enum.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2006, Digium, Inc.
 *
 * Mark Spencer <[email protected]>
 *
 * Funding provided by nic.at
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief ENUM Support for Asterisk
 *
 * \author Mark Spencer <[email protected]>
 *
 * \arg Funding provided by nic.at
 *
 * \par Enum standards
 *
 * - NAPTR records: http://ietf.nri.reston.va.us/rfc/rfc2915.txt
 * - DNS SRV records: http://www.ietf.org/rfc/rfc2782.txt
 * - ENUM http://www.ietf.org/rfc/rfc3761.txt
 * - ENUM for H.323: http://www.ietf.org/rfc/rfc3762.txt
 * - ENUM SIP: http://www.ietf.org/rfc/rfc3764.txt
 * - IANA ENUM Services: http://www.iana.org/assignments/enum-services
 *
 * - I-ENUM:
 *   http://tools.ietf.org/wg/enum/draft-ietf-enum-combined/
 *   http://tools.ietf.org/wg/enum/draft-ietf-enum-branch-location-record/
 *
 * \par Possible improvement
 * \todo Implement a caching mechanism for multile enum lookups
 * - See https://issues.asterisk.org/view.php?id=6739
 * \todo The service type selection needs to be redone.
 */

/*! \li \ref enum.c uses the configuration file \ref enum.conf
 * \addtogroup configuration_file Configuration Files
 */

/*!
 * \page enum.conf enum.conf
 * \verbinclude enum.conf.sample
 */

/*** MODULEINFO
   <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#ifdef __APPLE__
#include <arpa/nameser_compat.h>
#endif
#include <resolv.h>
#include <ctype.h>
#include <regex.h>

#include "asterisk/module.h"
#include "asterisk/enum.h"
#include "asterisk/dns.h"
#include "asterisk/channel.h"
#include "asterisk/config.h"
#include "asterisk/utils.h"
#include "asterisk/manager.h"

#ifdef __APPLE__
#undef T_NAPTR
#define T_NAPTR 35
#endif

#ifdef __APPLE__
#undef T_TXT
#define T_TXT 16
#endif

static char ienum_branchlabel[32] = "i";
/* how to do infrastructure enum branch location resolution? */
#define ENUMLOOKUP_BLR_CC       0
#define ENUMLOOKUP_BLR_TXT      1
#define ENUMLOOKUP_BLR_EBL      2
static int ebl_alg = ENUMLOOKUP_BLR_CC;

/* EBL record provisional type code */
#define T_EBL      65300

AST_MUTEX_DEFINE_STATIC(enumlock);

/*! \brief Determine the length of a country code when given an E.164 string */
/*
 * Input: E.164 number w/o leading +
 *
 * Output: number of digits in the country code
 *    0 on invalid number
 *
 * Algorithm:
 *   3 digits is the default length of a country code.
 *   country codes 1 and 7 are a single digit.
 *   the following country codes are two digits: 20, 27, 30-34, 36, 39,
 *     40, 41, 43-49, 51-58, 60-66, 81, 82, 84, 86, 90-95, 98.
 */
static int cclen(const char *number)
{
   int cc;
   char digits[3] = "";

   if (!number || (strlen(number) < 3)) {
      return 0;
   }

   strncpy(digits, number, 2);

   if (!sscanf(digits, "%30d", &cc)) {
      return 0;
   }

   if (cc / 10 == 1 || cc / 10 == 7)
      return 1;

   if (cc == 20 || cc == 27 || (cc >= 30 && cc <= 34) || cc == 36 ||
       cc == 39 || cc == 40 || cc == 41 || (cc >= 40 && cc <= 41) ||
       (cc >= 43 && cc <= 49) || (cc >= 51 && cc <= 58) ||
       (cc >= 60 && cc <= 66) || cc == 81 || cc == 82 || cc == 84 ||
       cc == 86 || (cc >= 90 && cc <= 95) || cc == 98) {
      return 2;
   }

   return 3;
}

struct txt_context {
   char txt[1024];      /* TXT record in TXT lookup */
   int txtlen;    /* Length */
};

/*! \brief Callback for TXT record lookup, /ol version */
static int txt_callback(void *context, unsigned char *answer, int len, unsigned char *fullanswer)
{
   struct txt_context *c = context;
   unsigned int i;

   c->txt[0] = 0; /* default to empty */
   c->txtlen = 0;

   if (answer == NULL) {
      return 0;
   }

   /* RFC1035:
    *
    * <character-string> is a single length octet followed by that number of characters.
    * TXT-DATA        One or more <character-string>s.
    *
    * We only take the first string here.
    */

   i = *answer++;
   len -= 1;

   if (i > len) { /* illegal packet */
      ast_log(LOG_WARNING, "txt_callback: malformed TXT record.\n");
      return 0;
   }

   if (i >= sizeof(c->txt)) { /* too long? */
      ast_log(LOG_WARNING, "txt_callback: TXT record too long.\n");
      i = sizeof(c->txt) - 1;
   }

   ast_copy_string(c->txt, (char *)answer, i + 1);  /* this handles the \0 termination */
   c->txtlen = i;

   return 1;
}

/*! \brief Determine the branch location record as stored in a TXT record */
/*
 * Input: CC code
 *
 * Output: number of digits in the number before the i-enum branch
 *
 * Algorithm:  Build <ienum_branchlabel>.c.c.<suffix> and look for a TXT lookup.
 *    Return atoi(TXT-record).
 *    Return -1 on not found.
 *
 */
static int blr_txt(const char *cc, const char *suffix)
{
   struct txt_context context;
   char domain[128] = "";
   char *p1, *p2;
   int ret;

   ast_mutex_lock(&enumlock);

   ast_verb(4, "blr_txt()  cc='%s', suffix='%s', c_bl='%s'\n", cc, suffix, ienum_branchlabel);

   if (sizeof(domain) < (strlen(cc) * 2 + strlen(ienum_branchlabel) + strlen(suffix) + 2)) {
      ast_mutex_unlock(&enumlock);
      ast_log(LOG_WARNING, "ERROR: string sizing in blr_txt.\n");
      return -1;
   }

   p1 = domain + snprintf(domain, sizeof(domain), "%s.", ienum_branchlabel);
   ast_mutex_unlock(&enumlock);

   for (p2 = (char *) cc + strlen(cc) - 1; p2 >= cc; p2--) {
      if (isdigit(*p2)) {
         *p1++ = *p2;
         *p1++ = '.';
      }
   }
   strcat(p1, suffix);

   ast_verb(4, "blr_txt() FQDN for TXT record: %s, cc was %s\n", domain, cc);

   ret = ast_search_dns(&context, domain, C_IN, T_TXT, txt_callback);

   if (ret > 0) {
      ret = atoi(context.txt);

      if ((ret >= 0) && (ret < 20)) {
         ast_verb(3, "blr_txt() BLR TXT record for %s is %d (apex: %s)\n", cc, ret, suffix);
         return ret;
      }
   }

   ast_verb(3, "blr_txt() BLR TXT record for %s not found (apex: %s)\n", cc, suffix);

   return -1;
}

struct ebl_context {
   unsigned char pos;
   char separator[256];    /* label to insert */
   int sep_len;         /* Length */
   char apex[256];         /* new Apex */
   int apex_len;        /* Length */
};

/*! \brief Callback for EBL record lookup */
static int ebl_callback(void *context, unsigned char *answer, int len, unsigned char *fullanswer)
{
   struct ebl_context *c = context;
   int i;

   c->pos = 0; /* default to empty */
   c->separator[0] = 0;
   c->sep_len = 0;
   c->apex[0] = 0;
   c->apex_len = 0;

   if (answer == NULL) {
      return 0;
   }

   /* draft-lendl-enum-branch-location-record-00
    *
    *      0  1  2  3  4  5  6  7
    *    +--+--+--+--+--+--+--+--+
    *    |       POSITION        |
    *    +--+--+--+--+--+--+--+--+
    *    /       SEPARATOR       /
    *    +--+--+--+--+--+--+--+--+
    *    /         APEX          /
    *    +--+--+--+--+--+--+--+--+
    *
    *  where POSITION is a single byte, SEPARATOR is a <character-string>
    *  and APEX is a <domain-name>.
    *
    */

   c->pos = *answer++;
   len -= 1;

   if ((c->pos > 15) || len < 2) {  /* illegal packet */
      ast_log(LOG_WARNING, "ebl_callback: malformed EBL record.\n");
      return 0;
   }

   i = *answer++;
   len -= 1;
   if (i > len) { /* illegal packet */
      ast_log(LOG_WARNING, "ebl_callback: malformed EBL record.\n");
      return 0;
   }

   ast_copy_string(c->separator, (char *)answer, i + 1);
   c->sep_len = i;

   answer += i;
   len -= i;

   if ((i = dn_expand((unsigned char *)fullanswer, (unsigned char *)answer + len,
            (unsigned char *)answer, c->apex, sizeof(c->apex) - 1)) < 0) {
      ast_log(LOG_WARNING, "Failed to expand hostname\n");
      return 0;
   }
   c->apex[i] = 0;
   c->apex_len = i;

   return 1;
}

/*! \brief Evaluate the I-ENUM branch as stored in an EBL record */
/*
 * Input: CC code
 *
 * Output: number of digits in the number before the i-enum branch
 *
 * Algorithm:  Build <ienum_branchlabel>.c.c.<suffix> and look for an EBL record
 *    Return pos and fill in separator and apex.
 *    Return -1 on not found.
 *
 */
static int blr_ebl(const char *cc, const char *suffix, char *separator, int sep_len, char* apex, int apex_len)
{
   struct ebl_context context;
   char domain[128] = "";
   char *p1,*p2;
   int ret;

   ast_mutex_lock(&enumlock);

   ast_verb(4, "blr_ebl()  cc='%s', suffix='%s', c_bl='%s'\n", cc, suffix, ienum_branchlabel);

   if (sizeof(domain) < (strlen(cc) * 2 + strlen(ienum_branchlabel) + strlen(suffix) + 2)) {
      ast_mutex_unlock(&enumlock);
      ast_log(LOG_WARNING, "ERROR: string sizing in blr_EBL.\n");
      return -1;
   }

   p1 = domain + snprintf(domain, sizeof(domain), "%s.", ienum_branchlabel);
   ast_mutex_unlock(&enumlock);

   for (p2 = (char *) cc + strlen(cc) - 1; p2 >= cc; p2--) {
      if (isdigit(*p2)) {
         *p1++ = *p2;
         *p1++ = '.';
      }
   }
   strcat(p1, suffix);

   ast_verb(4, "blr_ebl() FQDN for EBL record: %s, cc was %s\n", domain, cc);

   ret = ast_search_dns(&context, domain, C_IN, T_EBL, ebl_callback);
   if (ret > 0) {
      ret = context.pos;

      if ((ret >= 0) && (ret < 20)) {
         ast_verb(3, "blr_txt() BLR EBL record for %s is %d/%s/%s)\n", cc, ret, context.separator, context.apex);
         ast_copy_string(separator, context.separator, sep_len);
         ast_copy_string(apex, context.apex, apex_len);
         return ret;
      }
   }
   ast_verb(3, "blr_txt() BLR EBL record for %s not found (apex: %s)\n", cc, suffix);
   return -1;
}

/*! \brief Parse NAPTR record information elements */
static unsigned int parse_ie(char *data, unsigned int maxdatalen, unsigned char *src, unsigned int srclen)
{
   unsigned int len, olen;

   len = olen = (unsigned int) src[0];
   src++;
   srclen--;

   if (len > srclen) {
      ast_log(LOG_WARNING, "ENUM parsing failed: Wanted %u characters, got %u\n", len, srclen);
      return -1;
   }

   if (len > maxdatalen)
      len = maxdatalen;
   memcpy(data, src, len);

   return olen + 1;
}

/*! \brief Parse DNS NAPTR record used in ENUM ---*/
static int parse_naptr(unsigned char *dst, int dstsize, char *tech, int techsize, unsigned char *answer, int len, unsigned char *naptrinput)
{
   char tech_return[80];
   char *oanswer = (char *)answer;
   char flags[512] = "";
   char services[512] = "";
   char *p;
   char regexp[512] = "";
   char repl[512] = "";
   char tempdst[512] = "";
   char errbuff[512] = "";
   char delim;
   char *delim2;
   char *pattern, *subst, *d;
   int res;
   int regexp_len, rc;
   static const int max_bt = 10; /* max num of regexp backreference allowed, must remain 10 to guarantee a valid backreference index */
   int size, matchindex; /* size is the size of the backreference sub. */
   size_t d_len = sizeof(tempdst) - 1;
   regex_t preg;
   int re_flags = REG_EXTENDED | REG_NEWLINE;
   regmatch_t pmatch[max_bt];

   tech_return[0] = '\0';
   dst[0] = '\0';

   if (len < sizeof(struct naptr)) {
      ast_log(LOG_WARNING, "NAPTR record length too short\n");
      return -1;
   }
   answer += sizeof(struct naptr);
   len -= sizeof(struct naptr);
   if ((res = parse_ie(flags, sizeof(flags) - 1, answer, len)) < 0) {
      ast_log(LOG_WARNING, "Failed to get flags from NAPTR record\n");
      return -1;
   } else {
      answer += res;
      len -= res;
   }

   if ((res = parse_ie(services, sizeof(services) - 1, answer, len)) < 0) {
      ast_log(LOG_WARNING, "Failed to get services from NAPTR record\n");
      return -1;
   } else {
      answer += res;
      len -= res;
   }
   if ((res = parse_ie(regexp, sizeof(regexp) - 1, answer, len)) < 0) {
      ast_log(LOG_WARNING, "Failed to get regexp from NAPTR record\n");
      return -1;
   } else {
      answer += res;
      len -= res;
   }

   if ((res = dn_expand((unsigned char *)oanswer, (unsigned char *)answer + len, (unsigned char *)answer, repl, sizeof(repl) - 1)) < 0) {
      ast_log(LOG_WARNING, "Failed to expand hostname\n");
      return -1;
   }

   ast_debug(3, "NAPTR input='%s', flags='%s', services='%s', regexp='%s', repl='%s'\n",
      naptrinput, flags, services, regexp, repl);


   if (tolower(flags[0]) != 'u') {
      ast_log(LOG_WARNING, "NAPTR Flag must be 'U' or 'u'.\n");
      return -1;
   }

   p = strstr(services, "e2u+");
   if (p == NULL)
      p = strstr(services, "E2U+");
   if (p){
      p = p + 4;
      if (strchr(p, ':')){
         p = strchr(p, ':') + 1;
      }
      ast_copy_string(tech_return, p, sizeof(tech_return));
   } else {

      p = strstr(services, "+e2u");
      if (p == NULL)
         p = strstr(services, "+E2U");
      if (p) {
         *p = 0;
         p = strchr(services, ':');
         if (p)
            *p = 0;
         ast_copy_string(tech_return, services, sizeof(tech_return));
      }
   }

   regexp_len = strlen(regexp);
   if (regexp_len < 7) {
      ast_log(LOG_WARNING, "Regex too short to be meaningful.\n");
      return -1;
   }

   /* this takes the first character of the regexp (which is a delimiter)
    * and uses that character to find the index of the second delimiter */
   delim = regexp[0];
   delim2 = strchr(regexp + 1, delim);
   if ((delim2 == NULL)
      || ((regexp[regexp_len - 1] != 'i' || regexp[regexp_len - 2] != delim)
         && regexp[regexp_len - 1] != delim)) {
      ast_log(LOG_WARNING, "Regex delimiter error (on \"%s\").\n", regexp);
      return -1;
   } else if (strchr((delim2 + 1), delim) == NULL) { /* if the second delimiter is found, make sure there is a third instance.  this could be the end one instead of the middle */
      ast_log(LOG_WARNING, "Regex delimiter error (on \"%s\").\n", regexp);
      return -1;
   }

   /* Make the regex case-insensitive if the 'i' flag is present. This assumes you
    * aren't using 'i' as a delimiter which, altough dubious, does not appear to be
    * explicitly non-compliant */
   if (regexp[regexp_len - 1] == 'i') {
      re_flags |= REG_ICASE;
   }

   pattern = regexp + 1;   /* pattern is the regex without the begining and ending delimiter */
   *delim2 = 0;    /* zero out the middle delimiter */
   subst   = delim2 + 1; /* dst substring is everything after the second delimiter. */
   regexp[regexp_len - 1] = 0; /* zero out the last delimiter */

/*
 * now do the regex wizardry.
 */

   if (regcomp(&preg, pattern, re_flags)) {
      ast_log(LOG_WARNING, "NAPTR Regex compilation error (regex = \"%s\").\n", regexp);
      return -1;
   }

   if (preg.re_nsub > ARRAY_LEN(pmatch)) {
      ast_log(LOG_WARNING, "NAPTR Regex compilation error: too many subs.\n");
      regfree(&preg);
      return -1;
   }
   /* pmatch is an array containing the substring indexes for the regex backreference sub.
    * max_bt is the maximum number of backreferences allowed to be stored in pmatch */
   if ((rc = regexec(&preg, (char *) naptrinput, max_bt, pmatch, 0))) {
      regerror(rc, &preg, errbuff, sizeof(errbuff));
      ast_log(LOG_WARNING, "NAPTR Regex match failed. Reason: %s\n", errbuff);
      regfree(&preg);
      return -1;
   }
   regfree(&preg);

   d = tempdst;
   d_len--;

   /* perform the backreference sub. Search the subst for backreferences,
    * when a backreference is found, retrieve the backreferences number.
    * use the backreference number as an index for pmatch to retrieve the
    * beginning and ending indexes of the substring to insert as the backreference.
    * if no backreference is found, continue copying the subst into tempdst */
   while (*subst && (d_len > 0)) {
      if ((subst[0] == '\\') && isdigit(subst[1])) { /* is this character the beginning of a backreference */
         matchindex = (int) (subst[1] - '0');
         if (matchindex >= ARRAY_LEN(pmatch)) {
            ast_log(LOG_WARNING, "Error during regex substitution. Invalid pmatch index.\n");
            return -1;
         }
         /* pmatch len is 10. we are garanteed a single char 0-9 is a valid index */
         size = pmatch[matchindex].rm_eo - pmatch[matchindex].rm_so;
         if (size > d_len) {
            ast_log(LOG_WARNING, "Not enough space during NAPTR regex substitution.\n");
            return -1;
         }
         /* are the pmatch indexes valid for the input length */
         if ((strlen((char *) naptrinput) >= pmatch[matchindex].rm_eo) && (pmatch[matchindex].rm_so <= pmatch[matchindex].rm_eo)) {
            memcpy(d, (naptrinput + (int) pmatch[matchindex].rm_so), size);  /* copy input substring into backreference marker */
            d_len -= size;
            subst += 2;  /* skip over backreference characters to next valid character */
            d += size;
         } else {
            ast_log(LOG_WARNING, "Error during regex substitution. Invalid backreference index.\n");
            return -1;
         }
      } else if (isprint(*subst)) {
         *d++ = *subst++;
         d_len--;
      } else {
         ast_log(LOG_WARNING, "Error during regex substitution.\n");
         return -1;
      }
   }
   *d = 0;
   ast_copy_string((char *) dst, tempdst, dstsize);
   dst[dstsize - 1] = '\0';

   if (*tech != '\0'){ /* check if it is requested NAPTR */
      if (!strncasecmp(tech, "ALL", techsize)){
         return 0; /* return or count any RR */
      }
      if (!strncasecmp(tech_return, tech, sizeof(tech_return) < techsize ? sizeof(tech_return): techsize)){
         ast_copy_string(tech, tech_return, techsize);
         return 0; /* we got our RR */
      } else { /* go to the next RR in the DNS answer */
         return 1;
      }
   }

   /* tech was not specified, return first parsed RR */
   ast_copy_string(tech, tech_return, techsize);

   return 0;
}

/* do not return requested value, just count RRs and return thei number in dst */
#define ENUMLOOKUP_OPTIONS_COUNT       1
/* do an ISN style lookup */
#define ENUMLOOKUP_OPTIONS_ISN      2
/* do a infrastructure ENUM lookup */
#define ENUMLOOKUP_OPTIONS_IENUM 4
/* do a direct DNS lookup: no reversal */
#define ENUMLOOKUP_OPTIONS_DIRECT   8

/*! \brief Callback from ENUM lookup function */
static int enum_callback(void *context, unsigned char *answer, int len, unsigned char *fullanswer)
{
   struct enum_context *c = context;
   void *p = NULL;
   int res;

   res = parse_naptr((unsigned char *)c->dst, c->dstlen, c->tech, c->techlen, answer, len, (unsigned char *)c->naptrinput);

   if (res < 0) {
      ast_log(LOG_WARNING, "Failed to parse naptr\n");
      return -1;
   } else if ((res == 0) && !ast_strlen_zero(c->dst)) { /* ok, we got needed NAPTR */
      if (c->options & ENUMLOOKUP_OPTIONS_COUNT) { /* counting RRs */
         c->count++;
         snprintf(c->dst, c->dstlen, "%d", c->count);
      } else  {
         if ((p = ast_realloc(c->naptr_rrs, sizeof(*c->naptr_rrs) * (c->naptr_rrs_count + 1)))) {
            c->naptr_rrs = p;
            memcpy(&c->naptr_rrs[c->naptr_rrs_count].naptr, answer, sizeof(c->naptr_rrs->naptr));
            c->naptr_rrs[c->naptr_rrs_count].result = ast_strdup(c->dst);
            c->naptr_rrs[c->naptr_rrs_count].tech = ast_strdup(c->tech);
            c->naptr_rrs[c->naptr_rrs_count].sort_pos = c->naptr_rrs_count;
            c->naptr_rrs_count++;
         }
         c->dst[0] = 0;
      }
      return 0;
   }

   return 0;
}

/* ENUM lookup */
int ast_get_enum(struct ast_channel *chan, const char *number, char *dst, int dstlen, char *tech, int techlen, char* suffix, char* options, unsigned int record, struct enum_context **argcontext)
{
   struct enum_context *context;
   char tmp[512];
   char domain[256];
   char left[128];
   char middle[128];
   char naptrinput[128];
   char apex[128] = "";
   int ret = -1;
   /* for ISN rewrite */
   char *p1 = NULL;
   char *p2 = NULL;
   char *p3 = NULL;
   int k = 0;
   int i = 0;
   int z = 0;
   int spaceleft = 0;
   struct timeval time_start, time_end;

   if (ast_strlen_zero(suffix)) {
      ast_log(LOG_WARNING, "ast_get_enum need a suffix parameter now.\n");
      return -1;
   }

   ast_debug(2, "num='%s', tech='%s', suffix='%s', options='%s', record=%u\n", number, tech, suffix, options, record);

/*
  We don't need that any more, that "n" preceding the number has been replaced by a flag
  in the options paramter.
   ast_copy_string(naptrinput, number, sizeof(naptrinput));
*/
/*
 * The "number" parameter includes a leading '+' if it's a full E.164 number (and not ISN)
 * We need to preserve that as the regex inside NAPTRs expect the +.
 *
 * But for the domain generation, the '+' is a nuissance, so we get rid of it.
*/
   ast_copy_string(naptrinput, number[0] == 'n' ? number + 1 : number, sizeof(naptrinput));
   if (number[0] == '+') {
      number++;
   }

   if (!(context = ast_calloc(1, sizeof(*context)))) {
      return -1;
   }

   if ((p3 = strchr(naptrinput, '*'))) {
      *p3='\0';
   }

   context->naptrinput = naptrinput;   /* The number */
   context->dst = dst;        /* Return string */
   context->dstlen = dstlen;
   context->tech = tech;
   context->techlen = techlen;
   context->options = 0;
   context->position = record > 0 ? record : 1;
   context->count = 0;
   context->naptr_rrs = NULL;
   context->naptr_rrs_count = 0;

   /*
    * Process options:
    *
    * c  Return count, not URI
    * i  Use infrastructure ENUM
    * s  Do ISN transformation
    * d  Direct DNS query: no reversing.
    *
    */
   if (options != NULL) {
      if (strchr(options,'s')) {
         context->options |= ENUMLOOKUP_OPTIONS_ISN;
      } else if (strchr(options,'i')) {
         context->options |= ENUMLOOKUP_OPTIONS_IENUM;
      } else if (strchr(options,'d')) {
         context->options |= ENUMLOOKUP_OPTIONS_DIRECT;
      }
      if (strchr(options,'c')) {
         context->options |= ENUMLOOKUP_OPTIONS_COUNT;
      }
      if (strchr(number,'*')) {
         context->options |= ENUMLOOKUP_OPTIONS_ISN;
      }
   }
   ast_debug(2, "ENUM options(%s): pos=%d, options='%d'\n", options, context->position, context->options);
   ast_debug(1, "n='%s', tech='%s', suffix='%s', options='%d', record='%d'\n",
         number, tech, suffix, context->options, context->position);

   /*
    * This code does more than simple RFC3261 ENUM. All these rewriting
    * schemes have in common that they build the FQDN for the NAPTR lookup
    * by concatenating
    *    - a number which needs be flipped and "."-seperated   (left)
    *    - some fixed string              (middle)
    *    - an Apex.                 (apex)
    *
    * The RFC3261 ENUM is: left=full number, middle="", apex=from args.
    * ISN:  number = "middle*left", apex=from args
    * I-ENUM: EBL parameters build the split, can change apex
    * Direct: left="", middle=argument, apex=from args
    *
    */

   /* default: the whole number will be flipped, no middle domain component */
   ast_copy_string(left, number, sizeof(left));
   middle[0] = '\0';
   /*
    * I-ENUM can change the apex, thus we copy it
    */
   ast_copy_string(apex, suffix, sizeof(apex));
   /* ISN rewrite */
   if ((context->options & ENUMLOOKUP_OPTIONS_ISN) && (p1 = strchr(number, '*'))) {
      *p1++ = '\0';
      ast_copy_string(left, number, sizeof(left));
      ast_copy_string(middle, p1, sizeof(middle) - 1);
      strcat(middle, ".");
      ast_debug(2, "ISN ENUM: left=%s, middle='%s'\n", left, middle);
   /* Direct DNS lookup rewrite */
   } else if (context->options & ENUMLOOKUP_OPTIONS_DIRECT) {
      left[0] = 0; /* nothing to flip around */
      ast_copy_string(middle, number, sizeof(middle) - 1);
      strcat(middle, ".");
      ast_debug(2, "DIRECT ENUM:  middle='%s'\n", middle);
   /* Infrastructure ENUM rewrite */
   } else if (context->options & ENUMLOOKUP_OPTIONS_IENUM) {
      int sdl = 0;
      char cc[8];
      char sep[256], n_apex[256];
      int cc_len = cclen(number);
      sdl = cc_len;
      ast_mutex_lock(&enumlock);
      ast_copy_string(sep, ienum_branchlabel, sizeof(sep)); /* default */
      ast_mutex_unlock(&enumlock);

      switch (ebl_alg) {
      case ENUMLOOKUP_BLR_EBL:
         ast_copy_string(cc, number, cc_len); /* cclen() never returns more than 3 */
         sdl = blr_ebl(cc, suffix, sep, sizeof(sep) - 1, n_apex, sizeof(n_apex) - 1);

         if (sdl >= 0) {
            ast_copy_string(apex, n_apex, sizeof(apex));
            ast_debug(2, "EBL ENUM: sep=%s, apex='%s'\n", sep, n_apex);
         } else {
            sdl = cc_len;
         }
         break;
      case ENUMLOOKUP_BLR_TXT:
         ast_copy_string(cc, number, cc_len); /* cclen() never returns more than 3 */
         sdl = blr_txt(cc, suffix);

         if (sdl < 0) {
            sdl = cc_len;
         }
         break;

      case ENUMLOOKUP_BLR_CC: /* BLR is at the country-code level */
      default:
         sdl = cc_len;
         break;
      }

      if (sdl > strlen(number)) {   /* Number too short for this sdl? */
         ast_log(LOG_WARNING, "I-ENUM: subdomain location %d behind number %s\n", sdl, number);
         ast_free(context);
         return 0;
      }
      ast_copy_string(left, number + sdl, sizeof(left));

      ast_mutex_lock(&enumlock);
      ast_copy_string(middle, sep, sizeof(middle) - 1);
      strcat(middle, ".");
      ast_mutex_unlock(&enumlock);

      /* check the space we need for middle */
      if ((sdl * 2 + strlen(middle) + 2) > sizeof(middle)) {
         ast_log(LOG_WARNING, "ast_get_enum: not enough space for I-ENUM rewrite.\n");
         ast_free(context);
         return -1;
      }

      p1 = middle + strlen(middle);
      for (p2 = (char *) number + sdl - 1; p2 >= number; p2--) {
         if (isdigit(*p2)) {
            *p1++ = *p2;
            *p1++ = '.';
         }
      }
      *p1 = '\0';

      ast_debug(2, "I-ENUM: cclen=%d, left=%s, middle='%s', apex='%s'\n", cc_len, left, middle, apex);
   }

   if (strlen(left) * 2 + 2 > sizeof(domain)) {
      ast_log(LOG_WARNING, "string to long in ast_get_enum\n");
      ast_free(context);
      return -1;
   }

   /* flip left into domain */
   p1 = domain;
   for (p2 = left + strlen(left); p2 >= left; p2--) {
      if (isdigit(*p2)) {
         *p1++ = *p2;
         *p1++ = '.';
      }
   }
   *p1 = '\0';

   if (chan && ast_autoservice_start(chan) < 0) {
      ast_free(context);
      return -1;
   }

   spaceleft = sizeof(tmp) - 2;
   ast_copy_string(tmp, domain, spaceleft);
   spaceleft -= strlen(domain);

   if (*middle) {
      strncat(tmp, middle, spaceleft);
      spaceleft -= strlen(middle);
   }

   strncat(tmp,apex,spaceleft);
   time_start = ast_tvnow();
   ret = ast_search_dns(context, tmp, C_IN, T_NAPTR, enum_callback);
   time_end = ast_tvnow();

   ast_debug(2, "profiling: %s, %s, %" PRIi64 " ms\n",
         (ret == 0) ? "OK" : "FAIL", tmp, ast_tvdiff_ms(time_end, time_start));

   if (ret < 0) {
      ast_debug(1, "No such number found: %s (%s)\n", tmp, strerror(errno));
      context->naptr_rrs_count = -1;
      strcpy(dst, "0");
      ret = 0;
   }

   if (context->naptr_rrs_count >= context->position && ! (context->options & ENUMLOOKUP_OPTIONS_COUNT)) {
      /* sort array by NAPTR order/preference */
      for (k = 0; k < context->naptr_rrs_count; k++) {
         for (i = 0; i < context->naptr_rrs_count; i++) {
            /* use order first and then preference to compare */
            if ((ntohs(context->naptr_rrs[k].naptr.order) < ntohs(context->naptr_rrs[i].naptr.order)
                 && context->naptr_rrs[k].sort_pos > context->naptr_rrs[i].sort_pos)
                 || (ntohs(context->naptr_rrs[k].naptr.order) > ntohs(context->naptr_rrs[i].naptr.order)
                 && context->naptr_rrs[k].sort_pos < context->naptr_rrs[i].sort_pos)) {
               z = context->naptr_rrs[k].sort_pos;
               context->naptr_rrs[k].sort_pos = context->naptr_rrs[i].sort_pos;
               context->naptr_rrs[i].sort_pos = z;
               continue;
            }
            if (ntohs(context->naptr_rrs[k].naptr.order) == ntohs(context->naptr_rrs[i].naptr.order)) {
               if ((ntohs(context->naptr_rrs[k].naptr.pref) < ntohs(context->naptr_rrs[i].naptr.pref)
                    && context->naptr_rrs[k].sort_pos > context->naptr_rrs[i].sort_pos)
                    || (ntohs(context->naptr_rrs[k].naptr.pref) > ntohs(context->naptr_rrs[i].naptr.pref)
                    && context->naptr_rrs[k].sort_pos < context->naptr_rrs[i].sort_pos)) {
                  z = context->naptr_rrs[k].sort_pos;
                  context->naptr_rrs[k].sort_pos = context->naptr_rrs[i].sort_pos;
                  context->naptr_rrs[i].sort_pos = z;
               }
            }
         }
      }
      for (k = 0; k < context->naptr_rrs_count; k++) {
         if (context->naptr_rrs[k].sort_pos == context->position - 1) {
            ast_copy_string(context->dst, context->naptr_rrs[k].result, dstlen);
            ast_copy_string(context->tech, context->naptr_rrs[k].tech, techlen);
            break;
         }
      }
   } else if (!(context->options & ENUMLOOKUP_OPTIONS_COUNT)) {
      context->dst[0] = 0;
   } else if ((context->options & ENUMLOOKUP_OPTIONS_COUNT)) {
      snprintf(context->dst, context->dstlen, "%d", context->naptr_rrs_count + context->count);
   }

   if (chan) {
      ret |= ast_autoservice_stop(chan);
   }

   if (!argcontext) {
      for (k = 0; k < context->naptr_rrs_count; k++) {
         ast_free(context->naptr_rrs[k].result);
         ast_free(context->naptr_rrs[k].tech);
      }
      ast_free(context->naptr_rrs);
      ast_free(context);
   } else {
      *argcontext = context;
   }

   return ret;
}

/*! \internal
 * \brief Format a phone number as a domain in an ENUM-adjacent way.
 *
 * Creates a domain name suitable for query by:
 *
 * 1. Removing non-digits
 * 2. Adding a '.' between adjacent digits
 * 3. Reversing the string
 * 4. Appending the specified suffix (or e164.arpa if none is specified)
 */
static char *format_numeric_domain(const char *number, const char *suffix)
{
   char *buffer, *dst;
   size_t suffix_length;
   size_t number_length = strlen(number);
   const char *src = number + number_length - 1;

   if (!suffix) {
      suffix = "e164.arpa";
   }

   suffix_length = strlen(suffix);

   dst = buffer = ast_malloc(
      (number_length * 2) /* We need 2 bytes per input digit */
      + suffix_length     /* ... plus however long the suffix is */
      + 1                 /* ... plus room for the '.' separator */
      + 1                 /* ... and room for the \0 byte at the end */);

   if (buffer) {
      while (src >= number) {
         if (isdigit(*src)) {
            *dst++ = *src;
            *dst++ = '.';
         }
         src--;
      }

      /* The length arguments below make sure that the \0 byte is copied into
         the final string */
      if (*suffix == '.') {
         memcpy(dst, &suffix[1], suffix_length);
      } else {
         memcpy(dst, suffix, suffix_length + 1);
      }
   }

   return buffer;
}

int ast_get_txt(struct ast_channel *chan, const char *number, char *txt, int txtlen, char *suffix)
{
   struct txt_context context;
   char *domain;
   int ret;
   int autoservice = 0;

   ast_debug(4, "ast_get_txt: Number = '%s', suffix = '%s'\n", number, suffix);

   domain = format_numeric_domain(number, suffix);
   if (!domain) {
      return -1;
   }

   if (chan) {
      /* DNS might take a while, so service the channel while we're blocked */
      autoservice = !ast_autoservice_start(chan);
   }

   ret = ast_search_dns(&context, domain, C_IN, T_TXT, txt_callback);
   if (ret > 0) {
      ast_copy_string(txt, context.txt, txtlen);
   } else {
      ast_debug(2, "No such number found in ENUM: %s (%s)\n", domain, strerror(errno));
   }

   if (autoservice) {
      ast_autoservice_stop(chan);
   }

   ast_free(domain);
   return 0;
}

/*! \brief Initialize the ENUM support subsystem */
static int private_enum_init(int reload)
{
   struct ast_config *cfg;
   const char *string;
   struct ast_flags config_flags = { reload ? CONFIG_FLAG_FILEUNCHANGED : 0 };

   if ((cfg = ast_config_load2("enum.conf", "enum", config_flags)) == CONFIG_STATUS_FILEUNCHANGED)
      return 0;
   if (cfg == CONFIG_STATUS_FILEMISSING || cfg == CONFIG_STATUS_FILEUNCHANGED || cfg == CONFIG_STATUS_FILEINVALID) {
      return 0;
   }

   /* Destroy existing list */
   ast_mutex_lock(&enumlock);
   if (cfg) {
      if ((string = ast_variable_retrieve(cfg, "ienum", "branchlabel"))) {
         ast_copy_string(ienum_branchlabel, string, sizeof(ienum_branchlabel));
      }

      if ((string = ast_variable_retrieve(cfg, "ienum", "ebl_alg"))) {
         ebl_alg = ENUMLOOKUP_BLR_CC; /* default */

         if (!strcasecmp(string, "txt"))
            ebl_alg = ENUMLOOKUP_BLR_TXT;
         else if (!strcasecmp(string, "ebl"))
            ebl_alg = ENUMLOOKUP_BLR_EBL;
         else if (!strcasecmp(string, "cc"))
            ebl_alg = ENUMLOOKUP_BLR_CC;
         else
            ast_log(LOG_WARNING, "No valid parameter for ienum/ebl_alg.\n");
      }
      ast_config_destroy(cfg);
   }
   ast_mutex_unlock(&enumlock);
   return 0;
}

static int load_module(void)
{
   return private_enum_init(0) ? AST_MODULE_LOAD_FAILURE : AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
   return 0;
}

static int reload_module(void)
{
   return private_enum_init(1);
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS | AST_MODFLAG_LOAD_ORDER, "ENUM Support",
   .support_level = AST_MODULE_SUPPORT_CORE,
   .load = load_module,
   .unload = unload_module,
   .reload = reload_module,
   .load_pri = AST_MODPRI_CORE,
   .requires = "extconfig",
);