crossfire-loop.c

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/* This is a watchdog pgrogram from Christian Stieber.  It is not an
 * officially supported piece of crossfire (I hope it works, but I am not
 * going to be spending time debugging problems in this piece of code).  The
 * idea is that it periodically sends/gets udp messages to the server - if
 * the server isn't responding, it kills it off and starts a new one.  There
 * is a bit more logic to it - From Christian:
 *
 * The wrapper is just a hack. I'm using it on a Solaris machine, and it
 * seems to work fine. Notable features:
 * - uses the watchdog interface
 * - if the server crashes more than 10 times, with the time between
 *   successive crashes being less than 30 seconds, the wrapper terminates
 *   itself (to prevent bringing down the machine in case of startup problems)
 * - the server runs at nice 10
 *
 * Note that the main advantage the watchdog has over just the simple
 * crossloop scripts is in the case of infinite loops.  For simple crashes,
 * the crossloop programs do a fine job.
 */

/*
 * Version 1
 */

/************************************************************************/
/*
 * Configuration options
 */

/* server executable */
#define CROSSFIRE_SERVER        "/usr/stud/stieber/bin/server"

/* directory to cd to before starting the server */
#define CROSSFIRE_TMPDIR        "/usr/stud/stieber/crossfire/tmp/"

/* if the server crashes more than CRASH_COUNT times, with less than
 * CRASH_INTERVAL seconds between two successive crashes, the loop
 * program is terminated. */
#define CRASH_COUNT             10
#define CRASH_INTERVAL          30

#define USE_WATCHDOG
#define ERROR_SLEEP             30

/************************************************************************/

#include <sys/unistd.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <signal.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <errno.h>

/************************************************************************/

#ifdef USE_WATCHDOG
int Pipe[2];
#endif

/************************************************************************/

void SignalHandler(int Unused) {
    if (write(Pipe[1], "", 1) != 1) {
        perror("Pipe");
        exit(EXIT_FAILURE);
    }
}

/************************************************************************/

int main(void) {
    int CrashCount;
#ifdef USE_WATCHDOG
    struct protoent *protoent;
    struct sockaddr_in insock;
    int fd;

    memset(&insock, 0, sizeof(insock));

    if ((protoent = getprotobyname("udp")) == NULL) {
        perror("Can't get protobyname");
        return EXIT_FAILURE;
    }
    if ((fd = socket(PF_INET, SOCK_DGRAM, protoent->p_proto)) == -1) {
        perror("Can't create socket");
        return EXIT_FAILURE;
    }
    insock.sin_family = AF_INET;
    insock.sin_port = htons((unsigned short)13325);
    if (bind(fd, (struct sockaddr *)&insock, sizeof(insock)) == -1) {
        perror("Error on bind");
        return EXIT_FAILURE;
    }
#endif

    CrashCount = 0;
    nice(10-nice(0));
    while (CrashCount < CRASH_COUNT) {
        time_t StartTime;
        time_t EndTime;
        pid_t Server;

        chdir(CROSSFIRE_TMPDIR);
        time(&StartTime);
#ifdef USE_WATCHDOG
        if (pipe(Pipe) == 0) {
            void (*OldHandler)(int);

            OldHandler = signal(SIGCHLD, SignalHandler);
#endif
            switch (Server = fork()) {
            case 0:
                execl(CROSSFIRE_SERVER, CROSSFIRE_SERVER, "-server", NULL);
                return EXIT_FAILURE;

            case -1:
                sleep(ERROR_SLEEP);
                break;

            default:
#ifdef USE_WATCHDOG
                while (1) {
                    fd_set Files;
                    struct timeval Timeout;
                    int Max;

                    FD_ZERO(&Files);
                    FD_SET(Pipe[0], &Files);
                    FD_SET(fd, &Files);
                    Timeout.tv_sec = 5*60;
                    Timeout.tv_usec = 0;
                    if (fd > Pipe[0]) {
                        Max = fd+1;
                    } else {
                        Max = Pipe[0]+1;
                    }
                    while (select(Max, &Files, NULL, NULL, &Timeout) == -1) {
                        if (errno != EINTR) {
                            perror("Error on select");
                            return EXIT_FAILURE;
                        }
                    }
                    if (FD_ISSET(Pipe[0], &Files)) {
                        /* crash */
                        unlink("core");
                        waitpid(Server, NULL, 0);
                        printf("Server crash!\n");
                        break;
                    } else if (FD_ISSET(fd, &Files)) {
                        /* watchdog */
                        char t;

                        recv(fd, &t, 1, 0);
                    } else {
                        /* timeout */
                        printf("Watchdog timeout!\n");
                        if (kill(Server, SIGKILL) != 0) {
                            perror("Error on kill");
                            return EXIT_FAILURE;
                        }
                    }
                }
#else
                waitpid(Server, NULL, 0);
#endif
#ifdef USE_WATCHDOG
                signal(SIGCHLD, OldHandler);
#endif
                time(&EndTime);
                if (EndTime-StartTime < CRASH_INTERVAL) {
                    CrashCount++;
                } else {
                    CrashCount = 0;
                }
                break;
            }
#ifdef USE_WATCHDOG
            close(Pipe[0]);
            close(Pipe[1]);
        } else {
            sleep(ERROR_SLEEP);
        }
#endif
    }
#ifdef USE_WATCHDOG
    close(fd);
#endif
    return 0;
}