273 lines
6.8 KiB
C
Executable File
273 lines
6.8 KiB
C
Executable File
/*
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* ENUM Support for Asterisk
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*
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* Copyright (C) 2003 Digium
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*
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* Written by Mark Spencer <markster@digium.com>
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*
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* Funding provided by nic.at
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*
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* Distributed under the terms of the GNU GPL
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*
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*/
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#include <string.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <arpa/nameser.h>
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#include <resolv.h>
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#include <errno.h>
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#include <asterisk/logger.h>
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#include <asterisk/options.h>
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#include <asterisk/srv.h>
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#include <asterisk/channel.h>
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#include <asterisk/config.h>
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#define MAX_SIZE 4096
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typedef struct {
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unsigned id :16; /* query identification number */
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#if BYTE_ORDER == BIG_ENDIAN
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/* fields in third byte */
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unsigned qr: 1; /* response flag */
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unsigned opcode: 4; /* purpose of message */
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unsigned aa: 1; /* authoritive answer */
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unsigned tc: 1; /* truncated message */
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unsigned rd: 1; /* recursion desired */
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/* fields in fourth byte */
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unsigned ra: 1; /* recursion available */
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unsigned unused :1; /* unused bits (MBZ as of 4.9.3a3) */
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unsigned ad: 1; /* authentic data from named */
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unsigned cd: 1; /* checking disabled by resolver */
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unsigned rcode :4; /* response code */
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#endif
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#if BYTE_ORDER == LITTLE_ENDIAN || BYTE_ORDER == PDP_ENDIAN
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/* fields in third byte */
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unsigned rd :1; /* recursion desired */
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unsigned tc :1; /* truncated message */
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unsigned aa :1; /* authoritive answer */
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unsigned opcode :4; /* purpose of message */
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unsigned qr :1; /* response flag */
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/* fields in fourth byte */
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unsigned rcode :4; /* response code */
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unsigned cd: 1; /* checking disabled by resolver */
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unsigned ad: 1; /* authentic data from named */
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unsigned unused :1; /* unused bits (MBZ as of 4.9.3a3) */
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unsigned ra :1; /* recursion available */
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#endif
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/* remaining bytes */
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unsigned qdcount :16; /* number of question entries */
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unsigned ancount :16; /* number of answer entries */
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unsigned nscount :16; /* number of authority entries */
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unsigned arcount :16; /* number of resource entries */
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} dns_HEADER;
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struct dn_answer {
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unsigned short rtype;
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unsigned short class;
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unsigned int ttl;
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unsigned short size;
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} __attribute__ ((__packed__));
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struct srv {
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unsigned short priority;
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unsigned short weight;
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unsigned short portnum;
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} __attribute__ ((__packed__));
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static int skip_name(unsigned char *s, int len)
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{
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/* Shamelessly take from SER */
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int x = 0;
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while(x < len) {
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if (!*s) {
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s++;
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x++;
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break;
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}
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if (((*s) & 0xc0) == 0xc0) {
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s += 2;
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x += 2;
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break;
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}
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x += *s + 1;
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s += *s + 1;
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}
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if (x >= len)
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return -1;
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return x;
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}
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static int parse_ie(unsigned char *data, int maxdatalen, unsigned char *src, int srclen)
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{
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int len, olen;
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len = olen = (int)src[0];
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src++;
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srclen--;
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if (len > srclen) {
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ast_log(LOG_WARNING, "Want %d, got %d\n", len, srclen);
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return -1;
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}
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if (len > maxdatalen)
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len = maxdatalen;
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memcpy(data, src, len);
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return olen + 1;
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}
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static int parse_srv(unsigned char *host, int hostlen, int *portno, unsigned char *answer, int len, unsigned char *msg)
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{
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int res = 0;
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struct srv *srv = (struct srv *)answer;
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char repl[256] = "";
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if (len < sizeof(struct srv)) {
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printf("Length too short\n");
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return -1;
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}
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answer += sizeof(struct srv);
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len -= sizeof(struct srv);
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if ((res = dn_expand(msg,answer + len,answer, repl, sizeof(repl) - 1)) < 0) {
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ast_log(LOG_WARNING, "Failed to expand hostname\n");
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return -1;
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}
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if (res && strcmp(repl, ".")) {
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ast_verbose( VERBOSE_PREFIX_3 "parse_srv: SRV mapped to host %s, port %d\n", repl, ntohs(srv->portnum));
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if (host) {
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strncpy(host, repl, hostlen - 2);
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host[hostlen-1] = '\0';
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}
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if (portno)
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*portno = ntohs(srv->portnum);
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return(0);
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}
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return(-1);
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}
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static int parse_answer(unsigned char *host, int hostlen, int *port, char *answer, int len)
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{
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/*
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* This function is influenced by "ser" the SIP router.
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*/
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int x;
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int res;
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dns_HEADER *h;
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struct dn_answer *ans;
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/* int lastlit = 1; */
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char *oanswer = answer;
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host[0] = '\0';
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*port = 0;
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#if 0
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for (x=0;x<len;x++) {
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if ((answer[x] < 32) || (answer[x] > 127)) {
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if (lastlit)
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printf("\"");
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printf(" 0x%02x", answer[x]);
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lastlit = 0;
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} else {
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if (!lastlit)
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printf(" \"");
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printf("%c", answer[x]);
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lastlit = 1;
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}
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}
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printf("\n");
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#endif
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h = (dns_HEADER *)answer;
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/* Skip over DNS header */
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answer += sizeof(dns_HEADER);
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len -= sizeof(dns_HEADER);
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#if 0
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printf("Query count: %d\n", ntohs(h->qdcount));
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#endif
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for (x=0;x<ntohs(h->qdcount);x++) {
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if ((res = skip_name(answer, len)) < 0) {
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ast_log(LOG_WARNING, "Couldn't skip over name\n");
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return -1;
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}
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answer += res;
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len -= res;
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answer += 4; /* Skip QCODE / QCLASS */
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len -= 4;
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if (len < 0) {
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ast_log(LOG_WARNING, "Strange query size\n");
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return -1;
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}
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}
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#if 0
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printf("Length remaining: %d, already at %04x\n", len, 0x2a + (answer - oanswer));
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printf("Answer count: %d\n", ntohs(h->ancount));
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printf("Looking for %d/%d\n", C_IN, T_SRV);
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printf("Answer so far: %02x %02x %02x %02x %02x %02x\n", answer[0], answer[1], answer[2], answer[3], answer[4], answer[5]);
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#endif
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for (x=0;x<ntohs(h->ancount);x++) {
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if ((res = skip_name(answer, len)) < 0) {
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ast_log(LOG_WARNING, "Failed to skip name :(\n");
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return -1;
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}
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answer += res;
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len -= res;
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ans = (struct dn_answer *)answer;
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answer += sizeof(struct dn_answer);
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len -= sizeof(struct dn_answer);
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if (len < 0)
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return -1;
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#if 0
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printf("Type: %d (%04x), class: %d (%04x), ttl: %d (%08x), length: %d (%04x)\n", ntohs(ans->rtype), ntohs(ans->rtype), ntohs(ans->class), ntohs(ans->class),
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ntohl(ans->ttl), ntohl(ans->ttl), ntohs(ans->size), ntohs(ans->size));
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#endif
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len -= ntohs(ans->size);
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if (len < 0) {
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ast_log(LOG_WARNING, "Length exceeds frame by %d\n", -len);
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return -1;
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}
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if ((ntohs(ans->class) == C_IN) && (ntohs(ans->rtype) == T_SRV)) {
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if (parse_srv(host, hostlen, port, answer, ntohs(ans->size),oanswer))
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ast_log(LOG_WARNING, "Failed to parse srv :(\n");
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if (strlen(host))
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return 0;
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}
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answer += ntohs(ans->size);
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}
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return 0;
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}
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int ast_get_srv(struct ast_channel *chan, char *host, int hostlen, int *port, const char *service)
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{
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int res;
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int ret = -1;
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struct __res_state srvstate;
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char answer[MAX_SIZE];
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if (*port)
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*port = 0;
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res_ninit(&srvstate);
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if (chan && ast_autoservice_start(chan) < 0)
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return -1;
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res = res_nsearch(&srvstate, service, C_IN, T_SRV, answer, sizeof(answer));
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if (res > 0) {
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if ((res = parse_answer(host, hostlen, port, answer, res))) {
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ast_log(LOG_WARNING, "Parse error returned %d\n", res);
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ret = 0;
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} else {
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ast_log(LOG_DEBUG, "Found host '%s', port '%d'\n", host, *port);
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ret = 1;
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}
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} else {
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ast_log(LOG_DEBUG, "No such service found: %s (%s)\n", service, strerror(errno));
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ret = 0;
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}
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if (chan)
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ret |= ast_autoservice_stop(chan);
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res_nclose(&srvstate);
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return ret;
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}
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