACKET,
> > which needs listen() / connect() but other semantics
> > are similar to SOCK_DGRAM.
>
> I will add it through:
> if (variant->socket_type == SOCK_STREAM ||
>                 variant->socket_type == SOCK_SEQPACKET)
>
>
> in both the setup and teardown fixtures with a little bit of modification
>
> where necessary (especially in the setup fixture).
>
> And also the fixture_variant_add macro.
>
> >> +
> >> +FIXTURE_SETUP(unix_sock)
> >> +{
> >> +       struct sockaddr_un addr = {};
> >> +       int err;
> >> +
> >> +       addr.sun_family = AF_UNIX;
> >> +       strcpy(addr.sun_path, SOCK_PATH);
> >> +
> >> +       self->server = socket(AF_UNIX, variant->socket_type, 0);
> >> +       ASSERT_LT(-1, self->server);
> >> +
> >> +       err = bind(self->server, (struct sockaddr *)&addr, sizeof(addr));
> >> +       ASSERT_EQ(0, err);
> >> +
> >> +       if (variant->socket_type == SOCK_STREAM) {
> >> +               err = listen(self->server, 1);
> >> +               ASSERT_EQ(0, err);
> >> +
> >> +               self->client = socket(AF_UNIX, SOCK_STREAM, 0);
> >> +               ASSERT_LT(-1, self->client);
> >> +
> >> +               err = connect(self->client, (struct sockaddr *)&addr, sizeof(addr));
> >> +               ASSERT_EQ(0, err);
> >> +
> >> +               self->child = accept(self->server, NULL, NULL);
> >> +               ASSERT_LT(-1, self->child);
> >> +       } else {
> >> +               /* Datagram: bind and connect only */
> >> +               self->client = socket(AF_UNIX, SOCK_DGRAM | SOCK_NONBLOCK, 0);
> >> +               ASSERT_LT(-1, self->client);
> >> +
> >> +               err = connect(self->client, (struct sockaddr *)&addr, sizeof(addr));
> >> +               ASSERT_EQ(0, err);
> >> +       }
> >> +}
> >> +
> >> +FIXTURE_TEARDOWN(unix_sock)
> >> +{
> >> +       if (variant->socket_type == SOCK_STREAM)
> >> +               close(self->child);
> >> +
> >> +       close(self->client);
> >> +       close(self->server);
> >> +       remove_socket_file();
> >> +}
> >> +
> >> +/* Test 1: peer closes normally */
> >> +TEST_F(unix_sock, eof)
> >> +{
> >> +       char buf[16] = {};
> >> +       ssize_t n;
> >> +
> >> +       if (variant->socket_type != SOCK_STREAM)
> >> +               SKIP(return, "This test only applies to SOCK_STREAM");
> > Instead of skipping, let's define final ASSERT() results
> > for each type.
> >
> > Same for other 2 tests.
>
> can I use a switch statement in all the tests? say, for example

switch() is completely fine, but I guess "if" will be shorter :)

>
> test1:
>
> ...
>
> switch (variant->socket_type) {
>
> case SOCK_STREAM:
>
> case SOCK_SEQPACKET:
>
>          ASSERT_EQ(0, n);

You need break; here.

>
> case SOCK_DGRAM:
>
>          ASSERT(-1, n);
>
>          ASSERT_EQ(EAGAIN, errno);
>
>          break;

And also please make sure the compiler will not complain
without default: depending on inherited build options.

>
> }
>
> ...
>
> test2:
>
> ...
>
> switch (variant->socket_type) {
>
> case SOCK_STREAM:
>
> case SOCK_SEQPACKET:
>
>          ASSERT_EQ(-1, n);
>
>          ASSERT_EQ(ECONNRESET, errno);
>
>          break;
>
> case SOCK_DGRAM:
>
>          ASSERT(-1, n);
>
>          ASSERT_EQ(EAGAIN, errno);
>
>          break;
>
> }
> ...
>
> test 3:
>
> ...
>
> switch (variant->socket_type) {
>
> case SOCK_STREAM:
>
> case SOCK_SEQPACKET:
>
>          ASSERT_EQ(-1, n);
>
>          ASSERT_EQ(ECONNRESET, errno);
>
>          break;
>
> case SOCK_DGRAM:
>
>          ASSERT(-1, n);
>
>          ASSERT_EQ(EAGAIN, errno);
>
>          break;
>
> }
>
> ...
>
> if not these, could you kindly shed more light to what you meant
>
> >
> >
> >> +
> >> +       /* Peer closes normally */
> >> +       close(self->child);
> >> +
> >> +       n = recv(self->client, buf, sizeof(buf), 0);
> >> +       TH_LOG("%s: recv=%zd errno=%d (%s)", variant->name, n, errno, strerror(errno));
> >> +       if (n == -1)
> >> +               ASSERT_EQ(ECONNRESET, errno);
> > ... otherwise, we don't see an error here
> >
> >> +
> >> +       if (n != -1)
> >> +               ASSERT_EQ(0, n);
> > and this can be checked unconditionally.
> did you mean I should remove the if (n != -1) ASSERT_EQ(0, n); part?

If SOCK_DGRAM does not reuse this test, yes.

The point is we do not want to miss future regression by
preparing both if (n == -1) case and if  (n == 0) case, one
of which should never happen at this point.

Thanks!

Re: [PATCH v2] selftests: af_unix: Add tests for ECONNRESET and EOF semantics

[Sunday Adelodun]

On 10/31/25 20:41, Kuniyuki Iwashima wrote:
> On Thu, Oct 30, 2025 at 6:45 AM Sunday Adelodun
> <adelodunolaoluwa@yahoo.com> wrote:
>> On 10/28/25 19:28, Kuniyuki Iwashima wrote:
>>> On Sat, Oct 25, 2025 at 12:03 PM Sunday Adelodun
>>> <adelodunolaoluwa@yahoo.com> wrote:
>>>> Add selftests to verify and document Linux’s intended behaviour for
>>>> UNIX domain sockets (SOCK_STREAM and SOCK_DGRAM) when a peer closes.
>>>> The tests cover:
>>>>
>>>>     1. EOF returned when a SOCK_STREAM peer closes normally.
>>>>     2. ECONNRESET returned when a SOCK_STREAM peer closes with unread data.
>>>>     3. SOCK_DGRAM sockets not returning ECONNRESET on peer close.
>>>>
>>>> This follows up on review feedback suggesting a selftest to clarify
>>>> Linux’s semantics.
>>>>
>>>> Suggested-by: Kuniyuki Iwashima <kuniyu@google.com>
>>>> Signed-off-by: Sunday Adelodun <adelodunolaoluwa@yahoo.com>
>>>> ---
>>>> Changelog:
>>>>
>>>> Changes made from v1:
>>>>
>>>> - Patch prefix updated to selftest: af_unix:.
>>>>
>>>> - All mentions of “UNIX” changed to AF_UNIX.
>>>>
>>>> - Removed BSD references from comments.
>>>>
>>>> - Shared setup refactored using FIXTURE_VARIANT().
>>>>
>>>> - Cleanup moved to FIXTURE_TEARDOWN() to always run.
>>>>
>>>> - Tests consolidated to reduce duplication: EOF, ECONNRESET, SOCK_DGRAM peer close.
>>>>
>>>> - Corrected ASSERT usage and initialization style.
>>>>
>>>> - Makefile updated for new directory af_unix.
>>>>
>>>>    tools/testing/selftests/net/af_unix/Makefile  |   1 +
>>>>    .../selftests/net/af_unix/unix_connreset.c    | 161 ++++++++++++++++++
>>>>    2 files changed, 162 insertions(+)
>>>>    create mode 100644 tools/testing/selftests/net/af_unix/unix_connreset.c
>>>>
>>>> diff --git a/tools/testing/selftests/net/af_unix/Makefile b/tools/testing/selftests/net/af_unix/Makefile
>>>> index de805cbbdf69..5826a8372451 100644
>>>> --- a/tools/testing/selftests/net/af_unix/Makefile
>>>> +++ b/tools/testing/selftests/net/af_unix/Makefile
>>>> @@ -7,6 +7,7 @@ TEST_GEN_PROGS := \
>>>>           scm_pidfd \
>>>>           scm_rights \
>>>>           unix_connect \
>>>> +       unix_connreset \
>>>>    # end of TEST_GEN_PROGS
>>>>
>>>>    include ../../lib.mk
>>>> diff --git a/tools/testing/selftests/net/af_unix/unix_connreset.c b/tools/testing/selftests/net/af_unix/unix_connreset.c
>>>> new file mode 100644
>>>> index 000000000000..c65ec997d77d
>>>> --- /dev/null
>>>> +++ b/tools/testing/selftests/net/af_unix/unix_connreset.c
>>>> @@ -0,0 +1,161 @@
>>>> +// SPDX-License-Identifier: GPL-2.0
>>>> +/*
>>>> + * Selftest for AF_UNIX socket close and ECONNRESET behaviour.
>>>> + *
>>>> + * This test verifies that:
>>>> + *  1. SOCK_STREAM sockets return EOF when peer closes normally.
>>>> + *  2. SOCK_STREAM sockets return ECONNRESET if peer closes with unread data.
>>>> + *  3. SOCK_DGRAM sockets do not return ECONNRESET when peer closes.
>>>> + *
>>>> + * These tests document the intended Linux behaviour.
>>>> + *
>>>> + */
>>>> +
>>>> +#define _GNU_SOURCE
>>>> +#include <stdlib.h>
>>>> +#include <string.h>
>>>> +#include <fcntl.h>
>>>> +#include <unistd.h>
>>>> +#include <errno.h>
>>>> +#include <sys/socket.h>
>>>> +#include <sys/un.h>
>>>> +#include "../../kselftest_harness.h"
>>>> +
>>>> +#define SOCK_PATH "/tmp/af_unix_connreset.sock"
>>>> +
>>>> +static void remove_socket_file(void)
>>>> +{
>>>> +       unlink(SOCK_PATH);
>>>> +}
>>>> +
>>>> +FIXTURE(unix_sock)
>>>> +{
>>>> +       int server;
>>>> +       int client;
>>>> +       int child;
>>>> +};
>>>> +
>>>> +FIXTURE_VARIANT(unix_sock)
>>>> +{
>>>> +       int socket_type;
>>>> +       const char *name;
>>>> +};
>>>> +
>>>> +/* Define variants: stream and datagram */
>>>> +FIXTURE_VARIANT_ADD(unix_sock, stream) {
>>>> +       .socket_type = SOCK_STREAM,
>>>> +       .name = "SOCK_STREAM",
>>>> +};
>>>> +
>>>> +FIXTURE_VARIANT_ADD(unix_sock, dgram) {
>>>> +       .socket_type = SOCK_DGRAM,
>>>> +       .name = "SOCK_DGRAM",
>>>> +};
>>> Let's add coverage for SOCK_SEQPACKET,
>>> which needs listen() / connect() but other semantics
>>> are similar to SOCK_DGRAM.
>> I will add it through:
>> if (variant->socket_type == SOCK_STREAM ||
>>                  variant->socket_type == SOCK_SEQPACKET)
>>
>>
>> in both the setup and teardown fixtures with a little bit of modification
>>
>> where necessary (especially in the setup fixture).
>>
>> And also the fixture_variant_add macro.
>>
>>>> +
>>>> +FIXTURE_SETUP(unix_sock)
>>>> +{
>>>> +       struct sockaddr_un addr = {};
>>>> +       int err;
>>>> +
>>>> +       addr.sun_family = AF_UNIX;
>>>> +       strcpy(addr.sun_path, SOCK_PATH);
>>>> +
>>>> +       self->server = socket(AF_UNIX, variant->socket_type, 0);
>>>> +       ASSERT_LT(-1, self->server);
>>>> +
>>>> +       err = bind(self->server, (struct sockaddr *)&addr, sizeof(addr));
>>>> +       ASSERT_EQ(0, err);
>>>> +
>>>> +       if (variant->socket_type == SOCK_STREAM) {
>>>> +               err = listen(self->server, 1);
>>>> +               ASSERT_EQ(0, err);
>>>> +
>>>> +               self->client = socket(AF_UNIX, SOCK_STREAM, 0);
>>>> +               ASSERT_LT(-1, self->client);
>>>> +
>>>> +               err = connect(self->client, (struct sockaddr *)&addr, sizeof(addr));
>>>> +               ASSERT_EQ(0, err);
>>>> +
>>>> +               self->child = accept(self->server, NULL, NULL);
>>>> +               ASSERT_LT(-1, self->child);
>>>> +       } else {
>>>> +               /* Datagram: bind and connect only */
>>>> +               self->client = socket(AF_UNIX, SOCK_DGRAM | SOCK_NONBLOCK, 0);
>>>> +               ASSERT_LT(-1, self->client);
>>>> +
>>>> +               err = connect(self->client, (struct sockaddr *)&addr, sizeof(addr));
>>>> +               ASSERT_EQ(0, err);
>>>> +       }
>>>> +}
>>>> +
>>>> +FIXTURE_TEARDOWN(unix_sock)
>>>> +{
>>>> +       if (variant->socket_type == SOCK_STREAM)
>>>> +               close(self->child);
>>>> +
>>>> +       close(self->client);
>>>> +       close(self->server);
>>>> +       remove_socket_file();
>>>> +}
>>>> +
>>>> +/* Test 1: peer closes normally */
>>>> +TEST_F(unix_sock, eof)
>>>> +{
>>>> +       char buf[16] = {};
>>>> +       ssize_t n;
>>>> +
>>>> +       if (variant->socket_type != SOCK_STREAM)
>>>> +               SKIP(return, "This test only applies to SOCK_STREAM");
>>> Instead of skipping, let's define final ASSERT() results
>>> for each type.
>>>
>>> Same for other 2 tests.
>> can I use a switch statement in all the tests? say, for example
> switch() is completely fine, but I guess "if" will be shorter :)
I will go for if then.
>
>> test1:
>>
>> ...
>>
>> switch (variant->socket_type) {
>>
>> case SOCK_STREAM:
>>
>> case SOCK_SEQPACKET:
>>
>>           ASSERT_EQ(0, n);
> You need break; here.
Thank you. It was an omission
>
>> case SOCK_DGRAM:
>>
>>           ASSERT(-1, n);
>>
>>           ASSERT_EQ(EAGAIN, errno);
>>
>>           break;
> And also please make sure the compiler will not complain
> without default: depending on inherited build options.
I will look into this
>
>> }
>>
>> ...
>>
>> test2:
>>
>> ...
>>
>> switch (variant->socket_type) {
>>
>> case SOCK_STREAM:
>>
>> case SOCK_SEQPACKET:
>>
>>           ASSERT_EQ(-1, n);
>>
>>           ASSERT_EQ(ECONNRESET, errno);
>>
>>           break;
>>
>> case SOCK_DGRAM:
>>
>>           ASSERT(-1, n);
>>
>>           ASSERT_EQ(EAGAIN, errno);
>>
>>           break;
>>
>> }
>> ...
>>
>> test 3:
>>
>> ...
>>
>> switch (variant->socket_type) {
>>
>> case SOCK_STREAM:
>>
>> case SOCK_SEQPACKET:
>>
>>           ASSERT_EQ(-1, n);
>>
>>           ASSERT_EQ(ECONNRESET, errno);
>>
>>           break;
>>
>> case SOCK_DGRAM:
>>
>>           ASSERT(-1, n);
>>
>>           ASSERT_EQ(EAGAIN, errno);
>>
>>           break;
>>
>> }
>>
>> ...
>>
>> if not these, could you kindly shed more light to what you meant
>>
>>>
>>>> +
>>>> +       /* Peer closes normally */
>>>> +       close(self->child);
>>>> +
>>>> +       n = recv(self->client, buf, sizeof(buf), 0);
>>>> +       TH_LOG("%s: recv=%zd errno=%d (%s)", variant->name, n, errno, strerror(errno));
>>>> +       if (n == -1)
>>>> +               ASSERT_EQ(ECONNRESET, errno);
>>> ... otherwise, we don't see an error here
>>>
>>>> +
>>>> +       if (n != -1)
>>>> +               ASSERT_EQ(0, n);
>>> and this can be checked unconditionally.
>> did you mean I should remove the if (n != -1) ASSERT_EQ(0, n); part?
> If SOCK_DGRAM does not reuse this test, yes.
>
> The point is we do not want to miss future regression by
> preparing both if (n == -1) case and if  (n == 0) case, one
> of which should never happen at this point.
>
> Thanks!
>
Thank you for these.
I will work on them and send v3 shortly.

Thanks once again.