Add -d option to fork into background as a daemon

CMakeLists.txt

@@ -106,6 +106,12 @@ else()
         install(FILES ${CMAKE_BINARY_DIR}/trojan.service ${CMAKE_BINARY_DIR}/[email protected] DESTINATION ${SYSTEMD_SERVICE_PATH})
     endif()
 
+    include(CheckSymbolExists)
+    check_symbol_exists(daemon "stdlib.h;unistd.h" HAVE_DAEMON)
+    if(HAVE_DAEMON)
+        add_definitions(-DHAVE_DAEMON)
+    endif()
+
     enable_testing()
     add_test(NAME LinuxSmokeTest-basic
              COMMAND bash ${CMAKE_SOURCE_DIR}/tests/LinuxSmokeTest/basic.sh ${CMAKE_BINARY_DIR}/trojan)

docs/trojan.1

@@ -14,6 +14,9 @@ and start either a proxy client or a proxy server.
 .BR \-c, " " \-\-config=\fICONFIG\fR
 Set the config file to be loaded. Default is \fI/etc/trojan/config.json\fR.
 .TP
+.BR \-d, " " \-\-daemon
+Detach from the terminal and run in the background as a daemon.
+.TP
 .BR \-h, " " \-\-help
 Print help message.
 .TP

docs/usage.md

@@ -4,6 +4,7 @@
 usage: ./trojan [-htv] [-l LOG] [-k KEYLOG] [[-c] CONFIG]
 options:
   -c [ --config ] CONFIG specify config file
+  -d [ --daemon ]        fork into background
   -h [ --help ]          print help message
   -k [ --keylog ] KEYLOG specify keylog file location (OpenSSL >= 1.1.1)
   -l [ --log ] LOG       specify log file location

src/main.cpp

@@ -26,6 +26,9 @@
 #ifdef ENABLE_MYSQL
 #include <mysql.h>
 #endif // ENABLE_MYSQL
+#ifdef HAVE_DAEMON
+#include <unistd.h>
+#endif // HAVE_DAEMON
 #include "core/service.h"
 #include "core/version.h"
 using namespace std;
@@ -68,9 +71,11 @@ int main(int argc, const char *argv[]) {
         string log_file;
         string keylog_file;
         bool test;
+        bool do_daemon;
         po::options_description desc("options");
         desc.add_options()
             ("config,c", po::value<string>(&config_file)->default_value(DEFAULT_CONFIG)->value_name("CONFIG"), "specify config file")
+            ("daemon,d", po::bool_switch(&do_daemon), "fork into background")
             ("help,h", "print help message")
             ("keylog,k", po::value<string>(&keylog_file)->value_name("KEYLOG"), "specify keylog file location (OpenSSL >= 1.1.1)")
             ("log,l", po::value<string>(&log_file)->value_name("LOG"), "specify log file location")
@@ -83,7 +88,7 @@ int main(int argc, const char *argv[]) {
         po::store(po::command_line_parser(argc, argv).options(desc).positional(pd).run(), vm);
         po::notify(vm);
         if (vm.count("help")) {
-            Log::log(string("usage: ") + argv[0] + " [-htv] [-l LOG] [-k KEYLOG] [[-c] CONFIG]", Log::FATAL);
+            Log::log(string("usage: ") + argv[0] + " [-hdtv] [-l LOG] [-k KEYLOG] [[-c] CONFIG]", Log::FATAL);
             cerr << desc;
             exit(EXIT_SUCCESS);
         }
@@ -137,6 +142,16 @@ int main(int argc, const char *argv[]) {
         if (vm.count("keylog")) {
             Log::redirect_keylog(keylog_file);
         }
+#ifdef HAVE_DAEMON
+        if (do_daemon && daemon(0, 0) == -1) {
+           Log::log(string("Failed to fork into background: ") + strerror(errno), Log::FATAL);
+           exit(EXIT_FAILURE);
+        }
+#else // HAVE_DAEMON
+        if (do_daemon) {
+           Log::log("Daemon mode not supported on this system", Log::FATAL);
+        }
+#endif // HAVE_DAEMON
         bool restart;
         Config config;
         do {