swrap: introduce a socket_wrapper_noop.so and socket_wrapper.h to provide noop stubs

Applications with the need to call socket_wrapper_enabled() should link
against -lsocket_wrapper_noop in order to resolve the symbol at
link time.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14640

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>

4 files changed, 157 insertions, 4 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 73f8cd0..ac56c86 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -27,3 +27,35 @@ install(TARGETS socket_wrapper
 )
 
 set(SOCKET_WRAPPER_LOCATION "${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_SHARED_LIBRARY_PREFIX}socket_wrapper${CMAKE_SHARED_LIBRARY_SUFFIX}" PARENT_SCOPE)
+
+add_library(socket_wrapper_noop SHARED socket_wrapper_noop.c)
+target_include_directories(socket_wrapper_noop
+                           PRIVATE
+                               ${CMAKE_BINARY_DIR})
+target_compile_options(socket_wrapper_noop
+                       PRIVATE
+                          ${DEFAULT_C_COMPILE_FLAGS}
+                          -D_GNU_SOURCE)
+target_link_libraries(socket_wrapper_noop ${SWRAP_REQUIRED_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT})
+set_target_properties(socket_wrapper_noop
+                      PROPERTIES
+                          VERSION ${LIBRARY_VERSION}
+                          SOVERSION ${LIBRARY_SOVERSION})
+if (DEFINED DEFAULT_LINK_FLAGS)
+    set_target_properties(socket_wrapper_noop
+                          PROPERTIES
+                              LINK_FLAGS ${DEFAULT_LINK_FLAGS})
+endif()
+
+install(TARGETS socket_wrapper_noop
+        RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+        LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+        ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+)
+
+install(
+    FILES
+        ${CMAKE_CURRENT_SOURCE_DIR}/socket_wrapper.h
+    DESTINATION
+        ${CMAKE_INSTALL_INCLUDEDIR}
+)
diff --git a/src/socket_wrapper.c b/src/socket_wrapper.c
index 22e0246..63de148 100644
--- a/src/socket_wrapper.c
+++ b/src/socket_wrapper.c
@@ -2,8 +2,8 @@
  * BSD 3-Clause License
  *
  * Copyright (c) 2005-2008, Jelmer Vernooij <jelmer@samba.org>
- * Copyright (c) 2006-2018, Stefan Metzmacher <metze@samba.org>
- * Copyright (c) 2013-2018, Andreas Schneider <asn@samba.org>
+ * Copyright (c) 2006-2021, Stefan Metzmacher <metze@samba.org>
+ * Copyright (c) 2013-2021, Andreas Schneider <asn@samba.org>
  * Copyright (c) 2014-2017, Michael Adam <obnox@samba.org>
  * Copyright (c) 2016-2018, Anoop C S <anoopcs@redhat.com>
  * All rights reserved.
@@ -86,6 +86,8 @@
 #endif
 #include <pthread.h>
 
+#include "socket_wrapper.h"
+
 enum swrap_dbglvl_e {
 	SWRAP_LOG_ERROR = 0,
 	SWRAP_LOG_WARN,
@@ -392,8 +394,6 @@ static pthread_mutex_t mtu_update_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 /* Function prototypes */
 
-bool socket_wrapper_enabled(void);
-
 #if ! defined(HAVE_CONSTRUCTOR_ATTRIBUTE) && defined(HAVE_PRAGMA_INIT)
 /* xlC and other oldschool compilers support (only) this */
 #pragma init (swrap_constructor)
diff --git a/src/socket_wrapper.h b/src/socket_wrapper.h
new file mode 100644
index 0000000..f1a97e8
--- /dev/null
+++ b/src/socket_wrapper.h
@@ -0,0 +1,64 @@
+/*
+ * BSD 3-Clause License
+ *
+ * Copyright (c) 2005-2008, Jelmer Vernooij <jelmer@samba.org>
+ * Copyright (c) 2006-2021, Stefan Metzmacher <metze@samba.org>
+ * Copyright (c) 2013-2021, Andreas Schneider <asn@samba.org>
+ * Copyright (c) 2014-2017, Michael Adam <obnox@samba.org>
+ * Copyright (c) 2016-2018, Anoop C S <anoopcs@redhat.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the author nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef __SOCKET_WRAPPER_H__
+#define __SOCKET_WRAPPER_H__ 1
+
+#include <stdbool.h>
+
+/*
+   Socket wrapper advanced helpers.
+
+   Applications with the need to alter their behaviour when
+   socket wrapper is active, can link use these functions.
+
+   By default it's required for applications to use any of these
+   functions as libsocket_wrapper.so is injected at runtime via
+   LD_PRELOAD.
+
+   Applications using these functions should link against
+   libsocket_wrapper_noop.so by using -lsocket_wrapper_noop,
+   or implement their own noop stubs.
+*/
+
+/*
+ * This returns true when socket wrapper is actively in use.
+ */
+bool socket_wrapper_enabled(void);
+
+#endif /* __SOCKET_WRAPPER_H__ */
diff --git a/src/socket_wrapper_noop.c b/src/socket_wrapper_noop.c
new file mode 100644
index 0000000..45aff8f
--- /dev/null
+++ b/src/socket_wrapper_noop.c
@@ -0,0 +1,57 @@
+/*
+ * BSD 3-Clause License
+ *
+ * Copyright (c) 2005-2008, Jelmer Vernooij <jelmer@samba.org>
+ * Copyright (c) 2006-2021, Stefan Metzmacher <metze@samba.org>
+ * Copyright (c) 2013-2021, Andreas Schneider <asn@samba.org>
+ * Copyright (c) 2014-2017, Michael Adam <obnox@samba.org>
+ * Copyright (c) 2016-2018, Anoop C S <anoopcs@redhat.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the author nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+   Socket wrapper noop library.
+
+   Applications with the need to alter their behaviour when
+   socket wrapper is active, can link to this with -lsocket_wrapper_noop
+   in order to call get the required public functions at link time.
+
+   During runtime these are overloaded with LD_PRELOAD by the real
+   libsocket_wrapper.so.
+*/
+
+#include "config.h"
+#include "stdbool.h"
+#include "socket_wrapper.h"
+
+bool socket_wrapper_enabled(void)
+{
+	return false;
+}