On Sat, Nov 1, 2025 at 10:23 AM 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/af_unix/Makefile | 1 + > .../selftests/net/af_unix/unix_connreset.c | 179 ++++++++++++++++++ > 2 files changed, 180 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 \
patchwork caught this test is not added to .gitignore. https://patchwork.kernel.org/project/netdevbpf/patch/[email protected]/ Could you add it to this file ? tools/testing/selftests/net/.gitignore > # 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..6f43435d96e2 > --- /dev/null > +++ b/tools/testing/selftests/net/af_unix/unix_connreset.c > @@ -0,0 +1,179 @@ > +// 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; > +}; > + > +/* Define variants: stream and datagram */ nit: outdated, maybe simply remove ? > +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) { patchwork caught mis-alignment here and other places. I'm using this for emacs, and other editors will have a similar config. (setq-default c-default-style "linux") You can check if lines are aligned properly by $ git show --format=email | ./scripts/checkpatch.pl > + err = listen(self->server, 1); > + ASSERT_EQ(0, err); > + > + self->client = socket(AF_UNIX, variant->socket_type, 0); Could you add SOCK_NONBLOCK here too ? > + 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 || > + variant->socket_type == SOCK_SEQPACKET) > + 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; > + > + /* Peer closes normally */ > + if (variant->socket_type == SOCK_STREAM || > + variant->socket_type == SOCK_SEQPACKET) > + close(self->child); > + else > + 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)); errno is undefined if not set, and same for strerror(errno). Also, if ASSERT_XXX() below fails, the same information (test case, errno) is logged. So, TH_LOG() seems unnecessary. Maybe try modifying the condition below and see how the assertion is logged. > + 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) > +{ > + char buf[16] = {}; > + ssize_t n; > + > + /* 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)); > + if (variant->socket_type == SOCK_STREAM || > + variant->socket_type == SOCK_SEQPACKET) { > + ASSERT_EQ(-1, n); > + ASSERT_EQ(ECONNRESET, errno); > + } else { > + ASSERT_EQ(-1, n); > + ASSERT_EQ(EAGAIN, errno); > + } > +} > + > +/* Test 3: SOCK_DGRAM peer close */ Now Test 2 and Test 3 look identical ;) Thanks! > +TEST_F(unix_sock, dgram_reset) > +{ > + char buf[16] = {}; > + ssize_t n; > + > + 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)); > + if (variant->socket_type == SOCK_STREAM || > + variant->socket_type == SOCK_SEQPACKET) { > + ASSERT_EQ(-1, n); > + ASSERT_EQ(ECONNRESET, errno); > + } else { > + ASSERT_EQ(-1, n); > + ASSERT_EQ(EAGAIN, errno); > + } > +} > + > +TEST_HARNESS_MAIN > + > -- > 2.43.0 >
