*/smbclient: protect all libsmbclient calls with a mutex

libsmbclient is not thread-safe nor reentrant.  We must protect all
function calls with a global mutex, unfortunately.

Makefile.am

@@ -415,6 +415,7 @@ libfs_a_SOURCES = \
 
 SMBCLIENT_SOURCES = \
 	src/lib/smbclient/Domain.cxx src/lib/smbclient/Domain.hxx \
+	src/lib/smbclient/Mutex.cxx src/lib/smbclient/Mutex.hxx \
 	src/lib/smbclient/Init.cxx src/lib/smbclient/Init.hxx
 
 if ENABLE_DATABASE

src/input/plugins/SmbclientInputPlugin.cxx

@@ -20,6 +20,7 @@
 #include "config.h"
 #include "SmbclientInputPlugin.hxx"
 #include "lib/smbclient/Init.hxx"
+#include "lib/smbclient/Mutex.hxx"
 #include "../InputStream.hxx"
 #include "../InputPlugin.hxx"
 #include "util/StringUtil.hxx"
@@ -45,8 +46,10 @@ public:
 	}
 
 	~SmbclientInputStream() {
+		smbclient_mutex.lock();
 		smbc_close(fd);
 		smbc_free_context(ctx, 1);
+		smbclient_mutex.unlock();
 	}
 
 	InputStream *GetBase() {
@@ -58,7 +61,9 @@ public:
 	}
 
 	size_t Read(void *ptr, size_t size, Error &error) {
+		smbclient_mutex.lock();
 		ssize_t nbytes = smbc_read(fd, ptr, size);
+		smbclient_mutex.unlock();
 		if (nbytes < 0) {
 			error.SetErrno("smbc_read() failed");
 			nbytes = 0;
@@ -68,7 +73,9 @@ public:
 	}
 
 	bool Seek(InputStream::offset_type offset, int whence, Error &error) {
+		smbclient_mutex.lock();
 		off_t result = smbc_lseek(fd, offset, whence);
+		smbclient_mutex.unlock();
 		if (result < 0) {
 			error.SetErrno("smbc_lseek() failed");
 			return false;
@@ -105,6 +112,8 @@ input_smbclient_open(const char *uri,
 	if (!StringStartsWith(uri, "smb://"))
 		return nullptr;
 
+	const ScopeLock protect(smbclient_mutex);
+
 	SMBCCTX *ctx = smbc_new_context();
 	if (ctx == nullptr) {
 		error.SetErrno("smbc_new_context() failed");

src/lib/smbclient/Init.cxx

@@ -19,6 +19,8 @@
 
 #include "config.h"
 #include "Init.hxx"
+#include "Mutex.hxx"
+#include "thread/Mutex.hxx"
 #include "util/Error.hxx"
 
 #include <libsmbclient.h>
@@ -41,6 +43,8 @@ mpd_smbc_get_auth_data(gcc_unused const char *srv,
 bool
 SmbclientInit(Error &error)
 {
+	const ScopeLock protect(smbclient_mutex);
+
 	constexpr int debug = 0;
 	if (smbc_init(mpd_smbc_get_auth_data, debug) < 0) {
 		error.SetErrno("smbc_init() failed");

src/lib/smbclient/Mutex.cxx

@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "Mutex.hxx"
+#include "thread/Mutex.hxx"
+
+Mutex smbclient_mutex;

src/lib/smbclient/Mutex.hxx

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_SMBCLIENT_MUTEX_HXX
+#define MPD_SMBCLIENT_MUTEX_HXX
+
+class Mutex;
+
+/**
+ * Since libsmbclient is not thread-safe, this mutex must be locked
+ * during all libsmbclient function calls.
+ */
+extern Mutex smbclient_mutex;
+
+#endif

src/neighbor/plugins/SmbclientNeighborPlugin.cxx

@@ -21,6 +21,7 @@
 #include "SmbclientNeighborPlugin.hxx"
 #include "lib/smbclient/Init.hxx"
 #include "lib/smbclient/Domain.hxx"
+#include "lib/smbclient/Mutex.hxx"
 #include "neighbor/NeighborPlugin.hxx"
 #include "neighbor/Explorer.hxx"
 #include "neighbor/Listener.hxx"
@@ -175,6 +176,7 @@ static NeighborExplorer::List
 DetectServers()
 {
 	NeighborExplorer::List list;
+	const ScopeLock protect(smbclient_mutex);
 	ReadServers(list, "smb://");
 	return list;
 }

src/storage/plugins/SmbclientStorage.cxx

@@ -22,7 +22,9 @@
 #include "storage/StorageInterface.hxx"
 #include "storage/FileInfo.hxx"
 #include "lib/smbclient/Init.hxx"
+#include "lib/smbclient/Mutex.hxx"
 #include "util/Error.hxx"
+#include "thread/Mutex.hxx"
 
 #include <libsmbclient.h>
 
@@ -54,7 +56,9 @@ public:
 		:base(_base), ctx(_ctx) {}
 
 	virtual ~SmbclientStorage() {
+		smbclient_mutex.lock();
 		smbc_free_context(ctx, 1);
+		smbclient_mutex.unlock();
 	}
 
 	/* virtual methods from class Storage */
@@ -82,7 +86,10 @@ static bool
 GetInfo(const char *path, FileInfo &info, Error &error)
 {
 	struct stat st;
-	if (smbc_stat(path, &st) < 0) {
+	smbclient_mutex.lock();
+	bool success = smbc_stat(path, &st) == 0;
+	smbclient_mutex.unlock();
+	if (!success) {
 		error.SetErrno();
 		return false;
 	}
@@ -113,7 +120,9 @@ StorageDirectoryReader *
 SmbclientStorage::OpenDirectory(const char *uri_utf8, Error &error)
 {
 	std::string mapped = MapUTF8(uri_utf8);
+	smbclient_mutex.lock();
 	int handle = smbc_opendir(mapped.c_str());
+	smbclient_mutex.unlock();
 	if (handle < 0) {
 		error.SetErrno();
 		return nullptr;
@@ -133,12 +142,16 @@ SkipNameFS(const char *name)
 
 SmbclientDirectoryReader::~SmbclientDirectoryReader()
 {
+	smbclient_mutex.lock();
 	smbc_close(handle);
+	smbclient_mutex.unlock();
 }
 
 const char *
 SmbclientDirectoryReader::Read()
 {
+	const ScopeLock protect(smbclient_mutex);
+
 	struct smbc_dirent *e;
 	while ((e = smbc_readdir(handle)) != nullptr) {
 		name = e->name;
@@ -163,6 +176,7 @@ CreateSmbclientStorage(const char *base, Error &error)
 	if (!SmbclientInit(error))
 		return nullptr;
 
+	const ScopeLock protect(smbclient_mutex);
 	SMBCCTX *ctx = smbc_new_context();
 	if (ctx == nullptr) {
 		error.SetErrno("smbc_new_context() failed");