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#include "byte.h"
#include "dnsresolv.h"
#include "stralloc.h"
#include "uint_t.h"
/**
@file dns_mx.c
@author djb
@source qmail
@brief dns MX query
@param (on output) stralloc out
*/
static char *q = 0;
int dns_mx_packet(stralloc *out, const char *buf, unsigned int len)
{
unsigned int pos;
char header[12];
char pref[2];
uint16 numanswers;
uint16 datalen;
int ranswers = 0;
if (!stralloc_copys(out, "")) return DNS_MEM;
pos = dns_packet_copy(buf, len, 0, header, 12);
if (!pos) return DNS_ERR;
uint16_unpack_big(header + 6, &numanswers);
pos = dns_packet_skipname(buf, len, pos);
if (!pos) return DNS_ERR;
pos += 4;
while (numanswers--) {
pos = dns_packet_skipname(buf, len, pos);
if (!pos) return DNS_ERR;
pos = dns_packet_copy(buf, len, pos, header, 10);
if (!pos) return DNS_ERR;
uint16_unpack_big(header + 8, &datalen);
if (byte_equal(header, 2, DNS_T_MX)) {
if (byte_equal(header + 2, 2, DNS_C_IN)) {
if (!dns_packet_copy(buf, len, pos, pref, 2)) return DNS_ERR;
if (!dns_packet_getname(buf, len, pos + 2, &q)) return DNS_ERR;
if (!stralloc_catb(out, pref, 2)) return DNS_MEM;
if (dns_domain_todot_cat(out, q) <= 0) return DNS_ERR;
if (!stralloc_0(out)) return DNS_MEM;
}
}
pos += datalen;
++ranswers;
}
return ranswers;
}
int dns_mx(stralloc *out, const stralloc *fqdn)
{
int rc = 0;
if (dns_domain_fromdot(&q, fqdn->s, fqdn->len) <= 0) return DNS_ERR;
if (dns_resolve(q, DNS_T_MX) >= 0) {
if ((rc = dns_mx_packet(out, dns_resolve_tx.packet, dns_resolve_tx.packetlen)) < 0) return DNS_ERR;
dns_transmit_free(&dns_resolve_tx);
dns_domain_free(&q);
}
return rc;
}
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