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/**
* angel process for lighttpd
*
* the purpose is the run as root all the time and handle:
* - restart on crash
* - spawn on HUP to allow graceful restart
* - ...
*
* it has to stay safe and small to be trustable
*/
#include <sys/wait.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <time.h>
#include <signal.h>
#define BINPATH SBIN_DIR"/lighttpd"
static siginfo_t last_sigterm_info;
static siginfo_t last_sighup_info;
static volatile sig_atomic_t start_process = 1;
static volatile sig_atomic_t graceful_restart = 0;
static volatile pid_t pid = -1;
#define UNUSED(x) ( (void)(x) )
static void sigaction_handler(int sig, siginfo_t *si, void *context) {
int exitcode;
UNUSED(context);
switch (sig) {
case SIGINT:
case SIGTERM:
memcpy(&last_sigterm_info, si, sizeof(*si));
/** forward the sig to the child */
kill(pid, sig);
break;
case SIGHUP: /** do a graceful restart */
memcpy(&last_sighup_info, si, sizeof(*si));
/** do a graceful shutdown on the main process and start a new child */
kill(pid, SIGINT);
usleep(5 * 1000); /** wait 5 microsec */
start_process = 1;
break;
case SIGCHLD:
/** a child died, de-combie it */
wait(&exitcode);
break;
}
}
int main(int argc, char **argv) {
int is_shutdown = 0;
struct sigaction act;
UNUSED(argc);
/**
* we are running as root BEWARE
*/
memset(&act, 0, sizeof(act));
act.sa_handler = SIG_IGN;
sigaction(SIGPIPE, &act, NULL);
sigaction(SIGUSR1, &act, NULL);
act.sa_sigaction = sigaction_handler;
sigemptyset(&act.sa_mask);
act.sa_flags = SA_SIGINFO;
sigaction(SIGINT, &act, NULL);
sigaction(SIGTERM, &act, NULL);
sigaction(SIGHUP, &act, NULL);
sigaction(SIGALRM, &act, NULL);
sigaction(SIGCHLD, &act, NULL);
/* check that the compiled in path has the right user,
*
* BEWARE: there is a race between the check here and the exec later
*/
while (!is_shutdown) {
int exitcode = 0;
if (start_process) {
pid = fork();
if (0 == pid) {
/* i'm the child */
argv[0] = BINPATH;
execvp(BINPATH, argv);
exit(1);
} else if (-1 == pid) {
/** error */
return -1;
}
/* I'm the angel */
start_process = 0;
}
if ((pid_t)-1 == waitpid(pid, &exitcode, 0)) {
switch (errno) {
case EINTR:
/* someone sent a signal ...
* do we have to shutdown or restart the process */
break;
case ECHILD:
/**
* make sure we are not in a race between the signal handler
* and the process restart */
if (!start_process) is_shutdown = 1;
break;
default:
break;
}
} else {
/** process went away */
if (WIFEXITED(exitcode)) {
/** normal exit */
is_shutdown = 1;
fprintf(stderr, "%s.%d: child (pid=%d) exited normally with exitcode: %d\n",
__FILE__, __LINE__,
pid,
WEXITSTATUS(exitcode));
} else if (WIFSIGNALED(exitcode)) {
/** got a signal */
fprintf(stderr, "%s.%d: child (pid=%d) exited unexpectedly with signal %d, restarting\n",
__FILE__, __LINE__,
pid,
WTERMSIG(exitcode));
start_process = 1;
}
}
}
return 0;
}
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