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
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
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
>
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.
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!
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.
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