socket: Add new test for shutdown

This commit adds shutdown test with SHUT_RD, SHUT_WR, SHUT_RDWR for an
UNIX socket connection.

Reviewed-by: DJ Delorie <dj@redhat.com>

socket/Makefile

@@ -71,6 +71,7 @@ tests := \
   tst-cmsg_cloexec \
   tst-cmsghdr \
   tst-connect \
+  tst-shutdown \
   tst-sockopt \
   # tests
 

socket/tst-shutdown.c

@@ -0,0 +1,257 @@
+/* Test the shutdown function.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xsocket.h>
+#include <support/xunistd.h>
+#include <sys/socket.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <string.h>
+
+struct connection
+{
+  int sockets[2];
+};
+
+void
+establish_connection (struct connection *conn)
+{
+  if (socketpair (AF_UNIX, SOCK_STREAM, 0, conn->sockets) != 0)
+    {
+      FAIL_EXIT1 ("socketpair (AF_UNIX, SOCK_STREAM, 0): %m\n");
+    }
+}
+
+void
+close_connection (struct connection *conn)
+{
+  xclose (conn->sockets[0]);
+  xclose (conn->sockets[1]);
+}
+
+/* Open a file and check that shutdown fails with the ENOTSOCK error code.  */
+void
+do_test_enotsock (void)
+{
+  /* Open file and check that shutdown will fail with ENOTSOCK.  */
+  int fd = xopen ("/dev/null", O_RDWR, 0);
+
+  int result = shutdown (fd, SHUT_RD);
+  if (result == 0 || errno != ENOTSOCK)
+    {
+      FAIL_EXIT1 ("shutdown should fail with ENOTSOCK");
+    }
+  xclose (fd);
+}
+
+/* Test shutdown with SHUT_RD.  */
+void
+do_test_shut_rd (void)
+{
+  struct connection conn;
+  const char *str = "AAAAAAA";
+  int len = 8;
+  int ret;
+  void *s_buf = xmalloc (len);
+  bzero (s_buf, len);
+
+  establish_connection (&conn);
+  int server = conn.sockets[0];
+  int client = conn.sockets[1];
+
+  /* Call shutdown with SHUT_RD on server socket.  */
+  if (shutdown (server, SHUT_RD) != 0)
+    {
+      FAIL_EXIT1 ("shutdown with SHUT_RD on socket %d failed", server);
+    }
+
+  ret = send (server, str, len, 0);
+  if (ret <= 0)
+    {
+      FAIL_EXIT1 ("send (%d, data, %d): %m", server, len);
+    }
+
+  ret = recv (client, s_buf, len, 0);
+  if (ret <= 0)
+    {
+      FAIL_EXIT1 ("recv (%d, data, %d): %m", client, len);
+    }
+
+  TEST_COMPARE_BLOB (str, len, s_buf, len);
+
+  /* Send data should be disallowed on shutdown socket.  */
+  errno = 0;
+  ret = send (client, str, len, MSG_NOSIGNAL);
+  if (ret >= 0 || errno != EPIPE)
+    {
+      FAIL_EXIT1 ("Send on SHUT_RD socket should be disallowed: %m");
+    }
+
+  /* Recv should return zero and no error.  */
+  errno = 0;
+  ret = recv (server, s_buf, len, 0);
+  if (ret != 0 || errno != 0)
+    {
+      FAIL_EXIT1 ("recv should return 0 without error: %m");
+    }
+
+  close_connection (&conn);
+}
+
+/* Test shutdown with SHUT_WR.  */
+void
+do_test_shut_wr (void)
+{
+  struct connection conn;
+  const char *str1 = "CCCCCCC";
+  const char *str2 = "DDDDDDD";
+  const char *str3 = "EEEEEEE";
+  int len = 8;
+  int ret;
+  void *c_buf = xmalloc (len);
+  void *s_buf = xmalloc (len);
+
+  establish_connection (&conn);
+  int server = conn.sockets[0];
+  int client = conn.sockets[1];
+
+  xwrite (client, str1, len);
+
+  if (shutdown (client, SHUT_WR) != 0)
+    {
+      FAIL_EXIT1 ("shutdown with SHUT_WR on socket %d failed", client);
+    }
+
+  ret = send (client, str2, len, MSG_NOSIGNAL);
+  if (ret >= 0)
+    {
+      FAIL_EXIT1 ("send on SHUT_WR socket should fail");
+    }
+
+  /* Read data written before shutdown and check if it's correct.  */
+  xread (server, s_buf, len);
+  TEST_COMPARE_BLOB (str1, len, s_buf, len);
+
+  /* Second read should return zero without error.  */
+  errno = 0;
+  if (read (server, s_buf, len) != 0 || errno != 0)
+    {
+      FAIL_EXIT1 ("read after shutdown should return zero without error: %m");
+    }
+
+  /* Write some data to socket and check it still can be read on other side.  */
+  memcpy (s_buf, str3, len);
+  xwrite (server, s_buf, len);
+
+  xread (client, c_buf, len);
+  TEST_COMPARE_BLOB (s_buf, len, c_buf, len);
+
+  close_connection (&conn);
+}
+
+/* Test shutdown with SHUT_RDWR.  */
+void
+do_test_shut_rdwr (void)
+{
+  struct connection conn;
+  struct sockaddr peer;
+  socklen_t peer_len = sizeof (peer);
+
+  const char *str1 = "FFFFFFF";
+  const char *str2 = "GGGGGGG";
+  int len = 8;
+  int ret;
+  void *s_buf = xmalloc (len);
+  bzero (s_buf, len);
+
+  establish_connection (&conn);
+  int server = conn.sockets[0];
+  int client = conn.sockets[1];
+
+  /* Send some data to both sockets before shutdown.  */
+  xwrite (client, str1, len);
+  xwrite (server, str2, len);
+
+  /* Call shutdown with SHUT_RDWR on client socket.  */
+  if (shutdown (client, SHUT_RDWR) != 0)
+    {
+      FAIL_EXIT1 ("shutdown with SHUT_RDWR on socket %d failed", client);
+    }
+
+  /* Verify that socket is still connected.  */
+  xgetsockname (client, &peer, &peer_len);
+
+  /* Read data written before shutdown.  */
+  xread (client, s_buf, len);
+  TEST_COMPARE_BLOB (s_buf, len, str2, len);
+
+  /* Second read should return zero, but no error.  */
+  errno = 0;
+  if (read (client, s_buf, len) != 0 || errno != 0)
+    {
+      FAIL_EXIT1 ("read after shutdown should return zero without error: %m");
+    }
+
+  /* Send some data to shutdown socket and expect error.  */
+  errno = 0;
+  ret = send (server, str2, len, MSG_NOSIGNAL);
+  if (ret >= 0 || errno != EPIPE)
+    {
+      FAIL_EXIT1 ("send to RDWR shutdown socket should fail with EPIPE");
+    }
+
+  /* Read data written before shutdown.  */
+  xread (server, s_buf, len);
+  TEST_COMPARE_BLOB (s_buf, len, str1, len);
+
+  /* Second read should return zero, but no error.  */
+  errno = 0;
+  if (read (server, s_buf, len) != 0 || errno != 0)
+    {
+      FAIL_EXIT1 ("read after shutdown should return zero without error: %m");
+    }
+
+  /* Send some data to shutdown socket and expect error.  */
+  errno = 0;
+  ret = send (client, str1, len, MSG_NOSIGNAL);
+  if (ret >= 0 || errno != EPIPE)
+    {
+      FAIL_EXIT1 ("send to RDWR shutdown socket should fail with EPIPE");
+    }
+
+  close_connection (&conn);
+}
+
+static int
+do_test (void)
+{
+  do_test_enotsock ();
+  do_test_shut_rd ();
+  do_test_shut_wr ();
+  do_test_shut_rdwr ();
+
+  return 0;
+}
+
+#include <support/test-driver.c>