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/* ncmpc (Ncurses MPD Client)
* (c) 2004-2018 The Music Player Daemon Project
* Project homepage: http://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 "plugin.hxx"
#include "io/Path.hxx"
#include "util/Compiler.h"
#include "util/ScopeExit.hxx"
#include "util/UriUtil.hxx"
#include <boost/asio/steady_timer.hpp>
#include <boost/asio/posix/stream_descriptor.hpp>
#include <algorithm>
#include <memory>
#include <assert.h>
#include <stdlib.h>
#include <unistd.h>
#include <dirent.h>
#include <string.h>
#include <signal.h>
#include <sys/stat.h>
#include <sys/wait.h>
struct PluginCycle;
struct PluginPipe {
PluginCycle *cycle;
/** the pipe to the plugin process */
boost::asio::posix::stream_descriptor fd;
/** the output of the current plugin */
std::string data;
std::array<char, 256> buffer;
PluginPipe(boost::asio::io_service &io_service) noexcept
:fd(io_service) {}
~PluginPipe() noexcept {
Close();
}
void AsyncRead() noexcept {
fd.async_read_some(boost::asio::buffer(buffer),
std::bind(&PluginPipe::OnRead, this,
std::placeholders::_1,
std::placeholders::_2));
}
void OnRead(const boost::system::error_code &error,
std::size_t bytes_transferred) noexcept;
void Close() noexcept {
if (!fd.is_open())
return;
fd.cancel();
fd.close();
}
};
struct PluginCycle {
/** the plugin list; used for traversing to the next plugin */
PluginList *list;
/** arguments passed to execv() */
std::unique_ptr<char *[]> argv;
/** caller defined callback function */
plugin_callback_t callback;
/** caller defined pointer passed to #callback */
void *callback_data;
/** the index of the next plugin which is going to be
invoked */
unsigned next_plugin = 0;
/** the pid of the plugin process, or -1 if none is currently
running */
pid_t pid = -1;
/** the stdout pipe */
PluginPipe pipe_stdout;
/** the stderr pipe */
PluginPipe pipe_stderr;
/** list of all error messages from failed plugins */
std::string all_errors;
boost::asio::steady_timer delayed_fail_timer;
PluginCycle(boost::asio::io_service &io_service,
PluginList &_list, std::unique_ptr<char *[]> &&_argv,
plugin_callback_t _callback, void *_callback_data) noexcept
:list(&_list), argv(std::move(_argv)),
callback(_callback), callback_data(_callback_data),
pipe_stdout(io_service), pipe_stderr(io_service),
delayed_fail_timer(io_service) {}
void TryNextPlugin() noexcept;
void ScheduleDelayedFail() noexcept {
boost::system::error_code error;
delayed_fail_timer.expires_from_now(std::chrono::seconds(0),
error);
delayed_fail_timer.async_wait(std::bind(&PluginCycle::OnDelayedFail,
this,
std::placeholders::_1));
}
void OnEof() noexcept;
private:
int LaunchPlugin(const char *plugin_path) noexcept;
void OnDelayedFail(const boost::system::error_code &error) noexcept;
};
static bool
register_plugin(PluginList *list, std::string &&path) noexcept
{
struct stat st;
if (stat(path.c_str(), &st) < 0)
return false;
list->plugins.emplace_back(std::move(path));
return true;
}
static constexpr bool
ShallSkipDirectoryEntry(const char *name) noexcept
{
return name[0] == '.' && (name[1] == 0 || (name[1] == '.' && name[2] == 0));
}
bool
plugin_list_load_directory(PluginList *list, const char *path) noexcept
{
DIR *dir = opendir(path);
if (dir == nullptr)
return false;
AtScopeExit(dir) { closedir(dir); };
while (const auto *e = readdir(dir)) {
const char *name = e->d_name;
if (!ShallSkipDirectoryEntry(name))
register_plugin(list, BuildPath(path, name));
}
std::sort(list->plugins.begin(), list->plugins.end());
return true;
}
void
PluginCycle::OnEof() noexcept
{
/* Only if both pipes are have EOF status we are done */
if (pipe_stdout.fd.is_open() || pipe_stderr.fd.is_open())
return;
int status, ret = waitpid(pid, &status, 0);
pid = -1;
if (ret < 0 || !WIFEXITED(status) || WEXITSTATUS(status) != 0) {
/* If we encountered an error other than service unavailable
* (69), log it for later. If all plugins fail, we may get
* some hints for debugging.*/
if (!pipe_stderr.data.empty() &&
WEXITSTATUS(status) != 69) {
all_errors += "*** ";
all_errors += argv[0];
all_errors += " ***\n\n";
all_errors += pipe_stderr.data;
all_errors += "\n";
}
/* the plugin has failed */
pipe_stdout.data.clear();
pipe_stderr.data.clear();
TryNextPlugin();
} else {
/* success: invoke the callback */
callback(std::move(pipe_stdout.data), true,
argv[0], callback_data);
}
}
void
PluginPipe::OnRead(const boost::system::error_code &error,
std::size_t bytes_transferred) noexcept
{
if (error) {
if (error == boost::asio::error::operation_aborted)
/* this object has already been deleted; bail out
quickly without touching anything */
return;
fd.close();
cycle->OnEof();
return;
}
data.append(&buffer.front(), bytes_transferred);
AsyncRead();
}
/**
* This is a timer callback which calls the plugin callback "some time
* later". This solves the problem that plugin_run() may fail
* immediately, leaving its return value in an undefined state.
* Instead, install a timer which calls the plugin callback in the
* moment after.
*/
void
PluginCycle::OnDelayedFail(const boost::system::error_code &error) noexcept
{
if (error)
return;
assert(!pipe_stdout.fd.is_open());
assert(!pipe_stderr.fd.is_open());
assert(pid < 0);
callback(std::move(all_errors), false, nullptr,
callback_data);
}
static void
plugin_fd_add(PluginCycle *cycle, PluginPipe *p, int fd) noexcept
{
p->cycle = cycle;
p->fd.assign(fd);
p->AsyncRead();
}
int
PluginCycle::LaunchPlugin(const char *plugin_path) noexcept
{
assert(pid < 0);
assert(!pipe_stdout.fd.is_open());
assert(!pipe_stderr.fd.is_open());
assert(pipe_stdout.data.empty());
assert(pipe_stderr.data.empty());
/* set new program name, but free the one from the previous
plugin */
argv[0] = const_cast<char *>(GetUriFilename(plugin_path));
int fds_stdout[2];
if (pipe(fds_stdout) < 0)
return -1;
int fds_stderr[2];
if (pipe(fds_stderr) < 0) {
close(fds_stdout[0]);
close(fds_stdout[1]);
return -1;
}
pid = fork();
if (pid < 0) {
close(fds_stdout[0]);
close(fds_stdout[1]);
close(fds_stderr[0]);
close(fds_stderr[1]);
return -1;
}
if (pid == 0) {
dup2(fds_stdout[1], 1);
dup2(fds_stderr[1], 2);
close(fds_stdout[0]);
close(fds_stdout[1]);
close(fds_stderr[0]);
close(fds_stderr[1]);
close(0);
/* XXX close other fds? */
execv(plugin_path, argv.get());
_exit(1);
}
close(fds_stdout[1]);
close(fds_stderr[1]);
/* XXX CLOEXEC? */
plugin_fd_add(this, &pipe_stdout, fds_stdout[0]);
plugin_fd_add(this, &pipe_stderr, fds_stderr[0]);
return 0;
}
void
PluginCycle::TryNextPlugin() noexcept
{
assert(pid < 0);
assert(!pipe_stdout.fd.is_open());
assert(!pipe_stderr.fd.is_open());
assert(pipe_stdout.data.empty());
assert(pipe_stderr.data.empty());
if (next_plugin >= list->plugins.size()) {
/* no plugins left */
ScheduleDelayedFail();
return;
}
const char *plugin_path = (const char *)
list->plugins[next_plugin++].c_str();
if (LaunchPlugin(plugin_path) < 0) {
/* system error */
ScheduleDelayedFail();
return;
}
}
static auto
make_argv(const char*const* args) noexcept
{
unsigned num = 0;
while (args[num] != nullptr)
++num;
num += 2;
std::unique_ptr<char *[]> result(new char *[num]);
char **ret = result.get();
/* reserve space for the program name */
*ret++ = nullptr;
while (*args != nullptr)
*ret++ = const_cast<char *>(*args++);
/* end of argument vector */
*ret++ = nullptr;
return result;
}
PluginCycle *
plugin_run(boost::asio::io_service &io_service,
PluginList *list, const char *const*args,
plugin_callback_t callback, void *callback_data) noexcept
{
assert(args != nullptr);
auto *cycle = new PluginCycle(io_service, *list, make_argv(args),
callback, callback_data);
cycle->TryNextPlugin();
return cycle;
}
void
plugin_stop(PluginCycle *cycle) noexcept
{
if (cycle->pid > 0) {
/* kill the plugin process */
cycle->pipe_stdout.Close();
cycle->pipe_stderr.Close();
int status;
kill(cycle->pid, SIGTERM);
waitpid(cycle->pid, &status, 0);
}
delete cycle;
}
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