/* $Id: smtpdcheck.c,v 1.5 2004/12/28 16:37:25 dm Exp $ */

/*
 *
 * Copyright (C) 2004 David Mazieres (dm@uun.org)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2, or (at
 * your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 * USA
 *
 */

#include "avutil.h"
#include <ctype.h>
#include <setjmp.h>
#include <signal.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include "getopt_long.h"

char *progname;
char *stop_name;
struct in_addr stop_ip;
int stop_ip_set;

#ifndef HAVE_STRCASECMP
int
strcasecmp (const char *s1, const char *s2)
{
  while (tolower (*s1) == tolower (*s2++))
    if (!*s1++)
      return 0;
  return tolower (*s1) - tolower (s2[-1]);
}
#endif /* HAVE_STRCASECMP */

static int
check_stop (struct hostent *h)
{
  int i;
  if (stop_name && !strcasecmp (stop_name, h->h_name))
    return 1;
  for (i = 0; h->h_addr_list[i]; i++)
    if (stop_ip.s_addr == ((struct in_addr *) h->h_addr_list[i])->s_addr)
      return 1;
  return 0;
}

static sigjmp_buf tmojump;
static void
dojump (int sig)
{
  siglongjmp (tmojump, sig);
}

/* Return: 1 if server ok, 0 if server not ok, -1 if stop */
static int
check_server (const char *name, int timeout)
{
  struct hostent *h;
  struct sockaddr_in sin;
  int s;
  struct sigaction sa, osa;
  int n;
  char buf[4];

  s = socket (AF_INET, SOCK_STREAM, 0);
  bzero (&sin, sizeof (sin));
  sin.sin_family = AF_INET;
  if (s < 0 || bind (s, (struct sockaddr *) &sin, sizeof (sin)) < 0) {
    perror ("TCP socket");
    exit (2);
  }
  sin.sin_port = htons (25);

  bzero (&sa, sizeof (sa));
  sa.sa_handler = dojump;
  sa.sa_flags = SA_RESETHAND;
  if (sigaction (SIGALRM, &sa, &osa) < 0) {
    perror ("sigaction");
    exit (2);
  }
  if (sigsetjmp (tmojump, 1)) {
    sigaction (SIGALRM, &osa, NULL);
    close (s);
    return 0;
  }
  alarm (timeout);

  h = gethostbyname (name);
  if (!h) {
    alarm (0);
    sigaction (SIGALRM, &osa, NULL);
    close (s);
    return 0;
  }
  sin.sin_addr = *(struct in_addr *) h->h_addr;

  if (check_stop (h)) {
    alarm (0);
    sigaction (SIGALRM, &osa, NULL);
    close (s);
    return -1;
  }

  if (connect (s, (struct sockaddr *) &sin, sizeof (sin)) < 0) {
    alarm (0);
    sigaction (SIGALRM, &osa, NULL);
    close (s);
    return 0;
  }

  n = read (s, buf, sizeof (buf));
  alarm (0);
  sigaction (SIGALRM, &osa, NULL);
  close (s);

  if (n < 4 || buf[0] != '2' || !isdigit (buf[1]) || !isdigit (buf[2])
      || (buf[3] != ' ' && buf[3] != '-' && buf[3] != '\r'))
    return 0;
  return 1;
}

static void usage (void) __attribute__ ((noreturn));
static void
usage (void)
{
  fprintf (stderr,
	   "usage: %s [--stop {ip-addr|name}] [prio:]server1"
	   " [[prio:]server2 ...]\n",
	   progname);
  exit (1);
}

int
main (int argc, char **argv)
{
  struct option o[] = {
    { "version", no_argument, NULL, 'v' },
    { "stop", required_argument, NULL, 's' },
    { "timeout", required_argument, NULL, 't' },
    { NULL, 0, NULL, 0 }
  };
  int c, n;
  int timeout = 10;
  int ok_pri = -1;
  char *ok_name = NULL;

  progname = strrchr (argv[0], '/');
  if (progname)
    progname++;
  else
    progname = argv[0];

  while ((c = getopt_long (argc, argv, "+s:t:", o, NULL)) != -1)
    switch (c) {
    case 'v':
      version (progname, 1);
      break;
    case 's':
      if (stop_ip_set || stop_name)
	usage ();
      else if (inet_aton (optarg, &stop_ip) == 1)
	stop_ip_set = 1;
      else {
	struct hostent *h = gethostbyname (optarg);
	if (!h) {
	  fprintf (stderr, "%s: no such host\n", optarg);
	  exit (2);
	}
	stop_name = xmalloc (1 + strlen (h->h_name));
	strcpy (stop_name, h->h_name);
	stop_ip_set = 1;
	stop_ip = *(struct in_addr *) h->h_addr;
      }
      break;
    case 't':
      if (sscanf (optarg, "%u%n", &timeout, &n) != 1
	  || timeout < 0 || (size_t) n != strlen (optarg))
	usage ();
      break;
    default:
      usage ();
    }

  for (; optind < argc; optind++) {
    int pri;
    char *p;
    n = 0;
    sscanf (argv[optind], "%d:%n", &pri, &n);
    if (!n) {
      pri = -1;
      p = argv[optind];
    }
    else
      p = argv[optind] + n;

    if (ok_name && pri > ok_pri)
      break;

    switch (check_server (p, timeout)) {
    case -1:
      exit (0);
      break;
    case 1:
      ok_name = p;
      ok_pri = pri;
      break;
    }
  }

  if (ok_name) {
    printf ("%s\n", ok_name);
    exit (1);
  }

  exit (0);
}