unix: Condition Linux-specific abstract sockets on __linux__

This is nicer for cross-compiling, because AC_RUN_IFELSE can't work
there. In practice abstract sockets are supported on Linux since
2.2 (so, all relevant versions), and on no other platform; so it
seems futile to keep this complexity.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=34905
Signed-off-by: Simon McVittie <smcv@collabora.com>
Reviewed-by: Philip Withnall <withnall@endlessm.com>

8 files changed, 7 insertions, 132 deletions

diff --git a/README.cmake b/README.cmake
index facfaf09..69012fbe 100644
--- a/README.cmake
+++ b/README.cmake
@@ -158,10 +158,6 @@ DBUS_BUS_ENABLE_INOTIFY:BOOL=ON
 // enable kqueue as dir watch backend
 DBUS_BUS_ENABLE_KQUEUE:BOOL=ON
 
-not available on windows:
-// enable abstract socket transport
-DBUS_ENABLE_ABSTRACT_SOCKETS:BOOL=ON
-
 x11 only:
 // Build with X11 auto launch support
 DBUS_BUILD_X11:BOOL=ON
diff --git a/cmake/CMakeLists.txt b/cmake/CMakeLists.txt
index a003f282..a9f53780 100644
--- a/cmake/CMakeLists.txt
+++ b/cmake/CMakeLists.txt
@@ -121,7 +121,6 @@ if (WIN32)
 endif (WIN32)
 
 if(NOT WIN32)
-	option (DBUS_ENABLE_ABSTRACT_SOCKETS "enable support for abstract sockets" ON)
 	set (CMAKE_THREAD_PREFER_PTHREAD ON)
 	include (FindThreads)
 endif(NOT WIN32)
diff --git a/cmake/ConfigureChecks.cmake b/cmake/ConfigureChecks.cmake
index 6815178b..d83810a7 100644
--- a/cmake/ConfigureChecks.cmake
+++ b/cmake/ConfigureChecks.cmake
@@ -66,7 +66,6 @@ check_symbol_exists(raise        "signal.h"                 HAVE_RAISE)
 check_struct_member(cmsgcred cmcred_pid "sys/types.h sys/socket.h" HAVE_CMSGCRED)   #  dbus-sysdeps.c
 
 # missing:
-# HAVE_ABSTRACT_SOCKETS
 # DBUS_HAVE_GCC33_GCOV
 
 check_type_size("short"     SIZEOF_SHORT)
@@ -168,12 +167,3 @@ else(DBUS_HAVE_VA_COPY)
   endif(DBUS_HAVE___VA_COPY)
 endif(DBUS_HAVE_VA_COPY)
 endif(MSVC) # _not_ MSVC
-#### Abstract sockets
-
-if (DBUS_ENABLE_ABSTRACT_SOCKETS)
-
-  try_compile(HAVE_ABSTRACT_SOCKETS
-              ${CMAKE_BINARY_DIR}
-              ${CMAKE_SOURCE_DIR}/modules/CheckForAbstractSockets.c)
-
-endif(DBUS_ENABLE_ABSTRACT_SOCKETS)
diff --git a/cmake/config.h.cmake b/cmake/config.h.cmake
index 154353b7..202c0ab0 100644
--- a/cmake/config.h.cmake
+++ b/cmake/config.h.cmake
@@ -49,10 +49,6 @@
 /* doxygen */
 #cmakedefine DBUS_GCOV_ENABLED 1
 
-/* abstract-sockets */
-
-#cmakedefine HAVE_ABSTRACT_SOCKETS 1
-
 /* selinux */
 /* kqueue */
 #cmakedefine HAVE_CONSOLE_OWNER_FILE 1
diff --git a/cmake/modules/CheckForAbstractSockets.c b/cmake/modules/CheckForAbstractSockets.c
deleted file mode 100644
index 062b846c..00000000
--- a/cmake/modules/CheckForAbstractSockets.c
+++ /dev/null
@@ -1,33 +0,0 @@
-#include <stdlib.h>
-#include <string.h>
-#include <stdio.h>
-#include <sys/socket.h>
-#include <sys/un.h>
-#include <errno.h>
-
-int main() {
-  int listen_fd;
-  struct sockaddr_un addr;
-
-  listen_fd = socket (PF_UNIX, SOCK_STREAM, 0);
-
-  if (listen_fd < 0)
-    {
-      fprintf (stderr, "socket() failed: %s\n", strerror (errno));
-      exit (1);
-    }
-
-  memset (&addr, '\0', sizeof (addr));
-  addr.sun_family = AF_UNIX;
-  strcpy (addr.sun_path, "X/tmp/dbus-fake-socket-path-used-in-configure-test");
-  addr.sun_path[0] = '\0'; /* this is what makes it abstract */
-
-  if (bind (listen_fd, (struct sockaddr*) &addr, SUN_LEN (&addr)) < 0)
-    {
-      fprintf (stderr, "Abstract socket namespace bind() failed: %s\n",
-                strerror (errno));
-      exit (1);
-    }
-  else
-    exit (0);
-}
\ No newline at end of file
diff --git a/configure.ac b/configure.ac
index 5281db1b..2c29dd13 100644
--- a/configure.ac
+++ b/configure.ac
@@ -198,7 +198,6 @@ AC_ARG_ENABLE([ducktype-docs],
               AS_HELP_STRING([--enable-ducktype-docs],
                              [build Ducktype documentation (requires Ducktype)]),
               [enable_ducktype_docs=$enableval], [enable_ducktype_docs=auto])
-AC_ARG_ENABLE(abstract-sockets, AS_HELP_STRING([--enable-abstract-sockets],[use abstract socket namespace (linux only)]),enable_abstract_sockets=$enableval,enable_abstract_sockets=auto)
 AC_ARG_ENABLE(selinux, AS_HELP_STRING([--enable-selinux],[build with SELinux support]),enable_selinux=$enableval,enable_selinux=auto)
 AC_ARG_ENABLE([apparmor],
   [AS_HELP_STRING([--enable-apparmor], [build with AppArmor support])],
@@ -850,77 +849,6 @@ AC_CHECK_FUNCS(getpeerucred getpeereid)
 
 AC_CHECK_FUNCS(pipe2 accept4)
 
-#### Abstract sockets
-
-if test x$enable_abstract_sockets = xauto; then
-AC_LANG_PUSH(C)
-warn_on_xcompile=no
-AC_CACHE_CHECK([abstract socket namespace],
-		ac_cv_have_abstract_sockets,
-		[AC_RUN_IFELSE([AC_LANG_PROGRAM(
-[[
-#include <sys/types.h>
-#include <stdlib.h>
-#include <string.h>
-#include <stdio.h>
-#include <sys/socket.h>
-#include <sys/un.h>
-#include <errno.h>
-]],
-[[
-  size_t slen;
-  int listen_fd;
-  struct sockaddr_un addr;
-
-  listen_fd = socket (PF_UNIX, SOCK_STREAM, 0);
-
-  if (listen_fd < 0)
-    {
-      fprintf (stderr, "socket() failed: %s\n", strerror (errno));
-      exit (1);
-    }
-
-  memset (&addr, '\0', sizeof (addr));
-  addr.sun_family = AF_UNIX;
-  strcpy (addr.sun_path, "X/tmp/dbus-fake-socket-path-used-in-configure-test");
-  /* SUN_LEN uses strlen() so need to calculate it before adding \0 at the
-   * beginning.
-   */
-  slen = SUN_LEN(&addr);
-  addr.sun_path[0] = '\0'; /* this is what makes it abstract */
-
-  if (bind (listen_fd, (struct sockaddr*) &addr, slen) < 0)
-    {
-       fprintf (stderr, "Abstract socket namespace bind() failed: %s\n",
-                strerror (errno));
-       exit (1);
-    }
-  else
-    exit (0);
-]])],
-              [ac_cv_have_abstract_sockets=yes],
-              [ac_cv_have_abstract_sockets=no],
-              [
-                ac_cv_have_abstract_sockets=no
-                warn_on_xcompile=yes
-              ]
-)])
-if test x$warn_on_xcompile = xyes ; then
-  AC_MSG_WARN([Cannot check for abstract sockets when cross-compiling, please use --enable-abstract-sockets])
-fi
-AC_LANG_POP(C)
-fi
-
-if test x$enable_abstract_sockets = xyes; then
-    if test x$ac_cv_have_abstract_sockets = xno; then
-	AC_MSG_ERROR([Abstract sockets explicitly required, and support not detected.])
-    fi
-fi
-
-if test x$enable_abstract_sockets = xno; then
-   ac_cv_have_abstract_sockets=no;
-fi
-
 PKG_CHECK_MODULES([EXPAT], [expat])
 
 save_cflags="$CFLAGS"
@@ -1923,7 +1851,6 @@ echo "
         Building Ducktype docs:   ${enable_ducktype_docs}
         Building XML docs:        ${enable_xml_docs}
         Building launchd support: ${have_launchd}
-        Abstract socket names:    ${ac_cv_have_abstract_sockets}
         System bus socket:        ${DBUS_SYSTEM_SOCKET}
         System bus address:       ${DBUS_SYSTEM_BUS_DEFAULT_ADDRESS}
         System bus PID file:      ${DBUS_SYSTEM_PID_FILE}
diff --git a/dbus/dbus-server-unix.c b/dbus/dbus-server-unix.c
index fd9348ab..534e1d5f 100644
--- a/dbus/dbus-server-unix.c
+++ b/dbus/dbus-server-unix.c
@@ -145,7 +145,7 @@ _dbus_server_listen_platform_specific (DBusAddressEntry *entry,
             {
               dir = tmpdir;
 
-#ifdef HAVE_ABSTRACT_SOCKETS
+#ifdef __linux__
               /* Use abstract sockets for tmpdir if supported, so that it
                * never needs to be cleaned up. Use dir instead if you want a
                * path-based socket. */
diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c
index ea1a4b76..bebf2073 100644
--- a/dbus/dbus-sysdeps-unix.c
+++ b/dbus/dbus-sysdeps-unix.c
@@ -933,7 +933,7 @@ _dbus_connect_unix_socket (const char     *path,
 
   if (abstract)
     {
-#ifdef HAVE_ABSTRACT_SOCKETS
+#ifdef __linux__
       addr.sun_path[0] = '\0'; /* this is what says "use abstract" */
       path_len++; /* Account for the extra nul byte added to the start of sun_path */
 
@@ -947,12 +947,12 @@ _dbus_connect_unix_socket (const char     *path,
 
       strncpy (&addr.sun_path[1], path, path_len);
       /* _dbus_verbose_bytes (addr.sun_path, sizeof (addr.sun_path)); */
-#else /* HAVE_ABSTRACT_SOCKETS */
+#else /* !__linux__ */
       dbus_set_error (error, DBUS_ERROR_NOT_SUPPORTED,
                       "Operating system does not support abstract socket namespace\n");
       _dbus_close (fd, NULL);
       return -1;
-#endif /* ! HAVE_ABSTRACT_SOCKETS */
+#endif /* !__linux__ */
     }
   else
     {
@@ -1134,7 +1134,7 @@ _dbus_listen_unix_socket (const char     *path,
 
   if (abstract)
     {
-#ifdef HAVE_ABSTRACT_SOCKETS
+#ifdef __linux__
       /* remember that abstract names aren't nul-terminated so we rely
        * on sun_path being filled in with zeroes above.
        */
@@ -1151,12 +1151,12 @@ _dbus_listen_unix_socket (const char     *path,
 
       strncpy (&addr.sun_path[1], path, path_len);
       /* _dbus_verbose_bytes (addr.sun_path, sizeof (addr.sun_path)); */
-#else /* HAVE_ABSTRACT_SOCKETS */
+#else /* !__linux__ */
       dbus_set_error (error, DBUS_ERROR_NOT_SUPPORTED,
                       "Operating system does not support abstract socket namespace\n");
       _dbus_close (listen_fd, NULL);
       return -1;
-#endif /* ! HAVE_ABSTRACT_SOCKETS */
+#endif /* !__linux__ */
     }
   else
     {