Add ability to run the daemon in foreground

Useful for things like a Docker container or just running it in the
terminal.

Complements the stdout logging option. This is actually why the stdout
logging was added in the first place -- to be used in the foreground
mode, though nothing stops one from using stdout in the background
mode, which one could redirect to a file.

other/bootstrap_daemon/src/tox-bootstrapd.c

@@ -523,6 +523,7 @@ bool print_help()
 {
     // 2 space ident
     // make sure all lines fit into 80 columns
+    // make sure options are listed in alphabetical order
     write_log(LOG_LEVEL_INFO,
            "Usage: tox-bootstrapd [OPTION]... --config=FILE_PATH\n"
            "\n"
@@ -531,6 +532,8 @@ bool print_help()
            "                         This is a required option.\n"
            "                         Set FILE_PATH to a path to an empty file in order to\n"
            "                         use default settings.\n"
+           "  --foreground           Run the daemon in foreground. The daemon won't fork\n"
+           "                         (detach from the terminal) and won't use the PID file.\n"
            "  --help                 Print this help message.\n"
            "  --log-backend=BACKEND  Specify which logging backend to use.\n"
            "                         Valid BACKEND values (case sensetive):\n"
@@ -544,7 +547,7 @@ bool print_help()
 // Handels command line arguments, setting cfg_file_path and log_backend.
 // Terminates the application if incorrect arguments are specified.
 
-void handle_command_line_arguments(int argc, char *argv[], char **cfg_file_path, LOG_BACKEND *log_backend)
+void handle_command_line_arguments(int argc, char *argv[], char **cfg_file_path, LOG_BACKEND *log_backend, bool *run_in_foreground)
 {
     if (argc < 2) {
         write_log(LOG_LEVEL_ERROR, "Error: No arguments provided.\n\n");
@@ -557,6 +560,7 @@ void handle_command_line_arguments(int argc, char *argv[], char **cfg_file_path,
     static struct option long_options[] = {
         {"help",        no_argument,       0, 'h'},
         {"config",      required_argument, 0, 'c'}, // required option
+        {"foreground",  no_argument,       0, 'f'},
         {"log-backend", required_argument, 0, 'l'}, // optional, defaults to syslog
         {"version",     no_argument,       0, 'v'},
         {0,             0,                 0,  0 }
@@ -565,6 +569,8 @@ void handle_command_line_arguments(int argc, char *argv[], char **cfg_file_path,
     bool cfg_file_path_set = false;
     bool log_backend_set   = false;
 
+    *run_in_foreground = false;
+
     int opt;
 
     while ((opt = getopt_long(argc, argv, ":", long_options, NULL)) != -1) {
@@ -579,6 +585,10 @@ void handle_command_line_arguments(int argc, char *argv[], char **cfg_file_path,
                 cfg_file_path_set = true;
                 break;
 
+            case 'f':
+                *run_in_foreground = true;
+                break;
+
             case 'l':
                 if (strcmp(optarg, "syslog") == 0) {
                     *log_backend = LOG_BACKEND_SYSLOG;
@@ -620,16 +630,77 @@ void handle_command_line_arguments(int argc, char *argv[], char **cfg_file_path,
     }
 }
 
+// Demonizes the process, appending PID to the PID file and closing file descriptors based on log backend
+// Terminates the application if the daemonization fails.
+
+void daemonize(LOG_BACKEND log_backend, char *pid_file_path)
+{
+    // Check if the PID file exists
+    FILE *pid_file;
+
+    if ((pid_file = fopen(pid_file_path, "r"))) {
+        write_log(LOG_LEVEL_WARNING, "Another instance of the daemon is already running, PID file %s exists.\n", pid_file_path);
+        fclose(pid_file);
+    }
+
+    // Open the PID file for writing
+    pid_file = fopen(pid_file_path, "a+");
+    if (pid_file == NULL) {
+        write_log(LOG_LEVEL_ERROR, "Couldn't open the PID file for writing: %s. Exiting.\n", pid_file_path);
+        exit(1);
+    }
+
+    // Fork off from the parent process
+    const pid_t pid = fork();
+
+    if (pid > 0) {
+        fprintf(pid_file, "%d", pid);
+        fclose(pid_file);
+        write_log(LOG_LEVEL_INFO, "Forked successfully: PID: %d.\n", pid);
+        exit(0);
+    } else {
+        fclose(pid_file);
+    }
+
+    if (pid < 0) {
+        write_log(LOG_LEVEL_ERROR, "Forking failed. Exiting.\n");
+        exit(1);
+    }
+
+    // Create a new SID for the child process
+    if (setsid() < 0) {
+        write_log(LOG_LEVEL_ERROR, "SID creation failure. Exiting.\n");
+        exit(1);
+    }
+
+    // Change the file mode mask
+    umask(0);
+
+    // Change the current working directory
+    if ((chdir("/")) < 0) {
+        write_log(LOG_LEVEL_ERROR, "Couldn't change working directory to '/'. Exiting.\n");
+        exit(1);
+    }
+
+    // Go quiet
+    if (log_backend != LOG_BACKEND_STDOUT) {
+        close(STDOUT_FILENO);
+        close(STDIN_FILENO);
+        close(STDERR_FILENO);
+    }
+}
+
 int main(int argc, char *argv[])
 {
     char *cfg_file_path;
     LOG_BACKEND log_backend;
+    bool run_in_foreground;
 
     // choose backend for printing command line argument parsing output based on whether the daemon is being run from a terminal
     log_backend = isatty(STDOUT_FILENO) ? LOG_BACKEND_STDOUT : LOG_BACKEND_SYSLOG;
 
     open_log(log_backend);
-    handle_command_line_arguments(argc, argv, &cfg_file_path, &log_backend);
+    handle_command_line_arguments(argc, argv, &cfg_file_path, &log_backend, &run_in_foreground);
     close_log();
 
     open_log(log_backend);
@@ -660,14 +731,12 @@ int main(int argc, char *argv[])
         return 1;
     }
 
-    // Check if the PID file exists
+    if (!run_in_foreground) {
-    FILE *pid_file;
+        daemonize(log_backend, pid_file_path);
-
-    if ((pid_file = fopen(pid_file_path, "r"))) {
-        write_log(LOG_LEVEL_WARNING, "Another instance of the daemon is already running, PID file %s exists.\n", pid_file_path);
-        fclose(pid_file);
     }
 
+    free(pid_file_path);
+
     IP ip;
     ip_init(&ip, enable_ipv6);
 
@@ -690,7 +759,6 @@ int main(int argc, char *argv[])
         }
     }
 
-
     DHT *dht = new_DHT(net);
 
     if (dht == NULL) {
@@ -724,6 +792,8 @@ int main(int argc, char *argv[])
         return 1;
     }
 
+    free(keys_file_path);
+
     TCP_Server *tcp_server = NULL;
 
     if (enable_tcp_relay) {
@@ -754,56 +824,6 @@ int main(int argc, char *argv[])
 
     print_public_key(dht->self_public_key);
 
-    // Write the PID file
-    FILE *pidf = fopen(pid_file_path, "a+");
-
-    if (pidf == NULL) {
-        write_log(LOG_LEVEL_ERROR, "Couldn't open the PID file for writing: %s. Exiting.\n", pid_file_path);
-        return 1;
-    }
-
-    free(pid_file_path);
-    free(keys_file_path);
-
-    // Fork off from the parent process
-    const pid_t pid = fork();
-
-    if (pid > 0) {
-        fprintf(pidf, "%d", pid);
-        fclose(pidf);
-        write_log(LOG_LEVEL_INFO, "Forked successfully: PID: %d.\n", pid);
-        return 0;
-    } else {
-        fclose(pidf);
-    }
-
-    if (pid < 0) {
-        write_log(LOG_LEVEL_ERROR, "Forking failed. Exiting.\n");
-        return 1;
-    }
-
-    // Change the file mode mask
-    umask(0);
-
-    // Create a new SID for the child process
-    if (setsid() < 0) {
-        write_log(LOG_LEVEL_ERROR, "SID creation failure. Exiting.\n");
-        return 1;
-    }
-
-    // Change the current working directory
-    if ((chdir("/")) < 0) {
-        write_log(LOG_LEVEL_ERROR, "Couldn't change working directory to '/'. Exiting.\n");
-        return 1;
-    }
-
-    // Go quiet
-    if (log_backend != LOG_BACKEND_STDOUT) {
-        close(STDOUT_FILENO);
-        close(STDIN_FILENO);
-        close(STDERR_FILENO);
-    }
-
     uint64_t last_LANdiscovery = 0;
     const uint16_t htons_port = htons(port);
 
@@ -811,7 +831,7 @@ int main(int argc, char *argv[])
 
     if (enable_lan_discovery) {
         LANdiscovery_init(dht);
-        write_log(LOG_LEVEL_INFO, "Initialized LAN discovery.\n");
+        write_log(LOG_LEVEL_INFO, "Initialized LAN discovery successfully.\n");
     }
 
     while (1) {
@@ -829,7 +849,7 @@ int main(int argc, char *argv[])
         networking_poll(dht->net);
 
         if (waiting_for_dht_connection && DHT_isconnected(dht)) {
-            write_log(LOG_LEVEL_INFO, "Connected to other bootstrap node successfully.\n");
+            write_log(LOG_LEVEL_INFO, "Connected to another bootstrap node successfully.\n");
             waiting_for_dht_connection = 0;
         }