Assume that accept4 is always available and works

Simplify the Linux accept4 implementation based on the assumption
that it is available in some way.  __ASSUME_ACCEPT4_SOCKETCALL was
previously unused, so remove it.

For ia64, the accept4 system call (and socket call) were backported
in kernel version 3.2.18.  Reflect this in the installation
instructions.

ChangeLog

@@ -1,3 +1,35 @@
+2017-04-19  Florian Weimer  <fweimer@redhat.com>
+
+	* nscd/connections.c (have_accept4): Removed definition.
+	(nscd_run_worker, main_loop_poll, main_loop_epolll): Assume that
+	accept4 works.
+	* manual/install.texi (Linux): Require at least kernel 3.2.18 for
+	ia64 because that was the first version with accept4 support.
+	* support/Makefile (libsupport-routines): Add xaccept4.
+	* support/xsocket.h (xaccept4): Declare.
+	* support/xaccept4.c: New file.
+	* socket/tst-accept4.c: New file.
+	* socket/Makefile (tests): Add tst-accept4.
+	* sysdeps/mach/hurd/kernel-features.h (__ASSUME_ACCEPT4): Remove
+	definition.
+	* sysdeps/nacl/kernel-features.h (__ASSUME_ACCEPT4): Remove
+	comment.
+	* sysdeps/unix/sysv/linux/accept4.c: Assume that an accept4
+	implementation is available.
+	(accept4): Use the system call if available, otherwise use the
+	socket call.
+	* sysdeps/unix/sysv/linux/ia64/configure.ac (arch_minimum_kernel):
+	Set to 3.2.18.
+	* sysdeps/unix/sysv/linux/ia64/kernel-features.h
+	(__ASSUME_ACCEPT4_SYSCALL, __ASSUME_ACCEPT4): Do not undefine.
+	accept4 is unconditionally available in later 3.2 stable kernels.
+	(__ASSUME_ACCEPT4_SYSCALL): Define.
+	* sysdeps/unix/sysv/linux/kernel-features.h
+	(__ASSUME_ACCEPT4_SOCKETCALL, __ASSUME_ACCEPT4): Remove
+	definitions.
+	* sysdeps/unix/sysv/linux/i386/kernel-features.h
+	(__ASSUME_ACCEPT4_SYSCALL): Define for Linux 4.3 or later.
+
 2017-04-18  Joseph Myers  <joseph@codesourcery.com>
 
 	* conform/Makefile (tests-special): Do not make addition of

INSTALL

@@ -501,13 +501,15 @@ Specific advice for GNU/Linux systems
 
 If you are installing the GNU C Library on GNU/Linux systems, you need
 to have the header files from a 3.2 or newer kernel around for
-reference.  These headers must be installed using 'make
-headers_install'; the headers present in the kernel source directory are
-not suitable for direct use by the GNU C Library.  You do not need to
-use that kernel, just have its headers installed where the GNU C Library
-can access them, referred to here as INSTALL-DIRECTORY.  The easiest way
-to do this is to unpack it in a directory such as
-'/usr/src/linux-VERSION'.  In that directory, run 'make headers_install
+reference.  (For the ia64 architecture, you need version 3.2.18 or newer
+because this is the first version with support for the 'accept4' system
+call.)  These headers must be installed using 'make headers_install';
+the headers present in the kernel source directory are not suitable for
+direct use by the GNU C Library.  You do not need to use that kernel,
+just have its headers installed where the GNU C Library can access them,
+referred to here as INSTALL-DIRECTORY.  The easiest way to do this is to
+unpack it in a directory such as '/usr/src/linux-VERSION'.  In that
+directory, run 'make headers_install
 INSTALL_HDR_PATH=INSTALL-DIRECTORY'.  Finally, configure the GNU C
 Library with the option '--with-headers=INSTALL-DIRECTORY/include'.  Use
 the most recent kernel you can get your hands on.  (If you are

manual/install.texi

@@ -566,6 +566,8 @@ patches, although we try to avoid this.
 
 If you are installing @theglibc{} on @gnulinuxsystems{}, you need to have
 the header files from a 3.2 or newer kernel around for reference.
+(For the ia64 architecture, you need version 3.2.18 or newer because this
+is the first version with support for the @code{accept4} system call.)
 These headers must be installed using @samp{make headers_install}; the
 headers present in the kernel source directory are not suitable for
 direct use by @theglibc{}.  You do not need to use that kernel, just have

nscd/connections.c

@@ -257,10 +257,6 @@ int inotify_fd = -1;
 static int nl_status_fd = -1;
 #endif
 
-#ifndef __ASSUME_ACCEPT4
-static int have_accept4;
-#endif
-
 /* Number of times clients had to wait.  */
 unsigned long int client_queued;
 
@@ -1650,16 +1646,6 @@ nscd_run_worker (void *p)
       /* We are done with the list.  */
       pthread_mutex_unlock (&readylist_lock);
 
-#ifndef __ASSUME_ACCEPT4
-      if (have_accept4 < 0)
-	{
-	  /* We do not want to block on a short read or so.  */
-	  int fl = fcntl (fd, F_GETFL);
-	  if (fl == -1 || fcntl (fd, F_SETFL, fl | O_NONBLOCK) == -1)
-	    goto close_and_out;
-	}
-#endif
-
       /* Now read the request.  */
       request_header req;
       if (__builtin_expect (TEMP_FAILURE_RETRY (read (fd, &req, sizeof (req)))
@@ -2099,24 +2085,8 @@ main_loop_poll (void)
 	  if (conns[0].revents != 0)
 	    {
 	      /* We have a new incoming connection.  Accept the connection.  */
-	      int fd;
-
-#ifndef __ASSUME_ACCEPT4
-	      fd = -1;
-	      if (have_accept4 >= 0)
-#endif
-		{
-		  fd = TEMP_FAILURE_RETRY (accept4 (sock, NULL, NULL,
+	      int fd = TEMP_FAILURE_RETRY (accept4 (sock, NULL, NULL,
 						    SOCK_NONBLOCK));
-#ifndef __ASSUME_ACCEPT4
-		  if (have_accept4 == 0)
-		    have_accept4 = fd != -1 || errno != ENOSYS ? 1 : -1;
-#endif
-		}
-#ifndef __ASSUME_ACCEPT4
-	      if (have_accept4 < 0)
-		fd = TEMP_FAILURE_RETRY (accept (sock, NULL, NULL));
-#endif
 
 	      /* Use the descriptor if we have not reached the limit.  */
 	      if (fd >= 0)
@@ -2284,24 +2254,8 @@ main_loop_epoll (int efd)
 	if (revs[cnt].data.fd == sock)
 	  {
 	    /* A new connection.  */
-	    int fd;
-
-# ifndef __ASSUME_ACCEPT4
-	    fd = -1;
-	    if (have_accept4 >= 0)
-# endif
-	      {
-		fd = TEMP_FAILURE_RETRY (accept4 (sock, NULL, NULL,
+	    int fd = TEMP_FAILURE_RETRY (accept4 (sock, NULL, NULL,
 						  SOCK_NONBLOCK));
-# ifndef __ASSUME_ACCEPT4
-		if (have_accept4 == 0)
-		  have_accept4 = fd != -1 || errno != ENOSYS ? 1 : -1;
-# endif
-	      }
-# ifndef __ASSUME_ACCEPT4
-	    if (have_accept4 < 0)
-	      fd = TEMP_FAILURE_RETRY (accept (sock, NULL, NULL));
-# endif
 
 	    /* Use the descriptor if we have not reached the limit.  */
 	    if (fd >= 0)

socket/Makefile

@@ -31,6 +31,8 @@ routines := accept bind connect getpeername getsockname getsockopt	\
 	    setsockopt shutdown socket socketpair isfdtype opensock	\
 	    sockatmark accept4 recvmmsg sendmmsg
 
+tests := tst-accept4
+
 aux	 := sa_len
 
 include ../Rules

socket/tst-accept4.c

@@ -0,0 +1,131 @@
+/* Test the accept4 function with differing flags arguments.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <support/check.h>
+#include <support/xsocket.h>
+#include <support/xunistd.h>
+#include <sys/socket.h>
+
+static bool
+is_nonblocking (int fd)
+{
+  int status = fcntl (fd, F_GETFL);
+  if (status < 0)
+    FAIL_EXIT1 ("fcntl (F_GETFL): %m");
+  return status & O_NONBLOCK;
+}
+
+static bool
+is_cloexec (int fd)
+{
+  int status = fcntl (fd, F_GETFD);
+  if (status < 0)
+    FAIL_EXIT1 ("fcntl (F_GETFD): %m");
+  return status & FD_CLOEXEC;
+}
+
+struct client
+{
+  int socket;
+  struct sockaddr_in address;
+};
+
+/* Perform a non-blocking connect to *SERVER_ADDRESS.  */
+static struct client
+client_connect (const struct sockaddr_in *server_address)
+{
+  struct client result;
+  result.socket = xsocket (AF_INET,
+                           SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
+  TEST_VERIFY (is_nonblocking (result.socket));
+  TEST_VERIFY (is_cloexec (result.socket));
+  int ret = connect (result.socket, (const struct sockaddr *) server_address,
+                     sizeof (*server_address));
+  if (ret < 0 && errno != EINPROGRESS)
+    FAIL_EXIT1 ("client connect: %m");
+  socklen_t sa_len = sizeof (result.address);
+  xgetsockname (result.socket, (struct sockaddr *) &result.address,
+                &sa_len);
+  TEST_VERIFY (sa_len == sizeof (result.address));
+  return result;
+}
+
+static void
+check_same_address (const struct sockaddr_in *left,
+                    const struct sockaddr_in *right)
+{
+  TEST_VERIFY (left->sin_family == AF_INET);
+  TEST_VERIFY (right->sin_family == AF_INET);
+  TEST_VERIFY (left->sin_addr.s_addr == right->sin_addr.s_addr);
+  TEST_VERIFY (left->sin_port == right->sin_port);
+}
+
+static int
+do_test (void)
+{
+  /* Create server socket.  */
+  int server_socket = xsocket (AF_INET, SOCK_STREAM, 0);
+  TEST_VERIFY (!is_nonblocking (server_socket));
+  TEST_VERIFY (!is_cloexec (server_socket));
+  struct sockaddr_in server_address =
+    {
+      .sin_family = AF_INET,
+      .sin_addr = {.s_addr = htonl (INADDR_LOOPBACK) },
+    };
+  xbind (server_socket,
+         (struct sockaddr *) &server_address, sizeof (server_address));
+  {
+    socklen_t sa_len = sizeof (server_address);
+    xgetsockname (server_socket, (struct sockaddr *) &server_address,
+                  &sa_len);
+    TEST_VERIFY (sa_len == sizeof (server_address));
+  }
+  xlisten (server_socket, 5);
+
+  for (int do_nonblock = 0; do_nonblock < 2; ++do_nonblock)
+    for (int do_cloexec = 0; do_cloexec < 2; ++do_cloexec)
+      {
+        int sockflags = 0;
+        if (do_nonblock)
+          sockflags |= SOCK_NONBLOCK;
+        if (do_cloexec)
+          sockflags |= SOCK_CLOEXEC;
+
+        struct client client = client_connect (&server_address);
+        struct sockaddr_in client_address;
+        socklen_t sa_len = sizeof (client_address);
+        int client_socket = xaccept4 (server_socket,
+                                      (struct sockaddr *) &client_address,
+                                      &sa_len, sockflags);
+        TEST_VERIFY (sa_len == sizeof (client_address));
+        TEST_VERIFY (is_nonblocking (client_socket) == do_nonblock);
+        TEST_VERIFY (is_cloexec (client_socket) == do_cloexec);
+        check_same_address (&client.address, &client_address);
+        xclose (client_socket);
+        xclose (client.socket);
+      }
+
+  xclose (server_socket);
+  return 0;
+}
+
+#include <support/test-driver.c>

support/Makefile

@@ -50,6 +50,7 @@ libsupport-routines = \
   temp_file \
   write_message \
   xaccept \
+  xaccept4 \
   xasprintf \
   xbind \
   xcalloc \

support/xaccept4.c

@@ -0,0 +1,32 @@
+/* accept4 with error checking.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/xsocket.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+
+int
+xaccept4 (int fd, struct sockaddr *sa, socklen_t *salen, int flags)
+{
+  int clientfd = accept4 (fd, sa, salen, flags);
+  if (clientfd < 0)
+    FAIL_EXIT1 ("accept4 (%d, 0x%x): %m", fd, flags);
+  return clientfd;
+}

support/xsocket.h

@@ -30,6 +30,7 @@ void xconnect (int, const struct sockaddr *, socklen_t);
 void xbind (int, const struct sockaddr *, socklen_t);
 void xlisten (int, int);
 int xaccept (int, struct sockaddr *, socklen_t *);
+int xaccept4 (int, struct sockaddr *, socklen_t *, int);
 void xsendto (int, const void *, size_t, int,
               const struct sockaddr *, socklen_t);
 size_t xrecvfrom (int, void *, size_t, int, struct sockaddr *, socklen_t *);

sysdeps/mach/hurd/kernel-features.h

@@ -19,5 +19,3 @@
 /* This file can define __ASSUME_* macros checked by certain source files.
    Almost none of these are used outside of sysdeps/unix/sysv/linux code.
    But those referring to POSIX-level features like O_* flags can be.  */
-
-#define __ASSUME_ACCEPT4	1

sysdeps/nacl/kernel-features.h

@@ -19,7 +19,3 @@
 /* This file can define __ASSUME_* macros checked by certain source files.
    Almost none of these are used outside of sysdeps/unix/sysv/linux code.
    But those referring to POSIX-level features like O_* flags can be.  */
-
-/*
-#define __ASSUME_ACCEPT4	1
-*/

sysdeps/unix/sysv/linux/accept4.c

@@ -22,75 +22,20 @@
 
 #include <sysdep-cancel.h>
 #include <sys/syscall.h>
+#include <socketcall.h>
 #include <kernel-features.h>
 
+int
+accept4 (int fd, __SOCKADDR_ARG addr, socklen_t *addr_len, int flags)
+{
 /* Do not use the accept4 syscall on socketcall architectures unless
    it was added at the same time as the socketcall support or can be
    assumed to be present.  */
 #if defined __ASSUME_SOCKETCALL \
     && !defined __ASSUME_ACCEPT4_SYSCALL_WITH_SOCKETCALL \
     && !defined __ASSUME_ACCEPT4_SYSCALL
-# undef __NR_accept4
-#endif
-
-#ifdef __NR_accept4
-int
-accept4 (int fd, __SOCKADDR_ARG addr, socklen_t *addr_len, int flags)
-{
-  return SYSCALL_CANCEL (accept4, fd, addr.__sockaddr__, addr_len, flags);
-}
-#elif defined __NR_socketcall
-# include <socketcall.h>
-# ifdef __ASSUME_ACCEPT4_SOCKETCALL
-int
-accept4 (int fd, __SOCKADDR_ARG addr, socklen_t *addr_len, int flags)
-{
   return SOCKETCALL_CANCEL (accept4, fd, addr.__sockaddr__, addr_len, flags);
-}
-# else
-static int have_accept4;
-
-int
-accept4 (int fd, __SOCKADDR_ARG addr, socklen_t *addr_len, int flags)
-{
-  if (__glibc_likely (have_accept4 >= 0))
-    {
-      int ret = SOCKETCALL_CANCEL (accept4, fd, addr.__sockaddr__, addr_len,
-				   flags);
-      /* The kernel returns -EINVAL for unknown socket operations.
-	 We need to convert that error to an ENOSYS error.  */
-      if (__builtin_expect (ret < 0, 0)
-	  && have_accept4 == 0
-	  && errno == EINVAL)
-	{
-	  /* Try another call, this time with the FLAGS parameter
-	     cleared and an invalid file descriptor.  This call will not
-	     cause any harm and it will return immediately.  */
-	  ret = SOCKETCALL_CANCEL (invalid, -1);
-	  if (errno == EINVAL)
-	    {
-	      have_accept4 = -1;
-	      __set_errno (ENOSYS);
-	    }
-	  else
-	    {
-	      have_accept4 = 1;
-	      __set_errno (EINVAL);
-	    }
-	  return -1;
-	}
-      return ret;
-    }
-  __set_errno (ENOSYS);
-  return -1;
-}
-# endif /* __ASSUME_ACCEPT4_SOCKETCALL  */
-#else /* __NR_socketcall   */
-int
-accept4 (int fd, __SOCKADDR_ARG addr, socklen_t *addr_len, int flags)
-{
-  __set_errno (ENOSYS);
-  return -1;
-}
-stub_warning (accept4)
+#else
+  return SYSCALL_CANCEL (accept4, fd, addr.__sockaddr__, addr_len, flags);
 #endif
+}

sysdeps/unix/sysv/linux/ia64/configure

@@ -2,3 +2,7 @@
  # Local configure fragment for sysdeps/unix/sysv/linux/ia64
 
 ldd_rewrite_script=$dir/ldd-rewrite.sed
+
+# First version with support for the accept4 system call.
+# Linux 3.3 includes it as well.
+arch_minimum_kernel=3.2.18

sysdeps/unix/sysv/linux/ia64/configure.ac

@@ -2,3 +2,7 @@ GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
 # Local configure fragment for sysdeps/unix/sysv/linux/ia64
 
 ldd_rewrite_script=$dir/ldd-rewrite.sed
+
+# First version with support for the accept4 system call.
+# Linux 3.3 includes it as well.
+arch_minimum_kernel=3.2.18

sysdeps/unix/sysv/linux/ia64/kernel-features.h

@@ -22,13 +22,8 @@
 
 #include_next <kernel-features.h>
 
-/* Support for the accept4 syscall was added in 3.3.  */
-#if __LINUX_KERNEL_VERSION < 0x030300
-# undef __ASSUME_ACCEPT4_SYSCALL
-# undef __ASSUME_ACCEPT4
-#endif
-
 #define __ASSUME_RECV_SYSCALL   	1
 #define __ASSUME_SEND_SYSCALL		1
+#define __ASSUME_ACCEPT4_SYSCALL	1
 
 #endif /* _KERNEL_FEATURES_H */

sysdeps/unix/sysv/linux/kernel-features.h

@@ -75,18 +75,11 @@
    architectures using a separate syscall rather than socketcall that
    syscall was only added later, and some architectures first had
    socketcall support then a separate syscall.  Define
-   __ASSUME_ACCEPT4_SOCKETCALL if glibc uses socketcall on this
-   architecture and accept4 is available through socketcall,
    __ASSUME_ACCEPT4_SYSCALL if it is available through a separate
-   syscall, __ASSUME_ACCEPT4_SYSCALL_WITH_SOCKETCALL if it became
+   syscall, and __ASSUME_ACCEPT4_SYSCALL_WITH_SOCKETCALL if it became
    available through a separate syscall at the same time as through
-   socketcall, and __ASSUME_ACCEPT4 if the accept4 function is known
-   to work.  */
-#ifdef __ASSUME_SOCKETCALL
-# define __ASSUME_ACCEPT4_SOCKETCALL	1
-#endif
+   socketcall.  */
 #define __ASSUME_ACCEPT4_SYSCALL	1
-#define __ASSUME_ACCEPT4	1
 
 /* Support for the FUTEX_CLOCK_REALTIME flag was added in 2.6.29.  */
 #define __ASSUME_FUTEX_CLOCK_REALTIME	1