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:
- EOF returned when a SOCK_STREAM peer closes normally.
- ECONNRESET returned when a SOCK_STREAM peer closes with unread data.
- 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:
- 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.
- 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