Merge changes from CUPS trunk, r7566.

[thirdparty/cups.git] / backend / snmp.c

/*
 * "$Id: snmp.c 6649 2007-07-11 21:46:42Z mike $"
 *
 *   SNMP discovery backend for the Common UNIX Printing System (CUPS).
 *
 *   Copyright 2007-2008 by Apple Inc.
 *   Copyright 2006-2007 by Easy Software Products, all rights reserved.
 *
 *   These coded instructions, statements, and computer programs are the
 *   property of Apple Inc. and are protected by Federal copyright
 *   law.  Distribution and use rights are outlined in the file "LICENSE.txt"
 *   "LICENSE" which should have been included with this file.  If this
 *   file is missing or damaged, see the license at "http://www.cups.org/".
 *
 *   This file is subject to the Apple OS-Developed Software exception.
 *
 * Contents:
 *
 *   main()                    - Discover printers via SNMP.
 *   add_array()               - Add a string to an array.
 *   add_cache()               - Add a cached device...
 *   add_device_uri()          - Add a device URI to the cache.
 *   alarm_handler()           - Handle alarm signals...
 *   compare_cache()           - Compare two cache entries.
 *   debug_printf()            - Display some debugging information.
 *   fix_make_model()          - Fix common problems in the make-and-model
 *                               string.
 *   free_array()              - Free an array of strings.
 *   free_cache()              - Free the array of cached devices.
 *   get_interface_addresses() - Get the broadcast address(es) associated with
 *                               an interface.
 *   list_device()             - List a device we found...
 *   password_cb()             - Handle authentication requests.
 *   probe_device()            - Probe a device to discover whether it is a
 *                               printer.
 *   read_snmp_conf()          - Read the snmp.conf file.
 *   read_snmp_response()      - Read and parse a SNMP response...
 *   run_time()                - Return the total running time...
 *   scan_devices()            - Scan for devices using SNMP.
 *   try_connect()             - Try connecting on a port...
 *   update_cache()            - Update a cached device...
 */

/*
 * Include necessary headers.
 */

#include "backend-private.h"
#include <cups/array.h>
#include <cups/file.h>
#include <cups/http-private.h>
#include <regex.h>


/*
 * This backend implements SNMP printer discovery.  It uses a broadcast-
 * based approach to get SNMP response packets from potential printers,
 * requesting OIDs from the Host and Port Monitor MIBs, does a URI
 * lookup based on the device description string, and finally a probe of
 * port 9100 (AppSocket) and 515 (LPD).
 *
 * The current focus is on printers with internal network cards, although
 * the code also works with many external print servers as well.
 *
 * The backend reads the snmp.conf file from the CUPS_SERVERROOT directory
 * which can contain comments, blank lines, or any number of the following
 * directives:
 *
 *     Address ip-address
 *     Address @LOCAL
 *     Address @IF(name)
 *     Community name
 *     DebugLevel N
 *     DeviceURI "regex pattern" uri
 *     HostNameLookups on
 *     HostNameLookups off
 *     MaxRunTime N
 *
 * The default is to use:
 *
 *     Address @LOCAL
 *     Community public
 *     DebugLevel 0
 *     HostNameLookups off
 *     MaxRunTime 120
 *
 * This backend is known to work with the following network printers and
 * print servers:
 *
 *     Axis OfficeBasic, 5400, 5600
 *     Brother
 *     EPSON
 *     Genicom
 *     HP JetDirect
 *     Lexmark
 *     Sharp
 *     Tektronix
 *     Xerox
 *
 * It does not currently work with:
 *
 *     DLink
 *     Linksys
 *     Netgear
 *     Okidata
 *
 * (for all of these, they do not support the Host MIB)
 */

/*
 * Types...
 */

typedef struct device_uri_s             /**** DeviceURI values ****/
{
  regex_t       re;                     /* Regular expression to match */
  cups_array_t  *uris;                  /* URIs */
} device_uri_t;

typedef struct snmp_cache_s             /**** SNMP scan cache ****/
{
  http_addr_t   address;                /* Address of device */
  char          *addrname,              /* Name of device */
                *uri,                   /* device-uri */
                *id,                    /* device-id */
                *info,                  /* device-info */
                *make_and_model;        /* device-make-and-model */
} snmp_cache_t;


/*
 * Private CUPS API to set the last error...
 */

extern void             _cupsSetError(ipp_status_t status, const char *message);


/*
 * Local functions...
 */

static char             *add_array(cups_array_t *a, const char *s);
static void             add_cache(http_addr_t *addr, const char *addrname,
                                  const char *uri, const char *id,
                                  const char *make_and_model);
static device_uri_t     *add_device_uri(char *value);
static void             alarm_handler(int sig);
static int              compare_cache(snmp_cache_t *a, snmp_cache_t *b);
static void             debug_printf(const char *format, ...);
static void             fix_make_model(char *make_model,
                                       const char *old_make_model,
                                       int make_model_size);
static void             free_array(cups_array_t *a);
static void             free_cache(void);
static http_addrlist_t  *get_interface_addresses(const char *ifname);
static void             list_device(snmp_cache_t *cache);
static const char       *password_cb(const char *prompt);
static void             probe_device(snmp_cache_t *device);
static void             read_snmp_conf(const char *address);
static void             read_snmp_response(int fd);
static double           run_time(void);
static void             scan_devices(int fd);
static int              try_connect(http_addr_t *addr, const char *addrname,
                                    int port);
static void             update_cache(snmp_cache_t *device, const char *uri,
                                     const char *id, const char *make_model);


/*
 * Local globals...
 */

static cups_array_t     *Addresses = NULL;
static cups_array_t     *Communities = NULL;
static cups_array_t     *Devices = NULL;
static int              DebugLevel = 0;
static const int        DeviceDescOID[] = { CUPS_OID_hrDeviceDescr, 1, -1 };
static unsigned         DeviceDescRequest;
static const int        DeviceTypeOID[] = { CUPS_OID_hrDeviceType, 1, -1 };
static unsigned         DeviceTypeRequest;
static const int        DeviceIdOID[] = { CUPS_OID_ppmPrinterIEEE1284DeviceId, 1, -1 };
static unsigned         DeviceIdRequest;
static const int        DeviceUriOID[] = { CUPS_OID_ppmPortServiceNameOrURI, 1, 1, -1 };
static unsigned         DeviceUriRequest;
static cups_array_t     *DeviceURIs = NULL;
static int              HostNameLookups = 0;
static int              MaxRunTime = 120;
static struct timeval   StartTime;


/*
 * 'main()' - Discover printers via SNMP.
 */

int                                     /* O - Exit status */
main(int  argc,                         /* I - Number of command-line arguments (6 or 7) */
     char *argv[])                      /* I - Command-line arguments */
{
  int           fd;                     /* SNMP socket */
#if defined(HAVE_SIGACTION) && !defined(HAVE_SIGSET)
  struct sigaction action;              /* Actions for POSIX signals */
#endif /* HAVE_SIGACTION && !HAVE_SIGSET */


 /*
  * Check command-line options...
  */

  if (argc > 2)
  {
    fputs(_("Usage: snmp [host-or-ip-address]\n"), stderr);
    return (1);
  }

 /*
  * Set the password callback for IPP operations...
  */

  cupsSetPasswordCB(password_cb);

 /*
  * Catch SIGALRM signals...
  */

#ifdef HAVE_SIGSET
  sigset(SIGALRM, alarm_handler);
#elif defined(HAVE_SIGACTION)
  memset(&action, 0, sizeof(action));

  sigemptyset(&action.sa_mask);
  sigaddset(&action.sa_mask, SIGALRM);
  action.sa_handler = alarm_handler;
  sigaction(SIGALRM, &action, NULL);
#else
  signal(SIGALRM, alarm_handler);
#endif /* HAVE_SIGSET */

 /*
  * Open the SNMP socket...
  */

  if ((fd = _cupsSNMPOpen(AF_INET)) < 0)
    return (1);

 /*
  * Read the configuration file and any cache data...
  */

  read_snmp_conf(argv[1]);

  _cupsSNMPSetDebug(DebugLevel);

  Devices = cupsArrayNew((cups_array_func_t)compare_cache, NULL);

 /*
  * Scan for devices...
  */

  scan_devices(fd);

 /*
  * Close, free, and return with no errors...
  */

  _cupsSNMPClose(fd);

  free_array(Addresses);
  free_array(Communities);
  free_cache();

  return (0);
}


/*
 * 'add_array()' - Add a string to an array.
 */

static char *                           /* O - New string */
add_array(cups_array_t *a,              /* I - Array */
          const char   *s)              /* I - String to add */
{
  char  *dups;                          /* New string */


  dups = strdup(s);

  cupsArrayAdd(a, dups);

  return (dups);
}


/*
 * 'add_cache()' - Add a cached device...
 */

static void
add_cache(http_addr_t *addr,            /* I - Device IP address */
          const char  *addrname,        /* I - IP address or name string */
          const char  *uri,             /* I - Device URI */
          const char  *id,              /* I - 1284 device ID */
          const char  *make_and_model)  /* I - Make and model */
{
  snmp_cache_t  *temp;                  /* New device entry */


  debug_printf("DEBUG: add_cache(addr=%p, addrname=\"%s\", uri=\"%s\", "
                  "id=\"%s\", make_and_model=\"%s\")\n",
               addr, addrname, uri ? uri : "(null)", id ? id : "(null)",
               make_and_model ? make_and_model : "(null)");

  temp = calloc(1, sizeof(snmp_cache_t));
  memcpy(&(temp->address), addr, sizeof(temp->address));

  temp->addrname = strdup(addrname);

  if (uri)
    temp->uri = strdup(uri);

  if (id)
    temp->id = strdup(id);

  if (make_and_model)
    temp->make_and_model = strdup(make_and_model);

  cupsArrayAdd(Devices, temp);

  if (uri)
    list_device(temp);
}


/*
 * 'add_device_uri()' - Add a device URI to the cache.
 *
 * The value string is modified (chopped up) as needed.
 */

static device_uri_t *                   /* O - Device URI */
add_device_uri(char *value)             /* I - Value from snmp.conf */
{
  device_uri_t  *device_uri;            /* Device URI */
  char          *start;                 /* Start of value */


 /*
  * Allocate memory as needed...
  */

  if (!DeviceURIs)
    DeviceURIs = cupsArrayNew(NULL, NULL);

  if (!DeviceURIs)
    return (NULL);

  if ((device_uri = calloc(1, sizeof(device_uri_t))) == NULL)
    return (NULL);

  if ((device_uri->uris = cupsArrayNew(NULL, NULL)) == NULL)
  {
    free(device_uri);
    return (NULL);
  }

 /*
  * Scan the value string for the regular expression and URI(s)...
  */

  value ++; /* Skip leading " */

  for (start = value; *value && *value != '\"'; value ++)
    if (*value == '\\' && value[1])
      _cups_strcpy(value, value + 1);

  if (!*value)
  {
    fputs("ERROR: Missing end quote for DeviceURI!\n", stderr);

    cupsArrayDelete(device_uri->uris);
    free(device_uri);

    return (NULL);
  }

  *value++ = '\0';

  if (regcomp(&(device_uri->re), start, REG_EXTENDED | REG_ICASE))
  {
    fputs("ERROR: Bad regular expression for DeviceURI!\n", stderr);

    cupsArrayDelete(device_uri->uris);
    free(device_uri);

    return (NULL);
  }

  while (*value)
  {
    while (isspace(*value & 255))
      value ++;

    if (!*value)
      break;

    for (start = value; *value && !isspace(*value & 255); value ++);

    if (*value)
      *value++ = '\0';

    cupsArrayAdd(device_uri->uris, strdup(start));
  }

 /*
  * Add the device URI to the list and return it...
  */

  cupsArrayAdd(DeviceURIs, device_uri);

  return (device_uri);
}


/*
 * 'alarm_handler()' - Handle alarm signals...
 */

static void
alarm_handler(int sig)                  /* I - Signal number */
{
 /*
  * Do nothing...
  */

  (void)sig;

#if !defined(HAVE_SIGSET) && !defined(HAVE_SIGACTION)
  signal(SIGALRM, alarm_handler);
#endif /* !HAVE_SIGSET && !HAVE_SIGACTION */

  if (DebugLevel)
    write(2, "DEBUG: ALARM!\n", 14);
}


/*
 * 'compare_cache()' - Compare two cache entries.
 */

static int                              /* O - Result of comparison */
compare_cache(snmp_cache_t *a,          /* I - First cache entry */
              snmp_cache_t *b)          /* I - Second cache entry */
{
  return (strcasecmp(a->addrname, b->addrname));
}


/*
 * 'debug_printf()' - Display some debugging information.
 */

static void
debug_printf(const char *format,        /* I - Printf-style format string */
             ...)                       /* I - Additional arguments as needed */
{
  va_list       ap;                     /* Pointer to arguments */


  if (!DebugLevel)
    return;

  va_start(ap, format);
  vfprintf(stderr, format, ap);
  va_end(ap);
}


/*
 * 'fix_make_model()' - Fix common problems in the make-and-model string.
 */

static void
fix_make_model(
    char       *make_model,             /* I - New make-and-model string */
    const char *old_make_model,         /* I - Old make-and-model string */
    int        make_model_size)         /* I - Size of new string buffer */
{
  char  *mmptr;                         /* Pointer into make-and-model string */


 /*
  * Fix some common problems with the make-and-model string so
  * that printer driver detection works better...
  */

  if (!strncasecmp(old_make_model, "Hewlett-Packard", 15))
  {
   /*
    * Strip leading Hewlett-Packard and hp prefixes and replace
    * with a single HP manufacturer prefix...
    */

    mmptr = (char *)old_make_model + 15;

    while (isspace(*mmptr & 255))
      mmptr ++;

    if (!strncasecmp(mmptr, "hp", 2))
    {
      mmptr += 2;

      while (isspace(*mmptr & 255))
        mmptr ++;
    }

    make_model[0] = 'H';
    make_model[1] = 'P';
    make_model[2] = ' ';
    strlcpy(make_model + 3, mmptr, make_model_size - 3);
  }
  else if (!strncasecmp(old_make_model, "deskjet", 7))
    snprintf(make_model, make_model_size, "HP DeskJet%s", old_make_model + 7);
  else if (!strncasecmp(old_make_model, "officejet", 9))
    snprintf(make_model, make_model_size, "HP OfficeJet%s", old_make_model + 9);
  else if (!strncasecmp(old_make_model, "stylus_pro_", 11))
    snprintf(make_model, make_model_size, "EPSON Stylus Pro %s",
             old_make_model + 11);
  else
    strlcpy(make_model, old_make_model, make_model_size);

  if ((mmptr = strstr(make_model, ", Inc.,")) != NULL)
  {
   /*
    * Strip inc. from name, e.g. "Tektronix, Inc., Phaser 560"
    * becomes "Tektronix Phaser 560"...
    */

    _cups_strcpy(mmptr, mmptr + 7);
  }

  if ((mmptr = strstr(make_model, " Network")) != NULL)
  {
   /*
    * Drop unnecessary informational text, e.g. "Xerox DocuPrint N2025
    * Network LaserJet - 2.12" becomes "Xerox DocuPrint N2025"...
    */

    *mmptr = '\0';
  }

  if ((mmptr = strchr(make_model, ',')) != NULL)
  {
   /*
    * Drop anything after a trailing comma...
    */

    *mmptr = '\0';
  }
}


/*
 * 'free_array()' - Free an array of strings.
 */

static void
free_array(cups_array_t *a)             /* I - Array */
{
  char  *s;                             /* Current string */


  for (s = (char *)cupsArrayFirst(a); s; s = (char *)cupsArrayNext(a))
    free(s);

  cupsArrayDelete(a);
}


/*
 * 'free_cache()' - Free the array of cached devices.
 */

static void
free_cache(void)
{
  snmp_cache_t  *cache;                 /* Cached device */


  for (cache = (snmp_cache_t *)cupsArrayFirst(Devices);
       cache;
       cache = (snmp_cache_t *)cupsArrayNext(Devices))
  {
    free(cache->addrname);

    if (cache->uri)
      free(cache->uri);

    if (cache->id)
      free(cache->id);

    if (cache->make_and_model)
      free(cache->make_and_model);

    free(cache);
  }

  cupsArrayDelete(Devices);
  Devices = NULL;
}


/*
 * 'get_interface_addresses()' - Get the broadcast address(es) associated
 *                               with an interface.
 */

static http_addrlist_t *                /* O - List of addresses */
get_interface_addresses(
    const char *ifname)                 /* I - Interface name */
{
  struct ifaddrs        *addrs,         /* Interface address list */
                        *addr;          /* Current interface address */
  http_addrlist_t       *first,         /* First address in list */
                        *last,          /* Last address in list */
                        *current;       /* Current address */


  if (getifaddrs(&addrs) < 0)
    return (NULL);

  for (addr = addrs, first = NULL, last = NULL; addr; addr = addr->ifa_next)
    if ((addr->ifa_flags & IFF_BROADCAST) && addr->ifa_broadaddr &&
        addr->ifa_broadaddr->sa_family == AF_INET &&
        (!ifname || !strcmp(ifname, addr->ifa_name)))
    {
      current = calloc(1, sizeof(http_addrlist_t));

      memcpy(&(current->addr), addr->ifa_broadaddr,
             sizeof(struct sockaddr_in));

      if (!last)
        first = current;
      else
        last->next = current;

      last = current;
    }

  freeifaddrs(addrs);

  return (first);
}


/*
 * 'list_device()' - List a device we found...
 */

static void
list_device(snmp_cache_t *cache)        /* I - Cached device */
{
  if (cache->uri)
  {
    printf("network %s \"%s\" \"%s %s\" \"%s\"\n",
           cache->uri,
           cache->make_and_model ? cache->make_and_model : "Unknown",
           cache->info ? cache->info : "Unknown",
           cache->addrname,
           cache->id ? cache->id : "");
    fflush(stdout);
  }
}


/*
 * 'password_cb()' - Handle authentication requests.
 *
 * All we do right now is return NULL, indicating that no authentication
 * is possible.
 */

static const char *                     /* O - Password (NULL) */
password_cb(const char *prompt)         /* I - Prompt message */
{
  (void)prompt;                         /* Anti-compiler-warning-code */

  return (NULL);
}


/*
 * 'probe_device()' - Probe a device to discover whether it is a printer.
 *
 * TODO: Try using the Port Monitor MIB to discover the correct protocol
 *       to use - first need a commercially-available printer that supports
 *       it, though...
 */

static void
probe_device(snmp_cache_t *device)      /* I - Device */
{
  char          uri[1024],              /* Full device URI */
                *uriptr,                /* Pointer into URI */
                *format;                /* Format string for device */
  device_uri_t  *device_uri;            /* Current DeviceURI match */


  debug_printf("DEBUG: %.3f Probing %s...\n", run_time(), device->addrname);

#ifdef __APPLE__
 /*
  * TODO: Try an mDNS query first, and then fallback on direct probes...
  */

  if (!try_connect(&(device->address), device->addrname, 5353))
  {
    debug_printf("DEBUG: %s supports mDNS, not reporting!\n", device->addrname);
    return;
  }
#endif /* __APPLE__ */

 /*
  * Lookup the device in the match table...
  */

  for (device_uri = (device_uri_t *)cupsArrayFirst(DeviceURIs);
       device_uri;
       device_uri = (device_uri_t *)cupsArrayNext(DeviceURIs))
    if (device->make_and_model &&
        !regexec(&(device_uri->re), device->make_and_model, 0, NULL, 0))
    {
     /*
      * Found a match, add the URIs...
      */

      for (format = (char *)cupsArrayFirst(device_uri->uris);
           format;
           format = (char *)cupsArrayNext(device_uri->uris))
      {
        for (uriptr = uri; *format && uriptr < (uri + sizeof(uri) - 1);)
          if (*format == '%' && format[1] == 's')
          {
           /*
            * Insert hostname/address...
            */

            strlcpy(uriptr, device->addrname, sizeof(uri) - (uriptr - uri));
            uriptr += strlen(uriptr);
            format += 2;
          }
          else
            *uriptr++ = *format++;

        *uriptr = '\0';

        update_cache(device, uri, NULL, NULL);
      }

      return;
    }

 /*
  * Then try the standard ports...
  */

  if (!try_connect(&(device->address), device->addrname, 9100))
  {
    debug_printf("DEBUG: %s supports AppSocket!\n", device->addrname);

    snprintf(uri, sizeof(uri), "socket://%s", device->addrname);
    update_cache(device, uri, NULL, NULL);
  }
  else if (!try_connect(&(device->address), device->addrname, 515))
  {
    debug_printf("DEBUG: %s supports LPD!\n", device->addrname);

    snprintf(uri, sizeof(uri), "lpd://%s/", device->addrname);
    update_cache(device, uri, NULL, NULL);
  }
}


/*
 * 'read_snmp_conf()' - Read the snmp.conf file.
 */

static void
read_snmp_conf(const char *address)     /* I - Single address to probe */
{
  cups_file_t   *fp;                    /* File pointer */
  char          filename[1024],         /* Filename */
                line[1024],             /* Line from file */
                *value;                 /* Value on line */
  int           linenum;                /* Line number */
  const char    *cups_serverroot;       /* CUPS_SERVERROOT env var */
  const char    *debug;                 /* CUPS_DEBUG_LEVEL env var */
  const char    *runtime;               /* CUPS_MAX_RUN_TIME env var */


 /*
  * Initialize the global address and community lists...
  */

  Addresses   = cupsArrayNew(NULL, NULL);
  Communities = cupsArrayNew(NULL, NULL);

  if (address)
    add_array(Addresses, address);

  if ((debug = getenv("CUPS_DEBUG_LEVEL")) != NULL)
    DebugLevel = atoi(debug);

  if ((runtime = getenv("CUPS_MAX_RUN_TIME")) != NULL)
    MaxRunTime = atoi(runtime);

 /*
  * Find the snmp.conf file...
  */

  if ((cups_serverroot = getenv("CUPS_SERVERROOT")) == NULL)
    cups_serverroot = CUPS_SERVERROOT;

  snprintf(filename, sizeof(filename), "%s/snmp.conf", cups_serverroot);

  if ((fp = cupsFileOpen(filename, "r")) != NULL)
  {
   /*
    * Read the snmp.conf file...
    */

    linenum = 0;

    while (cupsFileGetConf(fp, line, sizeof(line), &value, &linenum))
    {
      if (!value)
        fprintf(stderr, "ERROR: Missing value on line %d of %s!\n", linenum,
                filename);
      else if (!strcasecmp(line, "Address"))
      {
        if (!address)
          add_array(Addresses, value);
      }
      else if (!strcasecmp(line, "Community"))
        add_array(Communities, value);
      else if (!strcasecmp(line, "DebugLevel"))
        DebugLevel = atoi(value);
      else if (!strcasecmp(line, "DeviceURI"))
      {
        if (*value != '\"')
          fprintf(stderr,
                  "ERROR: Missing double quote for regular expression on "
                  "line %d of %s!\n", linenum, filename);
        else
          add_device_uri(value);
      }
      else if (!strcasecmp(line, "HostNameLookups"))
        HostNameLookups = !strcasecmp(value, "on") ||
                          !strcasecmp(value, "yes") ||
                          !strcasecmp(value, "true") ||
                          !strcasecmp(value, "double");
      else if (!strcasecmp(line, "MaxRunTime"))
        MaxRunTime = atoi(value);
      else
        fprintf(stderr, "ERROR: Unknown directive %s on line %d of %s!\n",
                line, linenum, filename);
    }

    cupsFileClose(fp);
  }

 /*
  * Use defaults if parameters are undefined...
  */

  if (cupsArrayCount(Addresses) == 0)
  {
   /*
    * If we have no addresses, exit immediately...
    */

    fprintf(stderr,
            "DEBUG: No address specified and no Address line in %s...\n",
            filename);
    exit(0);
  }

  if (cupsArrayCount(Communities) == 0)
  {
    fputs("INFO: Using default SNMP Community public\n", stderr);
    add_array(Communities, "public");
  }
}


/*
 * 'read_snmp_response()' - Read and parse a SNMP response...
 */

static void
read_snmp_response(int fd)              /* I - SNMP socket file descriptor */
{
  char          addrname[256];          /* Source address name */
  cups_snmp_t   packet;                 /* Decoded packet */
  snmp_cache_t  key,                    /* Search key */
                *device;                /* Matching device */


 /*
  * Read the response data...
  */

  if (!_cupsSNMPRead(fd, &packet, -1.0))
  {
    fprintf(stderr, "ERROR: Unable to read data from socket: %s\n",
            strerror(errno));
    return;
  }

  if (HostNameLookups)
    httpAddrLookup(&(packet.address), addrname, sizeof(addrname));
  else
    httpAddrString(&(packet.address), addrname, sizeof(addrname));

  debug_printf("DEBUG: %.3f Received data from %s...\n", run_time(), addrname);

 /*
  * Look for the response status code in the SNMP message header...
  */

  if (packet.error)
  {
    fprintf(stderr, "ERROR: Bad SNMP packet from %s: %s\n", addrname,
            packet.error);

    return;
  }

  debug_printf("DEBUG: community=\"%s\"\n", packet.community);
  debug_printf("DEBUG: request-id=%d\n", packet.request_id);
  debug_printf("DEBUG: error-status=%d\n", packet.error_status);

  if (packet.error_status)
    return;

 /*
  * Find a matching device in the cache...
  */

  key.addrname = addrname;
  device       = (snmp_cache_t *)cupsArrayFind(Devices, &key);

 /*
  * Process the message...
  */

  if (packet.request_id == DeviceTypeRequest)
  {
   /*
    * Got the device type response...
    */

    if (device)
    {
      debug_printf("DEBUG: Discarding duplicate device type for \"%s\"...\n",
                   addrname);
      return;
    }

   /*
    * Add the device and request the device description...
    */

    add_cache(&(packet.address), addrname, NULL, NULL, NULL);

    _cupsSNMPWrite(fd, &(packet.address), CUPS_SNMP_VERSION_1, packet.community,
                  CUPS_ASN1_GET_REQUEST, DeviceDescRequest, DeviceDescOID);
    _cupsSNMPWrite(fd, &(packet.address), CUPS_SNMP_VERSION_1, packet.community,
                  CUPS_ASN1_GET_REQUEST, DeviceIdRequest, DeviceIdOID);
    _cupsSNMPWrite(fd, &(packet.address), CUPS_SNMP_VERSION_1, packet.community,
                  CUPS_ASN1_GET_REQUEST, DeviceUriRequest, DeviceUriOID);
  }
  else if (packet.request_id == DeviceDescRequest &&
           packet.object_type == CUPS_ASN1_OCTET_STRING)
  {
   /*
    * Update an existing cache entry...
    */

    char        make_model[256];        /* Make and model */


    if (!device)
    {
      debug_printf("DEBUG: Discarding device description for \"%s\"...\n",
                   addrname);
      return;
    }

    if (strchr(packet.object_value.string, ':') &&
        strchr(packet.object_value.string, ';'))
    {
     /*
      * Description is the IEEE-1284 device ID...
      */

      if (!device->id)
        device->id = strdup(packet.object_value.string);

      backendGetMakeModel(packet.object_value.string, make_model,
                          sizeof(make_model));
      device->info = strdup(make_model);
    }
    else
    {
     /*
      * Description is plain text...
      */

      fix_make_model(make_model, packet.object_value.string,
                     sizeof(make_model));

      device->info = strdup(packet.object_value.string);
    }

    if (!device->make_and_model)
      device->make_and_model = strdup(make_model);

   /*
    * List the device now if we have all the info...
    */

    if (device->id && device->info && device->make_and_model && device->uri)
      list_device(device);
  }
  else if (packet.request_id == DeviceIdRequest &&
           packet.object_type == CUPS_ASN1_OCTET_STRING)
  {
   /*
    * Update an existing cache entry...
    */

    char        make_model[256];        /* Make and model */


    if (!device)
    {
      debug_printf("DEBUG: Discarding device ID for \"%s\"...\n",
                   addrname);
      return;
    }

    if (device->id)
      free(device->id);

    device->id = strdup(packet.object_value.string);

   /*
    * Convert the ID to a make and model string...
    */

    backendGetMakeModel(packet.object_value.string, make_model,
                        sizeof(make_model));
    if (device->make_and_model)
      free(device->make_and_model);

    device->make_and_model = strdup(make_model);

   /*
    * List the device now if we have all the info...
    */

    if (device->id && device->info && device->make_and_model && device->uri)
      list_device(device);
  }
  else if (packet.request_id == DeviceUriRequest &&
           packet.object_type == CUPS_ASN1_OCTET_STRING)
  {
   /*
    * Update an existing cache entry...
    */

    if (!device)
    {
      debug_printf("DEBUG: Discarding device URI for \"%s\"...\n",
                   addrname);
      return;
    }

    if (!strncmp(packet.object_value.string, "lpr:", 4))
    {
     /*
      * We want "lpd://..." for the URI...
      */

      packet.object_value.string[2] = 'd';
    }

    device->uri = strdup(packet.object_value.string);

   /*
    * List the device now if we have all the info...
    */

    if (device->id && device->info && device->make_and_model && device->uri)
      list_device(device);
  }
}


/*
 * 'run_time()' - Return the total running time...
 */

static double                           /* O - Number of seconds */
run_time(void)
{
  struct timeval        curtime;        /* Current time */


  gettimeofday(&curtime, NULL);

  return (curtime.tv_sec - StartTime.tv_sec +
          0.000001 * (curtime.tv_usec - StartTime.tv_usec));
}


/*
 * 'scan_devices()' - Scan for devices using SNMP.
 */

static void
scan_devices(int fd)                    /* I - SNMP socket */
{
  char                  *address,       /* Current address */
                        *community;     /* Current community */
  fd_set                input;          /* Input set for select() */
  struct timeval        timeout;        /* Timeout for select() */
  time_t                endtime;        /* End time for scan */
  http_addrlist_t       *addrs,         /* List of addresses */
                        *addr;          /* Current address */
  snmp_cache_t          *device;        /* Current device */


 /*
  * Setup the request IDs...
  */

  gettimeofday(&StartTime, NULL);

  DeviceTypeRequest = StartTime.tv_sec;
  DeviceDescRequest = StartTime.tv_sec + 1;

 /*
  * First send all of the broadcast queries...
  */

  for (address = (char *)cupsArrayFirst(Addresses);
       address;
       address = (char *)cupsArrayNext(Addresses))
  {
    if (!strcmp(address, "@LOCAL"))
      addrs = get_interface_addresses(NULL);
    else if (!strncmp(address, "@IF(", 4))
    {
      char      ifname[255];            /* Interface name */


      strlcpy(ifname, address + 4, sizeof(ifname));
      if (ifname[0])
        ifname[strlen(ifname) - 1] = '\0';

      addrs = get_interface_addresses(ifname);
    }
    else
      addrs = httpAddrGetList(address, AF_INET, NULL);

    if (!addrs)
    {
      fprintf(stderr, "ERROR: Unable to scan \"%s\"!\n", address);
      continue;
    }

    for (community = (char *)cupsArrayFirst(Communities);
         community;
         community = (char *)cupsArrayNext(Communities))
    {
      debug_printf("DEBUG: Scanning for devices in \"%s\" via \"%s\"...\n",
                   community, address);

      for (addr = addrs; addr; addr = addr->next)
        _cupsSNMPWrite(fd, &(addr->addr), CUPS_SNMP_VERSION_1, community,
                      CUPS_ASN1_GET_REQUEST, DeviceTypeRequest, DeviceTypeOID);
    }

    httpAddrFreeList(addrs);
  }

 /*
  * Then read any responses that come in over the next 3 seconds...
  */

  endtime = time(NULL) + MaxRunTime;

  FD_ZERO(&input);

  while (time(NULL) < endtime)
  {
    timeout.tv_sec  = 2;
    timeout.tv_usec = 0;

    FD_SET(fd, &input);
    if (select(fd + 1, &input, NULL, NULL, &timeout) < 0)
    {
      fprintf(stderr, "ERROR: %.3f select() for %d failed: %s\n", run_time(),
              fd, strerror(errno));
      break;
    }

    if (FD_ISSET(fd, &input))
      read_snmp_response(fd);
    else
      break;
  }

 /*
  * Finally, probe all of the printers we discovered to see how they are
  * connected...
  */

  for (device = (snmp_cache_t *)cupsArrayFirst(Devices);
       device;
       device = (snmp_cache_t *)cupsArrayNext(Devices))
    if (MaxRunTime > 0 && run_time() >= MaxRunTime)
      break;
    else if (!device->uri)
      probe_device(device);

  debug_printf("DEBUG: %.3f Scan complete!\n", run_time());
}


/*
 * 'try_connect()' - Try connecting on a port...
 */

static int                              /* O - 0 on success or -1 on error */
try_connect(http_addr_t *addr,          /* I - Socket address */
            const char  *addrname,      /* I - Hostname or IP address */
            int         port)           /* I - Port number */
{
  int   fd;                             /* Socket */
  int   status;                         /* Connection status */


  debug_printf("DEBUG: %.3f Trying %s://%s:%d...\n", run_time(),
               port == 515 ? "lpd" : "socket", addrname, port);

  if ((fd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
  {
    fprintf(stderr, "ERROR: Unable to create socket: %s\n",
            strerror(errno));
    return (-1);
  }

  addr->ipv4.sin_port = htons(port);

  alarm(1);

  status = connect(fd, (void *)addr, httpAddrLength(addr));

  close(fd);
  alarm(0);

  return (status);
}


/*
 * 'update_cache()' - Update a cached device...
 */

static void
update_cache(snmp_cache_t *device,      /* I - Device */
             const char   *uri,         /* I - Device URI */
             const char   *id,          /* I - Device ID */
             const char   *make_model)  /* I - Device make and model */
{
  if (device->uri)
    free(device->uri);

  device->uri = strdup(uri);

  if (id)
  {
    if (device->id)
      free(device->id);

    device->id = strdup(id);
  }

  if (make_model)
  {
    if (device->make_and_model)
      free(device->make_and_model);

    device->make_and_model = strdup(make_model);
  }

  list_device(device);
}


/*
 * End of "$Id: snmp.c 6649 2007-07-11 21:46:42Z mike $".
 */