On 11/12/25 23:04, Kuniyuki Iwashima wrote:
On Wed, Nov 12, 2025 at 1:20 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 verify that:
- SOCK_STREAM returns EOF when the peer closes normally.
- SOCK_STREAM returns ECONNRESET if the peer closes with unread data.
- SOCK_SEQPACKET returns EOF when the peer closes normally.
- SOCK_SEQPACKET returns ECONNRESET if the peer closes with unread data.
- SOCK_DGRAM does not return ECONNRESET when the peer closes.
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
tools/testing/selftests/net/.gitignore | 1 + tools/testing/selftests/net/af_unix/Makefile | 1 + .../selftests/net/af_unix/unix_connreset.c | 178 ++++++++++++++++++ 3 files changed, 180 insertions(+) create mode 100644 tools/testing/selftests/net/af_unix/unix_connreset.c
diff --git a/tools/testing/selftests/net/.gitignore b/tools/testing/selftests/net/.gitignore index 439101b518ee..e89a60581a13 100644 --- a/tools/testing/selftests/net/.gitignore +++ b/tools/testing/selftests/net/.gitignore @@ -65,3 +65,4 @@ udpgso udpgso_bench_rx udpgso_bench_tx unix_connect +unix_connreset 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..9413f8a0814f --- /dev/null +++ b/tools/testing/selftests/net/af_unix/unix_connreset.c @@ -0,0 +1,178 @@ +// SPDX-License-Identifier: GPL-2.0 +/*
- Selftest for AF_UNIX socket close and ECONNRESET behaviour.
- This test verifies:
- SOCK_STREAM returns EOF when the peer closes normally.
- SOCK_STREAM returns ECONNRESET if peer closes with unread data.
- SOCK_SEQPACKET returns EOF when the peer closes normally.
- SOCK_SEQPACKET returns ECONNRESET if the peer closes with unread data.
- SOCK_DGRAM does not return ECONNRESET when the 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;+};
+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_VARIANT_ADD(unix_sock, seqpacket) {
.socket_type = SOCK_SEQPACKET,.name = "SOCK_SEQPACKET",+};
+FIXTURE_SETUP(unix_sock) +{
struct sockaddr_un addr = {};int err;addr.sun_family = AF_UNIX;strcpy(addr.sun_path, SOCK_PATH);remove_socket_file();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 ||variant->socket_type == SOCK_SEQPACKET) {err = listen(self->server, 1);ASSERT_EQ(0, err);}self->client = socket(AF_UNIX, variant->socket_type | 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 ||variant->socket_type == SOCK_SEQPACKET) & self->child > 0)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 ||variant->socket_type == SOCK_SEQPACKET) {self->child = accept(self->server, NULL, NULL);ASSERT_LT(-1, self->child);close(self->child);} else {close(self->server);}n = recv(self->client, buf, sizeof(buf), 0);if (variant->socket_type == SOCK_STREAM ||variant->socket_type == SOCK_SEQPACKET) {ASSERT_EQ(0, n);} else {ASSERT_EQ(-1, n);ASSERT_EQ(EAGAIN, errno);}+}
+/* Test 2: peer closes with unread data */ +TEST_F(unix_sock, reset_unread_behavior) +{
char buf[16] = {};ssize_t n;if (variant->socket_type == SOCK_DGRAM) {/* No real connection, just close the server */close(self->server);} else {/* Establish full connection first */self->child = accept(self->server, NULL, NULL);ASSERT_LT(-1, self->child);/* Send data that will remain unread */send(self->client, "hello", 5, 0);Could you move this send() before "if (...)" because we want to test unread_data behaviour for SOCK_DGRAM too ?
Otherwise looks good, so with that fixed:
Reviewed-by: Kuniyuki Iwashima kuniyu@google.com
Thanks!
Thank you for the prompt response. I thought of putting the send before the if the statement , but I was afraid STREAM and SEQPACKET connections won't be accepted before data sending.
I will start working on v5.
That part will look like this now: /* Test 2: peer closes with unread data */ TEST_F(unix_sock, reset_unread_behavior) { char buf[16] = {}; ssize_t n;
*/* Send data that will remain unread */ send(self->client, "hello", 5, 0);*
*if (variant->socket_type == SOCK_DGRAM) { /* No real connection, just close the server */ close(self->server); } else { /* Establish full connection first */ self->child = accept(self->server, NULL, NULL); ASSERT_LT(-1, self->child);
/* Peer closes before client reads */ close(self->child); }*
n = recv(self->client, buf, sizeof(buf), 0); ASSERT_EQ(-1, n);
if (variant->socket_type == SOCK_STREAM || variant->socket_type == SOCK_SEQPACKET) { ASSERT_EQ(ECONNRESET, errno); } else { ASSERT_EQ(EAGAIN, errno); } }
Thank you once again.
/* Peer closes before client reads */close(self->child);}n = recv(self->client, buf, sizeof(buf), 0);ASSERT_EQ(-1, n);if (variant->socket_type == SOCK_STREAM ||variant->socket_type == SOCK_SEQPACKET) {ASSERT_EQ(ECONNRESET, errno);} else {ASSERT_EQ(EAGAIN, errno);}+}
+/* Test 3: closing unaccepted (embryo) server socket should reset client. */ +TEST_F(unix_sock, reset_closed_embryo) +{
char buf[16] = {};ssize_t n;if (variant->socket_type == SOCK_DGRAM)SKIP(return, "This test only applies to SOCK_STREAM and SOCK_SEQPACKET");/* Close server without accept()ing */close(self->server);n = recv(self->client, buf, sizeof(buf), 0);ASSERT_EQ(-1, n);ASSERT_EQ(ECONNRESET, errno);+}
+TEST_HARNESS_MAIN
-- 2.43.0