Add selftests verifying the EOF and ECONNRESET behaviour of UNIX domain sockets (SOCK_STREAM and SOCK_DGRAM). The tests document Linux's semantics and clarify the long-standing differences with BSD.
Suggested-by: Kuniyuki Iwashima kuniyu@google.com Signed-off-by: Sunday Adelodun adelodunolaoluwa@yahoo.com --- tools/testing/selftests/net/unix/Makefile | 5 + .../selftests/net/unix/test_unix_connreset.c | 147 ++++++++++++++++++ 2 files changed, 152 insertions(+) create mode 100644 tools/testing/selftests/net/unix/Makefile create mode 100644 tools/testing/selftests/net/unix/test_unix_connreset.c
diff --git a/tools/testing/selftests/net/unix/Makefile b/tools/testing/selftests/net/unix/Makefile new file mode 100644 index 000000000000..a52992ba23d9 --- /dev/null +++ b/tools/testing/selftests/net/unix/Makefile @@ -0,0 +1,5 @@ +# SPDX-License-Identifier: GPL-2.0 +TEST_GEN_PROGS := test_unix_connreset + +include ../../lib.mk + diff --git a/tools/testing/selftests/net/unix/test_unix_connreset.c b/tools/testing/selftests/net/unix/test_unix_connreset.c new file mode 100644 index 000000000000..a8720c7565cb --- /dev/null +++ b/tools/testing/selftests/net/unix/test_unix_connreset.c @@ -0,0 +1,147 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Selftest for 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, + * unlike BSD where this error is observed. + * + * These tests document the intended Linux behaviour, distinguishing it from BSD. + * + */ + +#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/test_unix_connreset.sock" + +static void remove_socket_file(void) +{ + unlink(SOCK_PATH); +} + +/* Test 1: peer closes normally */ +TEST(stream_eof) +{ + int server, client, child; + struct sockaddr_un addr = {0}; + char buf[16] = {0}; + ssize_t n; + + server = socket(AF_UNIX, SOCK_STREAM, 0); + ASSERT_GE(server, 0); + + addr.sun_family = AF_UNIX; + strcpy(addr.sun_path, SOCK_PATH); + remove_socket_file(); + + ASSERT_EQ(bind(server, (struct sockaddr *)&addr, sizeof(addr)), 0); + ASSERT_EQ(listen(server, 1), 0); + + client = socket(AF_UNIX, SOCK_STREAM, 0); + ASSERT_GE(client, 0); + ASSERT_EQ(connect(client, (struct sockaddr *)&addr, sizeof(addr)), 0); + + child = accept(server, NULL, NULL); + ASSERT_GE(child, 0); + + /* Peer closes normally */ + close(child); + + n = recv(client, buf, sizeof(buf), 0); + EXPECT_EQ(n, 0); + TH_LOG("recv=%zd errno=%d (%s)", n, errno, strerror(errno)); + + close(client); + close(server); + remove_socket_file(); +} + +/* Test 2: peer closes with unread data */ +TEST(stream_reset_unread) +{ + int server, client, child; + struct sockaddr_un addr = {0}; + char buf[16] = {0}; + ssize_t n; + + server = socket(AF_UNIX, SOCK_STREAM, 0); + ASSERT_GE(server, 0); + + addr.sun_family = AF_UNIX; + strcpy(addr.sun_path, SOCK_PATH); + remove_socket_file(); + + ASSERT_EQ(bind(server, (struct sockaddr *)&addr, sizeof(addr)), 0); + ASSERT_EQ(listen(server, 1), 0); + + client = socket(AF_UNIX, SOCK_STREAM, 0); + ASSERT_GE(client, 0); + ASSERT_EQ(connect(client, (struct sockaddr *)&addr, sizeof(addr)), 0); + + child = accept(server, NULL, NULL); + ASSERT_GE(child, 0); + + /* Send data that will remain unread by client */ + send(client, "hello", 5, 0); + close(child); + + n = recv(client, buf, sizeof(buf), 0); + EXPECT_LT(n, 0); + EXPECT_EQ(errno, ECONNRESET); + TH_LOG("recv=%zd errno=%d (%s)", n, errno, strerror(errno)); + + close(client); + close(server); + remove_socket_file(); +} + +/* Test 3: SOCK_DGRAM peer close */ +TEST(dgram_reset) +{ + int server, client; + int flags; + struct sockaddr_un addr = {0}; + char buf[16] = {0}; + ssize_t n; + + server = socket(AF_UNIX, SOCK_DGRAM, 0); + ASSERT_GE(server, 0); + + addr.sun_family = AF_UNIX; + strcpy(addr.sun_path, SOCK_PATH); + remove_socket_file(); + + ASSERT_EQ(bind(server, (struct sockaddr *)&addr, sizeof(addr)), 0); + + client = socket(AF_UNIX, SOCK_DGRAM, 0); + ASSERT_GE(client, 0); + ASSERT_EQ(connect(client, (struct sockaddr *)&addr, sizeof(addr)), 0); + + send(client, "hello", 5, 0); + close(server); + + flags = fcntl(client, F_GETFL, 0); + fcntl(client, F_SETFL, flags | O_NONBLOCK); + + n = recv(client, buf, sizeof(buf), 0); + TH_LOG("recv=%zd errno=%d (%s)", n, errno, strerror(errno)); + /* Expect EAGAIN or EWOULDBLOCK because there is no datagram and peer is closed. */ + EXPECT_LT(n, 0); + EXPECT_TRUE(errno == EAGAIN); + + close(client); + remove_socket_file(); +} + +TEST_HARNESS_MAIN + -- 2.43.0
Thanks for adding tests.
[PATCH] selftests/unix: Add test for ECONNRESET and EOF behaviour
nit: The common prefix is "selftest: af_unix:".
On Thu, Oct 23, 2025 at 9:59 AM Sunday Adelodun adelodunolaoluwa@yahoo.com wrote:
Add selftests verifying the EOF and ECONNRESET behaviour of UNIX domain sockets (SOCK_STREAM and SOCK_DGRAM). The tests document Linux's semantics and clarify the long-standing differences with BSD.
Suggested-by: Kuniyuki Iwashima kuniyu@google.com Signed-off-by: Sunday Adelodun adelodunolaoluwa@yahoo.com
tools/testing/selftests/net/unix/Makefile | 5 + .../selftests/net/unix/test_unix_connreset.c | 147 ++++++++++++++++++ 2 files changed, 152 insertions(+) create mode 100644 tools/testing/selftests/net/unix/Makefile create mode 100644 tools/testing/selftests/net/unix/test_unix_connreset.c
The test for af_unix is placed under tools/testing/selftests/net/af_unix.
diff --git a/tools/testing/selftests/net/unix/Makefile b/tools/testing/selftests/net/unix/Makefile new file mode 100644 index 000000000000..a52992ba23d9 --- /dev/null +++ b/tools/testing/selftests/net/unix/Makefile @@ -0,0 +1,5 @@ +# SPDX-License-Identifier: GPL-2.0 +TEST_GEN_PROGS := test_unix_connreset
+include ../../lib.mk
diff --git a/tools/testing/selftests/net/unix/test_unix_connreset.c b/tools/testing/selftests/net/unix/test_unix_connreset.c new file mode 100644 index 000000000000..a8720c7565cb --- /dev/null +++ b/tools/testing/selftests/net/unix/test_unix_connreset.c @@ -0,0 +1,147 @@ +// SPDX-License-Identifier: GPL-2.0 +/*
- Selftest for UNIX socket close and ECONNRESET behaviour.
nit: s/UNIX/AF_UNIX/
- This test verifies that:
- SOCK_STREAM sockets return EOF when peer closes normally.
- SOCK_STREAM sockets return ECONNRESET if peer closes with unread data.
- SOCK_DGRAM sockets do not return ECONNRESET when peer closes,
unlike BSD where this error is observed.
- These tests document the intended Linux behaviour, distinguishing it from BSD.
I'd not mention BSD as it could be outdated again.
- */
+#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/test_unix_connreset.sock"
+static void remove_socket_file(void) +{
unlink(SOCK_PATH);+}
+/* Test 1: peer closes normally */ +TEST(stream_eof)
I think most of the code can be shared by defining FIXTURE_VARIANT().
e.g. variant->unread_data can consolidate Test 1&2.
+{
int server, client, child;struct sockaddr_un addr = {0};char buf[16] = {0};
IIRC, {0} only initialises the first entry and we had a problem in kernel code, so simply use "= {};" everywhere.
ssize_t n;server = socket(AF_UNIX, SOCK_STREAM, 0);
Try using variant->type for SOCK_STREAM, SOCK_DGRAM, and SOCK_SEQPACKET.
See unix_connect.c, or you could reuse the fixtures of err == 0 there.
ASSERT_GE(server, 0);
nit: The 1st arg is "expected", and the 2nd is "seen", so ASSERT_NE(-1, server) (or ASSERT_LT(-1, server)).
Same for other places.
addr.sun_family = AF_UNIX;strcpy(addr.sun_path, SOCK_PATH);remove_socket_file();ASSERT_EQ(bind(server, (struct sockaddr *)&addr, sizeof(addr)), 0);
I personally feel easy to read this style:
err = bind(); ASSERT_EQ(0, err);
ASSERT_EQ(listen(server, 1), 0);client = socket(AF_UNIX, SOCK_STREAM, 0);ASSERT_GE(client, 0);ASSERT_EQ(connect(client, (struct sockaddr *)&addr, sizeof(addr)), 0);child = accept(server, NULL, NULL);ASSERT_GE(child, 0);/* Peer closes normally */close(child);n = recv(client, buf, sizeof(buf), 0);EXPECT_EQ(n, 0);TH_LOG("recv=%zd errno=%d (%s)", n, errno, strerror(errno));
I printed errno just for visibility, and you can simply use ASSERT here too like
if (n == -1) ASSERT_EQ(ECONNRESET, errno)
(I'm assuming Test 1 & 2 will share most code)
close(client);close(server);remove_socket_file();
This will not be executed if the program fails at ASSERT_XX(), so move it to FIXTURE_TEARDOWN().
+}
+/* Test 2: peer closes with unread data */ +TEST(stream_reset_unread) +{
int server, client, child;struct sockaddr_un addr = {0};char buf[16] = {0};ssize_t n;server = socket(AF_UNIX, SOCK_STREAM, 0);ASSERT_GE(server, 0);addr.sun_family = AF_UNIX;strcpy(addr.sun_path, SOCK_PATH);remove_socket_file();ASSERT_EQ(bind(server, (struct sockaddr *)&addr, sizeof(addr)), 0);ASSERT_EQ(listen(server, 1), 0);client = socket(AF_UNIX, SOCK_STREAM, 0);ASSERT_GE(client, 0);ASSERT_EQ(connect(client, (struct sockaddr *)&addr, sizeof(addr)), 0);child = accept(server, NULL, NULL);ASSERT_GE(child, 0);/* Send data that will remain unread by client */send(client, "hello", 5, 0);close(child);n = recv(client, buf, sizeof(buf), 0);EXPECT_LT(n, 0);EXPECT_EQ(errno, ECONNRESET);TH_LOG("recv=%zd errno=%d (%s)", n, errno, strerror(errno));close(client);close(server);remove_socket_file();+}
+/* Test 3: SOCK_DGRAM peer close */ +TEST(dgram_reset) +{
int server, client;int flags;struct sockaddr_un addr = {0};char buf[16] = {0};ssize_t n;server = socket(AF_UNIX, SOCK_DGRAM, 0);ASSERT_GE(server, 0);addr.sun_family = AF_UNIX;strcpy(addr.sun_path, SOCK_PATH);remove_socket_file();ASSERT_EQ(bind(server, (struct sockaddr *)&addr, sizeof(addr)), 0);client = socket(AF_UNIX, SOCK_DGRAM, 0);ASSERT_GE(client, 0);ASSERT_EQ(connect(client, (struct sockaddr *)&addr, sizeof(addr)), 0);send(client, "hello", 5, 0);close(server);flags = fcntl(client, F_GETFL, 0);fcntl(client, F_SETFL, flags | O_NONBLOCK);
You can save fcntl() with socket(..., ... | SOCK_NONBLOCK, ...).
n = recv(client, buf, sizeof(buf), 0);TH_LOG("recv=%zd errno=%d (%s)", n, errno, strerror(errno));/* Expect EAGAIN or EWOULDBLOCK because there is no datagram and peer is closed. */EXPECT_LT(n, 0);EXPECT_TRUE(errno == EAGAIN);close(client);remove_socket_file();+}
+TEST_HARNESS_MAIN
-- 2.43.0
On 10/24/25 04:00, Kuniyuki Iwashima wrote:
Thanks for adding tests.
[PATCH] selftests/unix: Add test for ECONNRESET and EOF behaviour
nit: The common prefix is "selftest: af_unix:".
On Thu, Oct 23, 2025 at 9:59 AM Sunday Adelodun adelodunolaoluwa@yahoo.com wrote:
Add selftests verifying the EOF and ECONNRESET behaviour of UNIX domain sockets (SOCK_STREAM and SOCK_DGRAM). The tests document Linux's semantics and clarify the long-standing differences with BSD.
Suggested-by: Kuniyuki Iwashima kuniyu@google.com Signed-off-by: Sunday Adelodun adelodunolaoluwa@yahoo.com
tools/testing/selftests/net/unix/Makefile | 5 + .../selftests/net/unix/test_unix_connreset.c | 147 ++++++++++++++++++ 2 files changed, 152 insertions(+) create mode 100644 tools/testing/selftests/net/unix/Makefile create mode 100644 tools/testing/selftests/net/unix/test_unix_connreset.c
The test for af_unix is placed under tools/testing/selftests/net/af_unix.
diff --git a/tools/testing/selftests/net/unix/Makefile b/tools/testing/selftests/net/unix/Makefile new file mode 100644 index 000000000000..a52992ba23d9 --- /dev/null +++ b/tools/testing/selftests/net/unix/Makefile @@ -0,0 +1,5 @@ +# SPDX-License-Identifier: GPL-2.0 +TEST_GEN_PROGS := test_unix_connreset
+include ../../lib.mk
diff --git a/tools/testing/selftests/net/unix/test_unix_connreset.c b/tools/testing/selftests/net/unix/test_unix_connreset.c new file mode 100644 index 000000000000..a8720c7565cb --- /dev/null +++ b/tools/testing/selftests/net/unix/test_unix_connreset.c @@ -0,0 +1,147 @@ +// SPDX-License-Identifier: GPL-2.0 +/*
- Selftest for UNIX socket close and ECONNRESET behaviour.
nit: s/UNIX/AF_UNIX/
- This test verifies that:
- SOCK_STREAM sockets return EOF when peer closes normally.
- SOCK_STREAM sockets return ECONNRESET if peer closes with unread data.
- SOCK_DGRAM sockets do not return ECONNRESET when peer closes,
unlike BSD where this error is observed.
- These tests document the intended Linux behaviour, distinguishing it from BSD.
I'd not mention BSD as it could be outdated again.
- */
+#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/test_unix_connreset.sock"
+static void remove_socket_file(void) +{
unlink(SOCK_PATH);+}
+/* Test 1: peer closes normally */ +TEST(stream_eof)
I think most of the code can be shared by defining FIXTURE_VARIANT().
e.g. variant->unread_data can consolidate Test 1&2.
+{
int server, client, child;struct sockaddr_un addr = {0};char buf[16] = {0};IIRC, {0} only initialises the first entry and we had a problem in kernel code, so simply use "= {};" everywhere.
ssize_t n;server = socket(AF_UNIX, SOCK_STREAM, 0);Try using variant->type for SOCK_STREAM, SOCK_DGRAM, and SOCK_SEQPACKET.
See unix_connect.c, or you could reuse the fixtures of err == 0 there.
ASSERT_GE(server, 0);nit: The 1st arg is "expected", and the 2nd is "seen", so ASSERT_NE(-1, server) (or ASSERT_LT(-1, server)).
Same for other places.
addr.sun_family = AF_UNIX;strcpy(addr.sun_path, SOCK_PATH);remove_socket_file();ASSERT_EQ(bind(server, (struct sockaddr *)&addr, sizeof(addr)), 0);I personally feel easy to read this style:
err = bind(); ASSERT_EQ(0, err);
ASSERT_EQ(listen(server, 1), 0);client = socket(AF_UNIX, SOCK_STREAM, 0);ASSERT_GE(client, 0);ASSERT_EQ(connect(client, (struct sockaddr *)&addr, sizeof(addr)), 0);child = accept(server, NULL, NULL);ASSERT_GE(child, 0);/* Peer closes normally */close(child);n = recv(client, buf, sizeof(buf), 0);EXPECT_EQ(n, 0);TH_LOG("recv=%zd errno=%d (%s)", n, errno, strerror(errno));I printed errno just for visibility, and you can simply use ASSERT here too like
if (n == -1) ASSERT_EQ(ECONNRESET, errno)
(I'm assuming Test 1 & 2 will share most code)
close(client);close(server);remove_socket_file();This will not be executed if the program fails at ASSERT_XX(), so move it to FIXTURE_TEARDOWN().
+}
+/* Test 2: peer closes with unread data */ +TEST(stream_reset_unread) +{
int server, client, child;struct sockaddr_un addr = {0};char buf[16] = {0};ssize_t n;server = socket(AF_UNIX, SOCK_STREAM, 0);ASSERT_GE(server, 0);addr.sun_family = AF_UNIX;strcpy(addr.sun_path, SOCK_PATH);remove_socket_file();ASSERT_EQ(bind(server, (struct sockaddr *)&addr, sizeof(addr)), 0);ASSERT_EQ(listen(server, 1), 0);client = socket(AF_UNIX, SOCK_STREAM, 0);ASSERT_GE(client, 0);ASSERT_EQ(connect(client, (struct sockaddr *)&addr, sizeof(addr)), 0);child = accept(server, NULL, NULL);ASSERT_GE(child, 0);/* Send data that will remain unread by client */send(client, "hello", 5, 0);close(child);n = recv(client, buf, sizeof(buf), 0);EXPECT_LT(n, 0);EXPECT_EQ(errno, ECONNRESET);TH_LOG("recv=%zd errno=%d (%s)", n, errno, strerror(errno));close(client);close(server);remove_socket_file();+}
+/* Test 3: SOCK_DGRAM peer close */ +TEST(dgram_reset) +{
int server, client;int flags;struct sockaddr_un addr = {0};char buf[16] = {0};ssize_t n;server = socket(AF_UNIX, SOCK_DGRAM, 0);ASSERT_GE(server, 0);addr.sun_family = AF_UNIX;strcpy(addr.sun_path, SOCK_PATH);remove_socket_file();ASSERT_EQ(bind(server, (struct sockaddr *)&addr, sizeof(addr)), 0);client = socket(AF_UNIX, SOCK_DGRAM, 0);ASSERT_GE(client, 0);ASSERT_EQ(connect(client, (struct sockaddr *)&addr, sizeof(addr)), 0);send(client, "hello", 5, 0);close(server);flags = fcntl(client, F_GETFL, 0);fcntl(client, F_SETFL, flags | O_NONBLOCK);You can save fcntl() with socket(..., ... | SOCK_NONBLOCK, ...).
n = recv(client, buf, sizeof(buf), 0);TH_LOG("recv=%zd errno=%d (%s)", n, errno, strerror(errno));/* Expect EAGAIN or EWOULDBLOCK because there is no datagram and peer is closed. */EXPECT_LT(n, 0);EXPECT_TRUE(errno == EAGAIN);close(client);remove_socket_file();+}
+TEST_HARNESS_MAIN
-- 2.43.0
Hi Kuniyuki, Thank you very much for the detailed review and helpful suggestions. I will send a v2 patch incorporating these changes. Thanks again for taking the time to review and explain the details, I really appreciate it.
Best regards, Sunday Adelodun
linux-kselftest-mirror@lists.linaro.org
-
Kuniyuki Iwashima -
Sunday Adelodun