On Wed, Nov 12, 2025 at 1:20 PM Sunday Adelodun <[email protected]> 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: > > 1. SOCK_STREAM returns EOF when the peer closes normally. > 2. SOCK_STREAM returns ECONNRESET if the peer closes with unread data. > 3. SOCK_SEQPACKET returns EOF when the peer closes normally. > 4. SOCK_SEQPACKET returns ECONNRESET if the peer closes with unread data. > 5. 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 <[email protected]> > Signed-off-by: Sunday Adelodun <[email protected]> > --- > 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: > + * 1. SOCK_STREAM returns EOF when the peer closes normally. > + * 2. SOCK_STREAM returns ECONNRESET if peer closes with unread data. > + * 3. SOCK_SEQPACKET returns EOF when the peer closes normally. > + * 4. SOCK_SEQPACKET returns ECONNRESET if the peer closes with unread data. > + * 5. 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 <[email protected]> Thanks! > + > + /* 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 >
