/*
 * dumputmp.c
 *
 * Usage: dumputmp [-w pafh] [-u path] [-p pid]
 *
 * by shj@netwiz.co.jp
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <fcntl.h>
#include <unistd.h>
#include <utmp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <netdb.h>

int
dns_lookup(char *result, int size, int32_t *a)
{
    struct sockaddr_in sin;
    struct sockaddr_in6 sin6;
    struct sockaddr *sa;
    int salen, flags;
    int mapped = 0;

    if (a[0] == 0 && a[1] == 0 && a[2] == (int32_t)htonl (0xffff))
        mapped = 1;

    if (mapped || (a[1] == 0 && a[2] == 0 && a[3] == 0)) {
        /* IPv4 */
        sin.sin_family = AF_INET;
        sin.sin_port = 0;
        sin.sin_addr.s_addr = mapped ? a[3] : a[0];
        sa = (struct sockaddr *)&sin;
        salen = sizeof(sin);
    } else {
        /* IPv6 */
        memset(&sin6, 0, sizeof(sin6));
        sin6.sin6_family = AF_INET6;
        sin6.sin6_port = 0;
        memcpy(sin6.sin6_addr.s6_addr, a, 16);
        sa = (struct sockaddr *)&sin6;
        salen = sizeof(sin6);
    }

    return getnameinfo(sa, salen, result, size, NULL, 0, NI_NUMERICHOST);
}

int
fetchtmp(char *file, pid_t pid, int use_pid)
{
    struct utmp utmp;
    struct tm *tm;
    time_t t;
    int fd, count = 1;
    int year, month, day, hour, min, sec, usec;
    char domain[256];
    char buf[128];

    if ((fd = open(file, O_RDONLY)) >= 0)
    {
        while(read(fd, &utmp, sizeof(struct utmp))) {
            if (use_pid == 0 || (use_pid != 0 && pid == utmp.ut_pid)) {
                printf("FIELD NO.%d\n", count);
                printf("  TYPE   : %u\n", utmp.ut_type);
                printf("  PID    : %d\n", utmp.ut_pid);
                printf("  LINE   : %s\n", utmp.ut_line);
                printf("  ID     : %s\n", utmp.ut_id);
                printf("  USER   : %s\n", utmp.ut_user);
                printf("  HOST   : %s\n", utmp.ut_host);
                printf("  SESSION: %u\n", utmp.ut_session);

                dns_lookup(domain, sizeof(domain), (int32_t *)&utmp.ut_addr_v6);
                printf("  ADDR   : %s\n", domain);

                t = utmp.ut_tv.tv_sec;
                tm = localtime((time_t *)&t);
                strftime(buf, sizeof(buf), "%Y/%m/%d %H:%M:%S", tm);
                printf("  TIME   : %s\n", buf);
            }
            count++;
        }
        close(fd);
        return count;
    }
}

int
main(int argc, char *argv[])
{
    char *wtmp = "/var/log/wtmp";
    char *utmp = "/var/run/utmp";
    pid_t pid = 0;
    int use_pid = 0;
    int opt;

    while ((opt = getopt(argc, argv, "u:w:p:")) != -1) {
        switch (opt) {
          case 'w':
              wtmp = optarg;
              break;
          case 'u':
              utmp = optarg;
              break;
         case 'p':
              use_pid = 1;
              pid = atoi(optarg);
              break;
        }
    }

    printf("======== WTMP: %s ========\n", wtmp);
    fetchtmp(wtmp, pid, use_pid);
    
    printf("======== UTMP: %s ========\n", utmp);
    fetchtmp(utmp, pid, use_pid);

    return 0;
}