daemon.c

   1 /* Copyright (C) 1997 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
   2
   3 /** \file daemon.c Some helpers for programs that detach from the console. */
   4
   5 #include <regex.h>
   6 #include <pwd.h>
   7 #include <sys/types.h> /* getgrnam() */
   8 #include <grp.h>
   9 #include <signal.h>
  10 #include <sys/resource.h>
  11
  12 #include "para.h"
  13 #include "daemon.h"
  14 #include "string.h"
  15 #include "color.h"
  16
  17 /** The internal state of the daemon. */
  18 struct daemon {
  19         /** See \ref daemon_flags. */
  20         unsigned flags;
  21         /** Set by \ref daemon_set_logfile(). */
  22         char *logfile_name;
  23         /** Current loglevel, see \ref daemon_set_loglevel(). */
  24         int loglevel;
  25         /** Used by \ref server_uptime() and \ref uptime_str(). */
  26         time_t startuptime;
  27         /** The file pointer if the logfile is open. */
  28         FILE *logfile;
  29         /** Used by para_log() if \p DF_LOG_HOSTNAME is set. */
  30         char *hostname;
  31         /** Used for colored log messages. */
  32         char log_colors[NUM_LOGLEVELS][COLOR_MAXLEN];
  33         char *old_cwd;
  34         /*
  35          * If these pointers are non-NULL, the functions are called from
  36          * daemon_log() before and after writing each log message.
  37          */
  38         void (*pre_log_hook)(void);
  39         void (*post_log_hook)(void);
  40 };
  41
  42 static struct daemon the_daemon, *me = &the_daemon;
  43
  44 static void daemon_set_default_log_colors(void)
  45 {
  46         int i;
  47         static const char *default_log_colors[NUM_LOGLEVELS] = {
  48                 [LL_DEBUG] = "normal",
  49                 [LL_INFO] = "normal",
  50                 [LL_NOTICE] = "normal",
  51                 [LL_WARNING] = "yellow",
  52                 [LL_ERROR] = "red",
  53                 [LL_CRIT] = "magenta bold",
  54                 [LL_EMERG] = "red bold",
  55         };
  56         for (i = 0; i < NUM_LOGLEVELS; i++)
  57                 color_parse_or_die(default_log_colors[i], me->log_colors[i]);
  58 }
  59
  60 /**
  61  * Set the color for one loglevel.
  62  *
  63  * \param arg Must be of the form "ll:[fg [bg]] [attr]".
  64  */
  65 void daemon_set_log_color_or_die(const char *arg)
  66 {
  67         char *p = strchr(arg, ':');
  68         int ret, ll;
  69
  70         if (!p)
  71                 goto err;
  72         ret = get_loglevel_by_name(arg);
  73         if (ret < 0)
  74                 goto err;
  75         ll = ret;
  76         p++;
  77         color_parse_or_die(p, me->log_colors[ll]);
  78         return;
  79 err:
  80         PARA_EMERG_LOG("%s: invalid color argument\n", arg);
  81         exit(EXIT_FAILURE);
  82 }
  83
  84 /**
  85  * Initialize color mode if necessary.
  86  *
  87  * \param color_arg The argument given to --color.
  88  * \param color_arg_auto The value for automatic color detection.
  89  * \param color_arg_no The value to disable colored log messages.
  90  * \param logfile_given In auto mode colors are disabled if this value is true.
  91  *
  92  * If color_arg equals color_arg_no, color mode is disabled. That is, calls to
  93  * para_log() will not produce colored output. If color_arg equals
  94  * color_arg_auto, the function detects automatically whether to activate
  95  * colors. Otherwise color mode is enabled.
  96  *
  97  * If color mode is to be enabled, the default colors are set for each
  98  * loglevel. They can be overwritten by calling daemon_set_log_color_or_die().
  99  *
 100  * \return Whether colors have been enabled by the function.
 101  */
 102 bool daemon_init_colors_or_die(int color_arg, int color_arg_auto,
 103                 int color_arg_no, bool logfile_given)
 104 {
 105         if (color_arg == color_arg_no)
 106                 return false;
 107         if (color_arg == color_arg_auto) {
 108                 if (logfile_given)
 109                         return false;
 110                 if (!isatty(STDERR_FILENO))
 111                         return false;
 112         }
 113         daemon_set_flag(DF_COLOR_LOG);
 114         daemon_set_default_log_colors();
 115         return true;
 116 }
 117
 118 /**
 119  * Init or change the name of the log file.
 120  *
 121  * \param logfile_name The full path of the logfile.
 122  */
 123 void daemon_set_logfile(const char *logfile_name)
 124 {
 125         free(me->logfile_name);
 126         me->logfile_name = NULL;
 127         if (!logfile_name)
 128                 return;
 129         if (me->old_cwd && logfile_name[0] != '/')
 130                 me->logfile_name = make_message("%s/%s", me->old_cwd,
 131                         logfile_name);
 132         else
 133                 me->logfile_name = para_strdup(logfile_name);
 134 }
 135
 136 /**
 137  * Suppress log messages with severity lower than the given loglevel.
 138  *
 139  * \param loglevel The smallest level that should be logged.
 140  */
 141 void daemon_set_loglevel(const char *loglevel)
 142 {
 143         int ret = get_loglevel_by_name(loglevel);
 144
 145         assert(ret >= 0);
 146         me->loglevel = ret;
 147 }
 148
 149 /**
 150  * Register functions to be called before and after a message is logged.
 151  *
 152  * \param pre_log_hook Called before the message is logged.
 153  * \param post_log_hook Called after the message is logged.
 154  *
 155  * The purpose of this function is to provide a primitive for multi-threaded
 156  * applications to serialize the access to the log facility, preventing
 157  * interleaving log messages. This can be achieved by having the pre-log hook
 158  * acquire a lock which blocks the other threads on the attempt to log a
 159  * message at the same time.  The post-log hook is responsible for releasing
 160  * the lock.
 161  *
 162  * If these hooks are unnecessary, for example because the application is
 163  * single-threaded, this function does not need to be called.
 164  */
 165 void daemon_set_hooks(void (*pre_log_hook)(void), void (*post_log_hook)(void))
 166 {
 167         me->pre_log_hook = pre_log_hook;
 168         me->post_log_hook = post_log_hook;
 169 }
 170
 171 /**
 172  * Set one of the daemon config flags.
 173  *
 174  * \param flag The flag to set.
 175  *
 176  * \sa \ref daemon_flags.
 177  */
 178 void daemon_set_flag(unsigned flag)
 179 {
 180         me->flags |= flag;
 181 }
 182
 183 static bool daemon_test_flag(unsigned flag)
 184 {
 185         return me->flags & flag;
 186 }
 187
 188 /**
 189  * Do the usual stuff to become a daemon.
 190  *
 191  * \param parent_waits Whether the parent process should pause before exit.
 192  *
 193  * Fork, become session leader, cd to /, and dup fd 0, 1, 2 to /dev/null. If \a
 194  * parent_waits is false, the parent process terminates immediately.
 195  * Otherwise, a pipe is created prior to the fork() and the parent tries to
 196  * read a single byte from the reading end of the pipe. The child is supposed
 197  * to write to the writing end of the pipe after it completed its setup
 198  * procedure successfully. This behaviour is useful to let the parent process
 199  * die with an error if the child process aborts early, since in this case the
 200  * read() will return non-positive.
 201  *
 202  * \return This function either succeeds or calls exit(3). If parent_waits is
 203  * true, the return value is the file descriptor of the writing end of the
 204  * pipe. Otherwise the function returns zero.
 205  *
 206  * \sa fork(2), setsid(2), dup(2), pause(2).
 207  */
 208 int daemonize(bool parent_waits)
 209 {
 210         pid_t pid;
 211         int null, pipe_fd[2];
 212
 213         if (parent_waits && pipe(pipe_fd) < 0)
 214                 goto err;
 215         PARA_INFO_LOG("subsequent log messages go to %s\n", me->logfile_name?
 216                  me->logfile_name : "/dev/null");
 217         pid = fork();
 218         if (pid < 0)
 219                 goto err;
 220         if (pid) { /* parent exits */
 221                 if (parent_waits) {
 222                         char c;
 223                         close(pipe_fd[1]);
 224                         exit(read(pipe_fd[0], &c, 1) <= 0?
 225                                 EXIT_FAILURE : EXIT_SUCCESS);
 226                 }
 227                 exit(EXIT_SUCCESS);
 228         }
 229         if (parent_waits)
 230                 close(pipe_fd[0]);
 231         /* become session leader */
 232         if (setsid() < 0)
 233                 goto err;
 234         me->old_cwd = getcwd(NULL, 0);
 235         if (chdir("/") < 0)
 236                 goto err;
 237         null = open("/dev/null", O_RDWR);
 238         if (null < 0)
 239                 goto err;
 240         if (dup2(null, STDIN_FILENO) < 0)
 241                 goto err;
 242         if (dup2(null, STDOUT_FILENO) < 0)
 243                 goto err;
 244         if (dup2(null, STDERR_FILENO) < 0)
 245                 goto err;
 246         close(null);
 247         return parent_waits? pipe_fd[1] : 0;
 248 err:
 249         PARA_EMERG_LOG("fatal: %s\n", strerror(errno));
 250         exit(EXIT_FAILURE);
 251 }
 252
 253 /**
 254  * Close the log file of the daemon.
 255  */
 256 void daemon_close_log(void)
 257 {
 258         if (!me->logfile)
 259                 return;
 260         PARA_INFO_LOG("closing logfile\n");
 261         fclose(me->logfile);
 262         me->logfile = NULL;
 263 }
 264
 265 /**
 266  * fopen() the logfile in append mode.
 267  *
 268  * \return Either succeeds or exits.
 269  */
 270 void daemon_open_log_or_die(void)
 271 {
 272         FILE *new_log;
 273
 274         if (!me->logfile_name)
 275                 return;
 276         new_log = fopen(me->logfile_name, "a");
 277         if (!new_log) {
 278                 PARA_EMERG_LOG("can not open %s: %s\n", me->logfile_name,
 279                         strerror(errno));
 280                 exit(EXIT_FAILURE);
 281         }
 282         daemon_close_log();
 283         me->logfile = new_log;
 284         /* equivalent to setlinebuf(), but portable */
 285         setvbuf(me->logfile, NULL, _IOLBF, 0);
 286 }
 287
 288 /**
 289  * Log the startup message containing the paraslash version.
 290  *
 291  * \param name The name of the executable.
 292  *
 293  * First the given \a name is prefixed with the string "para_". Next the git
 294  * version is appended. The resulting string is logged with priority "INFO".
 295  */
 296 void daemon_log_welcome(const char *name)
 297 {
 298         PARA_INFO_LOG("welcome to para_%s-" PACKAGE_VERSION " \n", name);
 299 }
 300
 301 /**
 302  * Renice the calling process.
 303  *
 304  * \param prio The priority value to set.
 305  *
 306  * Errors are not considered fatal, but a warning message is logged if the
 307  * underlying call to setpriority(2) fails.
 308  */
 309 void daemon_set_priority(int prio)
 310 {
 311         if (setpriority(PRIO_PROCESS, 0, prio) < 0)
 312                 PARA_WARNING_LOG("could not set priority to %d: %s\n", prio,
 313                         strerror(errno));
 314 }
 315
 316 /**
 317  * Give up superuser privileges.
 318  *
 319  * \param username The user to switch to.
 320  * \param groupname The group to switch to.
 321  *
 322  * This function returns immediately if not invoked with EUID zero. Otherwise,
 323  * it tries to obtain the GID of \a groupname and the UID of \a username.  On
 324  * success, effective and real GID/UID and the saved set-group-ID/set-user-ID
 325  * are all set accordingly. On errors, an appropriate message is logged and
 326  * exit() is called to terminate the process.
 327  *
 328  * \sa getpwnam(3), getuid(2), setuid(2), getgrnam(2), setgid(2)
 329  */
 330 void daemon_drop_privileges_or_die(const char *username, const char *groupname)
 331 {
 332         struct passwd *p;
 333         char *tmp;
 334
 335         if (geteuid())
 336                 return;
 337         if (groupname) {
 338                 struct group *g = getgrnam(groupname);
 339                 if (!g) {
 340                         PARA_EMERG_LOG("failed to get group %s: %s\n",
 341                                 groupname, strerror(errno));
 342                         exit(EXIT_FAILURE);
 343                 }
 344                 if (setgid(g->gr_gid) < 0) {
 345                         PARA_EMERG_LOG("failed to set group id %d: %s\n",
 346                                 (int)g->gr_gid, strerror(errno));
 347                         exit(EXIT_FAILURE);
 348                 }
 349         }
 350         if (!username) {
 351                 PARA_EMERG_LOG("root privileges, but no user option given\n");
 352                 exit(EXIT_FAILURE);
 353         }
 354         tmp = para_strdup(username);
 355         p = getpwnam(tmp);
 356         free(tmp);
 357         if (!p) {
 358                 PARA_EMERG_LOG("%s: no such user\n", username);
 359                 exit(EXIT_FAILURE);
 360         }
 361         PARA_INFO_LOG("dropping root privileges\n");
 362         if (setuid(p->pw_uid) < 0) {
 363                 PARA_EMERG_LOG("failed to set effective user ID (%s)",
 364                         strerror(errno));
 365                 exit(EXIT_FAILURE);
 366         }
 367         PARA_DEBUG_LOG("uid: %d, euid: %d\n", (int)getuid(), (int)geteuid());
 368 }
 369
 370 /**
 371  * Set the startup time.
 372  *
 373  * This should be called once on startup. It sets the start time to the
 374  * current time. The stored time is used for retrieving the server uptime.
 375  *
 376  * \sa time(2), \ref daemon_get_uptime(), \ref daemon_get_uptime_str().
 377  */
 378 void daemon_set_start_time(void)
 379 {
 380         time(&me->startuptime);
 381 }
 382
 383 /**
 384  * Get the uptime.
 385  *
 386  * \param current_time The current time.
 387  *
 388  * The \a current_time pointer may be \p NULL. In this case the function
 389  * obtains the current time from the system.
 390  *
 391  * \return This returns the server uptime in seconds, i.e. the difference
 392  * between the current time and the value stored previously via \ref
 393  * daemon_set_start_time().
 394  */
 395 time_t daemon_get_uptime(const struct timeval *current_time)
 396 {
 397         time_t t;
 398
 399         if (current_time)
 400                 return current_time->tv_sec - me->startuptime;
 401         time(&t);
 402         return difftime(t, me->startuptime);
 403 }
 404
 405 /**
 406  * Construct a string containing the current uptime.
 407  *
 408  * \param current_time See a \ref daemon_get_uptime().
 409  *
 410  * \return A dynamically allocated string of the form "days:hours:minutes".
 411  */
 412 __malloc char *daemon_get_uptime_str(const struct timeval *current_time)
 413 {
 414         long t = daemon_get_uptime(current_time);
 415         return make_message("%li:%02li:%02li", t / 86400,
 416                 (t / 3600) % 24, (t / 60) % 60);
 417 }
 418
 419 /**
 420  * The log function for para_server and para_audiod.
 421  *
 422  * \param ll The log level.
 423  * \param fmt The format string describing the log message.
 424  */
 425 __printf_2_3 void daemon_log(int ll, const char* fmt,...)
 426 {
 427         va_list argp;
 428         FILE *fp;
 429         struct tm *tm;
 430         char *color;
 431         bool log_time = daemon_test_flag(DF_LOG_TIME), log_timing =
 432                 daemon_test_flag(DF_LOG_TIMING);
 433
 434         ll = PARA_MIN(ll, NUM_LOGLEVELS - 1);
 435         ll = PARA_MAX(ll, LL_DEBUG);
 436         if (ll < me->loglevel)
 437                 return;
 438
 439         fp = me->logfile? me->logfile : stderr;
 440         if (me->pre_log_hook)
 441                 me->pre_log_hook();
 442         color = daemon_test_flag(DF_COLOR_LOG)? me->log_colors[ll] : NULL;
 443         if (color)
 444                 fprintf(fp, "%s", color);
 445         if (log_time || log_timing) {
 446                 struct timeval tv;
 447                 clock_get_realtime(&tv);
 448                 if (daemon_test_flag(DF_LOG_TIME)) { /* print date and time */
 449                         time_t t1 = tv.tv_sec;
 450                         char str[100];
 451                         tm = localtime(&t1);
 452                         strftime(str, sizeof(str), "%b %d %H:%M:%S", tm);
 453                         fprintf(fp, "%s%s", str, log_timing? ":" : " ");
 454                 }
 455                 if (log_timing) /* print milliseconds */
 456                         fprintf(fp, "%04lu ", (long unsigned)tv.tv_usec / 1000);
 457         }
 458         if (daemon_test_flag(DF_LOG_HOSTNAME)) {
 459                 if (!me->hostname)
 460                         me->hostname = para_hostname();
 461                 fprintf(fp, "%s ", me->hostname);
 462         }
 463         if (daemon_test_flag(DF_LOG_LL)) /* log loglevel */
 464                 fprintf(fp, "(%d) ", ll);
 465         if (daemon_test_flag(DF_LOG_PID)) { /* log pid */
 466                 pid_t mypid = getpid();
 467                 fprintf(fp, "(%d) ", (int)mypid);
 468         }
 469         va_start(argp, fmt);
 470         vfprintf(fp, fmt, argp);
 471         va_end(argp);
 472         if (color)
 473                 fprintf(fp, "%s", COLOR_RESET);
 474         if (me->post_log_hook)
 475                 me->post_log_hook();
 476 }