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1.4.33

    1: /**
    2:  * angel process for lighttpd 
    3:  *
    4:  * the purpose is the run as root all the time and handle:
    5:  * - restart on crash
    6:  * - spawn on HUP to allow graceful restart
    7:  * - ...
    8:  *
    9:  * it has to stay safe and small to be trustable
   10:  */
   11: 
   12: #include <sys/wait.h>
   13: 
   14: #include <stdlib.h>
   15: #include <stdio.h>
   16: #include <string.h>
   17: #include <errno.h>
   18: #include <unistd.h>
   19: #include <time.h>
   20: #include <signal.h>
   21: 
   22: #define BINPATH SBIN_DIR"/lighttpd"
   23: 
   24: static siginfo_t last_sigterm_info;
   25: static siginfo_t last_sighup_info;
   26: 
   27: static volatile sig_atomic_t start_process    = 1;
   28: static volatile pid_t pid = -1;
   29: 
   30: #define UNUSED(x) ( (void)(x) )
   31: 
   32: static void sigaction_handler(int sig, siginfo_t *si, void *context) {
   33: 	int exitcode;
   34: 
   35: 	UNUSED(context);
   36: 	switch (sig) {
   37: 	case SIGINT: 
   38: 	case SIGTERM:
   39: 		memcpy(&last_sigterm_info, si, sizeof(*si));
   40: 
   41: 		/** forward the sig to the child */
   42: 		kill(pid, sig);
   43: 		break;
   44: 	case SIGHUP: /** do a graceful restart */
   45: 		memcpy(&last_sighup_info, si, sizeof(*si));
   46: 
   47: 		/** do a graceful shutdown on the main process and start a new child */
   48: 		kill(pid, SIGINT);
   49: 
   50: 		usleep(5 * 1000); /** wait 5 microsec */
   51: 		
   52: 		start_process = 1;
   53: 		break;
   54: 	case SIGCHLD:
   55: 		/** a child died, de-combie it */
   56: 		wait(&exitcode);
   57: 		break;
   58: 	}
   59: }
   60: 
   61: int main(int argc, char **argv) {
   62: 	int is_shutdown = 0;
   63: 	struct sigaction act;
   64: 
   65: 	UNUSED(argc);
   66: 
   67: 	/**
   68: 	 * we are running as root BEWARE
   69: 	 */
   70: 
   71: 	memset(&act, 0, sizeof(act));
   72: 	act.sa_handler = SIG_IGN;
   73: 	sigaction(SIGPIPE, &act, NULL);
   74: 	sigaction(SIGUSR1, &act, NULL);
   75: 
   76: 	act.sa_sigaction = sigaction_handler;
   77: 	sigemptyset(&act.sa_mask);
   78: 	act.sa_flags = SA_SIGINFO;
   79: 
   80: 	sigaction(SIGINT,  &act, NULL);
   81: 	sigaction(SIGTERM, &act, NULL);
   82: 	sigaction(SIGHUP,  &act, NULL);
   83: 	sigaction(SIGALRM, &act, NULL);
   84: 	sigaction(SIGCHLD, &act, NULL);
   85: 
   86: 	/* check that the compiled in path has the right user,
   87: 	 *
   88: 	 * BEWARE: there is a race between the check here and the exec later
   89: 	 */
   90: 
   91: 	while (!is_shutdown) {
   92: 		int exitcode = 0;
   93: 
   94: 		if (start_process) {
   95: 			pid = fork();
   96: 
   97: 			if (0 == pid) {
   98: 				/* i'm the child */
   99: 
  100: 				argv[0] = BINPATH;
  101: 
  102: 				execvp(BINPATH, argv);
  103: 
  104: 				exit(1);
  105: 			} else if (-1 == pid) {
  106: 				/** error */
  107: 
  108: 				return -1;
  109: 			}
  110: 
  111: 			/* I'm the angel */
  112: 			start_process = 0;
  113: 		}
  114: 	       
  115: 		if ((pid_t)-1 == waitpid(pid, &exitcode, 0)) {
  116: 			switch (errno) {
  117: 			case EINTR:
  118: 				/* someone sent a signal ... 
  119: 				 * do we have to shutdown or restart the process */
  120: 				break;
  121: 			case ECHILD:
  122: 				/** 
  123: 				 * make sure we are not in a race between the signal handler
  124: 				 * and the process restart */
  125: 				if (!start_process) is_shutdown = 1;
  126: 				break;
  127: 			default:
  128: 				break;
  129: 			}
  130: 		} else {
  131: 			/** process went away */
  132: 
  133: 			if (WIFEXITED(exitcode)) {
  134: 				/** normal exit */
  135: 
  136: 				is_shutdown = 1;
  137: 
  138: 				fprintf(stderr, "%s.%d: child (pid=%d) exited normally with exitcode: %d\n", 
  139: 						__FILE__, __LINE__,
  140: 						pid,
  141: 						WEXITSTATUS(exitcode));
  142: 
  143: 			} else if (WIFSIGNALED(exitcode)) {
  144: 				/** got a signal */
  145: 
  146: 				fprintf(stderr, "%s.%d: child (pid=%d) exited unexpectedly with signal %d, restarting\n", 
  147: 						__FILE__, __LINE__,
  148: 						pid,
  149: 						WTERMSIG(exitcode));
  150: 
  151: 				start_process = 1;
  152: 			}
  153: 		}
  154: 	}
  155: 
  156: 	return 0;
  157: }
  158: